LTC3105

400mA Step-Up DC/DC

Converter with Maximum Power
Point Control and 250mV Start-Up
FEATURES DESCRIPTION
n Low Start-Up Voltage: 250mV The LTC®3105 is a high efficiency step-up DC/DC converter
n Maximum Power Point Control that can operate from input voltages as low as 225mV. A
n Wide VIN Range: 225mV to 5V 250mV start-up capability and integrated maximum power
n Auxiliary 6mA LDO Regulator point controller (MPPC) enable operation directly from low
n Burst Mode® Operation: IQ = 24µA voltage, high impedance alternative power sources such as
n Output Disconnect and Inrush Current Limiting photovoltaic cells, TEGs (thermoelectric generators) and
n VIN > VOUT Operation fuel cells. A user programmable MPPC set point maximizes
n Antiringing Control the energy that can be extracted from any power source.
n Soft Start Burst Mode operation, with a proprietary self adjusting
n Automatic Power Adjust peak current, optimizes converter efficiency and output
n Power Good Indicator voltage ripple over all operating conditions.
n 10-Lead 3mm × 3mm × 0.75mm DFN and 12-Lead
The AUX powered 6mA LDO provides a regulated rail for
MSOP Packages
external microcontrollers and sensors while the main
output is charging. In shutdown, IQ is reduced to 10µA
APPLICATIONS and integrated thermal shutdown offers protection from
n Solar Powered Battery/Supercapacitor Chargers overtemperature faults. The LTC3105 is offered in 10-lead
n Energy Harvesting 3mm × 3mm × 0.75mm DFN and 12-lead MSOP packages.
n Remote Industrial Sensors L, 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 other
n Low Power Wireless Transmitters trademarks are the property of their respective owners.
n Cell Phone, MP3, PMP and GPS Accessory Chargers

TYPICAL APPLICATION
Single Photovoltaic Cell Li-Ion Trickle Charger Output Current vs Input Voltage
10µH 80
MPPC DISABLED
70
225mV TO 5V
VIN SW VOUT = 3.3V
60
+
OUTPUT CURRENT (mA)

VOUT
PHOTOVOLTAIC VOUT
10µF 4.1V 50
CELL – LTC3105 VOUT = 4.2V
1020k
40
FB VOUT = 5V
Li-Ion
30
MPPC PGOOD 332k
OFF ON SHDN LDO 2.2V 20
10µF
40.2k AUX FBLDO 10

1µF GND 4.7µF 0

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
3105 TA01a
INPUT VOLTAGE (V)
3105 TA01b

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LTC3105
ABSOLUTE MAXIMUM RATINGS (Note 1)

SW Voltage Maximum Junction Temperature (Note 4)............. 125°C

DC............................................................. –0.3V to 6V Storage Temperature.............................. –65°C to 150°C
Pulsed (<100ns)............................................–1V to 7V Lead Temperature (Soldering, 10 sec.)
Voltage, All Other Pins.................................. –0.3V to 6V MS Package....................................................... 300°C
Operating Junction Temperature
Range (Note 2)..........................................–40°C to 85°C

PIN CONFIGURATION
TOP VIEW
TOP VIEW
FB 1 10 AUX 1
FB 12 AUX
LDO 2 9 VOUT LDO 2 11 VOUT
11
FBLDO 3 8 PGOOD FBLDO 3 10 PGOOD
GND
SHDN 4 7 SW SHDN 4 9 SW
MPPC 5 8 VIN
MPPC 5 6 VIN 6
GND 7 GND

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

ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE 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, unless
otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Step-Up Converter
Input Operating Voltage l 0.225 5 V
Input Start-Up Voltage (Note 5) l 0.25 0.4 V
TJ = 0°C to 85°C (Note 5) 0.36 V
Output Voltage Adjust Range l 1.6 5.25 V
Feedback Voltage (FB Pin) l 0.984 1.004 1.024 V
VOUT IQ in Operation VFB = 1.10V 24 µA
VOUT IQ in Shutdown SHDN = 0V 10 µA
MPPC Pin Output Current VMPPC = 0.6V 9.72 10 10.28 µA
SHDN Input Logic High Voltage l 1.1 V
SHDN Input Logic Low Voltage l 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 0.5 Ω
P-Channel On-Resistance: SW to VOUT 0.5 Ω
Peak 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 %
LDO Regulator
LDO Output Adjust Range External Feedback Network, VAUX > VLDO l 1.4 5 V
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 l 6 12 mA
LDO Reverse-Blocking Leakage Current VIN = VAUX = VOUT = 0V, VSHDN = 0V 1 µA

Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 3: Current measurements are performed when the LTC3105 is not
may cause permanent damage to the device. Exposure to any Absolute switching. The current limit values measured in operation will be somewhat
Maximum Rating condition for extended periods may affect device higher due to the propagation delay of the comparators.
reliability and lifetime. Note 4: This IC includes over temperature protection that is intended
Note 2: The LTC3105 is tested under pulsed load conditions such that to protect the device during momentary overload conditions. Junction
TJ ≈ TA. The LTC3105E is guaranteed to meet specifications from temperature will exceed 125°C when overtemperature protection is active.
0°C to 85°C junction temperature. Specifications over the –40°C to 85°C Continuous operation above the specified maximum operating junction
operating junction temperature range are assured by design, character- temperature may impair device reliability.
ization and correlation with statistical process controls. Note that the Note 5: The LTC3105 has been optimized for use with high impedance
maximum ambient temperature consistent with these specifications is power sources such as photovoltaic cells and thermoelectric generators.
determined by specific operating conditions in conjunction with board The input start-up voltage is measured using an input voltage source with
layout, the rated package thermal impedance and other environmental a series resistance of approximately 200mΩ and MPPC enabled. Use of the
factors. 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 Shutdown Thresholds

vs Temperature vs Input Voltage IC Enable Delay vs Input Voltage
340 1000 120

900
320 IC ENABLE
800

THRESHOLD VOLTAGE (mV)

100
300
INPUT VOLTAGE (mV)

700

DELAY TIME (µs)

280 600
IC DISABLE
500 80
260
400

240 300
60
200
220
100
200 0 40
–45 –30 –15 0 15 30 45 60 75 90 1.25 2.25 3.25 4.25 5.25 1.25 2.25 3.25 4.25 5.25
TEMPERATURE (°C) SUPPLY VOLTAGE, VIN OR VAUX (V) SUPPLY VOLTAGE, VIN OR VAUX (V)
3105 G01 3105 G02 3105 G03

MPPC Current Variation LDO Soft-Start Duration

vs Temperature vs LDO Load
2.5 1.25

2.0
1.20
1.5
CHANGE FROM 25°C (%)

SOFT-START TIME (ms)

1.15
1.0

0.5 1.10

0
1.05
–0.5
1.00
–1.0

–1.5 0.95
–45 –30 –15 0 15 30 45 60 75 90 1 2 3 4 5 6
TEMPERATURE (°C) 3105 G05
LDO LOAD CURRENT (mA)
3105 G06

VOUT IQ vs Temperature
During Shutdown VIN for Synchronous Operation
22 5.0
SHDN = 0V
20 4.5
NONSYNCHRONOUS
MAXIMUM INPUT VOLTAGE (V)

18 4.0 OPERATION

16 3.5
3.0
14
IQ (µA)

2.5
12
2.0
10 SYNCHRONOUS
1.5 OPERATION
8 1.0
6 0.5
4 0
–45 –30 –15 0 15 30 45 60 75 90 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
TEMPERATURE (°C) 3105 G07
OUTPUT VOLTAGE (V)
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 IPEAK and IVALLEY Current Limit

Input Voltage Step Change vs Temperature Efficiency vs VIN
1.0 100
VIN VOLTAGE VMPPC = 400mV VOUT = 3V
IPEAK ILOAD = 10mA
200mV/DIV
0.5 LDO = 2.2V
90

CHANGE FROM 25°C (%)

0
80

EFFICIENCY (%)
INDUCTOR IVALLEY
CURRENT –0.5
100mA/DIV 70
–1.0
MPPC VOLTAGE
60
200mV/DIV –1.5

–2.0 50

–2.5 40
15µs/DIV 3105 G10
–45 –30 –15 0 15 30 45 60 75 90 0.25 1.25 2.25 3.25 4.25 5.25
TEMPERATURE (°C) INPUT VOLTAGE (V)
3105 G11 3105 G12

Efficiency vs Output Current and

Input and Output Burst Ripple Power Loss, VOUT = 3.3V
90 1000
VIN = 0.6V VOUT = 3.3V VIN = 0.6V
EFFICIENCY
CIN = 470µF IOUT = 15mA 80 VIN = 0.8V
COUT = 10µF VIN = 1V
70
OUTPUT 100
VOLTAGE

POWER LOSS (mW)

60
EFFICIENCY (%)

50mV/DIV
50
SW CURRENT 10
200mA/DIV 40
POWER LOSS
30
1
20
INPUT
VOLTAGE 10
5mV/DIV
0 0.1
50µs/DIV 0.01 0.1 1 10 100
3105 G13
OUTPUT CURRENT (mA) 3105 G14

Efficiency vs Output Current and No-Load Input Current

Power Loss, VOUT = 5V vs Input Voltage
100 1000 800
VIN = 3V VOUT = 3.3V
90 VIN = 2V 700
VIN = 1.5V
80 100 600
INPUT CURRENT (µA)
POWER LOSS (mW)

EFFICIENCY
EFFICIENCY (%)

70 500

60 10 400

50 300
POWER LOSS
40 1 200

30 100

20 0.1 0
0.01 0.1 1 10 100 0.2 0.4 0.6 0.8 1.0 1.2
OUTPUT CURRENT (mA) 3105 G15
INPUT VOLTAGE (V)
3105 G16

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LTC3105
PIN FUNCTIONS (DFN/MSOP)

FB (Pin 1/Pin 1): Step-Up Converter Feedback Input. GND (Exposed Pad Pin 11/Pins 6, 7) : Small Signal and
Connect the VOUT resistor divider tap to this input. The Power Ground for the IC. The GND connections should be
output voltage can be adjusted between 1.6V and 5.25V. soldered to the PCB ground using the lowest impedance
LDO (Pin 2/Pin 2): LDO Regulator Output. Connect a 4.7µF path possible.
or larger capacitor between LDO and GND. SW (Pin 7/Pin 9): Switch Pin. Connect an inductor between
FBLDO (Pin 3/Pin 3): LDO Feedback Input. Connect the SW and VIN. PCB trace lengths should be as short as pos-
sible to reduce EMI. While the converter is sleeping or is
LDO resistive divider tab to this input. Alternatively, con-
necting FBLDO directly to GND will configure the LDO in shutdown, the internal antiringing switch connects the
output voltage to be internally set at 2.2V (nominal). SW pin to the VIN pin in order to minimize EMI.
PGOOD (Pin 8/Pin 10): Power Good Indicator. This is an
SHDN (Pin 4/Pin 4): Logic Controlled Shutdown Input.
open-drain output. The pull-down is disabled when VOUT
With SHDN open, the converter is enabled by an internal
has achieved the voltage defined by the feedback divider
2MΩ pull-up resistor. The SHDN pin should be driven with
on the FB pin. The pull-down is also disabled while the IC
an open-drain or open-collector pull-down and floated until
is in shutdown or start-up mode.
the converter has entered normal operation. Excessive
loading on this pin may cause a failure to complete start-up. VOUT (Pin 9/Pin 11): Step-Up Converter Output. This is the
drain connection of the main output internal synchronous
SHDN = Low: IC Disabled
rectifier. A 10µF or larger capacitor must be connected
SHDN = High: IC Enabled between this pin and GND. The PCB trace length from the
MPPC (Pin 5/Pin 5): Set Point Input for Maximum VOUT pin to the output filter capacitor should be as short
Power Point Control. Connect a resistor from MPPC to and wide as possible.
GND to program the activation point for the MPPC loop. AUX (Pin 10/Pin 12): Auxiliary Voltage. Connect a 1µF
To disable the MPPC circuit, connect MPPC directly capacitor between this pin and GND. This pin is used by
to GND. the start-up circuitry to generate a voltage rail to power
VIN (Pin 6/Pin 8): Input Supply. Connect a decoupling internal circuitry until the main output reaches regulation.
capacitor between this pin and GND. The PCB trace length AUX and VOUT are internally connected together once VOUT
from the VIN pin to the decoupling capacitor should be as exceeds VAUX.
short and wide as possible. When used with high imped-
ance sources such as photovoltaic cells, this pin should
have a 10µF or larger decoupling capacitor.

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 LTC3105
BLOCK DIAGRAM (Pin Numbers for DFN Package Only)

L1
10µH

7
SHUTDOWN SW
OR WELL
SLEEP CONTROL
AUX
10
CAUX
SHORT 1µF
CONTROL
VIN LOW VOLTAGE VOUT 1.6V TO
225mV 6 CURRENT 9 5.25V
START-UP
TO 5V ADJUST
CIN COUT
10µF 10µF
LDO
SHUTDOWN VAUX 2
VCC – + – + CLDO
4.7µF
10µA
MPPC
5 –g PEAK CURRENT
m LIMIT
RMPPC VIN + SHUTDOWN
VCC VALLEY CURRENT LIMIT – +
SLEEP
2M LOGIC R3 R1
SHDN USER SHUTDOWN BURST FBLDO
4 1.004V 3
CONTROL
FB
– 1
PGOOD
VIN + 1.004V 8 R4 R2
VAUX
–
VCC FB
+
0.9V
EXPOSED PAD
SLEEP
11
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LTC3105
OPERATION
Introduction start-up mode. Once in normal operation, the SHDN pin
may be controlled using an open-drain or open-collector
The LTC3105 is a unique, high performance, synchronous
pull-down. Other external loads on this pin should be
boost converter that incorporates maximum power point
avoided, as they may result in the part failing to reach
control, 250mV start-up capability and an integrated LDO
regulation. In shutdown, the internal switch connecting
regulator. This part operates over a very wide range of input
AUX and VOUT is enabled.
voltages from 225mV to 5V. Its Burst Mode architecture
and low 24µA quiescent current optimize efficiency in low When the SHDN pin is released, the LTC3105 is enabled
power applications. and begins switching after a short delay. When either VIN
or VAUX is above 1.4V, this delay will typically range be-
An integrated maximum power point controller allows for tween 20µs and 100µs. Refer to the Typical Performance
operation directly from high impedance sources such as Characteristics section for more details.
photovoltaic cells by preventing the input power source
voltage from collapsing below the user programmable Start-Up Mode Operation
MPPC threshold. Peak current limits are automatically
The LTC3105 provides the capability to start with voltages
adjusted with proprietary techniques to maintain operation
as low as 250mV. During start-up the AUX output initially
at levels that maximize power extraction from the source.
is charged with the synchronous rectifiers disabled. Once
The 250mV start-up voltage and 225mV minimum VAUX has reached approximately 1.4V, the converter leaves
operating voltage enable direct operation from a single start-up mode and enters normal operation. Maximum
photovoltaic cell and other very low voltage, high series power point control is not enabled during start-up, however,
impedance power sources such as TEGs and fuel cells. the currents are internally limited to sufficiently low levels
to allow start-up from weak input sources.
Synchronous rectification provides high efficiency opera-
tion while eliminating the need for external Schottky diodes. While the converter is in start-up mode, the internal switch
The LTC3105 provides output disconnect which prevents between AUX and VOUT remains disabled and the LDO
large inrush currents during start-up. This is particularly is disabled. Refer to Figure 1 for an example of a typical
important for high internal resistance power sources like start-up sequence.
photovoltaic cells and thermoelectric generators which The LTC3105 is optimized for use with high impedance
can become overloaded if inrush current is not limited power sources such as photovoltaic cells. For operation
during start-up of the power converter. In addition, output from very low impedance, low input voltage sources, it may
disconnect isolates VOUT from VIN while in shutdown. be necessary to add several hundred milliohms of series
input resistance to allow for proper low voltage start-up.
VIN > VOUT Operation
The LTC3105 includes the ability to seamlessly maintain Normal Operation
regulation if VIN becomes equal to or greater than VOUT . When either VIN or VAUX is greater than 1.4V typical, the
With VIN greater than or equal to VOUT , the synchro- converter will enter normal operation.
nous rectifiers are disabled which may result in reduced The converter continues charging the AUX output until
efficiency. the LDO output enters regulation. Once the LDO output
is in regulation, the converter begins charging the VOUT
Shutdown Control
pin. VAUX is maintained at a level sufficient to ensure the
The SHDN pin is an active low input that places the IC LDO remains in regulation. If VAUX becomes higher than
into low current shutdown mode. This pin incorporates an required to maintain LDO regulation, charge is transferred
internal 2MΩ pull-up resistor which enables the converter from the AUX output to the VOUT output. If VAUX falls too
if the SHDN pin is not controlled by an external circuit. The low, current is redirected to the AUX output instead of
SHDN pin should be allowed to float while the part is in being used to charge the VOUT output. Once VOUT rises
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 LTC3105
OPERATION INDUCTOR CURRENT

TIME
OUTPUT VOLTAGE

VAUX VLDO VOUT

1.4V

TIME
VOUT IN
LDO IN REGULATION
REGULATION VOUT = VAUX
VOUT SYNCHRONOUS
START-UP MODE NORMAL OPERATION RECTIFIER ENABLED 3105 F01

Figure 1. Typical Converter Start-Up Sequence

above VAUX , an internal switch is enabled to connect the When VOUT reaches the regulation point, the N- and P-
two outputs together. channel MOSFETs connected to the SW pin are disabled
If VIN is greater than the voltage on the driven output (VOUT and the converter enters sleep.
or VAUX), or the driven output is less than 1.2V (typical),
Auxiliary LDO
the synchronous rectifiers are disabled. With the synchro-
nous rectifiers disabled, the converter operates in critical The integrated LDO provides a regulated 6mA rail to
conduction mode. In this mode, the N-channel MOSFET power microcontrollers and external sensors. When the
between SW and GND is enabled and remains on until the input voltage is above the minimum of 225mV, the LDO is
inductor current reaches the peak current limit. It is then powered from the AUX output allowing the LDO to attain
disabled and the inductor current discharges completely regulation while the main output is still charging. The LDO
before the cycle is repeated. has a 12mA current limit and an internal 1ms soft-start
to eliminate inrush currents. The LDO output voltage is
When the output voltage is greater than the input voltage
and greater than 1.2V, the synchronous rectifier is enabled. set by the FBLDO pin. If a resistor divider is connected
In this mode, the N-channel MOSFET between SW and to this pin, the ratio of the resistors determines the LDO
GND is enabled until the inductor current reaches the peak output voltage. If the FBLDO pin is connected directly to
current limit. Once current limit is reached, the N-channel GND, the LDO will use a 2MΩ internal divider network to
MOSFET turns off and the P-channel MOSFET between SW program a 2.2V nominal output voltage. The LDO should
and the driven output is enabled. This switch remains on be programmed for an output voltage less than the pro-
until the inductor current drops below the valley current grammed VOUT .
limit and the cycle is repeated.
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LTC3105
OPERATION
When the converter is placed in shutdown mode, the LDO capability at heavy load by adjusting the peak and valley
is forced into reverse-blocking mode with reverse current of the inductor current as a function of load. Lowering the
limited to under 1µA. After the shutdown event has ended, peak inductor current to 100mA at light load optimizes
the LDO remains in reverse-blocking mode until VAUX has efficiency by reducing conduction losses. As the load
risen above the LDO voltage. increases, the peak inductor current is automatically in-
creased to a maximum of 500mA. At intermediate loads,
MPPC Operation the peak inductor current can vary between 100mA to
The maximum power point control circuit allows the user 500mA. This function is overridden by the MPPC function
to set the optimal input voltage operating point for a given and will only be observed when the power source can
power source. The MPPC circuit dynamically regulates deliver more power than the load requires.
the average inductor current to prevent the input voltage
from dropping below the MPPC threshold. When VIN is PGOOD Operation
greater than the MPPC voltage, the inductor current is The power good output is used to indicate that VOUT is
increased until VIN is pulled down to the MPPC set point. in regulation. PGOOD is an open-drain output, and is
If VIN is less than the MPPC voltage, the inductor current disabled in shutdown. PGOOD will indicate that power
is reduced until VIN rises to the MPPC set point. is good at the beginning of the first sleep event after
the output voltage has risen above 90% of its regulation
Automatic Power Adjust value. PGOOD remains asserted until VOUT drops below
The LTC3105 incorporates a feature that maximizes ef- 90% of its regulation value at which point PGOOD will
ficiency at light load while providing increased power pull low.

APPLICATIONS INFORMATION
Component Selection should be large enough to allow the converter to complete
Low DCR power inductors with values between 4.7µH start-up mode using the energy stored in the input ca-
and 30µH are suitable for use with the LTC3105. For pacitor. When using bulk input capacitors that have high
most applications, a 10µH inductor is recommended. In ESR, a small valued parallel ceramic capacitor should be
applications where the input voltage is very low, a larger placed between VIN and GND as close to the converter
value inductor can provide higher efficiency and a lower pins as possible.
start-up voltage. In applications where the input voltage A 1µF ceramic capacitor should be connected between
is relatively high (VIN > 0.8V), smaller inductors may be AUX and GND. Larger capacitors should be avoided to
used to provide a smaller overall footprint. In all cases, minimize start-up time. A low ESR output capacitor should
the inductor must have low DCR and sufficient saturation be connected between VOUT and GND. The main output
current rating. If the DC resistance of the inductor is too capacitor should be 10µF or larger. The main output can
high, efficiency will be reduced and the minimum operating also be used to charge energy storage devices including
voltage will increase. tantalum capacitors, supercapacitors and batteries. When
Input capacitor selection is highly important in low voltage, using output bulk storage devices with high ESR, a small
high source resistance systems. For general applications, valued ceramic capacitor should be placed in parallel and
a 10µF ceramic capacitor is recommended between VIN located as close to the converter pins as possible.
and GND. For high impedance sources, the input capacitor

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 LTC3105

APPLICATIONS INFORMATION
Step-Up Converter Feedback Configuration MPPC Threshold Configuration
A resistor divider connected between the VOUT and FB pins The MPPC circuit controls the inductor current to main-
programs the step-up converter output voltage, as shown tain VIN at the voltage on the MPPC pin. The MPPC pin
in Figure 2. An optional 22pF feedforward capacitor, CFF1, voltage is set by connecting a resistor between the MPPC
can be used to reduce output ripple and improve load pin and GND, as shown in Figure 4. The MPPC voltage is
transient response. The equation for VOUT is: determined by the equation:
 R1  VMPPC = 10µA • RMPPC
VOUT = 1.004V •  +1
 R2  In photovoltaic cell applications, a diode can be used to
set the MPPC threshold so that it tracks the cell voltage
LDO Regulator Feedback Configuration over temperature, as shown in Figure 5. The diode should
Two methods can be used to program the LDO output be thermally coupled to the photovoltaic cell to ensure
voltage, as shown in Figure 3. A resistor divider connected proper tracking. A resistor placed in series with the diode
between the LDO and FBLDO pins can be used to program can be used to adjust the DC set point to better match
the LDO output voltage. The equation for the LDO output the maximum power point of a particular source if the
voltage is: selected diode forward voltage is too low. If the diode is
located far from the converter inputs, a capacitor may be
 R3  required to filter noise that may couple onto the MPPC
VLDO = 1.004V •  +1
 R4  pin, as shown in Figure 5. This method can be extended
to stacked cell sources through use of multiple series
Alternatively, the FBLDO pin can be connected directly to
connected diodes.
GND. In this configuration, the LDO is internally set to a
nominal 2.2V output.

VOUT
MPPC
10µA
CFF1 R1 LTC3105
RMPPC LTC3105
FB

R2

3105 F02
3105 F04

Figure 2. FB Configuration Figure 4. MPPC Configuration

LDO 2.2V LDO MPPC

10µA
R3 RMPPC
LTC3105 LTC3105 LTC3105

FBLDO FBLDO + C6
VFWD
R4 10nF
–

3105 F03 3105 F05

Figure 3. FBLDO Configuration Figure 5. MPPC Configuration with Temperature Adjustment

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LTC3105
APPLICATIONS INFORMATION
Industrial Current Loops
4mA TO 20mA
The low 250mV start-up and low voltage operation of the CURRENT LOOP
+
VIN

LTC3105 allow it to be supplied by power from a diode VFWD CIN LTC3105

placed in an industrial sensor current loop, as shown –
GND
in Figure 6. In this application, a large input capacitor RMPPC
is required due to the very low available supply current MPPC

(less than 4mA). The loop diode should be selected for a

minimum forward drop of 300mV. The MPPC pin voltage
3105 F06

should be set for a value approximately 50mV below the Figure 6. Current Loop Power Tap
minimum diode forward voltage.

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

VIN SW
+ VOUT
CIN VOUT 3.3V
– 10µF R1
LTC3105
2.26M
FB
THERMALLY COUT
COUPLED MPPC PGOOD R2 10µF
RMPPC OFF ON 1M
SHDN LDO 2.2V
9.09k
AUX FBLDO
CMPPC
D1* 10nF GND CLDO
CAUX
1µF 4.7µF

* MRA4003T3 3105 TA02

** COILCRAFT MSS5131-103MX

VMPPC vs Temperature MPPC Response to Input Source Current Step

0.7
VOUT = 2.8V
VMPPC = 0.4V
0.6 VFB = 0.94V

0.5
MPPC VOLTAGE (V)

0.4
0.38V
INPUT VOLTAGE
0.3 50mV/DIV

INPUT CURRENT 10mA

0.2
25mA/DIV
0.7mA
0.1 OUTPUT CURRENT
5mA/DIV
0
–45 –30 –15 0 15 30 45 60 75 90 25µs/DIV
TEMPERATURE (°C) 3105 TA02a 3105 TA02b

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 LTC3105
TYPICAL APPLICATIONS
3.3V from Multiple Stacked-Cell Photovoltaic with Source Temperature Tracking

L1**
6.8µH

+
– VIN SW
+ CIN VOUT
VOUT 3.3V
10µF
– LTC3105
R1
1.37M
RMPPC
THERMALLY FB
4.99k COUT
COUPLED 10µF
MPPC PGOOD R2
OFF ON 604k
SHDN LDO 2.2V
D1*
CMPPC AUX FBLDO
10nF
D2* GND CLDO
CAUX
1µF 4.7µF

3105 TA03
* MRA4003T3
** PANASONIC ELL-VEG6R8N

Thermoelectric Generator to 2.4V Super Capacitor Charger

L1**
10µH
∆T ≥ 10°C
+ VIN SW
TEG* VOUT
CIN VOUT 2.4V
100µF CFF R1
LTC3105 22pF 1.10M
FB COUT
1µF
MPPC PGOOD R2 + CBULK
787k 1F
OFF ON SHDN LDO 2.2V
2.5V
RMPPC AUX FBLDO
30.1k
GND CLDO
CAUX
1µF 4.7µF

3105 TA04

* MICROPELT MPG-D751
** COILCRAFT MSS5131-103MX

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

VIN SW
VOUT
R1
LTC3105
VFWD = 330mV 2M
4mA TO 20mA FB
CURRENT LOOP R2
CIN PGOOD EN
1M
D1*
470µF RPG +
499k µP 10µF
280mV VOUT, 3V
MPPC LDO
2.2V
VDD –
OFF ON SHDN CLDO
RMPPC 4.7µF
28k AUX FBLDO
CAUX GND
* MBRS190T3 1µF
** COILCRAFT MSS5131-103MX
3105 TA05

Transient Response to Load Pulse

with 4mA Loop Current Start-Up VIN, VOUT , VLDO

VOUT VOLTAGE
VOUT VOLTAGE 500mV/DIV
250mV/DIV
LDO VOLTAGE
500mV/DIV
VIN VOLTAGE
50mV/DIV

0V
VIN VOLTAGE
LOAD CURRENT 200mV/DIV
2mA/DIV
100mV

2ms/DIV 50ms/DIV 3105 TA05b

3105 TA05a

Single-Cell Photovoltaic NiMH Trickle Charger

L1, 10µH

VIN SW
+ CIN VOUT
VOUT
3.2V
10µF R1 COUT
+
– LTC3105
1.02M 10µF NiMH
FB + ×2
MPPC PGOOD R2
470k

OFF ON SHDN LDO 1.8V

RMPPC R3
40.2k 1M
CLDO
AUX FBLDO 4.7µF
CAUX GND R4
1µF 1.27M
3105 TA06

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14 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)

PACKAGE
OUTLINE

0.25 ±0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

R = 0.125 0.40 ±0.10
TYP
6 10

3.00 ±0.10 1.65 ±0.10

(4 SIDES) (2 SIDES) PIN 1 NOTCH
PIN 1 R = 0.20 OR
TOP MARK 0.35 × 45°
(SEE NOTE 6) CHAMFER
(DD) DFN REV C 0310

5 1
0.200 REF 0.75 ±0.05 0.25 ±0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
0.00 – 0.05
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

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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) 3.20 – 3.45
MIN (.126 – .136)

4.039 ±0.102
0.42 ±0.038 0.65 (.159 ±.004)
(.0165 ±.0015) (.0256) (NOTE 3) 0.406 ±0.076
TYP BSC
12 11 10 9 8 7 (.016 ±.003)
RECOMMENDED SOLDER PAD LAYOUT REF

DETAIL “A” 3.00 ±0.102

0.254 4.90 ±0.152
(.118 ±.004)
(.010) (.193 ±.006) (NOTE 4)
0° – 6° TYP
GAUGE PLANE

0.53 ±0.152
1 2 3 4 5 6
(.021 ±.006) 1.10 0.86
(.043) (.034)
DETAIL “A”
MAX REF
0.18 SEATING
(.007) PLANE

0.22 – 0.38 0.1016 ±0.0508

(.009 – .015) (.004 ±.002)
TYP 0.650
NOTE: (.0256)
MSOP (MS12) 0213 REV A

1. DIMENSIONS IN MILLIMETER/(INCH) BSC

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

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16 For more information www.linear.com/LTC3105

 LTC3105
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
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 VOUT range changed. 3
Changed G09 curve. 4
Changed feedback description. 6
Changed VOUT range. 7

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17
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 representa-
For more
tion that the interconnection information
of its circuits www.linear.com/LTC3105
as described herein will not infringe on existing patent rights.
LTC3105
TYPICAL APPLICATION
Single-Cell Powered Remote Wireless Sensor
L1*
10µH

VIN SW
+ VOUT
CIN VOUT
10µF 3.3V
– R1
LTC3105 2.32M
MPPC FB COUT XMTR
R2 100µF
RMPPC 1.02M
40.2k I/O
PGOOD EN A/D SENSOR
OFF ON
RPG µC
SHDN LDO 2.2V
499k
AUX FBLDO VDD GPIO
2N7000 GND GND
CAUX CLDO
1µF 4.7µF

* COILCRAFT MSS5131-103MX 3105 TA07

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and Power Manager Step-Up Transformers, IQ = 7μA; 4mm × 4mm QFN-20 SSOP-20 Packages, TEG
and Thermopiles
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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 550nA IQ; 1% Float Voltage Accuracy; <10nA Low Battery Disconnect;
Low Battery Disconnect 4.0V/4.1V/4.2V; 8-Lead 2mm × 3mm DFN and MSOP Packages
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LTC3588-2 MSOP-10E and 3mm × 3mm DFN-10 Packages

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18 Linear Technology Corporation

LT 1115 REV B • PRINTED IN USA

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  LINEAR TECHNOLOGY CORPORATION 2010