LTC3105
400mA Step-Up DC/DC
Converter with Maximum Power
Point Control and 250mV Start-Up
FEATURESDESCRIPTION

Low Start-Up Voltage: 250mV
n Maximum Power Point Control
n Wide V Range: 225mV to 5VINn Auxiliary 6mA LDO Regulator
n Burst Mode® Operation: I = 24µA
Q
n Output Disconnect and Inrush Current Limitingn V >VINOUT Operationn Antiringing Control
n Soft Startn Automatic Power Adjustn Power Good Indicatorn 10-Lead 3mm × 3mm × 0.75mm DFN and 12-Lead
MSOP Packages

The LTC®3105 is a high efficiency step-up DC/DC converter
that can operate from input voltages as low as 225mV. A
250mV start-up capability and integrated maximum power
point controller (MPPC) enable operation directly from low
voltage, high impedance alternative power sources such as
photovoltaic cells, TEGs (thermoelectric generators) and
fuel cells. A user programmable MPPC set point maximizes
the energy that can be extracted from any power source.
Burst Mode operation, with a proprietary self adjusting
peak current, optimizes converter efficiency and output
voltage ripple over all operating conditions.

n

The AUX powered 6mA LDO provides a regulated rail for
external microcontrollers and sensors while the main
output is charging. In shutdown, IQ is reduced to 10µA
and integrated thermal shutdown offers protection fromovertemperature faults. The LTC3105 is offered in 10-lead
3mm × 3mm × 0.75mm DFN and 12-lead MSOP packages.

APPLICATIONS
Solar Powered Battery/Supercapacitor Chargers
Energy Harvestingn Remote Industrial Sensors
n Low Power Wireless Transmittersn Cell Phone, MP3, PMP and GPS Accessory ChargersnnL, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All othertrademarks are the property of their respective owners.

TYPICAL APPLICATION
Single Photovoltaic Cell Li-Ion Trickle Charger

Output Current vs Input Voltage
80

10µH

MPPC DISABLED

225mV TO 5V
PHOTOVOLTAIC
CELL

VIN

+

SW

10µF

–

VOUT
4.1V

VOUT
LTC31051020k
FB

OFF ON
40.2k
1µF

MPPC

PGOOD

SHDN

LDO

AUX

FBLDO
GND

Li-Ion
332k
2.2V

10µF

OUTPUT CURRENT (mA)70
VOUT = 3.3V

60
50

VOUT = 4.2V

40

VOUT = 5V

30
20
10

4.7µF

0
3105 TA01a

0.2

0.3

0.4 0.5 0.6 0.7 0.8
INPUT VOLTAGE (V)

0.9

1.0

3105 TA01b

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LTC3105
ABSOLUTE MAXIMUM RATINGS (Note 1)
SW Voltage
DC............................................................. –0.3V to 6V
Pulsed (<100ns)............................................–1V to 7V
Voltage, All Other Pins.................................. –0.3V to 6V
Operating Junction Temperature
Range (Note 2)..........................................–40°C to 85°C

Maximum Junction Temperature (Note 4)............. 125°C
Storage Temperature.............................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)
MS Package....................................................... 300°C

PIN CONFIGURATIONTOP VIEW
FB

1

LDO

2

FBLDO

3

SHDN

4

MPPC

5

TOP VIEW
10 AUX

11
GND

FB 1
LDO 2
FBLDO 3SHDN 4MPPC 5GND 6

9 VOUT
8 PGOOD
7 SW
6 VIN

12
11
10
9
8
7

AUX
VOUT
PGOOD
SW
VIN
GND

DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFNMS PACKAGE
12-LEAD PLASTIC MSOPTJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCBTJMAX = 125°C, θJA = 130°C/W, θJC = 21°C/W

ORDER INFORMATIONLEAD FREE FINISH

TAPE AND REELPART MARKINGPACKAGE DESCRIPTIONTEMPERATURE RANGE

LTC3105EDD#PBF

LTC3105EDD#TRPBF

LFQC

10-Lead (3mm × 3mm) Plastic DFN–40°C to 85°C

LTC3105EMS#PBF

LTC3105EMS#TRPBF

3105

12-Lead Plastic MSOP

–40°C to 85°C

Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/

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LTC3105
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating

junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VAUX = VOUT = 3.3V, VLDO = 2.2V, VIN = 0.6V, unlessotherwise noted.

PARAMETERCONDITIONS

MIN

TYP

MAX

UNITS

5

V

0.4
0.36

V
V

5.25

V

1.024

V

Step-Up Converter
Input Operating Voltage
Input Start-Up Voltagel(Note 5)
TJ = 0°C to 85°C (Note 5)

0.225
0.25

l

Output Voltage Adjust Rangel

1.6

Feedback Voltage (FB Pin)

l

0.984

1.004

VOUT IQ in Operation

VFB = 1.10V

24µA

VOUT IQ in Shutdown

SHDN = 0V

10µA

MPPC Pin Output Current

VMPPC = 0.6V

9.72

SHDN Input Logic High Voltage

l

SHDN Input Logic Low Voltage

l

10

10.28

1.1

µA
V

0.3

V

N-Channel SW Pin Leakage Current

VIN = VSW = 5V, VSHDN = 0V

1

10

µA

P-Channel SW Pin Leakage Current

VIN = VSW = 0V, VOUT = VAUX = 5.25V

1

10

µA

N-Channel On-Resistance: SW to GND

0.5Ω

P-Channel On-Resistance: SW to VOUT

0.5

ΩPeak Current Limit

VFB = 0.90V, VMPPC = 0.4V (Note 3)

0.4

0.5

A

Valley Current Limit

VFB = 0.90V, VMPPC = 0.4V (Note 3)

0.275

0.35

A

PGOOD Threshold (% of Feedback Voltage)

VOUT Falling

85

90

95

%

5

V

LDO Regulator
LDO Output Adjust Range

External Feedback Network, VAUX > VLDOl

1.4

LDO Output Voltage

VFBLDO = 0V

l

2.148

2.2

2.236

V

Feedback Voltage (FBLDO Pin)

External Feedback Network

l

0.984

1.004

1.024

V

Load Regulation

ILDO = 1mA to 6mA

0.40

Line Regulation

VAUX = 2.5V to 5V

0.15

%

Dropout Voltage

ILDO = 6mA, VOUT = VAUX = 2.2V

105

mV

LDO Current Limit

VLDO 0.5V Below Regulation Voltage

12mA

LDO Reverse-Blocking Leakage Current

VIN = VAUX = VOUT = 0V, VSHDN = 0V

1

µA

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 LTC3105 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC3105E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specifications over the –40°C to 85°C
operating junction temperature range are assured by design, characterization and correlation with statistical process controls. Note that the
maximum ambient temperature consistent with these specifications isdetermined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors.

l

6%Note 3: Current measurements are performed when the LTC3105 is notswitching. The current limit values measured in operation will be somewhat
higher due to the propagation delay of the comparators.
Note 4: This IC includes over temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 5: The LTC3105 has been optimized for use with high impedance
power sources such as photovoltaic cells and thermoelectric generators.
The input start-up voltage is measured using an input voltage source witha series resistance of approximately 200mΩ and MPPC enabled. Use of the
LTC3105 with lower resistance voltage sources or with MPPC disabled may
result in a higher input start-up voltage.

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LTC3105
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VAUX = VOUT = 3.3V, VLDO = 2.2V,
VIN = 0.6V, unless otherwise noted.

Minimum Input Start-Up Voltage
vs Temperature

Shutdown Thresholds
vs Input Voltage

340

900

300
280
260
240
220

IC Enable Delay vs Input Voltage

IC ENABLE

800

100

700
600

DELAY TIME (µs)

THRESHOLD VOLTAGE (mV)

INPUT VOLTAGE (mV)

320

200
–45 –30 –15

120

1000

IC DISABLE

500
400
300

80

60

200
100

0 15 30 45 60
TEMPERATURE (°C)

0
1.25

75 90
3105 G01

2.25
4.25
3.25
SUPPLY VOLTAGE, VIN OR VAUX (V)MPPC Current Variation
vs Temperature

SOFT-START TIME (ms)

CHANGE FROM 25°C (%)

2.25
4.25
3.25
SUPPLY VOLTAGE, VIN OR VAUX (V)

5.25
3105 G03

1.20

1.5
1.0
0.5
0
–0.5

1.15
1.10
1.05
1.00

–1.0
–1.5
–45 –30 –15

0 15 30 45 60
TEMPERATURE (°C)

0.95

75 90

6

3
4
5
2
LDO LOAD CURRENT (mA)

3105 G06

VIN for Synchronous Operation
5.0

SHDN = 0V
MAXIMUM INPUT VOLTAGE (V)

4.5

18
16
14
12
10
8
6
4
–45 –30 –15

13105 G05

VOUT IQ vs Temperature
During Shutdown

IQ (µA)

3105 G02

1.25

2.0

20

40
1.25

LDO Soft-Start Duration
vs LDO Load

2.5

22

5.25

NONSYNCHRONOUS
OPERATION

4.0
3.5
3.0
2.5
2.0

SYNCHRONOUS
OPERATION

1.5
1.0
0.5

0 15 30 45 60
TEMPERATURE (°C)

75 90

0

1.5

2.0

3105 G07

2.5 3.0 3.5 4.0 4.5
OUTPUT VOLTAGE (V)

5.0

5.5
3105 G09

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LTC3105
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, VAUX = VOUT = 3.3V, VLDO = 2.2V,
VIN = 0.6V, unless otherwise noted.
Exiting MPPC Control on
Input Voltage Step

IPEAK and IVALLEY Current Limit
Change vs Temperature
100
IPEAK

CHANGE FROM 25°C (%)

0.5

INDUCTORCURRENT
100mA/DIVMPPC VOLTAGE
200mV/DIV

90

0
EFFICIENCY (%)

VMPPC = 400mVVIN VOLTAGE
200mV/DIV

Efficiency vs VIN

1.0

IVALLEY

–0.5
–1.0
–1.5

–2.5
–45 –30 –15

3105 G10

0 15 30 45 60
TEMPERATURE (°C)

60

VIN = 0.6V
VIN = 0.8V
VIN = 1V

70

1000

EFFICIENCY
100

60
50

10

40

POWER LOSS

30

1

20

INPUT
VOLTAGE
5mV/DIV

5.25
3105 G12

POWER LOSS (mW)EFFICIENCY (%)

2.25
3.25
4.25
INPUT VOLTAGE (V)Efficiency vs Output Current andPower Loss, VOUT = 3.3V

80

SW CURRENT
200mA/DIV

1.25

3105 G1190

VOUT = 3.3V
IOUT = 15mA
COUT = 10µF

OUTPUT
VOLTAGE
50mV/DIV

1050µs/DIV

00.01

3105 G13

90

1000

VIN = 3V
VIN = 2V
VIN = 1.5V

1050
POWER LOSS

1

0.1
100
3105 G14800

VOUT = 3.3V

600
500
400
300
200
100

30
20
0.01

POWER LOSS (mW)100
EFFICIENCY

60

40

10

700

80
70

1

No-Load Input Current
vs Input Voltage

INPUT CURRENT (µA)

100

0.1

OUTPUT CURRENT (mA)

Efficiency vs Output Current andPower Loss, VOUT = 5V

EFFICIENCY (%)

70

40
0.25

75 90

Input and Output Burst Ripple
VIN = 0.6V
CIN = 470µF

80

50

–2.0
15µs/DIVVOUT = 3V
ILOAD = 10mA
LDO = 2.2V

1
10
0.1
OUTPUT CURRENT (mA)

0.1
100

0
0.2

3105 G15

0.4

0.6
0.8
INPUT VOLTAGE (V)

1.0

1.2
3105 G16

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LTC3105
PIN FUNCTIONS (DFN/MSOP)FB (Pin 1/Pin 1): Step-Up Converter Feedback Input.
Connect the VOUT resistor divider tap to this input. The
output voltage can be adjusted between 1.6V and 5.25V.
LDO (Pin 2/Pin 2): LDO Regulator Output. Connect a 4.7µF
or larger capacitor between LDO and GND.
FBLDO (Pin 3/Pin 3): LDO Feedback Input. Connect the
LDO resistive divider tab to this input. Alternatively, connecting FBLDO directly to GND will configure the LDO
output voltage to be internally set at 2.2V (nominal).
SHDN (Pin 4/Pin 4): Logic Controlled Shutdown Input.
With SHDN open, the converter is enabled by an internal
2MΩ pull-up resistor. The SHDN pin should be driven with
an open-drain or open-collector pull-down and floated until
the converter has entered normal operation. Excessive
loading on this pin may cause a failure to complete start-up.
SHDN = Low: IC Disabled
SHDN = High: IC Enabled
MPPC (Pin 5/Pin 5): Set Point Input for Maximum
Power Point Control. Connect a resistor from MPPC to
GND to program the activation point for the MPPC loop.
To disable the MPPC circuit, connect MPPC directly
to GND.
VIN (Pin 6/Pin 8): Input Supply. Connect a decoupling
capacitor between this pin and GND. The PCB trace lengthfrom the VIN pin to the decoupling capacitor should be as
short and wide as possible. When used with high impedance sources such as photovoltaic cells, this pin shouldhave a 10µF or larger decoupling capacitor.

GND (Exposed Pad Pin 11/Pins 6, 7) : Small Signal andPower Ground for the IC. The GND connections should besoldered to the PCB ground using the lowest impedance
path possible.
SW (Pin 7/Pin 9): Switch Pin. Connect an inductor between
SW and VIN. PCB trace lengths should be as short as possible to reduce EMI. While the converter is sleeping or isin shutdown, the internal antiringing switch connects theSW pin to the VIN pin in order to minimize EMI.
PGOOD (Pin 8/Pin 10): Power Good Indicator. This is an
open-drain output. The pull-down is disabled when VOUT
has achieved the voltage defined by the feedback divider
on the FB pin. The pull-down is also disabled while the IC
is in shutdown or start-up mode.
VOUT (Pin 9/Pin 11): Step-Up Converter Output. This is thedrain connection of the main output internal synchronousrectifier. A 10µF or larger capacitor must be connected
between this pin and GND. The PCB trace length from the
VOUT pin to the output filter capacitor should be as shortand wide as possible.
AUX (Pin 10/Pin 12): Auxiliary Voltage. Connect a 1µF
capacitor between this pin and GND. This pin is used by
the start-up circuitry to generate a voltage rail to powerinternal circuitry until the main output reaches regulation.
AUX and VOUT are internally connected together once VOUT
exceeds VAUX.

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LTC3105
BLOCK DIAGRAM (Pin Numbers for DFN Package Only)
L1
10µH
7
SHUTDOWN
SLEEP

SW

OR

WELL
CONTROL
AUX

VIN

LOW VOLTAGE
START-UP

CURRENT
ADJUST

CIN
10µF
SHUTDOWN
VCC

5

VIN

RMPPC
VCC

4

– +

–g
m
+

1.6V TO
5.25V
COUT
10µF

9

2
CLDO
4.7µF

PEAK CURRENT
LIMIT

SHUTDOWN

VALLEY CURRENT LIMIT
LOGIC

2M

USER SHUTDOWN

SLEEP
BURST
CONTROL

–
+

VIN
VAUX

CAUX
1µF

10µA

MPPC

SHDN

– +

VOUT

LDO

VAUX

VCC

FBLDO

1.004V

FB
PGOOD

1.004V
FB
0.9V

EXPOSED PAD
11

+
–

6

– +

225mV
TO 5V

SHORT
CONTROL

10

R3

R1

R4

R2

3
1
8

SLEEP
3105 BD

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LTC3105
OPERATION
Introduction
The LTC3105 is a unique, high performance, synchronous
boost converter that incorporates maximum power point
control, 250mV start-up capability and an integrated LDO
regulator. This part operates over a very wide range of input
voltages from 225mV to 5V. Its Burst Mode architecture
and low 24µA quiescent current optimize efficiency in low
power applications.
An integrated maximum power point controller allows for
operation directly from high impedance sources such as
photovoltaic cells by preventing the input power source
voltage from collapsing below the user programmable
MPPC threshold. Peak current limits are automaticallyadjusted with proprietary techniques to maintain operation
at levels that maximize power extraction from the source.
The 250mV start-up voltage and 225mV minimum
operating voltage enable direct operation from a single
photovoltaic cell and other very low voltage, high series
impedance power sources such as TEGs and fuel cells.
Synchronous rectification provides high efficiency operation while eliminating the need for external Schottky diodes.
The LTC3105 provides output disconnect which prevents
large inrush currents during start-up. This is particularly
important for high internal resistance power sources like
photovoltaic cells and thermoelectric generators which
can become overloaded if inrush current is not limited
during start-up of the power converter. In addition, output
disconnect isolates VOUT from VIN while in shutdown.
VIN > VOUT Operation
The LTC3105 includes the ability to seamlessly maintainregulation if VIN becomes equal to or greater than VOUT .
With VIN greater than or equal to VOUT , the synchronous rectifiers are disabled which may result in reduced
efficiency.
Shutdown Control
The SHDN pin is an active low input that places the IC
into low current shutdown mode. This pin incorporates aninternal 2MΩ pull-up resistor which enables the converter
if the SHDN pin is not controlled by an external circuit. The
SHDN pin should be allowed to float while the part is instart-up mode. Once in normal operation, the SHDN pin
may be controlled using an open-drain or open-collector
pull-down. Other external loads on this pin should be
avoided, as they may result in the part failing to reachregulation. In shutdown, the internal switch connecting
AUX and VOUT is enabled.
When the SHDN pin is released, the LTC3105 is enabled
and begins switching after a short delay. When either VIN
or VAUX is above 1.4V, this delay will typically range between 20µs and 100µs. Refer to the Typical Performance
Characteristics section for more details.
Start-Up Mode Operation
The LTC3105 provides the capability to start with voltages
as low as 250mV. During start-up the AUX output initiallyis charged with the synchronous rectifiers disabled. Once
VAUX has reached approximately 1.4V, the converter leaves
start-up mode and enters normal operation. Maximum
power point control is not enabled during start-up, however,the currents are internally limited to sufficiently low levels
to allow start-up from weak input sources.
While the converter is in start-up mode, the internal switch
between AUX and VOUT remains disabled and the LDO
is disabled. Refer to Figure 1 for an example of a typicalstart-up sequence.
The LTC3105 is optimized for use with high impedance
power sources such as photovoltaic cells. For operationfrom very low impedance, low input voltage sources, it may
be necessary to add several hundred milliohms of series
input resistance to allow for proper low voltage start-up.
Normal Operation
When either VIN or VAUX is greater than 1.4V typical, theconverter will enter normal operation.
The converter continues charging the AUX output until
the LDO output enters regulation. Once the LDO output
is in regulation, the converter begins charging the VOUT
pin. VAUX is maintained at a level sufficient to ensure the
LDO remains in regulation. If VAUX becomes higher thanrequired to maintain LDO regulation, charge is transferredfrom the AUX output to the VOUT output. If VAUX falls too
low, current is redirected to the AUX output instead ofbeing used to charge the VOUT output. Once VOUT rises
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LTC3105

INDUCTOR CURRENTOPERATIONOUTPUT VOLTAGE

TIME

VAUX

VLDO

VOUT

1.4V

VOUT INREGULATIONLDO INREGULATIONSTART-UP MODE NORMAL OPERATIONTIMEVOUT = VAUXVOUT SYNCHRONOUS
RECTIFIER ENABLED

3105 F01

Figure 1. Typical Converter Start-Up Sequence

above VAUX , an internal switch is enabled to connect thetwo outputs together.
If VIN is greater than the voltage on the driven output (VOUT
or VAUX), or the driven output is less than 1.2V (typical),the synchronous rectifiers are disabled. With the synchronous rectifiers disabled, the converter operates in criticalconduction mode. In this mode, the N-channel MOSFET
between SW and GND is enabled and remains on until the
inductor current reaches the peak current limit. It is thendisabled and the inductor current discharges completely
before the cycle is repeated.
When the output voltage is greater than the input voltage
and greater than 1.2V, the synchronous rectifier is enabled.
In this mode, the N-channel MOSFET between SW and
GND is enabled until the inductor current reaches the peakcurrent limit. Once current limit is reached, the N-channel
MOSFET turns off and the P-channel MOSFET between SW
and the driven output is enabled. This switch remains on
until the inductor current drops below the valley current
limit and the cycle is repeated.

When VOUT reaches the regulation point, the N- and Pchannel MOSFETs connected to the SW pin are disabled
and the converter enters sleep.
Auxiliary LDO
The integrated LDO provides a regulated 6mA rail topower microcontrollers and external sensors. When the
input voltage is above the minimum of 225mV, the LDO is
powered from the AUX output allowing the LDO to attainregulation while the main output is still charging. The LDO
has a 12mA current limit and an internal 1ms soft-startto eliminate inrush currents. The LDO output voltage is
set by the FBLDO pin. If a resistor divider is connectedto this pin, the ratio of the resistors determines the LDO
output voltage. If the FBLDO pin is connected directly to
GND, the LDO will use a 2MΩ internal divider network toprogram a 2.2V nominal output voltage. The LDO should
be programmed for an output voltage less than the programmed VOUT .

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LTC3105
OPERATION
When the converter is placed in shutdown mode, the LDO
is forced into reverse-blocking mode with reverse current
limited to under 1µA. After the shutdown event has ended,
the LDO remains in reverse-blocking mode until VAUX has
risen above the LDO voltage.
MPPC Operation
The maximum power point control circuit allows the user
to set the optimal input voltage operating point for a given
power source. The MPPC circuit dynamically regulates
the average inductor current to prevent the input voltage
from dropping below the MPPC threshold. When VIN isgreater than the MPPC voltage, the inductor current isincreased until VIN is pulled down to the MPPC set point.
If VIN is less than the MPPC voltage, the inductor current
is reduced until VIN rises to the MPPC set point.
Automatic Power Adjust
The LTC3105 incorporates a feature that maximizes efficiency at light load while providing increased power

capability at heavy load by adjusting the peak and valleyof the inductor current as a function of load. Lowering thepeak inductor current to 100mA at light load optimizes
efficiency by reducing conduction losses. As the loadincreases, the peak inductor current is automatically increased to a maximum of 500mA. At intermediate loads,
the peak inductor current can vary between 100mA to
500mA. This function is overridden by the MPPC function
and will only be observed when the power source candeliver more power than the load requires.
PGOOD Operation
The power good output is used to indicate that VOUT isin regulation. PGOOD is an open-drain output, and isdisabled in shutdown. PGOOD will indicate that poweris good at the beginning of the first sleep event after
the output voltage has risen above 90% of its regulation
value. PGOOD remains asserted until VOUT drops below
90% of its regulation value at which point PGOOD willpull low.

APPLICATIONS INFORMATION
Component Selection
Low DCR power inductors with values between 4.7µH
and 30µH are suitable for use with the LTC3105. For
most applications, a 10µH inductor is recommended. In
applications where the input voltage is very low, a larger
value inductor can provide higher efficiency and a lower
start-up voltage. In applications where the input voltage
is relatively high (VIN > 0.8V), smaller inductors may be
used to provide a smaller overall footprint. In all cases,
the inductor must have low DCR and sufficient saturation
current rating. If the DC resistance of the inductor is too
high, efficiency will be reduced and the minimum operating
voltage will increase.
Input capacitor selection is highly important in low voltage,high source resistance systems. For general applications,
a 10µF ceramic capacitor is recommended between VIN
and GND. For high impedance sources, the input capacitor

should be large enough to allow the converter to complete
start-up mode using the energy stored in the input capacitor. When using bulk input capacitors that have high
ESR, a small valued parallel ceramic capacitor should beplaced between VIN and GND as close to the converter
pins as possible.
A 1µF ceramic capacitor should be connected between
AUX and GND. Larger capacitors should be avoided tominimize start-up time. A low ESR output capacitor should
be connected between VOUT and GND. The main output
capacitor should be 10µF or larger. The main output canalso be used to charge energy storage devices including
tantalum capacitors, supercapacitors and batteries. Whenusing output bulk storage devices with high ESR, a smallvalued ceramic capacitor should be placed in parallel andlocated as close to the converter pins as possible.

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LTC3105APPLICATIONS INFORMATION
Step-Up Converter Feedback Configuration

MPPC Threshold Configuration

A resistor divider connected between the VOUT and FB pins
programs the step-up converter output voltage, as shownin Figure 2. An optional 22pF feedforward capacitor, CFF1,
can be used to reduce output ripple and improve loadtransient response. The equation for VOUT is:

The MPPC circuit controls the inductor current to maintain VIN at the voltage on the MPPC pin. The MPPC pin
voltage is set by connecting a resistor between the MPPC
pin and GND, as shown in Figure 4. The MPPC voltage isdetermined by the equation:
VMPPC = 10µA • RMPPC R1 
VOUT = 1.004V • +1
 R2 LDO Regulator Feedback Configuration
Two methods can be used to program the LDO output
voltage, as shown in Figure 3. A resistor divider connected
between the LDO and FBLDO pins can be used to program
the LDO output voltage. The equation for the LDO output
voltage is: R3 
VLDO = 1.004V • +1
 R4 
Alternatively, the FBLDO pin can be connected directly to
GND. In this configuration, the LDO is internally set to anominal 2.2V output.

In photovoltaic cell applications, a diode can be used to
set the MPPC threshold so that it tracks the cell voltage
over temperature, as shown in Figure 5. The diode shouldbe thermally coupled to the photovoltaic cell to ensure
proper tracking. A resistor placed in series with the diodecan be used to adjust the DC set point to better matchthe maximum power point of a particular source if theselected diode forward voltage is too low. If the diode islocated far from the converter inputs, a capacitor may berequired to filter noise that may couple onto the MPPC
pin, as shown in Figure 5. This method can be extended
to stacked cell sources through use of multiple seriesconnected diodes.

VOUT
CFF1

R1

10µA

LTC3105

LTC3105

RMPPC

FB

MPPC

R2

3105 F02
3105 F04

Figure 4. MPPC Configuration

Figure 2. FB Configuration

LDO
R3

LTC3105
FBLDO

2.2V

LDO
RMPPC

LTC3105
FBLDO

+

VFWD

R4

–

3105 F03

Figure 3. FBLDO Configuration

10µA

MPPC
LTC3105

C6
10nF

3105 F05

Figure 5. MPPC Configuration with Temperature Adjustment
3105fbFor more information www.linear.com/LTC3105

11

LTC3105APPLICATIONS INFORMATION
Industrial Current Loops
4mA TO 20mA
CURRENT LOOP

The low 250mV start-up and low voltage operation of the
LTC3105 allow it to be supplied by power from a diodeplaced in an industrial sensor current loop, as shownin Figure 6. In this application, a large input capacitor
is required due to the very low available supply current(less than 4mA). The loop diode should be selected for aminimum forward drop of 300mV. The MPPC pin voltage
should be set for a value approximately 50mV below theminimum diode forward voltage.

VIN

+

VFWD

CIN

–

LTC3105
GND

RMPPC

MPPC
3105 F06

Figure 6. Current Loop Power Tap

TYPICAL APPLICATIONS
3.3V from a Single-Cell Photovoltaic Source with Temperature Tracking
L1**
10µH

VIN

+

CIN
10µF

–

R1
2.26M

LTC3105

PGOOD

MPPC
RMPPC OFF ON
9.09k
CMPPC
10nF

CAUX
1µF

SHDN

LDO

AUX

FBLDO

2.2V

GND

VMPPC vs Temperature

COUT
10µF

R2
1M

CLDO
4.7µF

* MRA4003T3** COILCRAFT MSS5131-103MX

3105 TA02MPPC Response to Input Source Current Step

0.7

VOUT = 2.8V
VMPPC = 0.4V
VFB = 0.94V

0.6
MPPC VOLTAGE (V)

VOUT
3.3V

FB

THERMALLY
COUPLED

D1*

SW
VOUT

0.5
0.4
0.3

INPUT VOLTAGE
50mV/DIV

0.2

INPUT CURRENT
25mA/DIV

0.1

OUTPUT CURRENT
5mA/DIV

0–45 –30 –15

0 15 30 45 60
TEMPERATURE (°C)

75 903105 TA02a

0.38V
10mA
0.7mA

25µs/DIV
3105 TA02b

3105fb12

For more information www.linear.com/LTC3105

LTC3105
TYPICAL APPLICATIONS
3.3V from Multiple Stacked-Cell Photovoltaic with Source Temperature Tracking
L1**
6.8µH

+
–
+

CIN
10µF

–

VIN

SW
R1
1.37M

LTC3105
RMPPC
4.99k

THERMALLY
COUPLED

FB
PGOOD

MPPC
OFF ON

D1*

VOUT
3.3V

VOUT

CMPPC
10nF

D2*

SHDN

LDO

AUX

FBLDO

2.2V

GND

CAUX
1µF

COUT
10µF

R2
604k

CLDO
4.7µF
3105 TA03* MRA4003T3** PANASONIC ELL-VEG6R8N

Thermoelectric Generator to 2.4V Super Capacitor Charger
L1**
10µH
∆T ≥ 10°C

+

VIN

TEG*

SW
VOUT

CIN
100µF

LTC3105

CFF
22pF

R1
1.10M

FB
OFF ON
RMPPC
30.1k

MPPC

PGOOD

SHDN

LDO

AUX
CAUX
1µF

2.2V

R2
787k

VOUT
2.4V
COUT
1µF

+

FBLDO
GND

CBULK
1F
2.5V

CLDO
4.7µF
3105 TA04* MICROPELT MPG-D751** COILCRAFT MSS5131-103MX

3105fbFor more information www.linear.com/LTC3105

13

LTC3105
TYPICAL APPLICATIONS
Industrial Sensor 4mA to 20mA Current Loop Power Tap
L1**
10µH
VIN

4mA TO 20mA
CURRENT LOOP

SW
VOUT
R1
2M

LTC3105

VFWD = 330mV

FB
CIN
470µF

D1*

PGOOD

280mV

LDO

MPPC

RMPPC
28k

OFF ONAUX* MBRS190T3** COILCRAFT MSS5131-103MX

µP

+

10µF

VOUT, 3V

–

VDD

2.2V
CLDO
4.7µF

SHDN

CAUX
1µF

R2
1M

EN

RPG
499k

FBLDO
GND

3105 TA05

Transient Response to Load Pulse
with 4mA Loop Current

Start-Up VIN, VOUT , VLDO
VOUT VOLTAGE
500mV/DIVVOUT VOLTAGE
250mV/DIVLDO VOLTAGE
500mV/DIVVIN VOLTAGE
50mV/DIV0V
VIN VOLTAGE
200mV/DIVLOAD CURRENT
2mA/DIV
100mV
2ms/DIV

50ms/DIV

3105 TA05a

3105 TA05b

Single-Cell Photovoltaic NiMH Trickle Charger
L1, 10µH

VIN

+
–

SW
VOUT

CIN
10µF

R1
1.02M

LTC3105

COUT
10µF

FB

OFF ON

MPPC

PGOOD

SHDN

LDO

R2
470k

CAUX
1µF

AUX

FBLDO
GND

NiMH

+ ×2

1.8V
R3
1M

RMPPC
40.2k

VOUT
3.2V

+

R4
1.27M

CLDO
4.7µF

3105 TA06

3105fb14

For more information www.linear.com/LTC3105

LTC3105
PACKAGE DESCRIPTION

Please refer to http://www.linear.com/product/LTC3105#packaging for the most recent package drawings.
DD Package
10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1699 Rev C)

0.70 ±0.05

3.55 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGEOUTLINE
0.25 ±0.05

0.50
BSC
2.38 ±0.05(2 SIDES)RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

3.00 ±0.10(4 SIDES)

R = 0.125
TYP
6

0.40 ±0.10101.65 ±0.10(2 SIDES)PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFERPIN 1
TOP MARK(SEE NOTE 6)
0.200 REF

0.75 ±0.05

0.00 – 0.05

51(DD) DFN REV C 0310

0.25 ±0.05
0.50 BSC

2.38 ±0.10(2 SIDES)
BOTTOM VIEW—EXPOSED PAD

NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
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 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE

3105fbFor more information www.linear.com/LTC3105

15

LTC3105
PACKAGE DESCRIPTION

Please refer to http://www.linear.com/product/LTC3105#packaging for the most recent package drawings.
MS Package
12-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1668 Rev A)
0.889 ±0.127(.035 ±.005)

5.10(.201)
MIN

3.20 – 3.45(.126 – .136)

4.039 ±0.102(.159 ±.004)(NOTE 3)0.65(.0256)BSC

0.42 ±0.038(.0165 ±.0015)
TYP

12 11 10 9 8 7RECOMMENDED SOLDER PAD LAYOUT

0.254(.010)DETAIL “A”

3.00 ±0.102(.118 ±.004)(NOTE 4)4.90 ±0.152(.193 ±.006)

0° – 6° TYP

0.406 ±0.076(.016 ±.003)
REF

GAUGE PLANE

0.53 ±0.152(.021 ±.006)
DETAIL “A”

0.18(.007)SEATING
PLANE

1 2 3 4 5 6

1.10(.043)
MAX

0.22 – 0.38(.009 – .015)
TYP

0.650
(.0256)BSC

NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

0.86(.034)
REF

0.1016 ±0.0508(.004 ±.002)
MSOP (MS12) 0213 REV A

3105fb16

For more information www.linear.com/LTC3105

LTC3105
REVISION HISTORY
REV

DATE

DESCRIPTION

A

01/11

Added (Note 5) notation to Input Start-Up Voltage conditions.

3

Added Note 5.

3

Updated Start-Up Mode Operation section.

8

B

11/15

PAGE NUMBER

VOUT range changed.

3

Changed G09 curve.

4

Changed feedback description.

6

Changed VOUT range.

73105fbInformation 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/LTC3105

17

LTC3105
TYPICAL APPLICATION
Single-Cell Powered Remote Wireless Sensor
L1*
10µH

+
–

VIN

SW

CIN
10µF

R1
2.32M

LTC3105
FB

MPPC
RMPPC
40.2k

COUT
100µF

R2
1.02M

XMTR

I/O
OFF ON

2N7000

VOUT
3.3V

VOUT

EN

PGOOD
SHDN

LDO

AUX

FBLDO

CAUX
1µF

GND

2.2V

µC

RPG
499k
VDD

CLDO
4.7µF

* COILCRAFT MSS5131-103MX

A/D

SENSOR

GPIO

GND

3105 TA07

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Step-Up Transformers, IQ = 7μA; 4mm × 4mm QFN-20 SSOP-20 Packages, TEG
and Thermopiles

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LTC3108-1

Ultralow Voltage Step-Up Converter and PowerManager

0.03V ≤ VIN ≤ 0.50V, Selectable VOUT of 2.5V, 3V, 3.7V or 4.5V Uses Compact
Step-Up Transformers, IQ = 7μA; 3mm × 4mm DFN-12 SSOP-16 Packages, TEG
and Thermopiles

LTC4070

Li-Ion/Polymer Shunt Battery Charger System

450nA IQ; 1% Float Voltage Accuracy; 50mA Shunt Current 4.0V/4.1V/4.2V,
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LTC4071

Li-Ion/Polymer Shunt Battery Charger System with
Low Battery Disconnect

550nA IQ; 1% Float Voltage Accuracy; <10nA Low Battery Disconnect;
4.0V/4.1V/4.2V; 8-Lead 2mm × 3mm DFN and MSOP Packages

LTC3588-1/
LTC3588-2

Piezoelectric Energy Harvesting Power Supply< 1µA IQ in Regulation; 2.7V to 20V Input Range; Integrated Bridge Rectifier.
MSOP-10E and 3mm × 3mm DFN-10 Packages

3105fb18 Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC3105(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3105

LT 1115 REV B • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2010