LTC3119
18V, 5A Synchronous
Buck-Boost DC/DC Converter
FEATURESDESCRIPTION

Input Voltage Range: 2.5V to 18V
nn Runs Down to V = 250mV After Start-UpIN
nn Output Voltage Range: 0.8V to 18V
nn 5A Output Current in Buck Mode, V > 6VIN
nn 3A Output Current for V = 3.6V, V
IN
OUT = 5V
nn Programmable Switching Frequency: 400kHz to 2MHz
nn Synchronizable with an External Clock Up to 2MHz
nn Accurate Run Comparator Threshold
nn Burst Mode® Operation, No-Load I = 35µA
Q
nn Ultralow Noise Buck-Boost PWM
nn Current Mode Control
nn Maximum Power Point Control
nn Power Good Indicator
nn Internal Soft-Start
nn 28-Lead 4mm × 5mm QFN and TSSOP Packages

The LTC®3119 is a high efficiency 18V monolithic buckboost converter that can deliver up to 5A of continuous
output current. Extensive feature integration and very
low resistance internal power switches minimize the totalsolution footprint for even the most demanding applications. A proprietary 4-switch PWM architecture provides
seamless low noise operation from input voltages above,
equal to, or below the output voltage.

APPLICATIONSOther features include: output short-circuit protection,
thermal overload protection, less than 3µA shutdown
current, power good indicator, Burst Mode operation, andmaximum power point control.

nn

Wide Input Range Power Supplies
1- to 4-Cell Lithium Battery Powered Products
nn RF Power Supplies
nn Solar Battery Chargers
nn System Backup Power Supplies
nn Lead Acid to 12V Regulatornnnn

External frequency programming as well as synchronization using an internal PLL enable operation over a wideswitching frequency range of 400kHz to 2MHz. The wide
2.5V to 18V input range is well suited for operation fromunregulated power sources including battery stacks andbackup capacitors. After start-up, operation is possible
with input voltages as low as 250mV.

The LTC3119 is offered in thermally enhanced 28-lead
4mm × 5mm QFN and TSSOP packages.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and PowerPath and No RSENSE are trademarks of Linear Technology Corporation. All othertrademarks are the property of their respective owners.

TYPICAL APPLICATION
Wide Input Range 5V Regulator

Efficiency Efficiency
100

3.3µH
0.1µF

VIN
2.5V TO 18V
10µF

100k

SW1
BST1
PVIN
VIN
RUN

BURST PWM

4.7µF

SW2
BST2
PVOUT
150µF

LTC3119536k

PWM/SYNC
FB
MPPC
VCC
PGOOD
SVCC
VC
RT
PGND GND
105k

VOUT
5V AT 5A, VIN > 6V
5V AT 3A, VIN = 3.6V

3119 TA01a

80
EFFICIENCY (%)

0.1µF

Burst Mode OPERATION

90

70
60
PWM

50
40
30

102k
78.7k
680pF

VIN = 3V
VIN = 5V
VIN = 9V

20
10
100μ

1m

10m
100m
LOAD CURRENT (A)1

103119 TA01b

3119f

For more information www.linear.com/LTC3119

1

LTC3119
ABSOLUTE MAXIMUM RATINGS (Note 1)
VIN, PVIN, PVOUT, RUN, PGOOD.................. –0.3V to 19V
FB, VC, RT, SYNC, MPPC, VCC, SVCC............ –0.3V to 6V
BST1 Voltage...................... (SW1 – 0.3V) to (SW1 + 6V)
BST2 Voltage......................(SW2 – 0.3V) to (SW2 + 6V)

Operating Junction Temperature (Notes 2, 3)
LTC3119E/LTC3119I............................ –40°C to 125°C
LTC3119H........................................... –40°C to 150°C
LTC3119MP........................................ –55°C to 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
FE...................................................................... 300°C

PIN CONFIGURATIONTOP VIEW
N/C

1

28 PWM/SYNC
26 BST1

28 27 26 25 24 23

PGND

4

25 PGND

SW2

524 SW1N/C

27 N/C

3

N/C

2

N/C

N/C
BST2

BST2

BST1

PWM/SYNCTOP VIEWPGND 1

22 PGND

SW2 2

21 SW1PVOUT 320 PVIN

PVOUT 419 PVIN

29
PGND

SW2 5

18 SW1

PGND 6

17 PGNDPGOOD 7

16 VIN

SVCC 815 RUN

7

SW2

8

PGND

9

23 PVIN
29
PGND

22 PVIN
21 SW1
20 PGND
19 VIN

SVCC 11

18 RUN

FB 12

17 RT

VC 13

16 VCC

SGND 1415 MPPC

RT

VCC

MPPC

SGND

FB

VC

6

PGOOD 10

9 10 11 12 13 14

UFD PACKAGE
28-LEAD (4mm × 5mm) PLASTIC QFNTJMAX = 125°C, θJA = 22°C/W
EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCB

PVOUT
PVOUT

FE PACKAGE
28-LEAD PLASTIC TSSOPTJMAX = 150°C, θJA = 21°C/W
EXPOSED PAD (PIN 29) IS PGND, MUST BE SOLDERED TO PCBORDER INFORMATION http://www.linear.com/product/LTC3119#orderinfo
LEAD FREE FINISH

TAPE AND REELPART MARKING*PACKAGE DESCRIPTIONTEMPERATURE RANGE

LTC3119EUFD#PBF

LTC3119EUFD#TRPBF

3119

28-Lead (4mm × 5mm) Plastic QFN–40°C to 125°C

LTC3119IUFD#PBF

LTC3119IUFD#TRPBF

3119

28-Lead (4mm × 5mm) Plastic QFN–40°C to 125°C

LTC3119EFE#PBF

LTC3119EFE#TRPBF

3119

28-Lead Plastic Enhanced TSSOP–40°C to 125°C

LTC3119IFE#PBF

LTC3119IFE#TRPBF

3119

28-Lead Plastic Enhanced TSSOP–40°C to 125°C

LTC3119HFE#PBF

LTC3119HFE#TRPBF

3119

28-Lead Plastic Enhanced TSSOP–40°C to 150°C

LTC3119MPFE#PBF

LTC3119MPFE#TRPBF

3119

28-Lead Plastic Enhanced TSSOP–55°C to 150°C

Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels throughdesignated sales channels with #TRMPBF suffix.

2

3119f

For more information www.linear.com/LTC3119

LTC3119
ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. VIN = PVIN = 12V, PVOUT = 5V, RT = 76.8k unless otherwise stated.
PARAMETER
Input Operating Voltage

CONDITIONSMINAfter Start-Up (Note 4)

Output Operating Voltage
VCC Undervoltage Lockout Threshold

VCC Rising
VCC Falling

MAX

UNITS

l
l

2.5
0.25

18
18

V
V

l

0.8

18

V

l
l

2.18

2.4

V
V

VCC Undervoltage Lockout Hysteresis

TYP

2.35
2.25
60

Input Current in Shutdown

RUN = 0V

Input Current in Sleep

FB = 0.9V

mV
3

31

µA

Oscillator Frequency

l

900

1100

kHz

Oscillator Operating Frequency

l

400

2000

kHz

PWM/SYNC Frequency Range

l

400

2000

kHz

PWM/SYNC Logic Threshold
PWM/SYNC Pulse Widthl

Minimum Low or High Duration

0.3

1000

µA

0.7

1.1

100

PWM/SYNC Pin Current

1Soft-Start Duration

6

50

nA
ms

795
795

803
811

mV
mV

Feedback Pin Current

1

50

nA

Error Amplifier Transconductance120

Feedback Voltagel

RUN Pin Logic Threshold
RUN Pin Comparator Threshold

VRUN Rising

787
779

V
ns

l

0.3

0.8

1

l

1.17

1.205

1.24

RUN Pin Hysteresis Current

0.25

RUN Pin Hysteresis Voltage
Percentage of FB Voltage Falling

PGOOD Hysteresis

Percentage of FB Voltage

l

–9.5

–8
700

VPGOOD = 18V

MPPC Pin Threshold

l

774

l

7

MPPC Pin Current
Inductor Current Limit(Note 3)

Burst Mode Operation Inductor
Current Limit

VIN > VOUT (Note 3)

Maximum Duty Cycle

Percentage of Period SW2 is Low in Boost Model90

Minimum Duty Cycle

Percentage of Period SW1 is High in Buck Model0SW1, SW2 Minimum Low Time

V
mV

–6.5

1.2

PGOOD Pull Down Resistance

V
µA

90

PGOOD Threshold

PGOOD Leakage

µS

%
%

2000

Ω

1

40

nA

798

822

mV

1

50

nA

8

A

0.6

A

92

%

90

ns

%

3119f

For more information www.linear.com/LTC3119

3

LTC3119
ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at TA = 25°C. VIN = PVIN = 12V, PVOUT = 5V, RT = 76.8k unless otherwise stated.
PARAMETERCONDITIONS

N-Channel Switch Resistance

Switch A (PVIN to SW1)
Switch B (SW1 to PGND)
Switch C (SW2 to PGND)
Switch D (SW2 to PVOUT)

MIN

30
30
30
30

N-Channel Switch Leakage

PVIN = PVOUT = 18V, SW1 = SW2 = 0V, 18V

1

10

3.70

3.85

VCC Regulation Voltage
VCC Dropout Voltage

l90

VCC Current Limit
VCC Reverse Current

180
VCC = 5V, VIN = 3V

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3119 is tested under pulsed load conditions suchthat TJ ≈ TA. The LTC3119E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specification over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3119I specifications are guaranteed over the –40°C to 125°C operating
junction temperature range. The LTC3119H specifications are guaranteed
over the –40°C to 150°C operating junction temperature range. The
LTC3119MP specifications are guaranteed and tested over the –55°C to
150°C operating junction temperature range. High temperatures degrade
operating lifetimes; operating lifetime is derated for junction temperatures
greater than 125°C.

4

3.55

VCC Current = 50mA, VIN = 3V

TYP

MAX

UNITS
mΩ
mΩ
mΩ
mΩ
µA
V
mV
mA

5

µA

Note 3: Current measurements are performed when the LTC3119 is
not switching. The current limit values measured in operation will besomewhat higher due to the propagation delay of the comparators.
Note 4: Minimum input voltage is governed by the VCC UVLO threshold. If
VCC is maintained though external bootstrapping, the part will continue tooperate until power transfer to the output is no longer possible.
Note 5: Switch timing measurements are made in an open-loop test
configuration. Timing in the application may vary somewhat from thesevalues due to differences in the switch pin voltage during the non-overlap
durations when switch pin voltage is influenced by the magnitude anddirection of the inductor current.
Note 6: This IC includes overtemperature protection that is intended toprotect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
OutputVoltage Line Regulation
Line Regulation

0.4

CHANGE IN VOUT (%)

0.6

0.4
0.2
0
–0.2
–0.4

0.2
0.0
–0.2
–0.4

–0.6

–0.6

–0.8

–0.8
6

8
10 12 14INPUT VOLTAGE (V)

16

–1.0
0.001

18

0.01
0.1
LOAD CURRENT (A)

1

35

38

32

26

20
–60

6

–30

0

30

60

90

TEMPERATURE (° C)

120

150

3119 G03

Run Pin Hysteresis Current vs
TemperaturePower Switch Resistance vs VCC

260

34

255

33
32
31
30
29
28
27

44

3119 G02

3119 G01

HYSTERESIS CURRENT (nA)

4

250
245
240
235
230
225

2

2.5

3
3.5
VCC VOLTAGE (V)

220
–60

4
3119 G04

Run Pin Comparator Threshold vs
Temperaturevs Temperature
1.35

1.25
1.20
1.15
1.10
1.05
–60

–30

0

30

60

90

TEMPERATURE (° C)

120

150

0

30

60

90

120

150

3119 G05

Run Pin Logic Threshold vs
Temperaturevs Temperature
850

RISINGFALLING

1.30–30

TEMPERATURE ( ° C)

RISINGFALLINGTHRESHOLD VOLTAGE (mV)

2

SWITCH RESISTANCE (mΩ)–1

50

PWM/SYNC = HIGH

0.8

0.6

THRESHOLD VOLTAGE (V)CHANGE IN VOUT (%)

1.0

LOAD = 1A
PWM/SYNC = HIGH

TemperaturevsTemperature

SWITCH RESISTANCE (mΩ)

10.8Power Switch Resistance vs

Output Voltage Load Regulation

770

690

610

530

450
–60

3119 G06

–30

0

30

60

90

TEMPERATURE (° C)

120

150

3119 G07

3119f

For more information www.linear.com/LTC3119

5

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Run Pin Current vs Run Pin

Oscillator Frequency vs RT
2.0

25

1.8

20
15
10
5
0
–5

0

2

4

6

8 10 12VOLTAGE (V)

14

16

1.6
1.4
1.2
1.0
0.8
0.6
0.4

18

1.0

CHANGE FROM VIN = 12V (%)

30
OSCILLATOR FREQUENCY (MHz)RUN PIN CURRENT (μA)

Voltage

20

50

80
110
140
170
RT PIN RESISTOR (kΩ)

Oscillator Frequency vsTemperature

–1.0
–1.5

2

4

6

8
10 12 14INPUT VOLTAGE (V)16183119 G10

0.1

CHANGE FROM 25 ° C (%)

0.7
CHANGE FROM 25 ° C (%)

–0.5

FB
FB Voltage
Voltage vsvs Temperature
Temperature

1.0

0.4
0.1
–0.2
–0.5
–0.8
–60

–30

0

30

60

90

TEMPERATURE (° C)

120

0.0

–0.1

–0.2

–0.3

–0.4
–60

150

3119 G11

0

30

60

90

120

150

3119 G12

SW1, SW2 Minimum Low Time vsTemperature
5

0.2

4

0.1
CHANGE FROM 25 ° C (%)

0.0
–0.1
–0.2
–0.3
–0.4
–0.5
–0.6
–60

–30

TEMPERATURE (° C)

MPPC Pin Voltage vs
Temperature
MPPC Voltage vs Temperature

CHANGE FROM 25 ° C (%)

03119 G09

3119 G08

3
2
1
0
–1
–2
–3
–4

–30

0

30

60

90

TEMPERATURE ( ° C)

6

0.5

–2.0

200

Oscillator Frequency vs VIN
IN

120

150

–5
–60

3119 G13

–30

0

30

60

90

TEMPERATURE (° C)

120

150

3119 G14

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
SW2 Maximum Duty Cycle vsTemperature
94.0

70

93.5

60

93.0

40
30
20
10

2

92.0
91.5

2.5

3
3.5
4
VCC VOLTAGE (V)

4.5

0

30

60

90

TEMPERATURE ( ° C)

35

fSW = 1MHz

120

16.0
–60

150

17
16
15
14
13
12

3119 G16VCC Current vs Switching
Frequency
VCC Current vs Switching Frequency

3
3.5
4
VCC VOLTAGE (V)

4.5

25
20
15

80

–1.0

0

30

60

90

120

150

3119 G20

Inductor Current Limit vsTemperature
9.0

0.4

8.5

0.2
0.1
0.0
–0.1
–0.2
–0.3

–1.2

–30

TEMPERATURE (° C)

CURRENT LIMIT (A)–0.8

3119 G17

90

60
–60

2.0

0.5

VCC CHANGE (%)

VCC CHANGE (%)

–0.6

–1.4

0.6 0.8 1 1.2 1.4 1.6 1.8
SWITCHING FREQUENCY (MHz)

0.3

–0.4

150

100

VCC Line Regulation

–0.2

120

110

3119 G19

fSW = 1MHz90

703119 G18

VCC
CC Load Regulation

60

120

5
0.4

5

30

130

10

2.5

0

VCC Dropout Voltage vs
Temperature

11
2

–30

TEMPERATURE (° C)30
VCC CURRENT (mA)

VCC CURRENT (mA)

–303119 G15

18

0.0

17.0

16.5

90.0
–60

5

VCC
CC Current vs VCC
CC

19

10

fSW = 1MHz

90.5

–10

20

92.5

91.0

0

VVCC
Current vsvs Temperature
Temperature
CC Current

17.5
VCC CURRENT (mA)

DUTY CYCLE (%)

CHANGE (%)

50

–20

18.0

DROPOUT VOLTAGE (mV)

80

SW1, SW2 Minimum Low Timevs VCC

8.0
7.5
7.0
6.5

–0.4
0

10 20 30 40 50 60 70 80 90 100
VCC LOAD CURRENT (mA)
3119 G21

–0.5

4

6

8
10
12
14
INPUT VOLTAGE (V)16183119 G22

6.0
–60

–30

0
30
60
90
TEMPERATURE (° C)

120

150

3119 G23

3119f

For more information www.linear.com/LTC3119

7

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
VCC UVLO Threshold vs
Temperature

Efficiency vs Switching Frequency

2.40

95
RISINGFALLING

2.38

94

2.34

93

EFFICIENCY (%)

THRESHOLD VOLTAGE (V)

2.36

2.32
2.30
2.28
2.26

92
91

2.24

90

2.22
2.20
–60

–30

0

30

60

90

120

TEMPERATURE ( ° C)

89
0.4

150

200
175

0.8

150

0.7
0.6
0.5
0.4

4

6

8
10 12 14INPUT VOLTAGE (V)

16

100
75
50
25
0

18

2

4

6

8
10 12 14INPUT VOLTAGE (V)16183119 G27

Maximum Reverse Current During
0.83)
MPPC Control (V MPPC <≤ 0.86)

180
REVERSE CURRENT (mA)

2.0

VOUT = 5V
fSW = 1MHz
L = 2.2μH

3119 G26

200

1.8

125

VOUT = 3.3V
VOUT = 5V
VOUT = 12V2

1 1.2 1.4 1.6
FREQUENCY (MHz)Minimum Current to Avoid Pulse
Skipping
Avoid Pulse Skipping

0.9

0.2

0.8

3119 G25

Burst Mode Operation
Threshold
IN

0.3

0.6

3119 G24

LOAD CURRENT (mA)

OUTPUT CURRENT (A)

1.0

VOUT = 5V
VOUT = 12V

160

VOUT = 12V
fSW = 1MHz

L = 2.2μH
L = 6.8μH

6

16

140
120
100
80
60
40
20
0

2

4

8
10 12 14INPUT VOLTAGE (V)183119 G2883119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
100

100

Burst Mode OPERATION

90

Efficiency, VOUT = 3.3V
ffSW
1MHz
SW == 1MHz

100

Burst Mode OPERATION

90
80

70

70

70

60
50

PWM

40
30
20
10
100μ

1m

10m
100m
LOAD CURRENT (A)

1

60
PWM

50
40
30

VIN = 2.5V
VIN = 5V
VIN = 12V

10
100μ

1m

10m
100m
LOAD CURRENT (A)

1

90

90

80

80

70

70

60
50

PWM

40
30

10
100μ

1m

10m
100m
LOAD CURRENT (A)

1

60
PWM

50
40

100

30

VIN = 3V
VIN = 5V
VIN = 12V
1m

10m
100m
LOAD CURRENT (A)

1

10
100μ

10

Efficiency, VOUT = 12V
fSW = 1MHz

100

Burst Mode OPERATION

90

70

1m

10m
100m
LOAD CURRENT (A)

1

60
PWM

50
40
30

3119 G35

10m
100m
LOAD CURRENT (A)

1

10
100μ

1m

10m
100m
LOAD CURRENT (A)1Burst Mode OPERATION

60
PWM

50
40

VIN = 5V
VIN = 12V
VIN = 15V

20
103119 G36

10Efficiency, VOUT = 12V
2MHz
ffSW
SW == 2MHz30

VIN = 5V
VIN = 12V
VIN = 15V

20
10

EFFICIENCY (%)

80

10
100μ

1m

3119 G34

70

20

VIN = 3V
VIN = 5V
VIN = 12V

2080

VIN = 5V
VIN = 12V
VIN = 15V

PWM

40

70

30

Burst Mode OPERATION

50

80

40

10

Efficiency, VOUT = 5V
fSW
SW = 2MHz

60

90

50

1

70

90

PWM

10m
100m
LOAD CURRENT (A)3119 G33

Efficiency, VOUT = 12V
f SW = 500kHz

60

1m

80
Burst Mode
OPERATION

10
100μ

10

Burst Mode
OPERATION

VIN = 2.5V
VIN = 5V
VIN = 12V

3119 G31

100

20

EFFICIENCY (%)

EFFICIENCY (%)

40

903119 G32

100

PWM

50

10
100μ

10

Efficiency, VOUT = 5V
fSW
SW = 1MHz30

VIN = 3V
VIN = 5V
VIN = 12V

20

60

20

EFFICIENCY (%)

100

EFFICIENCY (%)

EFFICIENCY (%)

Efficiency, VOUT = 5V
fSW
SW = 500kHz

Burst Mode
OPERATION

Burst Mode OPERATION

3119 G30

3119 G29

100

Efficiency, VOUT = 3.3V
fSW
SW = 2MHz30

VIN = 2.5V
VIN = 5V
VIN = 12V

20
10

EFFICIENCY (%)

80

80
EFFICIENCY (%)

EFFICIENCY (%)

90

Efficiency, VOUT = 3.3V
fSW = 500kHz

10
100μ

1m

10m
100m
LOAD CURRENT (A)1

103119 G37

3119f

For more information www.linear.com/LTC3119

9

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
PWM Mode No-Load Input
Current
Input
Current
46

65

38
34
30
26
22

4.0

55
50
45
40

3.5
3.0
2.5
2.0
1.5

18

35

1.0

14

30

0.5

10

25

2

4

6

8
10 12 14INPUT VOLTAGE (V)

16

18

2

4

6

8
10 12 14INPUT VOLTAGE (V)

Temperature
Load Current Rise vs Load Current

Temperature Rise vs Load Current

60
50
40
30
20

VIN = 9V
VIN = 12V
VIN = 15V

10
1.5

2

2.5 3 3.5 4
LOAD CURRENT (A)

4.5

DC2129A DEMO BOARD
118 VOUT = 12V
f = 2MHz106 SW
94
82
70
58
46
34

VIN = 9V
VIN = 12V
VIN = 15V

22
5

10

1

1.5

2

2.5 3 3.5 4
LOAD CURRENT (A)

60
50
40
30
VIN = 3V
VIN = 5V
VIN = 12V

10
0

1

1.5

2

80
70
60
50
40
30
20

VIN = 3V
VIN = 5V
VIN = 12V

105

2.5 3 3.5 4
LOAD CURRENT (A)

4.5

5

0

1

1.5

2

2.5 3 3.5 4
LOAD CURRENT (A)4.5

53119 G43

80
70
60
50
40
30
20
10

5

3119 G44

10

4.5

4.5

DC2129A DEMO BOARD
VIN = 13V
VOUT = 12V
fSW = 1MHz
500Hz PULSE LOAD = 5A
STANDBY LOAD = 0.25A

90
TEMPERATURE RISE (° C)

TEMPERATURE RISE (° C)

100

70

20

4

Temperature Rise vs Pulsed Load
Duty Cycle

DC2129A DEMO BOARD
VOUT = 5V
fSW = 2MHz80

2.5 3 3.5
BOOST RATIO

3119 G42

Temperature
Load Current Rise vs Load Current
90

2

DC2129A DEMO BOARD
VOUT = 5V
fSW = 1MHz

90

3119 G41100

1.5

Temperature
Load Current Rise vs Load Current
100

TEMPERATURE RISE (° C)

TEMPERATURE RISE (° C)7013119 G40

130

DC2129A DEMO BOARD
90 VOUT = 12V
f = 1MHz
80 SW

1

0

18

3119 G39

100

0

16

VOUT = 12V
fSW = 1MHz

4.5

60

3119 G38

TEMPERATURE RISE (° C)

5.0

VOUT = 3.3V
VOUT = 5V
VOUT = 12V

70

INPUT CURRENT (μA)

42
INPUT CURRENT (mA)75

VOUT = 3.3V
VOUT = 5V
VOUT = 12V

OUTPUT CURRENT (A)50

Maximum Output Current vs
Boost
Ratio
vs Boost
Ratio

Burst Mode Operation No–Load
Input Current

00

10 20 30 40 50 60 70 80 90 100
LOAD DUTY CYCLE (%)
3119 G45

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Burst Mode Operation Load Step
400mA to 4A, VIN = 9V

Burst Mode Operation
VOUT Ripple OUT

PWM Mode Load Step 400mA to
4A, VIN = 9V IN

FRONT PAGE APPLICATIONFRONT PAGE APPLICATIONILOAD = 50mA, VIN = 9V

FRONT PAGE APPLICATION

VOUT
200mV/DIV

VOUT
200mV/DIVOUTPUT
VOLTAGE
20mV/DIVINDUCTORCURRENT
5A/DIVINDUCTORCURRENT
5A/DIVINDUCTORCURRENT
250mA/DIVLOAD
CURRENT
5A/DIV
200µs/DIVLOAD
CURRENT
5A/DIV

3119 G46

200µs/DIV

3119 G47

20µs/DIV

Switching Waveforms, Buck
Mode Operation

Switching Waveforms, Boost
Mode Operation

FRONT PAGE APPLICATIONILOAD = 2A, VIN = 9V

FRONT PAGE APPLICATIONILOAD = 2A, VIN = 3V

SW1
10V/DIV

3119 G48

SW1
5V/DIV

SW2
5V/DIV

SW2
5V/DIVINDUCTORCURRENT
1A/DIVINDUCTORCURRENT
400mA/DIV
500ns/DIV

3119 G49

500ns/DIV

3119 G50

PIN FUNCTIONS (QFN/TSSOP)PGND (Pins 1, 6, 17, 22, Exposed Pad Pin 29/Pins 4, 9,
20, 25, Exposed Pad Pin 29): Power Ground Connection.
These pins should be connected to the power groundusing the shortest and widest connections possible. The
exposed pad must be soldered to the PCB and electricallyconnected to ground through the shortest and lowest
impedance path possible and to the PCB ground plane
for rated thermal performance.
SW2 (Pins 2, 5/Pins 5, 8): Buck-Boost Converter Power
Switch Pin. These pins should be connected to one sideof the Buck-Boost inductor.

PVOUT (Pins 3, 4/Pins 6, 7): Output Voltage Power
Connection. These pins is connected to switch D of the
buck-boost converter. Connect a low ESR 10µF or larger
capacitor between this pin and ground using the lowest
impedance path possible.
PGOOD (Pin 7/Pin 10): Open drain output that pulls toground when FB drops too far below its regulated voltage. Connect a pull-up resistor from this pin to a positive
supply. Refer to the Operation section of the data sheet
for more detail.
SVCC (Pin 8/Pin 11): Supplies voltage to internal circuits
used for production test. This pin must be tied to VCC.
3119f

For more information www.linear.com/LTC3119

11

LTC3119PIN FUNCTIONS (QFN/TSSOP)FB (Pin 9/Pin 12): Feedback Voltage Input. A resistor
divider connected to this pin sets the output voltage forthe buck-boost converter.
VC (Pin 10/Pin 13): Error Amplifier Output. A frequency
compensation network must be connected between thispin and SGND to stabilize the voltage control loop.
SGND (Pin 11/Pin 14): Signal Ground. This pin is theground connection for the control circuitry of the IC andmust be tied to ground in the application.
MPPC (Pin 12/Pin 15): Maximum Power Point Control
Setpoint. Connect this pin to a resistive divider from VIN
to GND to set the input regulation voltage. The MPPC pinshould be tied to VCC to disable MPPC operation.
VCC (Pin 13/Pin 16): Internal Regulator Output Voltage
and Supply Rail for Control Circuits. This pin is the outputof the internal low voltage linear regulator used to supply
the control circuitry. The VCC output may also be used to
power external loads of up to 10mA. A 4.7µF capacitor
should be connected between this pin and GND using theshortest trace possible.
RT (Pin 14/ Pin 17): Oscillator Frequency Programming
Input. Connect a resistor between this pin and GND to set
the buck-boost converter switching frequency.
RUN (Pin 15/Pin 18): Input to Enable and Disable the IC
and Set Custom Input UVLO Threshold. The RUN pin canbe driven by external logic signals to enable and disable
the IC. In addition, the voltage on this pin can be set by aresistor divider connected to the input voltage to provide
an accurate undervoltage lockout threshold. The IC isenabled if the RUN pin voltage exceeds 1.205V nominally.
Once enabled, a 250nA current is sourced from this pin
to provide additional hysteresis.

12

VIN (Pin 16/Pin 19): Input Voltage Pin for Internal VCC
Regulator.
PVIN (Pins 19, 20/Pins 22, 23): Input Voltage Power
Connection. These pins is connected to switch A of the
buck-boost converter. Connect a 10µF or larger capacitor
between this pin and GND using the lowest impedance
path possible.
SW1 (Pins 18, 21/Pins 21, 24): Buck-Boost Converter
Power Switch Pin. These pins should be connected to
one side of the Buck-Boost inductor.
BST1 (Pin 23/Pin 26): Power Rail for SWA Driver. Thispin must be connected to SW1 through a 0.1μF capacitor.
This pin is used to generate the gate drive rail for powerswitch A.
N/C (Pins 24, 26, 27/Pins 1, 2, 27): No Connection. Can
be connected to ground or left open. This pin does notconnect to any internal circuitry.
PWM/SYNC (Pin 25/Pin 28): Automatic Burst Mode
Operation/PWM Mode Control Pin and Synchronization
Input. Forcing this pin high causes the IC to operate in
fixed frequency PWM mode at all loads using the internal
oscillator at the frequency set by the RT Pin. Forcing thispin low causes the IC to enable Burst Mode operation atlight loads to maximize efficiency. Clocking this pin willcause the part to synchronize to the clock for frequencies
higher than the frequency programmed by the RT Pin.
When using this pin for synchronization, a minimum input
pulse width of 100ns should be used.
BST2 (Pin 28/Pin 3): Power Rail for SWA Driver. This pin
must be connected to SW2 through a 0.1μF capacitor.
This pin is used to generate the gate drive rail for powerswitch D.

3119f

For more information www.linear.com/LTC3119

LTC3119BLOCK DIAGRAM Pin numbers are shown for UFD package only.
16

3

4

VIN

13

5

21

18

20

19

SW1

D

REVERSEBLOCKING
LDO

VCC

2
SW2

PVOUT

PVIN

A
BST1

BST2

8 SVCC

28

7

12

9

10

14
25

B

PGND

PGND

8A

+
–

23

C

BST1
BST2

CURRENTLIMIT

ZERO
CURRENT

0A

SOFT-START
RAMP

PGOOD

–
+
MPPC
798mV

+
–

795mV

–
gm
+

FB

+
–

PWM

–
+
+

FB
731mV

VIN
0.25µA+–CHIP
ENABLE

VC
UVLO

RT

OSCILLATOR

1.205V
0.795VPWM/SYNC
MODE
SELECTIONBANDGAPREFERENCE

+
–

RUN

15

1.205V
VCC
2.35V

OVERTEMPERATURE

PGND
SGND EXPOSED PAD
1

6

17

22

11

29

3119 BD

3119f

For more information www.linear.com/LTC3119

13

LTC3119OPERATION
INTRODUCTION

PWM MODE OPERATIONThe LTC3119 is a 5A monolithic Buck-Boost DC/DC converter that can operate over a wide range of 2.5V to 18V
on VIN and 0.8V to 18V on VOUT. Integrated low RDS(ON)
N-Channel DMOS power switches reduce solution complexity and maximize conversion efficiency. Internal highside power switch drivers require only two small external
capacitors and further simplify application circuit design.
The LTC3119 incorporates many additional features toallow for maximum flexibility when designing application
solutions, including an accurate RUN pin comparator,
wide operating frequency range of 400kHz to 2MHz,external clock synchronization, power good indicator,and Maximum Power Point Control (MPPC) of the input
voltage for operation from current limited sources suchas photovoltaic arrays.

If the PWM/SYNC pin is held high, or the load current on
the converter is high enough to command PWM mode
operation with the PWM/SYNC pin held low, the LTC3119
operates in a fixed frequency PWM mode. The operating
frequency is defined by the resistance on the RT pin as
described in the Applications section of this data sheet.
PWM mode minimizes output voltage ripple and yields a
low noise switching frequency spectrum. A proprietary
switching algorithm provides seamless transitions between operating modes and eliminates discontinuities in
the average inductor current, inductor ripple current andloop transfer function throughout all modes of operation.
These advantages result in increased efficiency, improved
loop stability and lower output voltage ripple in comparison
to a traditional buck-boost converter. Figure 1 shows the
topology of the LTC3119 power stage which is comprisedof four N-channel DMOS switches and their associatedgate drivers.

High side drive and sense circuitry allow for operation to
0V on the output while maintaining current control andsynchronous switch operation. Operation to voltages below
2.5V on the input is also possible when bootstrapping the
VCC pin from VOUT, or other alternate sources, allowing
for maximum extraction of power from energy storage
devices such as supercapacitors.
A proprietary ultralow noise PWM switching algorithm
maintains output regulation with input voltages that are
below, equal to, or above the output voltage. Transitions
between buck and boost operating modes occur seamlessly without transients or subharmonic switching. The
LTC3119 has an internal oscillator that can be configured
to operate over a wide range of frequencies. Using a single
programming resistor, the operating frequency can be
configure between 400kHz and 2MHz allowing for flexibility when optimizing for board area and efficiency. Theinternal oscillator can also be synchronized to an external
clock applied to the PWM/SYNC pin in noise sensitive
applications.
Burst Mode operation allows for high efficiency operation
at light loads while automatically transitioning to PWM
mode at heavier loads. At low output currents, Burst Modeoperation is enabled, with a current of only 31µA (typical).
In shutdown the total supply current is further reduced
to 3µA (maximum).

14

CBST1

BST1

CBST2

L

PVIN

SW1

SW2 PVOUT

BST2
VCC

VCC
A

D
LTC3119

VCC
B

VCC
C

PGND

PGND
3119 F01

Figure 1. Power Stage Schematic

In PWM mode operation both switch pins transition on
every cycle independent of the input and output voltages.
The internal average current control loop commands thepulse width modulator to generate the appropriate switch
duty cycle to maintain regulation of the output voltage.
Oscillator and Phase-Locked Loop
The LTC3119 operates from an internal oscillator with aswitching frequency that is configured by a single external
resistor between the RT pin and GND. For noise sensitive
applications, an internal phase-locked loop allows the
3119f

For more information www.linear.com/LTC3119

LTC3119OPERATION
LTC3119 to be synchronized to an external clock signal
applied to the PWM/SYNC pin. The phase-locked loop is
only able to increase the frequency of the internal oscillator to obtain synchronization. Therefore, the resistor
RT must be chosen to program the internal oscillator toa lower frequency than the frequency of the clock applied to the PWM/SYNC pin. Sufficient margin must be
included to account for the frequency variation of theexternal synchronization clock as well as the worst-casevariation in frequency of the internal oscillator. Whether
operating from its internal oscillator or synchronized to an
external clock signal, the LTC3119 is able to operate witha switching frequency from 400kHz to 2MHz, providing
the ability to trade-off small solution size and optimum
power conversion efficiency.

In addition to serving as a logic-level input to enable theIC, the RUN pin features an accurate internal comparator allowing it to be used to set custom rising and falling
input undervoltage lockout thresholds with the additionof an external resistor divider. When the RUN pin is driven
above its logic threshold (typically 0.8V) the VCC regulator
is enabled which provides power to the internal control
circuitry of the IC and the accurate RUN pin comparator
is enabled. If the RUN pin voltage is increased further sothat it exceeds the RUN comparator threshold (1.205V
nominal), the buck-boost converter will be enabled. If the
RUN pin is brought below the RUN comparator threshold,the buck-boost converter will inhibit switching, but the
VCC regulator and control circuitry will remain powered
unless the RUN pin is brought below its logic threshold.
Therefore, in order to place the part in shutdown andreduce the input current to its minimum level (3μA) it isnecessary to ensure that the RUN pin is brought below
the worst-case logic threshold (0.3V).The RUN pin is ahigh voltage input and can be connected directly to VIN
to continuously enable the part when the input supply ispresent. If the RUN pin is forced above approximately 5V it
will sink a small current as given by the following equation:( VRUN − 5V )
5MΩ

VIN

LTC31190.25µAVIN

RUN Pin Comparator

IRUN =

With the addition of an external resistor divider as shownin Figure 2, the RUN pin can be used to establish a custom
input under voltage lockout threshold. The buck-boost
converter is enabled when the RUN pin reaches 1.205V
which allows the rising UVLO threshold to be set via
the resistor divider ratio. Once the RUN pin reaches thethreshold voltage, the comparator switches and the buckboost converter is enabled. When the part is enabled aninternal 0.25μA (typical) current source is enabled whichsources current out of the RUN pin raising the RUN pin
voltage away from the threshold.

R1

RUN

1.205V

–
+

+
–

R2
0.8V

ENA

ENABLE
SWITCHINGENABLEVCC REGULATOR AND
CONTROL CIRCUITSINPUT LOGICTHRESHOLDS
3119 F02

Figure 2. Accurate Run Pin Comparator

In order to disable the part, VIN must be reduced sufficiently
to overcome the hysteresis generated by this current aswell as the 90mV hysteresis of the RUN comparator. As
a result, the amount of hysteresis can be independently
programmed without affecting the rising UVLO thresholdby scaling the values of both resistors.
VCC REGULATOR
An internal low dropout regulator generates the 3.7V
(nominal) VCC rail from VIN. The VCC rail powers the internal control circuitry and power device gate drivers of the
LTC3119. In addition to powering the internal circuitry of
the LTC3119, the VCC regulator can also support an external load of 10mA. The VCC regulator is disabled when the
RUN pin is below its logic threshold to reduce quiescentcurrent and is enabled when the RUN pin is above its logic
threshold. The VCC regulator includes current limit protection to safeguard against short circuiting and overload
conditions. For applications where the output voltage is
3119f

For more information www.linear.com/LTC3119

15

LTC3119OPERATION
set to 5V, VCC can be driven from the output rail through a
Schottky diode. Bootstrapping in this manner can provide
a significant efficiency improvement, particularly at large
voltage step down ratios, and also allows operation down
to lower input voltages. The maximum operating voltage
for the VCC pin is 5.5V and care must be taken to ensurethat this limit is not exceeded when driving VCC externally.
CURRENT MODE CONTROLThe LTC3119 utilizes an average current mode control
scheme. Current mode control provides simplified loop
compensation, rapid response to load transients andinherent line voltage rejection. The voltage on the VC pin
defines the commanded average inductor current, and isadjusted by the error amplifiers to maintain regulation of
the active control loop (FB or MPPC).
The internal current mode control loop error amplifiercompares the sensed average inductor current and thecommanded average inductor current level to modulate
the SW1 and SW2 pins on a cycle-by-cycle basis.
The average current mode control technique is similar topeak current mode control except that the average current
amplifier, by virtue of its configuration as an integrator,
controls average current instead of the peak current. Thisdifference eliminates the peak to average current errorof peak current mode control, while maintaining most of
the advantages inherent to peak current mode control.
Compensation of the inner current loop is accomplishedby an internal compensation network that is optimized to
PVIN

A

D

CURRENTERRORAMPLIFIER

VC

–
+

B

C

PGND

PGND

Integrated into the LTC3119 are two separate error
amplifiers to control the input to the inner current mode
control loop. These amplifiers monitor voltages at the FB
and MPPC pins. The outputs from these amplifiers are
summed together and used as the commanded current
level for the inner current mode control loop. To ensurestability, a compensation network must be connected between the output of the error amplifiers (VC pin) and GND.
A Type II compensation network, as shown in Figure 4, isrecommended for most applications since it provides theflexibility to optimize converter response while minimizing
DC errors in the output voltage.
While the FB error amplifier is the only amplifier withthe ability to increase the commanded current level,
both amplifiers can reduce the commanded current tomaintain regulation for their associated control loop (seeBlock Diagram). At any given time, only one control loop
is active while the other is inactive. Priority is given to the
MPPC control loop, which can override the voltage loop
and reduce the commanded current level. When undercontrol of the MPPC error amplifier, the compensation
network of the VC pin is ignored.
VOUT

PVOUT
RTOP
FB
VC
LTC3119

COUT
RZ

RBOT

CP1

Figure 4. FB and VC Pin Configuration

CURRENT LIMIT AND ZERO CURRENT DETECTION

LOGIC

RAMP GENERATOR
3119 F03

Figure 3. Inner Average Current Loop Diagram

16

ERROR AMPLIFIERS

3119 F04

DRIVERS

–
+

PVOUT

provide high bandwidth and low regulation error under all
operating conditions.

The LTC3119 incorporates limits for both the maximum
peak and maximum average inductor current. Using thecurrent sense information, if the inductor current reaches apeak level of 11A (typical), switch A is immediately turned
off to ensure that the inductor current remains controlled.
3119f

For more information www.linear.com/LTC3119

LTC3119OPERATION
The average current mode control loop also clamps the
maximum average current in the inductor to 8A (typical).
These two current limits help to ensure a smooth transition into regulation as well as protecting against current
conditions beyond the capability of the IC.
The LTC3119 incorporates dedicated zero current detection comparators to minimize reverse current duringswitching and provide discontinuous mode operation.
The zero current detection thresholds are adjusted basedon operating conditions to avoid subharmonic switching
and may result in small amounts of negative current undersome conditions. When the part is being controlled by the
MPPC control loop, the zero cross comparators are set toapproximately 150mA to help prevent any reverse current
from discharging the output storage element.
SOFT-START
The LTC3119 soft-start circuit minimizes input current
transients and output voltage overshoot on initial power-up.
The required timing components for soft-start are internal
to the LTC3119 and produce a typical soft-start durationof 6ms. The internal soft-start circuit slowly ramps thecommand signal to the current mode control loop (VC pin
voltage). In doing so, the inductor current is also slowly
increased, starting from zero. Soft-start is reset by the
VCC UVLO, the RUN pin accurate enable comparator, andthermal shutdown.
MAXIMUM POWER POINT CONTROL (MPPC)
The MPPC input of the LTC3119 can be used with an
optional external voltage divider to dynamically adjust
the commanded inductor current in order to maintaina minimum input voltage. This is primarily useful whenusing resistive sources, such as photovoltaic panels, tomaximize input power transfer and prevent VIN from dropping too low under load. Referring to Figure 5, the MPPC
pin is internally connected to the noninverting input of atransconductance amplifier. If the MPPC pin voltage falls
below the reference voltage, the output of the amplifier
reduces the commanded average inductor current (VC
pin voltage) to reduce the input current and regulate VIN
to the programmed minimum voltage.

External compensation may also be required and is generally provided by a series resistor and capacitor connected
between the MPPC pin and GND. This compensation
network is in parallel with the lower resistor of the VIN
voltage divider network.
LTC3119
VIN

PVIN

798mV

–

R5
CIN
R6

RC2

MPPC

CC2

+
VC
3119 F05

Figure 5. MPPC Pin Configuration

BURST MODE OPERATION
When the PWM/SYNC pin is held low, the LTC3119 isconfigured for Burst Mode operation. As a result, thebuck-boost DC/DC converter will operate with continuous
PWM switching until the output current drops to low levels
at which point the converter will automatically transition
to power saving Burst Mode operation at lower output
currents. When operating in Burst Mode operation, theLTC3119 will go into a sleep state when the output voltage
achieves its nominal regulation level. The sleep state halts
PWM switching and powers down all nonessential functionsof the IC, reducing the quiescent current of the LTC3119
to just 31μA (typical). This greatly improves overall power
conversion efficiency for light loads. Since the converter
is not switching in sleep, the output voltage will slowly
decay at a rate determined by the output load resistanceand the output capacitor value. When the output voltage
has decayed by a small amount, the LTC3119 will wakeand initiate PWM switching operation until the output voltage on VOUT is restored to the previous level. If the load isvery light, the LTC3119 may only need to switch for a few
cycles to restore VOUT and will sleep for extended periodsof time, significantly improving efficiency. If the load issuddenly increased above the burst transition threshold,the part will automatically enter continuous PWM operation until the load is once again reduced. Note that Burst
Mode operation is inhibited until soft-start is completed
and VOUT has reached regulation. Burst Mode operationis also inhibited when the MPPC loop is in control.
3119f

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17

LTC3119OPERATION
POWER GOOD INDICATOR
The LTC3119 provides an open-drain PGOOD output
that pulls low if VOUT falls more than 8% (typical) below
its programmed value. When VOUT rises to within 6.5%
(typical) of its programmed value, the internal PGOOD
pull-down will turn off and PGOOD will go high if anexternal pull-up resistor has been provided. An internalfilter prevents nuisance trips of PGOOD due to shorttransients on VOUT. Note that PGOOD can be pulled up to
any voltage, as long as the absolute maximum rating of
19V is not exceeded. The PGOOD function is active when
the RUN pin voltage is above the logic enable thresholdof 0.8V (typical). When the RUN pin voltage is below 0.8V
(typical) and the VCC supply is still present, the PGOOD
pull-down will be enabled.
THERMAL CONSIDERATIONS
The power switches in the LTC3119 are designed to operate continuously with currents up to the internal current

limit thresholds. Operating at high current levels resultsin significant heat generated within the IC. In addition, inmany applications the VCC regulator is operated with large
input-to-output voltage differentials resulting in significant
additional power dissipation in the pass element. As aresult, careful consideration must be given to the thermal
environment of the IC in order to optimize efficiency andensure that the LTC3119 is able to provide its full-rated
output current. Specifically, the exposed die attach pad ofboth the QFN and TSSOP packages must be soldered to the
PC board. The PC board should be designed to maximize
the conduction of heat out of the IC package, utilizing
multiple vias from the die attach pad connection to a large
area of exposed copper. If the die temperature exceeds
approximately 165°C, the IC will enter overtemperature
shutdown and all switching will be inhibited. The part willremain disabled until the die cools by approximately 10°C.
The soft-start circuit is re-initialized in over temperature
shutdown to provide a smooth recovery when the fault
condition is removed.

APPLICATIONS INFORMATIONVCC Capacitor Selection
The VCC output on the LTC3119 is generated from the
input voltage by an internal low dropout regulator. The
VCC regulator has been designed for stable operation witha wide range of output capacitors. For most applications,a 4.7µF low ESR ceramic capacitor is a good choice.
The capacitor should connect to the VCC pin and groundthrough the shortest traces possible.
Bootstrapping the VCC Regulator
For output voltages between 4.5V and 6V, the VCC regulator
can be held up using a diode from VOUT to VCC as shownin Figure 6. The appropriate diode should be selected toensure that the output voltage, less the diode forward
voltage, is within the acceptable external forcing voltageof 4.2V to 5.5V. This may be accomplished through theuse of Schottky diodes or silicon diodes. In either case,

18

PVOUT

VOUT

LTC3119VCC
4.7µF

3119 F06

Figure 6. Bootstrapping VCC to VOUT

the diode should have sufficient current handling capability
to drive the VCC pin.
For applications that use an output voltage that is beyond
the maximum ratings for the VCC pin (i.e. VOUT = 7V), a
diode-OR can be used between the input voltage andoutput voltage to power the internal VCC regulator. This isaccomplished by tying the diode-OR node to the VIN pin
and connecting the PVIN pins to the input source. In thisconfiguration, an additional bypass capacitor is required
3119f

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LTC3119APPLICATIONS INFORMATION
between the VIN pin and GND in addition to the bypass
capacitor located between PVIN and GND. This configuration is shown in Figure 7.

VIN
R1

LTC3119
RUN

R2

GND

4.7µF
3119 F08

VIN

0.25V TO 18V

PVIN
4.7µF

VOUT > 6V

PVOUT

LTC3119VCC
4.7µF

3119 F07

Figure 7. Diode-OR of Input Supply and VOUT
Powers VCC Regulator

Programming Custom VIN UVLO Thresholds
With the addition of an external resistive divider connected
to VIN as shown in Figure 8, the RUN pin can be used toprogram the input voltage at which the LTC3119 is enabled
and disabled.
For a rising input voltage, the LTC3119 is enabled when VINreaches a threshold given by the following equation, where
R1 and R2 are the values of the resistor divider resistors:

Figure 8. Setting the Input UVLO and Hysteresis

Therefore, the rising UVLO threshold and the amount ofhysteresis can be independently programmed via appropriate selection of resistors R1 and R2. For high levelsof hysteresis the value of R1 can become larger than isdesirable in a practical implementation. In such cases, theamount of hysteresis can be increased further through theaddition of an additional resistor RH, as shown in Figure 9.
When using the additional RH resistor, the rising RUN pin
threshold remains as given by the original equation andthe hysteresis is given by the following expression:
 R R2+RHR1+R1R2  0.25µA +  R1+R2  0.09V
VHYST =  H



R2


 R2 
VIN

 R1+R2 
VTH(RISING) = 1.205V  R2 

R1

RH

LTC3119
RUN

R2

To ensure robust operation in the presence of noise, the RUN
pin has two forms of hysteresis. A fixed 90mV hysteresis
within the RUN pin comparator provides hysteresis equal
to 7.5% of the input turn-on voltage independent of theresistor divider values. In addition, an internal hysteresis
current that is sourced from the RUN pin during operation generates an additive level of hysteresis which canbe programmed by the value of R1 to increase the overall
hysteresis to suit the requirements of specific applications.
Once the IC is enabled, it will remain enabled until the
input voltage drops below the comparator threshold by
the hysteresis voltage, VHYST, as given by the following
equation where R1 and R2 are the values of the voltage
divider: R1+R2  • 0.09V
VHYST =R1• 0.25µA + 
 R2 

GND

3119 F09

Figure 9. Increasing Input UVLO hysteresis

To improve the noise robustness and accuracy of the UVLO
threshold, the RUN pin input can be filtered by adding a
470pF capacitor from RUN to GND. Larger valued capacitors should not be utilized because they could interferewith operation of the hysteresis.
Switching Frequency Selection
The switching frequency is set by the value of a resistor
connected between the RT pin and ground. The switchingfrequency is related to the resistor value by the following
equation where RT is the resistance:fSW =100MHz
8 + (1.2• R T / kΩ)
3119f

For more information www.linear.com/LTC3119

19

LTC3119APPLICATIONS INFORMATION
Higher switching frequencies facilitate the use of smaller
inductors as well as smaller input and output filter capacitors which results in a smaller solution size and reduced
component height. However, higher switching frequencies
also generally reduce conversion efficiency due to theincreased switching losses.
Output Capacitor Selection
A low ESR output capacitor should be utilized at the buckboost converter output in order to minimize output voltage
ripple. Multilayer ceramic capacitors are an excellent option
as they have low ESR and are available in small footprints.
The capacitor value should be chosen large enough toreduce the output voltage ripple to acceptable levels.
Neglecting the capacitor ESR and ESL, the peak-to-peak
output voltage ripple can be calculated by the following
formulas, where fSW is the switching frequency, COUT is
the output capacitance, tLOW is the switch pin minimum
low time, and ILOAD is the output current. Curves for thevalue of tLOW as a function of switching frequency andtemperature can be found in Typical Performance Characteristics section of this data sheet.
It∆VP-P(BUCK ) @ LOAD LOW
COUT V −V +tf V I∆VP-P(BOOST ) @ LOAD  OUT IN LOW SW IN 
COUT VOUTThe output voltage ripple increases with load current andis generally higher in boost mode than in buck mode.
These expressions only take into account the output
voltage ripple that results from the output current being
discontinuous. They provide a good approximation to theripple at any significant load current but underestimate
the output voltage ripple at very light loads where output
voltage ripple is dominated by the inductor current ripple.
In addition to output voltage ripple generated across theoutput capacitance, there is also output voltage ripple
produced across the internal resistance of the output
capacitor. The ESR-generated output voltage ripple is
proportional to the series resistance of the output capacitor
and is given by the following expressions where RESR is20

the series resistance of the output capacitor and all otherterms are as previously defined.
I
R∆VP-P(BUCK ) @ LOAD ESR @ILOADRESR
1− tLOW fSW
V 
R V
I
∆VP-P(BOOST ) @ LOAD ESR OUT @ILOADRESR  OUT 
VIN (1− tLOW fSW ) VIN Input Capacitor Selection
The PVIN pin carries the full inductor current and provides
power to internal control circuits in the IC. To minimize
input voltage ripple and ensure proper operation of the IC,a low ESR bypass capacitor with a value of at least 10μF
should be located as close to this pin as possible. The
traces connecting this capacitor to PVIN and the groundplane should be made as short as possible. The VIN pin
provides power to the VCC regulator and other internal
circuitry. If the PCB trace connecting VIN to PVIN is long, it
may be necessary to add an additional small value bypass
capacitor near the VIN pin.
When powered through long leads or from a high ESR
power source, a larger value bulk input capacitor may berequired. In such applications, a 47μF to 100μF electrolytic
capacitor in parallel with a 1μF ceramic capacitor generally
yields a high performance, low cost solution.
When powered through an inductive connection such asa long cable, the inductance of the power source and the
input bypass capacitor form a high-Q resonant LC filter. In
such applications, hot-plugging into a powered source canlead to a significant voltage overshoot, even up to twice thenominal input source voltage. Care must be taken in suchsituations to ensure that the absolute maximum input voltage
rating of the LTC3119 is not violated. See Linear Technology
Application Note 88 for solutions to increase damping in
the input filter and minimize this voltage overshoot.
Inductor Selection
The choice of inductor used in LTC3119 application circuits
influences the maximum deliverable output current, theconverter bandwidth, the magnitude of the inductor current
ripple and the overall converter efficiency. The inductor musthave a low DC series resistance, when compared to the3119f

For more information www.linear.com/LTC3119

LTC3119APPLICATIONS INFORMATION
internal switch resistance (30mΩ), or output current capability and efficiency will be compromised. Larger inductor
values reduce inductor current ripple but may not increase
output current capability as is the case with peak current
mode control as described in the Maximum Output Current
section. Larger value inductors also tend to have a higher
DC series resistance for a given case size, which will have anegative impact on efficiency. Larger values of inductancewill also lower the right half plane zero (RHPZ) frequency
when operating in boost mode, which can compromise loop
stability. Nearly all LTC3119 application circuits deliver thebest performance with an inductor value between 1.5μH
and 15μH. Buck mode only applications can use the larger
inductor values as they are unaffected by the RHPZ, whilemostly boost applications generally require inductance on thelower end of this range depending on how large the step-up
ratio is. Regardless of inductor value, the saturation current
rating should be selected such that it is greater than the worst
case average inductor current plus half of the ripple current.
The peak-to-peak inductor current ripple for each operational mode can be calculated from the following formula,where fSW is the programmed switching frequency, L is
the inductance and tLOW is the switch pin minimum low
time, typically 90ns.
 V −V  1
V
∆IL(P-P )(BUCK ) @ OUT  IN OUT  − tLOW L 
VIN  fSW∆IL(P-P )(BOOST ) @
VIN  VOUT − VIN   1
−
t
LOW

L  VOUT   fSW

It should be noted that the worst-case peak-to-peak inductor ripple current occurs when the duty cycle in buckmode is minimum (highest VIN) and in boost mode when
the duty cycle is 50% (VOUT @ 2 • VIN).
As an example, if VIN (minimum) = 2.5V and VIN (maximum) = 15V, VOUT = 5V, fSW = 1MHz and L = 4.7μH, thepeak-to-peak inductor ripples at the voltage extremes (15V
VIN for buck and 2.5V VIN for boost) are:5  15− 5 
∆IL (P-P )(BUCK ) @• 910ns = 645mA
4.7µH  15 
2.5  5− 2.5 ∆IL (P-P )(BOOST ) @• 910ns = 242mA
4.7µH  5 

One half of this inductor ripple current must be added tothe highest expected average inductor current in order toselect the proper saturation current rating for the inductor.
Programming the Output Voltage
The output voltage is set via the external resistive divider
comprised of resistors RTOP and RBOT as shown in Figure 4.
The resistor divider values determine the output regulation
voltage according to: R
VOUT = 0.795V •  1+ TOP  RBOT 

Programming the MPPC Voltage
The LTC3119 includes an MPPC function to optimize
performance when operating from current limited input
sources. Using an external voltage divider from VIN (refer toFigure 5), the MPPC function takes control of the average
inductor current when necessary to maintain a minimum
input voltage VMPPC, as programmed by the user.
 R5 
VMPPC = 0.798V •  1+  R6 

This is useful for such applications as photovoltaic powered
converters, since the maximum power transfer point occurs
when the photovoltaic panel is operated at approximately
75% of its open-circuit voltage. For example, when operating from a photovoltaic panel with an open-circuit voltageof 10V, the maximum power transfer point will be when thepanel is loaded such that its output voltage is about 7.5V.
When using the MPPC function, the input capacitor should
be sized between 100µF and 470µF. Resistor R6 should
be chosen between 50k and 250k. Lower values will resultin smaller undershoot of the MPPC tracking point during
line and load transient conditions, but will draw morecurrent from the input supply. For this example, a valueof 100k will be used.
 V

 7.5

R5 =  MPPC −1 • R6 = −1 • 100kΩ
 0.798  0.798V = 838kΩ @ 845kΩ

3119f

For more information www.linear.com/LTC3119

21

LTC3119APPLICATIONS INFORMATIONThe MPPC loop requires compensation to maintainstability of the input voltage regulation loop. This can beaccomplished by means of a pole-zero pair on the MPPC
pin created with a series RC network in parallel with thelower MPPC resistor R6.
The pole and zero locations should be selected to createa low frequency pole at or below approximately 360Hz
and a zero at a frequency that is scaled based on the sizeof the input capacitor. The equations for determining thevalues for the compensation capacitor CC2, and zero
resistor RC2 are:CC2 =1
2π • R6 • 360Hz

Using the divider values determined previously, and a
220µF input capacitor, the following compensation values
are obtained:1= 4.42nF @ 4.7nF
2π•100kΩ•360Hz
220µF
RC2 =
= 7.45kΩ @ 7.50kΩ
2π• 4.7nF

22

The LTC3119 incorporates an average current mode control
architecture which consists of two control loops. Both theinner average current mode control loop and outer control
loop require compensation to maintain stability. The innercurrent mode control loop is internally compensated tomaintain wide bandwidth and good transient response.
For many applications, the inner current loop can betreated like a voltage controlled current source (VCCS).
This current source is commanded by the voltage error
amplifier to regulate the output load formed primarily by
the load resistance (RLOAD) and output capacitor (COUT).
This simplified version is illustrated in Figure 10, showing the key components that need to be considered whencompensating the converter.
VOLTAGECONTROLLED
CURRENTSOURCE+–VOLTAGE LOOP
ERROR
AMP
gm

VOUT
FB
0.795V

COUT

RTOP
RBOT

RCOSER

RLOAD

VC
gm = 10.8A/V

0.96V

GND

RZ

CP2

CP1

3119 F10

Figure 10. Simplified Representationof Control Loop Components

The bandwidth of the output voltage control loop should
be set low enough to avoid the small signal effects of
the inner current loop. The maximum loop bandwidth isdetermined using the inductor value to be approximately:FVLOOP ≤CIN
RC2 =2π • CC2CC2 =Compensation of the Buck-Boost Converter+–

Using these resistor values, the MPPC function is programmed to control the maximum input current so as
to maintain VIN at a minimum of 7.56V. Note that if thephotovoltaic panel can provide more power than the
LTC3119 can draw or the load requires, the input voltage
will rise above the programmed MPPC point. Higher input
voltages do not present a problem so long as the input
voltage does not exceed the maximum operating input
voltage. For photovoltaic panel applications, it may be also
desirable to use the programmable RUN feature to disable
the part when VIN drops too low due to lack of sufficient
light. Using the RUN pin provides a well controlled behavior
when the input power source is dropping out. Preventing
switching while under these conditions is important tominimize discharging of the output storage element due
to switching while the input source is dropping out. This
custom input UVLO voltage should be programmed to be
below the MPPC tracking voltage with sufficient margin toensure the part does not disable under transient conditions.

(4.7µH•100kHz)
10 •L

With a full-scale command on VC, the LTC3119 buckboost converter will generate an average inductor currentof 8A. With a VC voltage range of 220mV to 960mV, theresulting current gain for the inner average current loop
is 10.8A/V. Similar to peak current mode control, the inneraverage current mode control loop effectively turns theinductor into a current source over the frequency range
of interest, resulting in a frequency response from the3119f

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LTC3119APPLICATIONS INFORMATION
power stage that exhibits a single pole (–20dB/decade)roll off. The output capacitor (COUT) and load resistance(RLOAD) form the normally dominant low frequency poleand the effective series resistance of the output capacitor
and its capacitance form a zero, usually at a high enoughfrequency to be ignored. A potentially troublesome righthalf plane zero (RHPZ) is also encountered if the LTC3119
is operated in boost mode. The RHPZ causes an increasein gain, like a zero, but a decrease in phase, like a pole.
This will ultimately limit the maximum converter bandwidththat can be achieved with the LTC3119. The RHPZ is notpresent when operating in buck mode. The overall open
loop gain at DC is the product of the following terms:
Voltage Error Amplifier Gain:
GEA = gm • REA = 120µs • 5MΩ = 600
Voltage Divider Gain:
VFB 0.795V
=
VOUT
VOUT
Current Loop Transconductance:
GCS =

8A
= 10.8A / V
0.74V

It is important to note that GCS is the transconductancegain from the control voltage VC to the inductor current
level, which equals the output current level in buck mode.
In boost mode, the output current level will be reducedby the efficiency divided by the boost ratio. Refer to thetypical curves for efficiency information.
GCS(OUT) = 10.8A / V
GCS(OUT) = 10.8A / V •(Buck Mode)
VIN
•Eff
VOUT

(Boost Mode)

Frequency dependent terms that affect the loop gain include:
Output Load Pole (P1)fP1 =1
2π•RLOAD •COUT

Error Amplifier Compensation (P2, Z1)
fP2 =1
Hz (close to DC)
2π • REA C P1

fZ1 =

1
Hz
2π•R ZCP1

Right Half Plane Zero (RHPZ)
fRHPZ =

VIN 2 •RLOAD

VOUT 2 •2π•L

Hz

In some cases it may not be possible to achieve sufficientloop bandwidth and phase margin using a simple RC network connected to the VC pin. In these cases, additional
compensation may be required. This is accomplished by theaddition of a feed forward RC network in parallel with the
top resistor of the feedback divider. A small feed forward
capacitor alone may be sufficient in some applications.
A common situation that may require a feed forward network is when the converter is operating in boost modeand the closed loop crossover frequency (fCC) is close theRight Half Plane Zero (RHPZ). This may be done in orderto reduce output capacitance requirements by increasing
the loop bandwidth. Due to the phase additions of the
RHPZ, a simple compensator on the VC pin may not beable to provide sufficient phase boost to stabilize the loop.
Compensation Example
This section will demonstrate how to derive and select thecompensation components for a 5V output supplying 2Afrom an input voltage as low as 3V. Designing compensation for most other applications is simply a matter ofsubstituting in different values to the equations given in
the example and reviewing the resulting Bode Plot, adjusting as needed. Since the compensation design procedureuses a simplified model of the LTC3119, results should
be checked using time domain step response tests tovalidate the effectiveness of the compensation chosen. It
is assumed that values and types for capacitors and theinductor will be selected based on the guidance given
elsewhere in this data sheet. Particular attention should
3119f

For more information www.linear.com/LTC3119

23

LTC3119APPLICATIONS INFORMATION
be paid to voltage biasing effects on capacitors used for
input and output bypassing. Similarly, it is assumed thatinductor values and current ratings are selected based on
application requirements.
Example Operating Conditions:
VIN = 3V to 15V
ILOAD(MAX) = 2A
COUT = 150µF

Using this information, the gain and phase contributions
from the output filter are calculated.

L = 3.3µH
fSW = 1MHzFirst it is necessary to determine the lowest frequency for
fRHPZ. This will determine the maximum bandwidth thatcan safely be configured for the converter while operating
in boost mode.
fRHPZ =

VOUT 2 • 2π • L= 43.4kHz

In order to ensure sufficient safety margin, a closed loop
crossover frequency (fCC) should be sufficiently below the
RHPZ frequency to account for variability of the internal
components of the IC as well as variability of external influences on the converter response at the cost of possibly
higher loop bandwidth. If sufficient phase margin exists
at the crossover frequency, a higher loop bandwidth may
be realizable while still maintaining stability and goodtransient response. In this example, we will use crossover frequency equal to one sixth of the RHPZ frequency.

f
fCC = RHPZ @7.24kHz
6
The RHPZ will have a negligible effect on the gain at theloop crossover, however it will have a phase contributionthat must be considered.
 fcc  = tan−1  1  = 9.5o
ϕRHPZ = tan−1 

 6
 
 fRHPZ 

24

Looking in the Typical Curves section, we find the efficiency
to be roughly 77%. Using this information, the effective
output current gain can be calculated.
V
GCS(OUT) =  GCS • IN • Eff = 4.99 A V
VOUT



VOUT = 5V

VIN 2 • RLOAD

Since the converter will be operating in boost mode, the
GCS term must be scaled to represent the commanded
output current.

GOUT = GCS(OUT) •RLOAD 2
= 0.729
 fCC  2

fP1 +1
 fcc  = tan−1  7240  = 86.5°
ϕP1 = tan−1  424 
 fP1 Choosing a phase margin of 50 degrees, the required
phase boost from the compensation network is determinedby summing together the phase contributions that were
calculated above. A phase contribution of 90° is assumed
for P2.
ϕZ1 = 50 +ϕP2 +ϕP1 +ϕRHPZ −180 = 56°
The compensation network gain is used to adjust the loop
gain to crossover at the desired frequency. Using the
feedback divider gain and output gain, the compensation
network gain is calculated.
 −1
 V


REF
GCOMP = • GOUT  = 8.57
 VOUT
The compensation network resistor is then found using
the error amplifier transconductance and the requiredcompensation gain found above.
RZ =GCOMP 8.57=
= 71.4kΩ
gm
120µs

3119f

For more information www.linear.com/LTC3119

LTC3119APPLICATIONS INFORMATIONWith the value of RZ now known, the compensation
capacitor can be chosen to place the zero Z1 in the correct
location.
CP1 =tan ( ϕZ1)
= 455pF
2π • fCC • R Z

Selecting standard value components, values of
RZ = 71.5kΩ and CP1 = 470pF are used.
PCB Layout Considerations
The LTC3119 buck-boost converter switches large currents at high frequencies. Special attention should be
paid to the PC board layout to ensure a stable, noise-freeand efficient application circuit. Figures 11 and 12 show
a representative PCB layout for each package option to
outline some of the primary considerations. A few key
guidelines are provided below:
1. The parasitic inductance and resistance of all circulating high current paths should be minimized. Thiscan be accomplished by keeping the routes to all boldcomponents in Figures 11 and 12 as short and as wide
as possible. Capacitor ground connections should via
down to the ground plane by way of the shortest routepossible. The bypass capacitors on PVIN, PVOUT and
VCC should be placed as close to the IC as possible
and should have the shortest possible paths to ground.

2. The exposed pad is the electrical ground connection
for the LTC3119. Multiple vias should connect theback pad directly to the ground plane. In addition,
maximization of the metallization connected to theback pad will improve the thermal environment andimprove the power handling capabilities of the IC inboth the FE and UFD packages.
3. There should be an uninterrupted ground plane underthe entire converter in order to minimize the crosssectional area of the high frequency current loops.
This minimizes EMI and reduces the inductive drops
in these loops thereby minimizing SW pin overshootand ringing.
4. Connections to all of the components shown in boldshould be made as wide as possible to reduce theseries resistance. This will improve efficiency andmaximize the output current capability of the buckboost converter.
5. To prevent large circulating currents in the groundplane from disrupting operation of the LTC3119, allsmall-signal grounds should return directly to GND
by way of a dedicated Kelvin route. This includes theground connection for the RT pin resistor, and theground connection for the feedback network as shownin Figures 11 and 12.
6. Keep the routes connecting to the high impedance,noise sensitive inputs FB and RT as short as possible
to reduce noise pick-up.

3119f

For more information www.linear.com/LTC3119

25

LTC3119APPLICATIONS INFORMATIONKELVINTO VOUT

N/C

1

28 PWM/SYNC

N/C

2

27 N/C

BST2

3

26 BST1

PGND

425 PGND

SW2

524 SW1PVOUT

623 PVIN

PVOUT

7

22 PVIN

SW2

8

21 SW1PGND

920 PGNDPGOOD 1019 VINRTOP

SVCC 11FB
1218 RUN
RT
17

RBOT

VC 13

16 VCC

SGND

14

RT

15 MPPC

UNINTERRUPTED GROUND PLANE SHOULD EXIST UNDER ALL COMPONENTS
SHOWN IN BOLD AND UNDER TRACES CONNECTING TO THOSE COMPONENTS
VIA TO GROUND PLANE(AND TO INNER LAYER WHERE SHOWN)

3119 F11

23 BST1

24 N/C

25 PWM/SYNC

26 N/C

27 N/C

28 BST2

Figure 11. PCB Layout Recommended for the FE Package

PGND

1

22 PGND

PVOUT

419 PVIN

SW2

5

18 SW1PGND

617 PGND

PGOOD

716 VINSVCC

815 RUNSGNDMPPC 12FBKELVINTO VOUTVCC 13RT
14

20 PVIN

11

21 SW1

3

VC 10

2

9

SW2
PVOUT

RT

RBOT

UNINTERRUPTED GROUND PLANE SHOULD EXIST UNDER ALL COMPONENTS
SHOWN IN BOLD AND UNDER TRACES CONNECTING TO THOSE COMPONENTS
VIA TO GROUND PLANE(AND TO INNER LAYER WHERE SHOWN)

3119 F12

Figure 12. PCB Layout Recommended for the UFD Package

26

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL APPLICATIONS
3.3V, 400kHz Wide Input Regulator
3.3µH
0.1µF

0.1µF

VIN
2.5V TO 18V
10µF

100k

SW1
BST1

SW2
BST2

PVIN
VIN

PVOUT
220µF

LTC3119RUN
PWM/SYNC
MPPC
VCC
SVCC
RT

22pF

316k
FB
PGOOD

PGND GND

100k

VC
39.2k

3119 TA03

4.7µF

VOUT
3.3V

200k

560pF

VIN = 2.5; IOUT = 2.4A; EFFICIENCY = 78%
VIN = 5.0; IOUT = 5A; EFFICIENCY = 84%

3.3V, 750kHz Wide Input Regulator
3.3µH
0.1µF

0.1µF
SW1
BST1
VIN
2.5V TO 18V

10µF

100k

SW2
BST2

PVIN
VIN

PVOUT
330µF

LTC3119RUN
PWM/SYNC
MPPC
VCC
SVCC
RT

316k
FB
PGOOD

PGND GND

4.7µF

100k

VC

3119 TA04

105k

VOUT
3.3V

80.4k
560pF

VIN = 2.5; IOUT = 2A; EFFICIENCY = 78%
VIN = 5.0; IOUT = 5A; EFFICIENCY = 82%3119f

For more information www.linear.com/LTC3119

27

LTC3119TYPICAL APPLICATIONS
3.3V, 1.5MHz Wide Input Regulator
2.2µH
0.1µF

0.1µF
SW1
BST1
VIN
2.5V TO 18V

10µF

100k

SW2
BST2

PVIN
VIN

PVOUT
150µF

LTC3119RUN

316k

PWM/SYNC
MPPC
VCC
SVCC
RT

FB
PGOOD

PGND GND

100k

VC

3119 TA05

4.7µF

VOUT
3.3V

52.3k

48.7k

470pF

VIN = 2.5; IOUT = 1.75A; EFFICIENCY = 73%
VIN = 5.0; IOUT = 5A; EFFICIENCY = 80%

3.3V, 500kHz Wide Input Regulator
4.7µH
0.1µF
VIN
1.3V TO 18V
STARTS AT 2.5V

0.1µF
SW1
BST1

10µF

100k

PVIN
VIN

PVOUT
220µF

LTC3119RUN
PWM/SYNC
MPPC
VCC
SVCC
RT

4.7µF

316k

VOUT
3.3V AT 5A, VIN > 4V
3.3V AT 1A, VIN = 1.6V

FB
PGOOD
PGND GND

VC

3119 TA06

162k

28

SW2
BST2

100k
78.7k
820pF

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL APPLICATIONS
5V, 500kHz Wide Input Regulator
4.7µH
0.1µF

0.1µF
SW1
BST1
VIN
2.5V TO 18V

10µF

SW2
BST2

PVIN
VIN

100k

220µF

LTC3119

RUN

536k

PWM/SYNC
MPPC
VCC
SVCC
RT

FB
PGOOD

PGND GND

102k

VC

3119 TA07

4.7µF

VOUT
5.0V

PVOUT

100k

162k

560pF

VIN = 2.5; IOUT = 1.5A; EFFICIENCY = 78%
VIN = 6.0; IOUT = 5A; EFFICIENCY = 88%

5V, 1MHz Wide Input Regulator
2.2µH
0.1µF

0.1µF
SW1
BST1
VIN
2.5V TO 18V

10µF

100k

SW2
BST2

PVIN
VIN
RUN

PVOUT
150µF

LTC3119

VOUT
5.0V
536k

PWM/SYNC
MPPC
VCC
SVCC
RT

FB
PGOOD
PGND GND

3119 TA08

4.7µF

76.8k

102k

VC
127k
330pF

VIN =2.5; IOUT = 1.2A; EFFICIENCY = 73%
VIN =6.0; IOUT = 5A; EFFICIENCY = 83%3119f

For more information www.linear.com/LTC3119

29

LTC3119TYPICAL APPLICATIONS
5V, 2MHz Wide Input Regulator
1.5µH
0.1µF

VIN
2.5V TO 18V

0.1µF

SW2
BST2

PVIN
VIN

100k

10µF

SW1
BST1

PVOUT
100µF

LTC3119536k

RUN
PWM/SYNC
MPPC
VCC
SVCC
RT

FB
PGOOD
PGND GND

102k

VC
124k

3119 TA09

34.8k

4.7µF

VOUT
5.0V

270pF

VIN = 2.5; IOUT = 1A; EFFICIENCY = 70%
VIN = 6.0; IOUT = 4.5A; EFFICIENCY = 80%

12V to 12V, 1MHz Line Conditioner with 8.5V Undervoltage Lockout Threshold
2.2µH
0.1µF
VIN
9V TO 15V
1210k

SW1
BST1
PVIN
VIN
RUN

10µF

SW2
BST2
PVOUT

47µF

LTC3119

MPPC
VCC
SVCC
RT

FB
PGOOD

PGND GND

97.6k

VC

3119 TA10

4.7µF

VOUT
12.0V
1370k

PWM/SYNC

200k

0.1µF

76.8k

100k
180pF

VIN = 9; IOUT =3A; EFFICIENCY = 92.5%
VIN = 13; IOUT =5A; EFFICIENCY = 93.5%
ENABLE AT VIN > 8.5V

30

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL APPLICATIONS
12V, 2MHz Wide Input Regulator
1.5µH
0.1µF
VIN
2.5V TO 18V
10µF

100k

SW1
BST1
PVIN
VIN

0.1µF

PVOUT
47µF

LTC3119RUN
PWM/SYNC
MPPC
VCC
SVCC
RT
PGND

4.7µF

SW2
BST2

VOUT
12V
1370k

FB
PGOOD

GND

VC

3119 TA11

34.8k

97.6k
155k
350pF

3119f

For more information www.linear.com/LTC3119

31LTC3119TYPICAL APPLICATIONS
12V, 750kHz Regulator with Input Supply Rundown
3.3µH

4.7µF

0.1µF

0.1µF
SW1
BST1
PVIN

VIN

SW2
BST2

VIN
4.22M

1.87M

4700μF

FB
MPPC
VCC
PGOOD
SVCC
VC
RT
PGND GND

VIN (ENABLE) = 5V
VIN (DISABLE) = 0V

80k3119 TA12a

4.7µF

105k

1370k

97.6k

2200pF

Rundown Behavior After Input
Disconnect

Output Holdup Time vsInput Bulk Capacitor Size150

ILOAD = 300mA

ILOAD = 600mA

125
HOLDUP TIME (ms)

INDUCTORCURRENT
1.0A/DIV

47µF

LTC3119

VOUT
12V

PWM/SYNC

604k

4.7µF

RUN

PVOUT

VOUT
10V/DIV
VIN
10V/DIVINPUT SUPPLY REMOVED
20ms/DIV

3119 TA12b

100

75

50

25

2

4
6
8
10
INPUT BULK CAPACITANCE (mF)

123119 TA12c

32

3119f

For more information www.linear.com/LTC3119

LTC3119TYPICAL APPLICATIONS
Selectable 12V or 3.3V Output, 1MHz Regulator
3.3µH
0.1µF
VIN
5V TO 18V
10µF

100k

SW1
BST1
PVIN
VIN
RUN

BURST PWM

0.1µF
VOUT SELECTABLE
VOUT = 3.3V/12V, IOUT = 2A

PVOUT

VIN

100µF

LTC31191400k

PWM/SYNC
MPPC
VCC
SVCC
RT

4.7µF

SW2
BST2

FB
PGOOD

PGND GND

442k

130k

VC
60k
GPIO

69.8k
1200pFVOUT SELECT
12V
3.3V

741G05500k

GPIO3119 TA13a

Output Voltage Transition

3.3V 3.3V
to 12Vto 12V
fromVOUT = 3.3V/12V
fSW = 1MHz
VOUT SELECT
5V/DIV
VOUT
10A/DIV
PGOOD
10V/DIV

200µs/DIV

3119 TA13b

3119f

For more information www.linear.com/LTC3119

33

LTC3119
PACKAGE DESCRIPTION

Please refer to http://www.linear.com/product/LTC3119#packaging for the most recent package drawings.
UFD Package
28-Lead Plastic QFN (4mm × 5mm)

(Reference LTC DWG # 05-08-1712 Rev C)

0.70 ±0.05

4.50 ±0.05
3.10 ±0.05
2.50 REF

2.65 ±0.05
3.65 ±0.05

PACKAGE OUTLINE

0.25 ±0.05
0.50 BSC
3.50 REF
4.10 ±0.05
5.50 ±0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONSAPPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
4.00 ±0.10(2 SIDES)

0.75 ±0.05

R = 0.05
TYP

PIN 1 NOTCH
R = 0.20 OR 0.35
× 45° CHAMFER

2.50 REF
R = 0.115
TYP
27

28
0.40 ±0.10

PIN 1
TOP MARK(NOTE 6)1
2

5.00 ±0.10(2 SIDES)

3.50 REF
3.65 ±0.10
2.65 ±0.10(UFD28) QFN 0816 REV C

0.200 REF
0.00 – 0.05

0.25 ±0.05
0.50 BSC
BOTTOM VIEW—EXPOSED PAD

NOTE:
1. DRAWING PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGHD-3).
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATIONON THE TOP AND BOTTOM OF PACKAGE

34

3119f

For more information www.linear.com/LTC3119

LTC3119
PACKAGE DESCRIPTION

Please refer to http://www.linear.com/product/LTC3119#packaging for the most recent package drawings.
FE Package
28-Lead Plastic TSSOP (4.4mm)(Reference LTC DWG # 05-08-1663 Rev K)
Exposed Pad Variation EA
9.60 – 9.80*(.378 – .386)
7.56(.298)

7.56(.298)

28 2726 25 24 23 22 21 20 19 18 1716 15
6.60 ±0.10
4.50 ±0.10

3.05(.120)SEE NOTE 4

0.45 ±0.05

EXPOSEDPAD HEAT SINKON BOTTOM OFPACKAGE

6.40
3.05 (.252)(.120) BSC

1.05 ±0.10
0.65 BSC
RECOMMENDED SOLDER PAD LAYOUT

4.30 – 4.50*(.169 – .177)

0.50 – 0.75(.020 – .030)

0.09 – 0.20(.0035 – .0079)

NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN MILLIMETERS(INCHES)3. DRAWING NOT TO SCALE

1 2 3 4 5 6 7 8 9 10 11 12 13 14

0.25
REF

1.20
(.047)
MAX
0° – 8°0.65(.0256)
BSC

0.195 – 0.30(.0077 – .0118)
TYP

0.05 – 0.15(.002 – .006)
FE28 (EA) TSSOP REV K 0913

4. RECOMMENDED MINIMUM PCB METAL SIZEFOR EXPOSED PAD ATTACHMENT*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASHSHALL NOT EXCEED 0.150mm (.006") PER SIDE

3119f

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnectionof its circuits
as describedherein will not infringe on existing patent rights.
For more
informationwww.linear.com/LTC3119

35

LTC3119TYPICAL APPLICATION
Photovoltaic Panel Input Lead-Acid Charger with Temperature Correction (1MHz)
4.7µH
0.1µF

SW1
BST1

VIN
220µF

1020k

SW2
BST2

PVIN
VIN

100k

RUN

PHOTOVOLTAIC
PANELV(MPP) = 9V

PVOUT
10µF

LTC3119

PWM/SYNC

4.7nF

MPPC
VCC
SVCC
RT

100k

7.5k

PGOOD
PGND GND

6-CELLLEAD-CELLBATTERY

2000k

NTC
68k

FB

220k

TEMPERATURE
COMPENSATION

VC

3119 TA02

4.7µF

0.1µF

52.3k

69.8k

127k

5.6nF

RELATED PARTS
PART NUMBER DESCRIPTIONCOMMENTS

LTC3113

5V, 3A Synchronous Buck-Boost

VIN = 1.8V to 5.5V, VOUT = 1.8V to 5.25V, IQ = 30μA, ISD <1μA, DFN and TSSOP Packages

LTC3129/
LTC3129-1

15V, 200mA Synchronous Buck-Boost with 1.3µA IQ

VIN = 2.42V to 15V, VOUT = 2.5V to 14V, IQ = 1.3μA, ISD =10nA, QFN and MSOP Packages

LTC3112

15V, 2.5A Synchronous Buck-Boost

VIN = 2.7V to 15V, VOUT = 2.5V to 14V, IQ = 40μA, ISD < 1μA,
DFN and TSSOP Packages

LTC3118

18V, 2A Dual Input PowerPath™ Buck-Boost Converter

VIN = 2.2V to 18V, VOUT = 2V to 14V, IQ = 50μA, ISD < 2μA,
QFN and TSSOP Packages

LTC3130/
LTC3130-1

25V, 600mA Synchronous Buck-Boost Converter

VIN = 2.4V to 25V, VOUT = 1V to 25V, IQ = 1.2µA, ISD = 500nA

LTC3114-1

40V, 1A Synchronous Buck-Boost

VIN = 2.2V to 40V, VOUT = 2.7V to 15V, IQ = 30µA, ISD < 3µA,
DFN and TSSOP Packages

LTC3115-1/
LTC3115-2

40V, 2A Synchronous Buck-Boost

VIN = 2.7V to 40V, VOUT = 2.7V to 40V, IQ = 30μA, ISD < 3μA,
DFN and TSSOP Packages

LTC3785

10V, High Efficiency, Synchronous, No RSENSE™ Buck-Boost Controller

VIN = 2.7V to 10V, VOUT = 2.7V to 10V, IQ = 86μA, ISD < 15μA,
QFN Package

LTC3789

38V, High Efficiency, Synchronous, 4-Switch Buck-Boost Controller

VIN = 4V to 38V, VOUT = 0.8V to 38V, IQ = 3mA, ISD < 60µA,
SSOP-28, QFN-28 Packages

LT379060V, Synchronous, 4-Switch Buck-Boost Controller

VIN = 4.7V to 60V, VOUT = 1.2V to 60V, IQ = 3mA, ISD < 1µA,
TSSOP Package

QFN and MSOP Packages

36 Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC3119(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3119

3119f
LT 1016 • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2016