LTM8074
40VIN, 1.2A Silent SwitcherµModule Regulator
FEATURESDESCRIPTION

Low Noise Silent Switcher® Architecturen CISPR22 Class B Compliancen Wide Input Voltage Range: 3.2V to 40V
n Wide Output Voltage Range: 0.8V to 12V
n 1.2A Continuous Output Current at 24V , 5V
IN
OUT,
TA = 85°C
n 1.75A Peak Output Current at 3.3V
OUT
n Selectable Switching Frequency: 200kHz to 2.2MHzn External Synchronizationn Configurable as an Inverter
n 4mm × 4mm × 1.82mm BGA Package

The LTM®8074 is a 40VIN, 1.2A continuous, 1.75A peak,
step-down µModule® (power module) regulator. The Silent
Switcher architecture minimizes EMI while delivering highefficiency at frequencies up to 2.2MHz. Included in the
package are the switching controller, power switches,
inductor, and all support components. Operating over an
input voltage range of 3.2V to 40V, the LTM8074 supports
an output voltage range of 0.8V to 12V and a switchingfrequency range of 200kHz to 2.2MHz, each set by a single
resistor. Only the input and output filter capacitors areneeded to finish the design.

n

The low profile package enables utilization of unused
space on the bottom of PC boards for high density pointof load regulation. The LTM8074 is packaged in a thermallyenhanced, compact over-molded ball grid array (BGA)
package suitable for automated assembly by standard surface mount equipment. The LTM8074 is RoHS compliant.

APPLICATIONS
Automotive Battery Regulation
Power for Portable Products
n Distributed Supply Regulationn Industrial Supplies
n Wall Transformer Regulationnn

All registered trademarks and trademarks are the property of their respective owners.

TYPICAL APPLICATION
3.3VOUT from 4.5VIN to 40VIN Step-Down Converter
VIN

VIN
4.5V TO 40V

LTM8074

RUN

55
VOUT

RT
25.5k

GND

SYNC

FB

76.8k

10µF

3 METER PEAK LIMITS

VOUT
3.3V

8074 TA01a

1.5MHzPINS NOT USED IN THIS CIRCUIT: TR/SS, PG

45
AMPLITUDE (dBuV/m)

1µF

CISPR22 Class B Emissions
DC2753A Demo Board
VOUT = 3.3V, 1.2A Load
No EMI Filter (FB1, L1 Shorted)

35
25
15
5
–5

MAX PEAK EMISSIONSCSPR22 CLASS B LIMITS
0

200

400
600
FREQUENCY (MHz)

800

1000
8074 TA01b

Rev. B

Document Feedback

For more information www.analog.com

1

LTM8074
ABSOLUTE MAXIMUM RATINGSPIN CONFIGURATION(Notes 1, 2)

TOP VIEW

VIN, RUN, PG Voltage ............................................... 42V
VOUT Voltage ............................................................ 19V
FB, TR/SS Voltage ..................................................... 4V
SYNC Voltage ............................................................. 6V
Maximum Internal Temperature ........................... 125°C
Storage Temperature ............................ –55°C to 125°C
Peak Reflow Solder Body Temperature ................ 260°C

A
B
C
D

GND

RUN

GND

VIN

PG

RT
GND

TR/SS

BANK 1

FB

SYNC

VOUT

E
1

2

3

4

5

BGA PACKAGE
25-PIN (4mm × 4mm × 1.82mm) BGA PACKAGETJMAX = 125°C, θJA = 48.9°C/W, θJCbottom = 17.2°C/W
θJCtop = 33.4°C/W, θJB = 19.4°C/W, WEIGHT = 0.08g
θ VALUES DETERMINED PER JESD51-9, 51-12

ORDER INFORMATIONPART MARKING*PART NUMBERTERMINAL FINISH

DEVICEFINISH CODE

PACKAGETYPE

MSL
RATING

LTM8074EY#PBF

SAC305 (RoHS)

8074

Y

BGA

3

–40°C to 125°C

LTM8074IY#PBF

SAC305 (RoHS)

8074

Y

BGA

3

–40°C to 125°C

LTM8074IY

SnPb (63/37)

8074

Y

BGA

3

–40°C to 125°C• Contact the factory for parts specified with wider operating temperature ranges.
*Pad or ball finish code is per IPC/JEDEC J-STD-609.

TEMPERATURE RANGE(NOTES 3, 4)• Recommended LGA and BGA PCB Assembly and Manufacturing
Procedures• LGA and BGA Package and Tray Drawings

Rev. B2

For more information www.analog.com

LTM8074
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at TJ = 25°C. VIN = 12V, RUN = 2V, unless otherwise noted.
PARAMETERCONDITIONSMinimum Input Voltage

VIN Rising

MIN

Output DC Voltage

RFB Open
RFB = 17.4k, VIN = 40V

Peak Output DC Current

VOUT = 3.3V, fSW = 1.0MHz

Quiescent Current into VIN

RUN = 0V
No Load, SYNC = 0V, Not Switching

TYP

l

MAX

UNITS

3.2

V

0.8
12

V
V

1.75

A
3
8

µA
µA

Line Regulation

5.5V < VIN < 36V, IOUT = 1.2A

0.5

0.8

%

Load Regulation

0.1A < IOUT < 1.2A

0.5

0.8

%

Output Voltage Ripple

IOUT = 1.2A

15mV

Switching Frequency

RT = 221k, VIN = 5V
RT = 40.2k
RT = 16.2k

200
1
2.2

kHz
MHz
MHz

Voltage at FB

l

760

774

RUN Threshold Voltage (Rising)
RUN Threshold Voltage (Falling)

786

mV

1.2

V

0.9

V

RUN Current

±50

nA

TR/SS Current

TR/SS = 0V

2

µA

TR/SS Pull-Down

TR/SS = 0.1V

300

Ω

PG Threshold Voltage at FB (Upper)

FB Falling (Note 5)

0.84

V

PG Threshold Voltage at FB (Lower)

FB Rising (Note 5)

0.7

V

PG Leakage Current

PG = 42V

PG Sink Current

PG = 0.1V

SYNC Threshold Voltage

Synchronization

0.4

1.5

V

SYNC Voltage

To Enable Spread Spectrum

2.9

4.2

V

SYNC Current

SYNC = 2V

5µA

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: Unless otherwise noted, the absolute minimum voltage is zero.
Note 3: The LTM8074E is guaranteed to meet performance specifications
from 0°C to 125°C internal. Specifications over the full –40°C to
125°C internal operating temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTM8074I is guaranteed to meet specifications over the full –40°C to

1
150

µA
µA

125°C internal operating temperature range. Note that the maximum
internal temperature is determined by specific operating conditions inconjunction with board layout, the rated package thermal resistance andother environmental factors.
Note 4: The LTM8074 contains overtemperature protection that is
intended to protect the device during momentary overload conditions. Theinternal temperature exceeds the maximum operating junction temperaturewhen the overtemperature protection is active. Continuous operation
above the specified maximum operating junction temperature may impair
device reliability.
Note 5: PG transitions from low to high.

Rev. BFor more information www.analog.com

3

LTM8074
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, operating per Table 1 unlessotherwise noted.

40

1000

2000
12VIN
24VIN
36VIN

1500
1000

500
20

POWER LOSS
0

0.5
1
LOAD CURRENT (A)

2500
2000

65
12VIN
24VIN
36VIN

45

1500
1000

500

500

POWER LOSS
0
1.5

20

0

POWER LOSS
0
1.5

0.5
1
LOAD CURRENT (A)8074 G0125

08074 G03

Efficiency and Power Loss,
VOUT = 1.8V, fSW = 1MHz

85

3000

85

3000

Efficiency and Power Loss,
VOUT = 2V, fSW = 1.2MHz

3000

EFFICIENCYEFFICIENCYEFFICIENCY

0
1.5

0.5
1
LOAD CURRENT (A)8074 G02

Efficiency and Power Loss,
VOUT = 1.5V, fSW = 1MHz
85

3000

EFFICIENCY

2500

60

40

Efficiency and Power Loss,
VOUT = 1.2V, fSW = 1MHz

2500

2500

2500

12VIN
24VIN
36VIN

55

1500
1000

EFFICIENCY (%)

1000

EFFICIENCY (%)

EFFICIENCY (%)

45

2000

POWER LOSS (mW)

1500

12VIN
24VIN
36VIN

POWER LOSS (mW)

2000

2000

65
12VIN
24VIN
36VIN

1500
1000

45

POWER LOSS (mW)

70
65

POWER LOSS (mW)

1500

12VIN
24VIN
36VIN

85

POWER LOSS (mW)

2000

60

3000

EFFICIENCY

2500
POWER LOSS (mW)EFFICIENCY (%)

EFFICIENCY80

Efficiency and Power Loss,
VOUT = 1V, fSW = 850kHzEFFICIENCY (%)

3000

EFFICIENCY (%)

80

Efficiency and Power Loss,
VOUT = 0.8V, fSW = 850kHz

40
500

500
POWER LOSS
0

25
0.0

0
1.5

0.5
1
LOAD CURRENT (A)Efficiency and Power Loss,
VOUT = 2.5V, fSW = 1.4MHz

90

3000

EFFICIENCY

Efficiency and Power Loss,
VOUT = 3.3V, fSW = 1.5MHz

0

0.5
1
LOAD CURRENT (A)

12VIN
24VIN
36VIN

0
1.5
8074 G07

1500
1000

50

500

POWER LOSS
25

EFFICIENCY (%)

EFFICIENCY (%)

1000

45

2000

70

0

0.5
1
LOAD CURRENT (A)

12VIN
24VIN
36VIN

0
1.5
8074 G08

1500
1000

50

500

POWER LOSS
30

2000

70

500

POWER LOSS
30

0

0.5
1
LOAD CURRENT (A)POWER LOSS (mW)

1500

3000

EFFICIENCY

2500
POWER LOSS (mW)

12VIN
24VIN
36VIN

90

Efficiency and Power Loss,
VOUT = 3.3V, fSW = 2MHz

2500
POWER LOSS (mW)

2000

0
1.5

0.5
1
LOAD CURRENT (A)8074 G06

3000

EFFICIENCY

2500
65

0

8074 G05

8074 G04

85

25

0
1.5

0.5
1.0
LOAD CURRENT (A)EFFICIENCY (%)

25

500

POWER LOSS

POWER LOSS

0
1.58074 G09

Rev. B

4

For more information www.analog.com

LTM8074
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, operating per Table 1 unlessotherwise noted.

75

2000

12VIN
24VIN
36VIN

55

2000

15

0
1.5

0

Efficiency and Power Loss,
VOUT = 12V, fSW = 2MHz

Efficiency and Power Loss,
VOUT = –3.3V, fSW = 1.5MHz

EFFICIENCY (%)

EFFICIENCY (%)

12VIN
24VIN
36VIN

2000

45

0
1.5

3000

12VIN
24VIN

25

0

4000

1000

0.5
1
LOAD CURRENT (A)POWER LOSS
0
1.5

25

0

0.3

4000

3000
EFFICIENCY (%)

3000
70
12VIN
24VIN

2000

50

1000

12VIN
24VIN
36VIN

0.25
0.5
0.75
LOAD CURRENT (A)18074 G16

0

30

0

0.25
0.5
LOAD CURRENT (A)

0.2

0.1

1000

POWER LOSS

POWER LOSS

POWER LOSS (mW)

POWER LOSS (mW)

50

0
1.5
8074 G15

EFFICIENCY

2000

0.5
1
LOAD CURRENT (A)Input vs Load Current,
VOUT = 0.8V

90

EFFICIENCY

12VIN
24VIN

2000

45

8074 G14

70

4000

EFFICIENCY

65

Efficiency and Power Loss,
VOUT = –12V, fSW = 2MHz90

EFFICIENCY (%)

85

POWER LOSS

Efficiency and Power Loss,
VOUT = –8V, fSW = 1.7MHz

0Efficiency and Power Loss,
VOUT = –5V, fSW = 1.5MHz

1000

1000

POWER LOSS

0
1.5

POWER LOSS (mW)

658074 G1330

0.5
1
LOAD CURRENT (A)8074 G12

POWER LOSS (mW)

2000

POWER LOSS (mW)

24VIN
36VIN

0.5
1
LOAD CURRENT (A)

1000

3000

3000

0

0

EFFICIENCY

80

20

15

4000

85

EFFICIENCY

40

2000

POWER LOSS

8074 G11

4000

100

0
1.5

0.5
1
LOAD CURRENT (A)8074 G10

60

24VIN
36VIN

55

POWER LOSSEFFICIENCY (%)

0.5
1
LOAD CURRENT (A)

3000

35

INPUT CURRENT (A)

0

4000

EFFICIENCY

75

1000

POWER LOSS
15

95

3000

35

1000

35

4000

EFFICIENCY

Efficiency and Power Loss,
VOUT = 8V, fSW = 1.7MHz

POWER LOSS (mW)EFFICIENCY (%)

3000
POWER LOSS (mW)

12VIN
24VIN
36VIN

55

95

POWER LOSS (mW)

75

4000

Efficiency and Power Loss,
VOUT = 5V, fSW = 2MHz

EFFICIENCY (%)

EFFICIENCYEFFICIENCY (%)

95

Efficiency and Power Loss,
VOUT = 5V, fSW = 1.5MHz00.758074 G17

0

0

0.5

1
1.5
LOAD CURRENT (A)28074 G18

Rev. BFor more information www.analog.com

5

LTM8074
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, operating per Table 1 unlessotherwise noted.

0.4

12VIN
24VIN
36VIN

0.3

INPUT CURRENT (A)INPUT CURRENT (A)

0.4

0.2

0.1

0

0

0.5

1
1.5
LOAD CURRENT (A)

0

0.5

1
1.5
LOAD CURRENT (A)

0.6

0

0.5

1
1.5
LOAD CURRENT (A)

0.8

12VIN
24VIN
36VIN

0.4

0.2

0

2

0

0.5

1
1.5
LOAD CURRENT (A)Input vs Load Current
VOUT = 5V

2

0.4

0.2

0

2

12VIN
24VIN
36VIN

0

0.5

1
1.5
LOAD CURRENT (A)28074 G24

Input vs Load Current
VOUT = 12V
1.0

24VIN
36VIN

24VIN
36VIN

0.4

INPUT CURRENT (A)

0.8
INPUT CURRENT (A)INPUT CURRENT (A)

0.6

0.6

0.4

0.2

0.2

0

1
1.5
LOAD CURRENT (A)Input vs Load Current
VOUT = 3.3V

0.6

Input vs Load Current
VOUT = 8V

12VIN
24VIN
36VIN

0.8

0.5

8074 G23

8074 G22

1.008074 G21

INPUT CURRENT (A)INPUT CURRENT (A)INPUT CURRENT (A)

0

2

0.1

0

0.2

8074 G20

12VIN
24VIN
36VIN

0.2

0.3

0.1

Input vs Load Current
VOUT = 2V

0.3

12VIN
24VIN
36VIN

0.4

0.1

Input vs Load Current
VOUT = 1.8V

0.4

0.5

0.2

8074 G19

0.5

Input vs Load Current
VOUT = 1.5V

12VIN
24VIN
36VIN

0.3

0

2

Input vs Load Current
VOUT = 1.2V

INPUT CURRENT (A)Input vs Load Current
VOUT = 1V

0.6

0.4

0.2

0

0.5

1
1.5
LOAD CURRENT (A)28074 G25

0

0

0.5
1
LOAD CURRENT (A)

1.5
8074 G26

0

0

0.5
1
LOAD CURRENT (A)

1.5
8074 G27

Rev. B

6

For more information www.analog.com

LTM8074
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, operating per Table 1 unlessotherwise noted.

Input vs Load Current
VOUT = –5V
0.8

0.4

0.2

0.5
1
LOAD CURRENT (A)

0.6

0.4

0.2

0

1.5

0

0.5
1
LOAD CURRENT (A)8074 G28

MAXIMUM LOAD CURRENT (A)INPUT CURRENT (A)

0.4

0.2

0.25
0.50
LOAD CURRENT (A)

1.0–3.3VOUT–5VOUT–8VOUT–12VOUT

0.5

0

2.5

MAXIMUM LOAD CURRENT (A)

200

100

0

10

20
VIN (V)

900

600

300

0

40

30

40
8074 G34

0

2.0

1.5

1.0

0

12VIN
24VIN
36VIN
0

1
1.5
LOAD CURRENT (A)2

Derating, VOUT = 1V,
DC2753A Demo Board
2.0

0LFM

0.5

0.5

8074 G33

Derating, VOUT = 0.8V,
DC2753A Demo Board

500

INPUT CURRENT (mA)

20
30
INPUT VOLTAGE (V)1200

8074 G32

Input Current vs VIN
VOUT Short Circuited

0

10

1

1500

1.5

8074 G31

300

0.25
0.50
0.75
LOAD CURRENT (A)Dropout Voltage vs Load Current
VOUT = 5V, BIAS = 5V

LIMITED BY MAX CURRENT
PLEASE ALSO REFER TO THE
2.0 DERATING CURVES

0

0.75

400

0

8074 G30

2.5

12VIN
24VIN

0

0.2

Maximum Load Current vs VIN

0.6

0

0.4

8074 G29

Input vs Load Current
VOUT = –12V
0.8

12VIN
24VIN

0.6

0

1.5

DROPOUT VOLTAGE (mV)

0

0.8

12VIN
24VIN

MAXIMUM LOAD CURRENT (A)0

Input vs Load Current
VOUT = –8V

INPUT CURRENT (A)

12VIN
24VIN
36VIN
INPUT CURRENT (A)INPUT CURRENT (A)0.6

Input vs Load Current
VOUT = –3.3V

25
50
75
100
AMBIENT TEMPERATURE (° C)

1258074 G35

0LFM

1.5

1.0

0.5

0

12VIN
24VIN
36VIN
0

25
50
75
100
AMBIENT TEMPERATURE (° C)

1258074 G36

Rev. BFor more information www.analog.com

7

LTM8074
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, operating per Table 1 unlessotherwise noted.

Derating, VOUT = 1.5V,
DC2753A Demo Board

1.5

1.0

0.5
12VIN
24VIN
36VIN
25
50
75
100
AMBIENT TEMPERATURE (° C)

1.5

1.0

0.5

0

125

12VIN
24VIN
36VIN
0

8074 G37

MAXIMUM LOAD CURRENT (A)MAXIMUM LOAD CURRENT (A)

2.0

0LFM

1.5

1.0

0.5
12VIN
24VIN
36VIN
25
50
75
100
AMBIENT TEMPERATURE ( ° C)

1.0

0.5

0

125

0.5
12VIN
24VIN
36VIN
0

25
50
75
100
AMBIENT TEMPERATURE ( ° C)

125

25
50
75
100
AMBIENT TEMPERATURE (° C)

2.0

12VIN
24VIN
36VIN
0

25
50
75
100
AMBIENT TEMPERATURE (° C)

2.0

0LFM

1.0

0.5

0

125

12VIN
24VIN
36VIN
0

25
50
75
100
AMBIENT TEMPERATURE (° C)8074 G42

2.0

0LFM

1.0

0.5
12VIN
24VIN
36VIN
0

125

Derating, VOUT = 5V, fSW = 2MHz
DC2753A Demo Board

1.5

0

125

1.5

Derating, VOUT = 5V,
fSW = 1.5MHz,
DC2753A Demo Board

MAXIMUM LOAD CURRENT (A)MAXIMUM LOAD CURRENT (A)1.008074 G41

0 LFM
fSW = 2MHz

1.5

12VIN
24VIN
36VIN

8074 G39

0LFM

1.5

Derating, VOUT = 3.3V, fSW = 2MHz
DC2753A Demo Board

0

0.5

Derating, VOUT = 3.3V,
DC2753A Demo Board

8074 G40

2.0

1.0

Derating, VOUT = 2.5V,
DC2753A Demo Board

2.0

0

1.5

0

125

0LFM

8074 G38

Derating, VOUT = 2V,
DC2753A Demo Board

0

25
50
75
100
AMBIENT TEMPERATURE (° C)

MAXIMUM LOAD CURRENT (A)

0

2.0

0LFM

MAXIMUM LOAD CURRENT (A)

0

2.0

0LFM
MAXIMUM LOAD CURRENT (A)MAXIMUM LOAD CURRENT (A)

2.0

Derating, VOUT = 1.8V,
DC2753A Demo Board

MAXIMUM LOAD CURRENT (A)Derating, VOUT = 1.2V,
DC2753A Demo Board

25
50
75
100
AMBIENT TEMPERATURE (° C)

1258074 G448074 G43

0LFM
fSW = 2MHz

1.5

1.0

0.5

0

12VIN
24VIN
36VIN
0

25
50
75
100
AMBIENT TEMPERATURE ( ° C)

1258074 G45

Rev. B8

For more information www.analog.com

LTM8074
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, operating per Table 1 unlessotherwise noted.

Derating, VOUT = 8V,
DC2753A Demo Board

Derating, VOUT = 12V,
DC2753A Demo Board

0.5

24VIN
36VIN
0

25
50
75
100
AMBIENT TEMPERATURE (° C)

1.0

0.5

0

125

0

25
50
75
100
AMBIENT TEMPERATURE ( °C)

0.5

0.50

0.25

0

125

12VIN
24VIN
0

25
50
75
100
AMBIENT TEMPERATURE (° C)

0.2
12VIN
24VIN
0

55
3 METER PEAK LIMITS45
AMPLITUDE (dBuV/m)

0.7
0.6
0.5
0.4
0.3
0.2

100

35
25
15
5

MAX PEAK EMISSIONSCSPR22 CLASS B LIMITS

0.1
0

0.2

0.4
0.6
0.8
LOAD CURRENT (A)

1.0

1.2

0

125

CISPR22 Class B Emissions
DC2753A Demo Board
VOUT = 3.3V, 1.2A Load
No EMI Filter (FB1, L1 Shorted)

0.8

200

25
50
75
100
AMBIENT TEMPERATURE (° C)8074 G51

0.9

FB VOLTAGE (V)DROPOUT VOLTAGE (mV)

0.4

Soft-Start Tracking

300

0

0.6

0

125

1.0

VIN = 5V
VOUT SET TO REGULATE AT 5V

125

0LFM

8074 G50

Dropout Voltage

400

25
50
75
100
AMBIENT TEMPERATURE (° C)

0.8

0LFM

8074 G49

500

0

Derating, VOUT = –12V,
DC2753A Demo Board

0.75

12VIN
24VIN
25
50
75
100
AMBIENT TEMPERATURE (° C)

12VIN
24VIN
36VIN

8074 G48

MAXIMUM LOAD CURRENT (A)MAXIMUM LOAD CURRENT (A)MAXIMUM LOAD CURRENT (A)

1.00

1.0

600

0

125

Derating, VOUT = –8V,
DC2753A Demo Board
0LFM

0

0.5

8074 G47

Derating, VOUT = –5V,
DC2753A Demo Board
1.5

0LFM

1.0

24VIN
36VIN

8074 G46

0

1.5

0LFM
MAXIMUM LOAD CURRENT (A)

1.0

0

1.5

0LFM
MAXIMUM LOAD CURRENT (A)MAXIMUM LOAD CURRENT (A)

1.5

Derating, VOUT = –3.3V,
DC2753A Demo Board0

0.1 0.2 0.4 0.5 0.6 0.7 0.8 1.0 1.1 1.2
SS VOLTAGE (V)8074 G53

8074 G52

–5

0

200

400
600
FREQUENCY (MHz)

800

1000
8074 G54

Rev. BFor more information www.analog.com

9

LTM8074
PIN FUNCTIONSGND (Bank 1, Pin A1): Tie these GND pins to a local
ground plane below the LTM8074 and the circuit components. In most applications, the bulk of the heat flow out of
the LTM8074 is through these pads, so the printed circuitdesign has a large impact on the thermal performance ofthe part. See the PCB Layout and Thermal Considerations
sections for more details.
RUN (Pin A2): Pull the RUN pin below 0.9V to shut down
the LTM8074. Tie to 1.2V or more for normal operation. If
the shutdown feature is not used, tie this pin to the VIN pin.

creates a voltage ramp. If TR/SS is less than about 0.77V,
the FB voltage tracks to this value. The soft-start ramp
time is approximated by the equation t = 0.39 • C where C
is in μF and t is in sec. For tracking, tie a resistor divider
to this pin from the tracked output. This pin is pulled to
ground with an internal MOSFET during shutdown andfault conditions; use a series resistor if driving from a
low impedance output. This pin may be left floating if the
tracking function is not needed.

FB (Pin D1): The LTM8074 regulates its FB pin to 0.774V.
Connect
the adjust resistor from this pin to ground. The
VIN (Pins A3, A4): VIN supplies current to the LTM8074’s
internal regulator and to the internal power switches. value of RFB is given by the equation RFB = 192.73/
These pins must be locally bypassed with an external, (VOUT – 0.774), where RFB is in kΩ.
low ESR capacitor; see Table 1 for recommended values. SYNC (Pin D5): External clock synchronization input and
PG (Pin B1): The PG pin is the open-collector output of an operational mode. This pin programs four different operatinternal comparator. PG remains low until the FB pin volt- ing modes:

age is within about 10% of the final regulation voltage. The 1. Burst Mode® operation. Tie this pin to ground for Burst
PG signal is valid when VIN is above 3.2V. If VIN is above
Mode operation at low output loads—this will result in
3.2V and RUN is low, PG will drive low. If this function is
ultralow quiescent current.
not used, leave this pin floating.
2. Pulse-skipping mode. Float this pin for pulse-skipping
RT (Pin B5): The RT pin is used to program the switchingmode. This mode offers full frequency operation down
frequency of the LTM8074 by connecting a resistor fromto low output loads before pulse skipping occurs.
this pin to ground. The Applications Information section of 3. Spread spectrum mode. Tie this pin high (between 2.9V
the data sheet includes a table to determine the resistanceand 4.2V) for pulse-skipping mode with spread specvalue based on the desired switching frequency. Minimize
trum modulation.
capacitance at this pin. Do not drive this pin.
4. Synchronization mode. Drive this pin with a clock source
TR/SS (Pin C1): The TR/SS pin is used to provide a softto synchronize to an external frequency. During synchrostart or tracking function. The internal 2μA pull-up current
nization the part will operate in pulse-skipping mode.
in combination with an external capacitor tied to this pin
VOUT (Pins E1, E2): Power Output Pins. Apply the output
filter capacitor and the output load between these pins
and GND pins.

Rev. B10

For more information www.analog.com

LTM8074
BLOCK DIAGRAM
VIN

0.2µF

CURRENT
MODE
CONTROLLER

2µH

VOUT
249k
±1%

10pF
3.3nF

GND
FB

RUN
TR/SS

PG

SYNC
RT

8074 BD

Rev. BFor more information www.analog.com

11

LTM8074
OPERATION
The LTM8074 is a stand-alone non-isolated step-down
switching DC/DC power supply that can deliver up to 1.75A
at 3.3VOUT. At lower VOUT the output current capability
may be higher. The continuous current is determined by
the internal operating temperature. It provides a precisely
regulated output voltage programmable via one external
resistor from 0.8V to 12V. The input voltage range is 3.2V
to 40V. Given that the LTM8074 is a step-down converter,
make sure that the input voltage is high enough to support
the desired output voltage and load current. A simplified
Block Diagram is given above.

The oscillator reduces the LTM8074’s operating frequency
when the voltage at the FB pin is low. This frequency foldback helps to control the output current during start-up
and overload.

The RUN pin is used to place the LTM8074 in shutdown,
reducing the input current to a few µA.

an external resistor to pull the PG pin high. The PG signal
is valid when VIN is above 3.2V. If VIN is above 3.2V and
RUN is low, PG will drive low.

The TR/SS node acts as an auxiliary input to the error amplifier. The voltage at FB servos to the TR/SS voltage until TR/
SS goes above 0.77V. Soft-start is implemented by generating a voltage ramp at the TR/SS pin using an external
capacitor which is charged by an internal constant current.
Alternatively, driving the TR/SS pin with a signal source orresistive network provides a tracking function. Do not drive
The LTM8074 contains a current mode controller, power the TR/SS pin with a low impedance voltage source. See theswitching elements, power inductor and a modest amount Applications Information section for more details.
of input and output capacitance. The LTM8074 is a fixed The LTM8074 contains a power good comparator which
frequency PWM regulator. The switching frequency is set trips when the FB pin is at about 90% to 110% of its
by simply connecting the appropriate resistor value from regulated value. The PG output is an open-drain transisthe RT pin to GND.
tor that is off when the output is in regulation, allowing

To enhance efficiency, the LTM8074 automatically switches
to Burst Mode operation in light or no load situations.
Between bursts, all circuitry associated with controllingthe output switch is shut down reducing the input supply
current to just a few µA.

The LTM8074 is equipped with a thermal shutdown that
inhibits power switching at high junction temperatures.
The activation threshold of this function is above the maximum temperature rating to avoid interfering with normal
operation, so prolonged or repetitive operation under acondition in which the thermal shutdown activates may
damage or impair the reliability of the device.

Rev. B12

For more information www.analog.com

LTM8074
APPLICATIONS INFORMATION
For most applications, the design process is straight-for- relationship between the input and output voltage magward, summarized as follows:
nitude and polarity and other factors. Please refer to the
1. Look at Table 1 and find the row that has the desired graphs in the Typical Performance Characteristics section
for guidance.
input range and output voltage.
The maximum frequency (and attendant RT value) at
which the LTM8074 should be allowed to switch is given
in Table 1 in the Maximum fSW column, while the recomWhile these component combinations have been tested for mended frequency (and RT value) for optimal efficiency
proper operation, it is incumbent upon the user to verify over the given input condition is given in the fSW column.
proper operation over the intended system’s line, load and There are additional conditions that must be satisfied if
environmental conditions. Bear in mind that the maximum the synchronization function is used. Please refer to the
output current is limited by junction temperature, the Synchronization section for details.
2. Apply the recommended, C IN , C OUT , R FB and
RT values.

Table 1. Recommended Component Values and Configuration (TA = 25ºC)
VIN

VOUT

RFB
(kΩ)

CIN**

COUT

fSW

RT
(kΩ)

MAXIMUMfSW

MIN RT(kΩ)

3.2V to 40V

0.8

7500

0.47µF 50V X5R 0603

47µF 6.3V 0805 X5R

850kHz48.7

950kHz42.2

3.2V to 40V

1866

0.47µF 50V X5R 0603

47µF 6.3V 0805 X5R

850kHz48.7

1.1MHz36.5

3.2V to 40V

1.2

453

1µF 50V X5R 0603

47µF 6.3V 0805 X5R

1MHz

40.2

1.3MHz30.1

3.2V to 40V

1.5

267

1µF 50V X5R 0603

47µF 6.3V 0805 X5R

1MHz

40.2

1.5MHz25.5

3.2V to 40V

1.8

187

1µF 50V X5R 0603

47µF 6.3V 0805 X5R

1MHz

40.2

1.7MHz22.1

3.2V to 40V2158

1µF 50V X5R 0603

47µF 6.3V 0805 X5R

1.2MHz33.2

1.8MHz20.5

3.5V to 40V

2.5

110

1µF 50V X5R 0603

22µF 6.3V 0805 X5R

1.4MHz27.4

2.2MHz16.2

4.5V to 40V*

3.3

76.8

1µF 50V X5R 0603

10µF 10V 0805 X5R

1.5MHz25.5

2.2MHz16.2

7V to 40V*

5

45.3

1µF 50V X5R 0805

10µF 10V 0805 X5R

1.5MHz25.5

2.2MHz16.2

14V to 40V*

8

26.7

1µF 50V X5R 0805

10µF 10V 0805 X5R

1.7MHz22.1

2.2MHz16.2

21V to 40V*

12

17.4

1µF 50V X5R 0805

10µF 16V 0805 X7S

2MHz

18.2

2.2MHz16.2

3.2V to 36V

–3.3

76.8

1µF 50V X5R 0603

10µF 10V 0805 X5R

1.5MHz25.5

2.2MHz16.2

3.2V to 35V

–5

45.3

1µF 50V X5R 0805

10µF 10V 0805 X5R

1.5MHz25.5

2.2MHz16.2

3.2V to 32V

–8

26.7

1µF 50V X5R 0805

10µF 10V 0805 X5R

1.7MHz22.1

2.2MHz16.2

4V to 28V

–12

17.4

1µF 50V X5R 0805

10µF 16V 0805 X7S

2MHz

18.2

2.2MHz16.2*The LTM8074 may be capable of lower input voltages but may skip switching cycles or reduce its operating frequency.
**An input bulk capacitor is required.

Rev. BFor more information www.analog.com

13

LTM8074
APPLICATIONS INFORMATION
Capacitor Selection Considerations

ground. Table 2 provides a list of RT resistor values and
The CIN and COUT capacitor values in Table 1 are the mini- their resultant frequencies.
mum recommended values for the associated operating Table 2. SW Frequency vs RT Value
conditions. Applying capacitor values below those indifSW (MHz)RT (kΩ)cated in Table 1 is not recommended and may result in
0.2
221
undesirable operation. Using larger values is generally
0.300
143
acceptable, and can yield improved dynamic response, if
0.400
110
it is necessary. Again, it is incumbent upon the user to
0.500
86.6
verify proper operation over the intended system’s line,
0.600
71.5
load and environmental conditions.
0.700
60.4
Ceramic capacitors are small, robust and have very low ESR.
However, not all ceramic capacitors are suitable. X5R and
X7R types are stable over temperature and applied voltage
and give dependable service. Other types, including Y5V andZ5U have very large temperature and voltage coefficients ofcapacitance. In an application circuit they may have only asmall fraction of their nominal capacitance resulting in muchhigher output voltage ripple than expected.
Ceramic capacitors are also piezoelectric. In Burst Modeoperation, the LTM8074’s switching frequency depends on
the load current, and can excite a ceramic capacitor at audio
frequencies, generating audible noise. Since the LTM8074
operates at a lower current limit during Burst Mode operation, the noise is typically very quiet to a casual ear.
If this audible noise is unacceptable, use a high performance electrolytic capacitor at the output. It may also be aparallel combination of a ceramic capacitor and a low cost
electrolytic capacitor.

0.800

52.3

0.900

46.4

1.000

40.2

1.200

33.2

1.400

27.4

1.600

23.7

1.800

20.5

2.000

18.2

2.200

16.2

Operating Frequency Trade-Offs
It is recommended that the user apply the optimal RT
value given in Table 1 for the input and output operating
condition. System level or other considerations, however,
may necessitate another operating frequency. While theLTM8074 is flexible enough to accommodate a wide range
of operating frequencies, the typical minimum OFF time of
LTM8074 is 88nS, a haphazardly chosen one may result inundesirable operation under certain operating or fault conditions. A frequency that is too high can reduce efficiency,
generate excessive heat or even damage the LTM8074 if
the output is overloaded or short-circuited. A frequency
that is too low can result in a final design that has too muchoutput ripple or too large of an output capacitor.

A final precaution regarding ceramic capacitors concerns the maximum input voltage rating of the LTM8074.
A ceramic input capacitor combined with trace or cableinductance forms a high-Q (underdamped) tank circuit.
If the LTM8074 circuit is plugged into a live supply, theinput voltage can ring to twice its nominal value, possi- Maximum Loadbly exceeding the device’s rating. This situation is easily
The maximum practical continuous load that the LTM8074
avoided; see the Hot-Plugging Safely section.
can drive, while rated at 1.2A, actually depends upon boththe internal current limit and the internal temperature. The
Frequency Selection
internal current limit is designed to prevent damage to the
The LTM8074 uses a constant frequency PWM archi- LTM8074 in the case of overload or short-circuit. The intertecture that can be programmed to switch from 200kHz nal temperature of the LTM8074 depends upon operating
to 2.2MHz by using a resistor tied from the RT pin to conditions such as the ambient temperature, the power
Rev. B14

For more information www.analog.com

LTM8074
APPLICATIONS INFORMATION
delivered, and the heat sinking capability of the system.
For example, if the LTM8074 is configured to regulate at
3.3V, it may continuously deliver 1.75A from 12VIN if theambient temperature is controlled to less than 55°C. Thisis higher than the 1.2A continuous rating. Please see the“Derating, VOUT = 3.3V” curve in the Typical Performance
Characteristics section. Similarly, if the output voltage is
12V and the ambient temperature is 100°C, the LTM8074
will deliver about 250mA from 36VIN, which is less than
the 1.2A continuous rating.
Load Sharing
The LTM8074 is not designed to load share. For more
output current, please consider LTM8063.
Burst Mode Operation
To enhance efficiency at light loads, the LTM8074 automatically switches to Burst Mode operation which keeps
the output capacitor charged to the proper voltage while
minimizing the input quiescent current. During Burst
Mode operation, the LTM8074 delivers single cycle burstsof current to the output capacitor followed by sleep periods where most of the internal circuitry is powered off
and energy is delivered to the load by the output capacitor.
During the sleep time, VIN quiescent current is greatly
reduced, so, as the load current decreases towards a noload condition, the percentage of time that the LTM8074
operates in sleep mode increases and the average input
current is greatly reduced, resulting in higher light load
efficiency.

capacitor on TR/SS enables soft starting the output toreduce current surges on the input supply. During thesoft-start ramp the output voltage will proportionally track
the TR/SS pin voltage. For output tracking applications,
TR/SS can be externally driven by another voltage source.
From 0V to 0.77V, the TR/SS voltage will override theinternal 0.77V reference input to the error amplifier, thus
regulating the FB pin voltage to that of the TR/SS pin.
When TR/SS is above 0.77V, tracking is disabled and thefeedback voltage will regulate to the internal reference
voltage. The TR/SS pin may be left floating if the function
is not needed.
An active pull-down circuit is connected to the TR/SS pin
which will discharge the external soft-start capacitor in
the case of fault conditions and restart the ramp when thefaults are cleared. Fault conditions that clear the soft-startcapacitor are the RUN pin transitioning low, VIN voltage
falling too low, or thermal shutdown.
Pre-Biased Output
As discussed in the Output Voltage Tracking and SoftStart section, the LTM8074 regulates the output to theFB voltage determined by the TR/SS pin whenever TR/
SS is less than 0.77V. If the LTM8074 output is higher
than the target output voltage, the LTM8074 will attempt
to regulate the output to the target voltage by returning asmall amount of energy back to the input supply. If there
is nothing loading the input supply, its voltage may rise.
Take care that it does not rise so high that the input voltage
exceeds the absolute maximum rating of the LTM8074.

Burst Mode operation is enabled by tying SYNC to GND.

Frequency Foldback

Minimum Input Voltage

The LTM8074 is equipped with frequency foldback whichacts to reduce the thermal and energy stress on the internal power elements during a short circuit or output overload condition. If the LTM8074 detects that the output
has fallen out of regulation, the switching frequency is
reduced as a function of how far the output is below thetarget voltage. This in turn limits the amount of energythat can be delivered to the load under fault. During thestart-up time, frequency foldback is also active to limit
the energy delivered to the potentially large output capacitance of the load. When a clock is applied to the SYNC pin,

The LTM8074 is a step-down converter, so a minimum
amount of headroom is required to keep the output inregulation. Keep the input above 3.2V to ensure proper
operation. Voltage transients or ripple valleys that cause
the input to fall below 3.2V may turn off the LTM8074.
Output Voltage Tracking and Soft-Start
The LTM8074 allows the user to adjust its output voltage
ramp rate by means of the TR/SS pin. An internal 2μA
pulls up the TR/SS pin to about 2.4V. Putting an external

Rev. BFor more information www.analog.com

15

LTM8074
APPLICATIONS INFORMATION
the SYNC pin is floated or held high, the frequency foldback is disabled, and the switching frequency will slow
down only during overcurrent conditions.
Synchronization
To select low ripple Burst Mode operation, tie the SYNC
pin below about 0.4V (this can be ground or a logic low
output). To synchronize the LTM8074 oscillator to an
external frequency, connect a square wave (with about
20% to 80% duty cycle) to the SYNC pin. The squarewave amplitude should have valleys that are below 0.4V
and peaks above 1.5V.
The LTM8074 will not enter Burst Mode operation at low
output loads while synchronized to an external clock,but instead will pulse skip to maintain regulation. The
LTM8074 may be synchronized over a 200kHz to 2.2MHz
range. The RT resistor should be chosen to set the switching frequency equal to or below the lowest synchronization input. For example, if the synchronization signal
will be 500kHz and higher, the RT should be selected for
500kHz.
For some applications it is desirable for the LTM8074 tooperate in pulse-skipping mode, offering two major differences from Burst Mode operation. The first is that theclock stays awake at all times and all switching cycles arealigned to the clock. The second is that full switching frequency is reached at lower output load than in Burst Modeoperation. These two differences come at the expenseof increased quiescent current. To enable pulse-skipping
mode, the SYNC pin is floated.
The LTM8074 features spread spectrum operation to further reduce EMI/EMC emissions. To enable spread spectrum operation, apply between 2.9V and 4.2V to the SYNC
pin. In this mode, triangular frequency modulation is used
to vary the switching frequency between the value programmed by RT to about 20% higher than that value. The
modulation frequency is about 3kHz. For example, whenthe LTM8074 is programmed to 2MHz, the frequency willvary from 2MHz to 2.4MHz at a 3kHz rate. When spread
spectrum operation is selected, Burst Mode operation isdisabled, and the part will run in pulse-skipping mode.

The LTM8074 does not operate in forced continuousmode regardless of SYNC signal.
Negative Output
The LTM8074 is capable of generating a negative output
voltage by connecting its VOUT to system GND and the
LTM8074 GND to the negative voltage rail. An exampleof this is shown in the Typical Application section. The
most versatile way to generate a negative output is touse a dedicated regulator that was designed to generatea negative voltage, but using a buck regulator like theLTM8074 to generate a negative voltage is a simple andcost effective solution, as long as certain restrictions are
kept in mind.
Figure 1 shows a typical negative output voltage application. Note that LTM8074 VOUT is tied to system GND
and input power is applied from VIN to LTM8074 VOUT.
As a result, the LTM8074 is not behaving as a true buckregulator, and the maximum output current depends upon
the input voltage. In the example shown in the TypicalApplication section, there is an attending graph thatshows how much current the LTM8074 can deliver for
given input voltages.
VIN
VIN

VOUT
LTM8074
GND
8074 F01

NEGATIVEOUTPUT VOLTAGE

Figure 1. The LTM8074 Can Be Used to Generate a
Negative Voltage

Note that this configuration requires that any load current
transient will directly impress the transient voltage onto
the LTM8074 GND, as shown in Figure 2, so fast loadtransients can disrupt the LTM8074’s operation or evencause damage.

Rev. B16

For more information www.analog.com

LTM8074
APPLICATIONS INFORMATION
VIN
VIN

VOUT
LTM8074
GND

FAST LOAD
TRANSIENT

8074 F02

OUTPUT TRANSIENTRESPONSE

Figure 2. Any Output Voltage Transient Appears on LTM8074 GND

The CIN and COUT capacitors in Figure 3 form an AC divider
at the negative output voltage node. If VIN is hot-plugged
or rises quickly, the resultant VOUT will be a positive transient, which may be unhealthy for the application load.
An anti-parallel Schottky diode may be able to prevent
this positive transient from damaging the load. The location of this Schottky diode is important. For example, ina system where the LTM8074 is far away from the load,
placing the Schottky diode closest to the most sensitive
load component may be the best design choice. Carefully
evaluate whether the negative buck configuration is suitable for the application.
FAST VIN
TRANSIENTOUTPUT EXPERIENCES
A POSITIVE TRANSIENT

VIN
VIN
CIN

VOUT
LTM8074COUT

GND
AC DIVIDEROPTIONALSCHOTTKY
DIODE

LTM8074’s internal circuitry pulls its quiescent current
through its internal power switch. This is fine if yoursystem can tolerate a few milliamps in this state. If you
ground the RUN pin, the internal current drops to essentially zero. However, if the VIN pin is grounded while theoutput is held high, parasitic diodes inside the LTM8074
can pull large currents from the output through the VIN
pin. Figure 4 shows a circuit that runs only when the input
voltage is present and that protects against a shorted orreversed input.
VIN

VIN
LTM8074RUN
8074 F04

Figure 4. The Input Diode Prevents a Shorted Input
from Discharging a Backup Battery Tied to the Output.
It Also Protects the Circuit from a Reversed Input. The
LTM8074 Runs Only When the Input Is Present

PCB Layout
Most of the headaches associated with PCB layout havebeen alleviated or even eliminated by the high level ofintegration of the LTM8074. The LTM8074 is nevertheless a switching power supply, and care must be taken tominimize EMI and ensure proper operation. Even with thehigh level of integration, you may fail to achieve specified
operation with a haphazard or poor layout. See Figure 5
for a suggested layout. Ensure that the grounding andheat sinking are acceptable.

8074 F03

Figure 3. A Schottky Diode Can Limit the Transient Caused
by a Fast Rising VIN to Safe Levels

Shorted Input Protection
Care needs to be taken in systems where the output isheld high when the input to the LTM8074 is absent. Thismay occur in battery charging applications or in battery
backup systems where a battery or some other supply
is diode ORed with the LTM8074’s output. If the VIN pin
is allowed to float and the RUN pin is held high (either
by a logic signal or because it is tied to VIN), then the

A few rules to keep in mind are:
1. Place RFB and RT as close as possible to their respective pins.
2. Place the CIN capacitor as close as possible to the VIN
and GND connection of the LTM8074.
3. Place the COUT capacitor as close as possible to the
VOUT and GND connection of the LTM8074.
4. Place the CIN and COUT capacitors such that their
ground currents flow directly adjacent to or underneaththe LTM8074.
Rev. BFor more information www.analog.com

17

LTM8074
APPLICATIONS INFORMATION
5. Connect all of the GND connections to as large a copperpour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8074.
6. Use vias to connect the GND copper area to the board’s
internal ground planes. Liberally distribute these GND
vias to provide both a good ground connection andthermal path to the internal planes of the printed circuit board. Pay attention to the location and density ofthe thermal vias in Figure 5. The LTM8074 can benefit
from the heat-sinking afforded by vias that connect
to internal GND planes at these locations, due to theirproximity to internal power handling components.
The optimum number of thermal vias depends upon
the printed circuit board design. For example, a board
might use very small via holes. It should employ more
thermal vias than a board that uses larger holes.

Thermal Considerations

GND

The LTM8074 output current may need to be derated if
it is required to operate in a high ambient temperature.
The amount of current derating is dependent upon the
input voltage, output power and ambient temperature.
The derating curves given in the Typical Performance
Characteristics section can be used as a guide. These
curves were generated by the LTM8074 mounted toa 58cm2 4-layer FR4 printed circuit board. Boards ofother sizes and layer count can exhibit different thermal
behavior, so it is incumbent upon the user to verify proper
operation over the intended system’s line, load and environmental operating conditions.

GND
CIN
RUN

cause problems if the LTM8074 is plugged into a live supply (see Analog Devices Application Note 88 for a complete
discussion). The low loss ceramic capacitor combined withstray inductance in series with the power source forms anunderdamped tank circuit, and the voltage at the VIN pin of
the LTM8074 can ring to more than twice the nominal input
voltage, possibly exceeding the LTM8074’s rating and damaging the part. If the input supply is poorly controlled or the
LTM8074 is hot-plugged into an energized supply, the input
network should be designed to prevent this overshoot. Thiscan be accomplished by installing a small resistor in series
to VIN, but the most popular method of controlling input voltage overshoot is add an electrolytic bulk cap to the VIN net.
This capacitor’s relatively high equivalent series resistancedamps the circuit and eliminates the voltage overshoot. The
extra capacitor improves low frequency ripple filtering andcan slightly improve the efficiency of the circuit, though it islikely to be the largest component in the circuit.

VIN
RT

FB
VOUT
GND

COUT
GND/THERMAL VIAS
8074 F05

Figure 5. Layout Showing Suggested
External Components, GND Plane andThermal Vias

For increased accuracy and fidelity to the actual application, many designers use FEA (Finite Element Analysis)
to predict thermal performance. To that end, Page 2 ofthe data sheet typically gives four thermal coefficients:
θJA – Thermal resistance from junction to ambientθJCbottom – Thermal resistance from junction to thebottom of the product case

Hot-Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8074. However, these capacitors canθJCtop – Thermal resistance from junction to top of the
product case
θJB – Thermal resistance from junction to the printed
circuit board.
Rev. B18

For more information www.analog.com

LTM8074
APPLICATIONS INFORMATION
While the meaning of each of these coefficients may
seem to be intuitive, JEDEC has defined each to avoid
confusion and inconsistency. These definitions are given
in JESD 51-12, and are quoted or paraphrased below:
θJA is the natural convection junction-to-ambient air thermal resistance measured in a one cubic foot sealed enclosure. This environment is sometimes referred to as “stillair” although natural convection causes the air to move.
This value is determined with the part mounted to a JESD
51-9 defined test board, which does not reflect an actual
application or viable operating condition.
θJCbottom is the junction-to-board thermal resistance withall of the component power dissipation flowing throughthe bottom of the package. In the typical µModule regulator, the bulk of the heat flows out the bottom of the package, but there is always heat flow out into the ambientenvironment. As a result, this thermal resistance value
may be useful for comparing packages but the test conditions don’t generally match the user’s application.
θJCtop is determined with nearly all of the component power
dissipation flowing through the top of the package. As theelectrical connections of the typical µModule regulator areon the bottom of the package, it is rare for an application
to operate such that most of the heat flows from the junction to the top of the part. As in the case of θJCbottom, thisvalue may be useful for comparing packages but the test
conditions don’t generally match the user’s application.
θJB is the junction-to-board thermal resistance where
almost all of the heat flows through the bottom of theµModule regulator and into the board, and is really thesum of the θJCbottom and the thermal resistance of thebottom of the part through the solder joints and through a
portion of the board. The board temperature is measured
a specified distance from the package, using a two sided,
two layer board. This board is described in JESD 51-9.
Given these definitions, it should now be apparent thatnone of these thermal coefficients reflects an actual physical operating condition of a µModule regulator. Thus, noneof them can be individually used to accurately predict thethermal performance of the product. Likewise, it would
be inappropriate to attempt to use any one coefficient tocorrelate to the junction temperature vs load graphs givenin the product’s data sheet. The only appropriate way to
use the coefficients is when running a detailed thermal
analysis, such as FEA, which considers all of the thermal
resistances simultaneously.
A simplified graphical representation of these thermal
resistances is given in Figure 6. The blue resistances arecontained within the µModule regulator, and the green
are outside.
The die temperature of the LTM8074 must be lower thanthe maximum rating, so care should be taken in the layoutof the circuit to ensure good heat sinking of the LTM8074.
The bulk of the heat flow out of the LTM8074 is throughthe bottom of the package and the pads into the printed
circuit board. Consequently a poor printed circuit board
design can cause excessive heating, resulting in impaired
performance or reliability. Please refer to the PCB Layout
section for printed circuit board design suggestions.

JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
JUNCTION-TO-CASE (TOP)RESISTANCE

JUNCTION

CASE (TOP)-TO-AMBIENTRESISTANCE

JUNCTION-TO-BOARD RESISTANCE
JUNCTION-TO-CASE
CASE (BOTTOM)-TO-BOARD(BOTTOM) RESISTANCERESISTANCEAMBIENTBOARD-TO-AMBIENTRESISTANCE

8074 F06µModule DEVICE

Figure 6. Simplified Graphical Representation of the Thermal Resistance Between the Device Junction and Ambient
Rev. BFor more information www.analog.com

19

LTM8074
TYPICAL APPLICATIONS
1.2VOUT from 3.2VIN to 40VIN Step-Down Converter
VIN

VIN
3.2V TO 40V
1µF
X5R
0603

LTM8074

RUN
VOUT
RT

40.2k

GND

453k

FB

SYNC

VOUT
1.2V

47µF
X5R
0805

8074 TA02

1MHz
PINS NOT USED IN THIS CIRCUIT: TR/SS, PG

3.3VOUT from 4.5VIN to 40VIN Step-Down Converter
VIN

VIN*
4.5V TO 40V
1µF
X5R
0603

LTM8074

RUN
VOUT
RT

25.5k

GND

SYNC

76.8k

FB

10µF
X5R
0805

VOUT
3.3V

8074 TA03

1.5MHzPINS NOT USED IN THIS CIRCUIT: TR/SS, PG*VIN MAY BE AS LOW AS 3.6V WITH OFF-CYCLE SKIPPING–5VOUT from 3.2VIN to 35VIN Positive to Negative Converter
Maximum Load Current vs VIN

VIN

+

4.7µF
OPTIONAL
BULK CAP

1µF
X5R
0603

LTM8074

2.5

LIMITED BY MAX CURRENT
PLEASE ALSO REFER TO THE
DERATING CURVES

RUN
VOUT
FB

RT
25.5k

GND

SYNC
8074 TA04a

1.5MHz

45.3k

10µF
X5R
0805
VOUT
–5V

PINS NOT USED IN THIS CIRCUIT: TR/SS, PG

MAXIMUM LOAD CURRENT (A)

VIN
3.2V
TO 35V

2.0

1.5

1.0

0.5

0

0

10

20
30
INPUT VOLTAGE (V)408074 TA04b

Rev. B20

For more information www.analog.com

LTM8074
PACKAGE PHOTOS Part marking is either ink mark or laser mark

PACKAGE DESCRIPTION
Table 3. LTM8074 Pinout (Sorted by Pin Number)
PIN

PIN NAME

PIN

PIN NAME

PIN

PIN NAME

PIN

PIN NAME

PIN

PIN NAME

A1

GND

B1

PG

C1

TR/SS

D1

FB

E1

VOUT

A2

RUN

B2

GND

C2

GND

D2

GND

E2

VOUT

A3

VIN

B3

GND

C3

GND

D3

GND

E3

GND

A4

VIN

B4

GND

C4

GND

D4

GND

E4

GND

A5

GND

B5

RT

C5

GND

D5

SYNC

E5

GND

Rev. BFor more information www.analog.com

21

For more information www.analog.com

PACKAGE TOP VIEW

E

0.65

1.30

SUGGESTED PCB LAYOUTTOP VIEW

0.000

aaa Z

2×

0.35 ±0.025 Ø 25x

4

0.65

PIN 1
CORNER

1.30

22
X

1.30

0.65

0.000

0.65

1.30

Y

D

2×

aaa Z

// bbb Z

MAX
1.98
0.37
1.61
0.45
0.38

DIMENSIONS
NOM
1.82
0.30
1.52
0.40
0.35
4.00
4.00
0.65
2.60
2.60
0.32 REF
1.20 REF

A2

A

SUBSTRATE THKMOLD CAP HTBALL DIMENSIONPAD DIMENSIONBALL HTNOTESDETAIL B
PACKAGE SIDE VIEW

0.15
0.20
0.10
0.15
0.08
TOTAL NUMBER OF BALLS: 25

MIN
1.66
0.23
1.43
0.35
0.32

H1

SUBSTRATE

ddd M Z X Y
eee M ZDETAIL A

Øb (25 PLACES)SYMBOL
A
A1
A2
b
b1
D
E
e
F
G
H1
H2
aaa
bbb
ccc
ddd
eee

b1

DETAIL B

H2

MOLD
CAP

ccc Z

A1
Z

(Reference LTC DWG# 05-08-1566 Rev A)Z

BGA Package
25-Lead (4mm × 4mm × 1.82mm)

e

b

4

G

3

2

e

1

PACKAGE BOTTOM VIEW

5

E

D

C

B

A

PIN 1

6

SEE NOTESDETAILS OF PIN 1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PIN 1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE

4

TRAY PIN 1BEVELCOMPONENT
PIN 1

6

!

PACKAGE IN TRAY LOADING ORIENTATIONLTMXXXXµModuleBGA 25 0718 REV A

PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGELAYOUT CAREFULLY

5. PRIMARY DATUM -Z- IS SEATING PLANE

BALL DESIGNATION PER JEP95

3

2. ALL DIMENSIONS ARE IN MILLIMETERSNOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994

F

b

3

SEE NOTESDETAIL A

LTM8074

PACKAGE DESCRIPTION

Rev. BLTM8074
REVISION HISTORY
REV

DATE

DESCRIPTION

A

11/18

Added VOUT = 3.3V, 1.2A Load No EMI Filter (FB1, L1 Shorted) to EMI graph description.

PAGE NUMBER
1, 9

Changed Pin from D4 to D5 in LTM8074 Pinout Table 3.

20

B

10/22

Changed lead to pin in the Pin Configuration drawing.

2

Amended RUN Threshold.

3

Amend graphs.

5

Corrected Table 1 data.

13

Added ink marking statement to package photos.

21

Rev. B

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license For
is granted
implication orotherwise under any patent or patent rights of Analog Devices.
more byinformationwww.analog.com

23

LTM8074
TYPICAL APPLICATION
2.5VOUT from 3.5VIN to 40VIN Step-Down Converter
VIN

VIN*
3.5V TO 40V
1µF
X5R
0603

LTM8074

RUN
VOUT
RT

27.4k

GND

SYNC

FB

110k

22µF
X5R
0805

VOUT
2.5V

8074 TA05

1.4MHzPINS NOT USED IN THIS CIRCUIT: TR/SS, PG*VIN MAY BE AS LOW AS 3.2V WITH OFF-CYCLE SKIPPINGDESIGN RESOURCESSUBJECTDESCRIPTIONµModule Design and Manufacturing Resources

Design:• Selector Guides• Demo Boards and Gerber Files• Free Simulation ToolsµModule Regulator Products Search

1. Sort table of products by parameters and download the result as a spread sheet.

Manufacturing:• Quick Start Guide• PCB Design, Assembly and Manufacturing Guidelines• Package and Board Level Reliability

2. Search using the Quick Power Search parametric table.

Digital Power System Management

Analog Devices’ family of digital power supply management ICs are highly integrated solutions thatoffer essential functions, including power supply monitoring, supervision, margining and sequencing,and feature EEPROM for storing user configurations and fault logging.

RELATED PARTSNUMBERDESCRIPTIONCOMMENTS

LTM8032

36V, 2A Low EMI Step-Down μModule Regulator

3.6V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ 10V, EN55022B Compliant

LTM8063

40V, 2A Silent Switcher Step-Down μModule Regulator

3.2V ≤ VIN ≤ 40V, 0.8V ≤ VOUT ≤ 15V, 6.25mm × 4mm × 2.22mm BGA Package

LTM8050

58V, 2A Step-Down μModule Regulator

3.6V ≤ VIN ≤ 58V, 0.8V ≤ VOUT ≤ 24V

LTM8065

40V, 2.5A Silent Switcher Step-Down μModule Regulator

3.4V ≤ VIN ≤ 40V, 0.97V ≤ VOUT ≤ 18V, 6.25mm × 6.25mm × 2.32mm BGA Package

LTM8002

40V, 2.5A Silent Switcher Step-Down μModule Regulator

3.4V ≤ VIN ≤ 40V, 0.97V ≤ VOUT ≤ 18V, 6.25mm × 6.25mm × 2.22mm BGA Package

LTM8033

36V, 3A Low EMI Step-Down μModule Regulator

3.6V ≤ VIN ≤ 36V. 0.8V ≤ VOUT ≤ 24V, EN55022B Compliant

LTM8003

3.5A Version of LTM8002, 40V, 3.5A, IQ = 25μA,
FMEA Compliant

3.4V ≤ VIN ≤ 40V, 0.97V ≤ VOUT ≤ 18V, 6.25mm × 9mm × 3.32 BGA Package

LTM8053

40V, 3.5A Step-Down μModule Regulator

3.4V ≤ VIN ≤ 40V. 0.97V ≤ VOUT ≤ 15V. 6.25mm × 9mm × 3.32mm BGA Package

LTM8027

60V, 4A Step-Down μModule Regulator

4.5V ≤ VIN ≤ 60V, 2.5V ≤ VOUT ≤ 24V
Rev. B

24

D17100-0-10/22

www.analog.com
For more information www.analog.com

 ANALOG DEVICES, INC. 2018-2022