LTC3109EGN#PBF - Linear Technology

LTC3109

3109fa

TYPICAL APPLICATION

FEATURES DESCRIPTION

Auto-Polarity, Ultralow

Voltage Step-Up Converter

and Power Manager

The LTC

3109 is a highly integrated DC/DC converter ideal

for harvesting surplus energy from extremely low input

voltage sources such as TEGs (thermoelectric genera-

tors) and thermopiles. Its unique, proprietary autopolarity

topology* allows it to operate from input voltages as low

as 30mV, regardless of polarity.

Using two compact step-up transformers and external

energy storage elements, the LTC3109 provides a com-

plete power management solution for wireless sensing

and data acquisition. The 2.2V LDO can power an external

microprocessor, while the main output can be programmed

to one of four ﬁ xed voltages. The power good indicator

signals that the main output is within regulation. A second

output can be enabled by the host. A storage capacitor (or

battery) can also be charged to provide power when the

input voltage source is unavailable. Extremely low quies-

cent current and high efﬁ ciency maximizes the harvested

energy available for the application.

The LTC3109 is available in a small, thermally enhanced

20-lead (4mm × 4mm) QFN package and a 20-lead SSOP

package.

VOUT Current vs TEG Voltage

APPLICATIONS

n Operates from Inputs as Low as ±30mV

n Less Than ±1°C Needed Across TEG to Harvest

Energy

n Proprietary Auto-Polarity Architecture

n Complete Energy Harvesting Power Management

System

– Selectable VOUT of 2.35V, 3.3V, 4.1V or 5V

– 2.2V, 5mA LDO

– Logic-Controlled Output

– Energy Storage Capability for Operation During

Power Interruption

n Power Good Indicator

n Uses Compact Step-up Transformers

n Small, 20-lead (4mm × 4mm) QFN Package or

20-Lead SSOP

n Remote Sensor and Radio Power

n HVAC Systems

n Automatic Metering

n Building Automation

n Predictive Maintenance

n Industrial Wireless Sensing

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

*Patent pending.

GND 1μF

5.25V

2.2V

LTC3109

3.3V

CSTORE

3109 TA01a

C1A

1nF

2.2μF

470pF

47μF

1nF

470pF

1:100

TEG

(THERMOELECTRIC GENERATOR)

±30mV TO ±500mV

••

1:100

••

VOUT2

C2A

C1B

C2B

SWB

VINB

VS1

VS2

SWA

VINA

VOUT

VLDO

PG00D

VOUT2_EN

VSTOREVAUX

VAUX +

470μF

OPTIONAL SWITCHED OUTPUT FOR SENSORS

μP

LOW POWER

RADIO

SENSOR(S)

VTEG (mV)

–300

IVOUT (μA)

100

300

400

500

100

900

3109 TA01b

200

–100

–200 200

0300

600

700

800

1:100 TRANSFORMERS

C1A = C1B = 1nF

VOUT = 3.3V

LTC3109

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ABSOLUTE MAXIMUM RATINGS

SWA, SWB, VINA, VINB Voltage .................... –0.3V to 2V

C1A, C1B Voltage ......................................... –0.3V to 6V

C2A, C2B Voltage (Note 6) .............................. –8V to 8V

VOUT2, VOUT2_EN .......................................... –0.3V to 6V

VS1, VS2, VOUT, PGOOD .............................. –0.3V to 6V

(Note 1)

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC3109EUF#PBF LTC3109EUF#TRPBF 3109 20-Lead (4mm × 4mm) Plastic QFN –40°C to 125°C

LTC3109IUF#PBF LTC3109IUF#TRPBF 3109 20-Lead (4mm × 4mm) Plastic QFN –40°C to 125°C

LTC3109EGN#PBF LTC3109EGN#TRPBF LTC3109GN 20-Lead Plastic SSOP –40°C to 125°C

LTC3109IGN#PBF LTC3109IGN#TRPBF LTC3109GN 20-Lead Plastic SSOP –40°C to 125°C

Consult LTC Marketing for parts speciﬁ ed with wider operating temperature ranges. *The temperature grade is identiﬁ ed by a label on the shipping container.

Consult LTC Marketing for information on non-standard lead based ﬁ nish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁ cations, go to: http://www.linear.com/tapeandreel/

20 19 18 17 16

678

TOP VIEW

GND

UF PACKAGE

20-LEAD (4mm s 4mm) PLASTIC QFN

9 10

VSTORE

VAUX

VOUT

VOUT2

VOUT2_EN

SWA

VINA

VINB

SWB

GND

VS2

VS1

C1A

C2A

GND

PGOOD

VLDO

GND

C1B

C2B

TJMAX = 125°C, θJA = 37°C/W

EXPOSED PAD (PIN 21) IS GND (Note 5)

GN PACKAGE

20-LEAD PLASTIC SSOP

TOP VIEW

VS1

VS2

VSTORE

VAUX

VOUT

VOUT2

VOUT2_EN

PGOOD

VLDO

GND

C1A

C2A

GND

SWA

VINA

VINB

SWB

GND

C2B

C1B

TJMAX = 125°C, θJA = 90°C/W

PIN CONFIGURATION

VLDO, VSTORE ............................................ –0.3V to 6V

VAUX ...................................................... 15mA Into VAUX

Operating Junction Temperature Range

(Note 2) .................................................. –40°C to 125°C

Storage Temperature Range .................. –65°C to 125°C

LTC3109

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ELECTRICAL CHARACTERISTICS

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 LTC3109 is tested under pulsed load conditions such that

TJ ≈ TA. The LTC3109E is guaranteed to meet speciﬁ cations from

The l denotes the speciﬁ cations which apply over the full operating

junction temperature range, otherwise speciﬁ cations are for TA = 25°C (Note 2). VAUX = 5V unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Start-Up Voltage Using 1:100 Transformer Turns Ratio, VAUX = 0V ±30 ±50 mV

No-Load Input Current Using 1:100 Transformer Turns Ratios,

VIN = 30mV, VOUT2_EN = 0V, All Outputs Charged

and in Regulation

6mA

Input Voltage Range Using 1:100 Transformer Turns Ratios lVSTARTUP ±500 mV

Output Voltage VS1 = VS2 = GND

VS1 = VAUX, VS2 = GND

VS1 = GND, VS2 = VAUX

VS1 = VS2 = VAUX

2.30

3.234

4.018

4.875

2.350

3.300

4.100

5.000

2.40

3.366

4.182

5.10

VAUX Quiescent Current No Load, All Outputs Charged 7 10 μA

VAUX Clamp Voltage Current Into VAUX = 5mA l5.0 5.25 5.55 V

VOUT Quiescent Current VOUT = 3.3V, VOUT2_EN = 0V 0.2 μA

VOUT Current Limit VOUT = 0V l61526 mA

N-Channel MOSFET On-Resistance C2B = C2A = 5V (Note 3) Measured from VINA or

SWA, VINB or SWB to GND

0.35 Ω

LDO Output Voltage 0.5mA Load On VLDO l2.134 2.2 2.30 V

LDO Load Regulation For 0mA to 2mA Load 0.5 1 %

LDO Line Regulation For VAUX from 2.5V to 5V 0.05 0.2 %

LDO Dropout Voltage ILDO = 2mA l100 200 mV

LDO Current Limit VLDO = 0V l512 mA

VSTORE Leakage Current VSTORE = 5V 0.1 0.3 μA

VSTORE Current Limit VSTORE = 0V l61526 mA

VOUT2 Leakage Current VOUT2 = 0V, VOUT2_EN = 0V 50 nA

VS1, VS2 Threshold Voltage l0.4 0.85 1.2 V

VS1, VS2 Input Current VS1 = VS2 = 5V 1 50 nA

PGOOD Threshold (Rising) Measured Relative to the VOUT Voltage –7.5 %

PGOOD Threshold (Falling) Measured Relative to the VOUT Voltage –9 %

PGOOD VOL Sink Current = 100μA 0.12 0.3 V

PGOOD VOH Source Current = 0 2.1 2.2 2.3 V

PGOOD Pull-Up Resistance 1MΩ

VOUT2_EN Threshold Voltage VOUT2_EN Rising l0.4 1.0 1.3 V

VOUT2_EN Threshold Hysteresis 100 mV

VOUT2_EN Pull-Down Resistance 5MΩ

VOUT2 Turn-On Time 0.5 μs

VOUT2 Turn-Off Time (Note 3) 0.15 μs

VOUT2 Current Limit VOUT = 3.3V l0.2 0.3 0.5 A

VOUT2 Current Limit Response Time (Note 3) 350 ns

VOUT2 P-Channel MOSFET On-Resistance VOUT = 5V (Note 3) 1.0 Ω

0°C to 85°C junction temperature. Speciﬁ cations over the –40°C to

125°C operating junction temperature range are assured by design,

characterization and correlation with statistical process controls. The

LTC3109I is guaranteed over the full –40°C to 125°C operating junction

temperature range. Note that the maximum ambient temperature

is determined by speciﬁ c operating conditions in conjunction with

LTC3109

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TYPICAL PERFORMANCE CHARACTERISTICS

ELECTRICAL CHARACTERISTICS

board layout, the rated thermal package thermal resistance and other

environmental factors. The junction temperature (TJ) is calculated from

the ambient temperature (TA) and power dissipation (PD) according to

the formula: TJ = TA + (PD • θJA°C/W), where θJA is the package thermal

impedance.

Note 3: Speciﬁ cation is guaranteed by design and not 100% tested in

production.

Note 4: Current measurements are made when the output is not switching.

Note 5: Failure to solder the exposed backside of the QFN package to the

PC board ground plane will result in a thermal resistance much higher

than 37°C/W.

Note 6: The Absolute Maximum Rating is a DC rating. Under certain

conditions in the applications shown, the peak AC voltage on the C2A and

C2B pins may exceed ±8V. This behavior is normal and acceptable because

the current into the pin is limited by the impedance of the coupling

capacitor.

Input Resistance vs VIN Efﬁ ciency vs VIN

Open-Circuit Start-Up Voltage

vs Source Resistance

IIN vs VIN IVOUT vs VIN

VIN (mV)

IIN (mA)

100

1000

100 1000

3109 G01

1:100 RATIO, C1 = 1nF

1:50 RATIO, C1 = 4.7nF

1:20 RATIO, C1 = 10nF

VOUT = 0V

VIN (mV)

IVOUT (μA)

100

1000

10000

100 1000

3109 G02

1:100 RATIO, C1 = 1nF

1:50 RATIO, C1 = 4.7nF

1:20 RATIO, C1 = 10nF

VOUT = 3.3V

NO LOAD ON VLDO

VIN (mV)

2.0

RIN (Ω)

3.0

4.0

5.0

6.0

100 1000

3109 G03

7.0

2.5

3.5

4.5

5.5

6.5

1:100 RATIO, C1 = 1nF

1:50 RATIO, C1 = 4.7nF

1:20 RATIO, C1 = 10nF

VOUT = 0V

SOURCE RESISTANCE (Ω)

VSTARTUP (OPEN CIRCUIT) (mV)

6789

3109 G05

12345 10

VIN (mV)

EFFICIENCY (%)

100 1000

3109 G04

45 1:100 RATIO, C1 = 1nF

1:50 RATIO, C1 = 4.7nF

1:20 RATIO, C1 = 10nF

VOUT = 0V

TA = 25°C, unless otherwise noted.

VIN (mV)

0.1

PVOUT (mW)

100

100 1000

3109 G18

1:50 RATIO

C1 = 4.7nF

VOUT = 5V

VOUT = 3.3V

PVOUT vs VIN

LTC3109

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TYPICAL PERFORMANCE CHARACTERISTICS

Resonant Switching Waveforms LDO Load Regulation LDO Dropout Voltage

Start-Up Voltage Sequencing

VOUT and PGOOD Response

During a Step Load VOUT Ripple

VOUT and VLDO vs Temperature

VAUX Clamp Voltage

vs Shunt Current

PVOUT vs dT and TEG Size,

1:100 Ratio, VOUT = 5V

TA = 25°C, unless otherwise noted.

TEMPERATURE (°C)

–50

CHANGE (%) (RELATIVE TO 25°C)

0.75

3109 G06

–0.50

–25 0 50

–0.75

–1.00

1.00

0.50

0.25

–0.25

75 100 125

VLDO

VOUT

VAUX SHUNT CURRENT (mA)

VAUX (V)

5.3

5.4

5.5

3109 G07

5.2

5.1

5.0 36915

dT (°K)

PVOUT (mW)

1.0

2.0

3.0

0.5

1.5

2.5

2468

3109 G08

10103579

FERROTEC 9500/127/100B

40mm

FERROTEC 9501/071/040B

22mm

20μs/DIV

C1 A OR B

2V/DIV

C2 A OR B

2V/DIV

3109 G9

LDO LOAD (mA)

–1.00

DROP IN VLDO (%)

–0.75

–0.50

0.5 11.5 2 32.5 3.5

–0.25

0.00

3109 G10 LDO LOAD (mA)

0.00

DROPOUT VOLTAGE (V)

0.04

0.08

0.12

0.5 11.5 2 32.5 3.5

0.16

0.20

0.02

0.06

0.10

0.14

0.18

3109 G11

10SEC/DIV 3109 G12

CH1

VSTORE

1V/DIV

CH2, VOUT

1V/DIV

CH3, VLDO

1V/DIV

VIN = 50mV

1:100 RATIO TRANSFORMER

COUT = 220μF

CSTORE = 470μF

CLDO = 2.2μF

5ms/DIV 3109 G13

CH2

VOUT

1V/DIV

CH1

PGD

1V/DIV

50mA LOAD STEP

COUT = 220μF

100ms/DIV 3109 G14

20mV/

DIV

30μA LOAD

COUT = 220μF

LTC3109

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LDO Step Load Response Enable Input and VOUT2 Running on Storage Capacitor

PIN FUNCTIONS

(QFN/SSOP)

VSTORE (Pin 1/Pin 3): Output for the Storage Capacitor or

Battery. A large storage capacitor may be connected from

this pin to GND for powering the system in the event the

input voltage is lost. It will be charged up to the maximum

VAUX clamp voltage. If not used, this pin should be left

open or tied to VAUX.

VAUX (Pin 2/Pin 4): Output of the Internal Rectiﬁ er Cir-

cuit and VCC for the IC. Bypass VAUX with at least 1μF of

capacitance to ground. An active shunt regulator clamps

VAUX to 5.25V (typical).

VOUT (Pin 3/Pin 5): Main Output of the Converter. The

voltage at this pin is regulated to the voltage selected by

VS1 and VS2 (see Table 1). Connect this pin to a reservoir

capacitor or to a rechargeable battery. Any high current

pulse loads must be fed by the reservoir capacitor on

this pin.

VOUT2 (Pin 4/ Pin 6): Switched Output of the Converter.

Connect this pin to a switched load. This output is open

until VOUT_EN is driven high, then it is connected to VOUT

through a 1Ω PMOS switch. If not used, this pin should

be left open or tied to VOUT

VOUT2_EN (Pin 5/Pin 7): Enable Input for VOUT2. VOUT2

will be enabled when this pin is driven high. There is an

internal 5M pull-down resistor on this pin. If not used,

this pin can be left open or grounded.

PGOOD (Pin 6/Pin 8): Power Good Output. When VOUT

is within 7.5% of its programmed value, this pin will be

pulled up to the LDO voltage through a 1M resistor. If

VOUT drops 9% below its programmed value PGOOD will

go low. This pin can sink up to 100μA.

VLDO (Pin 7/Pin 9): Output of the 2.2V LDO. Connect a

2.2μF or larger ceramic capacitor from this pin to GND.

If not used, this pin should be tied to VAUX.

GND (Pins 8, 11, 16, Exposed Pad Pin 21/Pins 10, 13,

18): Ground Pins. Connect these pins directly to the ground

plane. The exposed pad serves as a ground connection and

as a means of conducting heat away from the die.

VS2 (Pin 20/Pin 2): V

OUT Select Pin 2. Connect this

pin to ground or VAUX to program the output voltage

(see Table 1).

VS1 (Pin 19/Pin 1): V

OUT Select Pin 1. Connect this

pin to ground or VAUX to program the output voltage

(see Table 1).

Table 1. Regulated Output Voltage Using Pins VS1 and VS2

VS2 VS1 VOUT

GND GND 2.35V

GND VAUX 3.3V

VAUX GND 4.1V

VAUX VAUX 5.0V

TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C, unless otherwise noted.

VLDO

20mV/DIV

ILDO

5mA/DIV

200μs/DIV 3109 G15

0mA TO 3mA LOAD STEP

CLDO = 2.2μF

1ms/DIV 3109 G16

CH2

VOUT2

1V/DIV

CH1

VOUT2_EN

1V/DIV

10mA LOAD ON VOUT2

COUT = 220μF

5SEC/DIV 3109 G17

CH2, VOUT

1V/DIV

CH1, VIN

50mV/DIV

CH3

VSTORE

1V/DIV

CH4, VLDO

1V/DIV

CSTORE = 470μF

VOUT LOAD = 100μA

LTC3109

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PIN FUNCTIONS

(DFN/SSOP)

C1B (Pin 9/Pin 11): Input to the Charge Pump and Rectiﬁ er

Circuit for Channel B. Connect a capacitor from this pin

to the secondary winding of the “B” step-up transformer.

See the Applications Information section for recommended

capacitor values.

C1A (Pin 18/Pin 20): Input to the Charge Pump and Recti-

ﬁ er Circuit for Channel A. Connect a capacitor from this pin

to the secondary winding of the “A” step-up transformer.

See the Applications Information section for recommended

capacitor values.

C2B (Pin 10/Pin 12): Input to the Gate Drive Circuit for

SWB. Connect a capacitor from this pin to the secondary

winding of the “B” step-up transformer. See the Applications

Information section for recommended capacitor values.

C2A (Pin 17/Pin 19): Input to the Gate Drive Circuit for

SWA. Connect a capacitor from this pin to the secondary

winding of the “A” step-up transformer. See the Applications

Information section for recommended capacitor values.

SWA (Pin 15/Pin 17): Connection to the Internal N-Chan-

nel Switch for Channel A. Connect this pin to the primary

winding of the “A” transformer.

SWB (Pin 12/Pin 14): Connection to the Internal N-Chan-

nel Switch for Channel B. Connect this pin to the primary

winding of the “B” transformer.

VINA (Pin 14/Pin 16): Connection to the Internal N-Channel

Switch for Channel A. Connect this pin to one side of the

input voltage source (see Typical Applications).

VINB (Pin 13/Pin 15): Connection to the Internal N-Channel

Switch for Channel B. Connect this pin to the other side of

the input voltage source (see Typical Applications).

LTC3109

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BLOCK DIAGRAM

VS1

VOUT

VOUT2_EN

VOUT2

1Ω

VOUT

COUT

VOUT2

VOUT

PROGRAM

VS2

VSTORE

VLDO

PG00D PG00D

VREF

1.2V

–

VREF

VSTORE

VOUT

VREF

VAUX

CAUX

1μF CLDO

2.2μF

VLDO

2.2V

VOUT

5.25V

C1A

CHARGE

CONTROL

POWER

SWITCHES

LDO

SYNC

RECTIFY

SYNC

RECTIFY

REFERENCE

C2A

C1B

C2B

SWA

VINA

VINB

SWB

••

VIN

GND

CSTORE

3109 BD

LTC3109

3109fa

OPERATION

(Refer to the Block Diagram)

The LTC3109 is designed to use two small external

step-up transformers to create an ultralow input voltage

step-up DC/DC converter and power manager that can

operate from input voltages of either polarity. This unique

capability enables energy harvesting from thermoelectric

generators (TEGs) in applications where the temperature

differential across the TEG may be of either (or unknown)

polarity. It can also operate from low level AC sources. It

is ideally suited for low power wireless sensors and other

applications in which surplus energy harvesting is used to

generate system power because traditional battery power

is inconvenient or impractical.

The LTC3109 is designed to manage the charging and

regulation of multiple outputs in a system in which the

average power draw is very low, but where periodic pulses

of higher load current may be required. This is typical of

wireless sensor applications, where the quiescent power

draw is extremely low most of the time, except for transmit

pulses when circuitry is powered up to make measure-

ments and transmit data.

The LTC3109 can also be used to trickle charge a standard

capacitor, super capacitor or rechargeable battery, using

energy harvested from a TEG or low level AC source.

Resonant Oscillator

The LTC3109 utilizes MOSFET switches to form a reso-

nant step-up oscillator that can operate from an input of

either polarity using external step-up transformers and

small coupling capacitors. This allows it to boost input

voltages as low as 30mV high enough to provide multiple

regulated output voltages for powering other circuits. The

frequency of oscillation is determined by the inductance

of the transformer secondary winding, and is typically

in the range of 10kHz to 100kHz. For input voltages as

low as 30mV, transformers with a turns ratio of about

1:100 is recommended. For operation from higher input

voltages, this ratio can be lower. See the Applications

Information section for more information on selecting

the transformers.

Charge Pump and Rectiﬁ er

The AC voltage produced on the secondary winding of

the transformer is boosted and rectiﬁ ed using an external

charge pump capacitor (from the secondary winding to

pin C1A or C1B) and the rectiﬁ ers internal to the LTC3109.

The rectiﬁ er circuit feeds current into the VAUX pin, provid-

ing charge to the external VAUX capacitor and the other

outputs.

VAUX

The active circuits within the LTC3109 are powered from

VAUX, which should be bypassed with a 1μF minimum

capacitor. Once VAUX exceeds 2.5V, the main VOUT is al-

lowed to start charging.

An internal shunt regulator limits the maximum voltage

on VAUX to 5.25V typical. It shunts to ground any excess

current into VAUX when there is no load on the converter

or the input source is generating more power than is

required by the load. This current should be limited to

15mA max.

Voltage Reference

The LTC3109 includes a precision, micropower reference,

for accurate regulated output voltages. This reference

becomes active as soon as VAUX exceeds 2V.

Synchronous Rectiﬁ ers

Once VAUX exceeds 2V, synchronous rectiﬁ ers in paral-

lel with each of the internal rectiﬁ er diodes take over the

job of rectifying the input voltage at pins C1A and C1B,

improving efﬁ ciency.

Low Dropout Linear Regulator (LDO)

The LTC3109 includes a low current LDO to provide a

regulated 2.2V output for powering low power proces-

sors or other low power ICs. The LDO is powered by

the higher of VAUX or VOUT

. This enables it to become

active as soon as VAUX has charged to 2.3V, while the

LTC3109

3109fa

VOUT storage capacitor is still charging. In the event of a

step load on the LDO output, current can come from the

main VOUT reservoir capacitor. The LDO requires a 2.2μF

ceramic capacitor for stability. Larger capacitor values

can be used without limitation, but will increase the time

it takes for all the outputs to charge up. The LDO output

is current limited to 5mA minimum.

VOUT

The main output voltage on VOUT is charged from the VAUX

supply, and is user-programmed to one of four regulated

voltages using the voltage select pins VS1 and VS2, ac-

cording to Table 2. Although the logic-threshold voltage

for VS1 and VS2 is 0.85V typical, it is recommended that

they be tied to ground or VAUX.

Table 2

VS2 VS1 VOUT

GND GND 2.35V

GND VAUX 3.3V

VAUX GND 4.1V

VAUX VAUX 5V

When the output voltage drops slightly below the regulated

value, the charging current will be enabled as long as VAUX

is greater than 2.5V. Once VOUT has reached the proper

value, the charging current is turned off. The resulting

ripple on VOUT is typically less than 20mV peak to peak

The internal programmable resistor divider, controlled by

VS1 and VS2, sets VOUT

, eliminating the need for very

high value external resistors that are susceptible to noise

pickup and board leakages.

In a typical application, a reservoir capacitor (typically a

few hundred microfarads) is connected to VOUT

. As soon

as VAUX exceeds 2.5V, the VOUT capacitor will begin to

charge up to its regulated voltage. The current available

to charge the capacitor will depend on the input voltage

and transformer turns ratio, but is limited to about 15mA

typical. Note that for very low input voltages, this current

may be in the range of 1μA to 1000μA.

PGOOD

A power good comparator monitors the VOUT voltage.

The PGOOD pin is an open-drain output with a weak pull-

up (1MΩ) to the LDO voltage. Once VOUT has charged

to within 7.5% of its programmed voltage, the PGOOD

output will go high. If VOUT drops more than 9% from its

programmed voltage, PGOOD will go low. The PGOOD

output is designed to drive a microprocessor or other

chip I/O and is not intended to drive a higher current load

such as an LED. The PGOOD pin can also be pulled low in

a wire-OR conﬁ guration with other circuitry.

VOUT2

VOUT2 is an output that can be turned on and off by the

host using the VOUT2_EN pin. When enabled, VOUT2 is con-

nected to VOUT through a 1Ω P-channel MOSFET switch.

This output, controlled by a host processor, can be used

to power external circuits such as sensors and ampliﬁ ers,

that don’t have a low power “sleep” or shutdown capabil-

ity. VOUT2 can be used to power these circuits only when

they are needed.

Minimizing the amount of decoupling capacitance on

VOUT2 enables it to be switched on and off faster, allow-

ing shorter pulse times and therefore smaller duty cycles

in applications such as a wireless sensor/transmitter. A

small VOUT2 capacitor will also minimize the energy that

will be wasted in charging the capacitor every time VOUT2

is enabled.

VOUT2 has a current limiting circuit that limits the peak

current to 0.3A typical.

The VOUT2 enable input has a typical threshold of 1V

with 100mV of hysteresis, making it logic compatible. If

VOUT2_EN (which has an internal 5M pull-down resistor)

is low, VOUT2 will be off. Driving VOUT2_EN high will turn

on the VOUT2 output.

Note that while VOUT2_EN is high, the current limiting cir-

cuitry for VOUT2 draws an extra 8μA of quiescent current

from VOUT

. This added current draw has a negligible effect

OPERATION

(Refer to the Block Diagram)

LTC3109

3109fa

on the application and capacitor sizing, since the load on

the VOUT2 output, when enabled, is likely to be orders of

magnitude higher than 8μA.

VSTORE

The VSTORE output can be used to charge a large storage

capacitor or rechargeable battery. Once VOUT has reached

regulation, the VSTORE output will be allowed to charge

up to the clamped VAUX voltage (5.25V typical). The

storage element on VSTORE can then be used to power

the system in the event that the input source is lost, or

is unable to provide the current demanded by the VOUT

VOUT2 and LDO outputs.

If VAUX drops below VSTORE, the LTC3109 will automati-

cally draw current from the storage element. Note that it

may take a long time to charge a large storage capacitor,

depending on the input energy available and the loading

on VOUT and VLDO.

Since the maximum charging current available at the

VSTORE output is limited to about 15mA, it can safely be

used to trickle charge NiCd or NiMH batteries for energy

storage when the input voltage is lost.

Note that VSTORE is not intended to supply high pulse

load currents to VOUT

. Any pulse load on VOUT must be

handled by the VOUT reservoir capacitor.

Short-Circuit Protection

All outputs of the LTC3109 are current limited to protect

against short circuits to ground.

Output Voltage Sequencing

A timing diagram showing the typical charging and voltage

sequencing of the outputs is shown in Figure 1. Note that

the horizontal (time) axis is not to scale, and is used for

illustration purposes to show the relative order in which

the output voltages come up.

OPERATION

(Refer to the Block Diagram)

5.0 VSTORE

PGOOD

VOUT

VLDO

3.0

2.0

1.0

3.0

2.0

1.0

2.5

5.0

2.5

0010203040

TIME (ms) 3109 F01

50 60 70 80

5.0

2.5

VOLTAGE (V)

VAUX

Figure 1. Output Voltage Sequencing

(with VOUT Programmed for 3.3V). Time Not to Scale

LTC3109

3109fa

APPLICATIONS INFORMATION

INTRODUCTION

The LTC3109 is designed to gather energy from very low

input voltage sources and convert it to usable output

voltages to power microprocessors, wireless transmit-

ters and analog sensors. Its architecture is speciﬁ cally

tailored to applications where the input voltage polarity is

unknown, or can change. This “auto-polarity” capability

makes it ideally suited to energy harvesting applications

using a TEG whose temperature differential may be of

either polarity.

Applications such as wireless sensors typically require

much more peak power, and at higher voltages, than

the input voltage source can produce. The LTC3109 is

designed to accumulate and manage energy over a long

period of time to enable short power pulses for acquiring

and transmitting data. The pulses must occur at a low

enough duty cycle that the total output energy during the

pulse does not exceed the average source power integrated

over the accumulation time between pulses. For many

applications, this time between pulses could be seconds,

minutes or hours.

The PGOOD signal can be used to enable a sleeping

microprocessor or other circuitry when VOUT reaches

regulation, indicating that enough energy is available for

a transmit pulse.

INPUT VOLTAGE SOURCES

The LTC3109 can operate from a number of low input

voltage sources, such as Peltier cells (thermoelectric

generators), or low level AC sources. The minimum input

voltage required for a given application will depend on the

transformer turns ratios, the load power required, and the

internal DC resistance (ESR) of the voltage source. Lower

ESR sources will allow operation from lower input voltages,

and provide higher output power capability.

For a given transformer turns ratio, there is a maximum

recommended input voltage to avoid excessively high

secondary voltages and power dissipation in the shunt

regulator. It is recommended that the maximum input

voltage times the turns ratio be less than 50.

Note that a low ESR decoupling capacitor may be required

across a DC input source to prevent large voltage droop and

ripple caused by the source’s ESR and the peak primary

switching current (which can reach hundreds of milliamps).

Since the input voltage may be of either polarity, a ceramic

capacitor is recommended.

PELTIER CELL (THERMOELECTRIC GENERATOR)

A Peltier cell is made up of a large number of series-con-

nected P-N junctions, sandwiched between two parallel

ceramic plates. Although Peltier cells are often used as

coolers by applying a DC voltage to their inputs, they will

also generate a DC output voltage, using the Seebeck effect,

when the two plates are at different temperatures.

When used in this manner, they are referred to as thermo-

electric generators (TEGs). The polarity of the output voltage

will depend on the polarity of the temperature differential

between the TEG plates. The magnitude of the output volt-

age is proportional to the magnitude of the temperature

differential between the plates.

The low voltage capability of the LTC3109 design allows it

to operate from a typical TEG with temperature differentials

as low as 1°C of either polarity, making it ideal for harvest-

ing energy in applications where a temperature difference

exists between two surfaces or between a surface and

the ambient temperature. The internal resistance (ESR)

of most TEGs is in the range of 1Ω to 5Ω, allowing for

reasonable power transfer. The curves in Figure 2 show the

open-circuit output voltage and maximum power transfer

for a typical TEG with an ESR of 2Ω, over a 20°C range of

temperature differential (of either polarity).

dT (°C)

TEG VOPEN-CIRCUIT (mV)

TEG MAXIMUM POUT – IDEAL (mW)

100

1000

0.1

100

10 100

3109 F02

TEG: 30mm SQUARE

127 COUPLES

R = 2Ω

VOC MAX POUT

(IDEAL)

Figure 2. Typical Performance of a Peltier Cell

Acting as a Power Generator (TEG)

LTC3109

3109fa

APPLICATIONS INFORMATION

TEG LOAD MATCHING

The LTC3109 was designed to present an input resistance

(load) in the range of 2Ω to 10Ω, depending on input volt-

age, transformer turns ratio and the C1A and C2A capacitor

values (as shown in the Typical Performance curves). For

a given turns ratio, as the input voltage drops, the input

resistance increases. This feature allows the LTC3109 to

optimize power transfer from sources with a few Ohms

of source resistance, such as a typical TEG. Note that a

lower source resistance will always provide more output

current capability by providing a higher input voltage

under load.

UNIPOLAR APPLICATIONS

The LTC3109 can also be conﬁ gured to operate from two

independent unipolar voltage sources, such as two TEGs

in different locations. In this conﬁ guration, energy can be

harvested from either or both sources simultaneously. See

the Typical Applications for an example.

The LTC3109 can also be conﬁ gured to operate from a

single unipolar source, using a single step-up transformer,

by ganging its VIN and SW pins together. In this manner,

it can extract the most energy from very low resistance

sources. See Figure 3 for an example of this conﬁ guration,

along with the performance curves.

PELTIER CELL (TEG) SUPPLIERS

Peltier cells are available in a wide range of sizes and power

capabilities, from less than 10mm square to over 50mm

square. They are typically 2mm to 5mm in height. A list

of some Peltier cell manufacturers is given in Table 3 and

some recommended part numbers in Table 4.

COMPONENT SELECTION

Step-Up Transformer

The turns ratio of the step-up transformers will determine

how low the input voltage can be for the converter to start.

Due to the auto-polarity architecture, two identical step-up

transformers should be used, unless the temperature drop

across the TEG is signiﬁ cantly different in one polarity, in

which case the ratios may be different.

Table 3. Peltier Cell Manufacturers

CUI Inc

www.cui.com

Ferrotec

www.ferrotec.com/products/thermal/modules/

Fujitaka

www.fujitaka.com/pub/peltier/english/thermoelectric_power.html

Hi-Z Technology

www.hi-z.com

Kryotherm

www.kryotherm

Laird Technologies

www.lairdtech.com

Micropelt

www.micropelt.com

Nextreme

www.nextreme.com

TE Technology

www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html

Tellurex

www.tellurex.com/

Table 4. Recommended TEG Part Numbers by Size

MANUFACTURER 15mm 20mm 30mm 40mm

CUI Inc. (Distributor) CP60133 CP60233 CP60333 CP85438

Ferrotec 9501/031/030 B 9501/071/040 B 9500/097/090 B 9500/127/100 B

Fujitaka FPH13106NC FPH17106NC FPH17108AC FPH112708AC

Kryotherm TGM-127-1.0-0.8 LCB-127-1.4-1.15

Laird Technology PT6.7.F2.3030.W6 PT8.12.F2.4040.TA.W6

Marlow Industries RC3-8-01 RC6-6-01 RC12-8-01LS

Tellurex C2-15-0405 C2-20-0409 C2-30-1505 C2-40-1509

TE Technology TE-31-1.0-1.3 TE-31-1.4-1.15 TE-71-1.4-1.15 TE-127-1.4-1.05

LTC3109

3109fa

APPLICATIONS INFORMATION

GND 10μF

LTC3109

3109 F03a

C1A

1nF

330k

•• VOUT2 VOUT2

C2A

C1B

C2B

SWB

VINB

VS1

VOUT

SET VS2

SWA

VINA

VOUT

VLDO VLDO

VOUT

2.2μF

CIN

VIN

PG00D

VOUT2_EN

PG00D

VOUT2_ENABLE

NOTE: VALUES FOR CIN, T1, C1 AND COUT

ARE DETERMINED BY THE APPLICATION

VSTORE

VAUX

COUT

Figure 3. Unipolar Application

Typical IVOUT vs VIN for Unipolar

Conﬁ guration

Typical Efﬁ ciency vs VIN for

Unipolar Conﬁ guration

VIN (mV)

IVOUT (μA)

100

1000

10000

100 1000

3109 F03b

1:100, C1 = 6.8nF

1:50, C1 = 33nF

1:20, C1 = 68nF

VOUT = 3.3V

VIN (mV)

EFFICIENCY (%)

100 1000

3109 F03c

1:100, C1 = 6.8nF

1:50, C1 = 33nF

1:20, C1 = 68nF

Typical Input Current vs VIN for

Unipolar Conﬁ guration

Typical RIN vs VIN for Unipolar

Conﬁ guration

VIN (mV)

200

INPUT CURRENT (mA)

300

400

100 1000

3109 F03d

100

600

500

150

250

350

550

450

1:100, C1 = 6.8nF

1:50, C1 = 33nF

1:20, C1 = 68nF

VIN (mV)

INPUT RESISTANCE (Ω)

1.0

2.0

100 1000

3109 F03e

4.0

3.0

1.5

0.5

3.5

2.5

1:100, C1 = 6.8nF

1:50, C1 = 33nF

1:20, C1 = 68nF

dT (°K)

100

0.1

POUT (mW)

3109 F03f

VOUT = 5V

VOUT = 3.3V

FERROTEC 9500/127/100B, 40mm TEG

C1 = 33nF,

T1 = COILCRAFT LPR6235-123QML

1:50 RATIO

Typical PVOUT vs dT for Unipolar

Conﬁ guration

LTC3109

3109fa

APPLICATIONS INFORMATION

Using a 1:100 primary-secondary ratio yields start-up

voltages as low as 30mV. Other factors that affect per-

formance are the resistance of the transformer windings

and the inductance of the windings. Higher DC resistance

will result in lower efﬁ ciency and higher start-up volt-

ages. The secondary winding inductance will determine

the resonant frequency of the oscillator, according to the

formula below.

Freq =1

2•π•L

SEC •C Hz

where LSEC is the inductance of one of the secondary

windings and C is the load capacitance on the second-

ary winding. This is comprised of the input capacitance

at pin C2A or C2B, typically 70pF each, in parallel with

the transformer secondary winding’s shunt capacitance.

The recommended resonant frequency is in the range of

10kHz to 100kHz. Note that loading will also affect the

resonant frequency. See Table 5 for some recommended

transformers.

Table 5. Recommended Transformers

VENDOR

TYPICAL START-

UP VOLTAGE PART NUMBER

Coilcraft

www.coilcraft.com

25mV

35mV

85mV

LPR6235-752SML (1:100 ratio)

LPR6235-123QML (1:50 ratio)

LPR6235-253PML (1:20 ratio)

Würth

www.we-online

25mV

35mV

85mV

S11100034 (1:100 Ratio)

S11100033 (1:50 Ratio)

S11100032 (1:20 Ratio)

USING EXTERNAL CHARGE PUMP RECTIFIERS

The synchronous rectiﬁ ers in the LTC3109 have been

optimized for low frequency, low current operation, typical

of low input voltage applications. For applications where

the resonant oscillator frequency exceeds 100kHz, or a

transformer turns ratio of less than 1:20 is used, or the

C1A and C1B capacitor values are greater than 68nF, the

use of external charge pump rectiﬁ ers (1N4148 or 1N914

or equivalent) is recommended. See the Typical Application

circuits for an example. Avoid the use of Schottky recti-

ﬁ ers, as their low forward voltage increases the minimum

start-up voltage.

C1 CAPACITOR

The charge pump capacitor that is connected from each

transformer’s secondary winding to the corresponding

C1A and C1B pins has an effect on converter input resis-

tance and maximum output current capability. Generally

a minimum value of 1nF is recommended when operating

from very low input voltages using a transformer with

a ratio of 1:100. Capacitor values of 2.2nF to 10nF will

provide higher output current at higher input voltages,

however larger capacitor values can compromise perfor-

mance when operating at low input voltage or with high

resistance sources. For higher input voltages and lower

turns ratios, the value of the C1 capacitor can be increased

for higher output current capability. Refer to the Typical

Applications examples for the recommended value for a

given turns ratio.

C2 CAPACITOR

The C2 capacitors connect pins C2A and C2B to their

respective transformer secondary windings. For most

applications a capacitor value of 470pF is recommended.

Smaller capacitor values tend to raise the minimum

start-up voltage, and larger capacitor values can lower

efﬁ ciency.

Note that the C1 and C2 capacitors must have a voltage

rating greater than the maximum input voltage times the

transformer turns ratio.

VOUT AND VSTORE CAPACITOR

For pulsed load applications, the VOUT capacitor should

be sized to provide the necessary current when the load

is pulsed on. The capacitor value required will be dictated

by the load current (ILOAD), the duration of the load pulse

(tPULSE), and the amount of VOUT voltage droop the ap-

plication can tolerate (ΔVOUT). The capacitor must be

rated for whatever voltage has been selected for VOUT by

VS1 and VS2:

COUT(μF) ≥ILOAD(mA)•t

PULSE(ms)

ΔVOUT (V)

LTC3109

3109fa

APPLICATIONS INFORMATION

Note that there must be enough energy available from the

input voltage source for VOUT to recharge the capacitor

during the interval between load pulses (as discussed in

Design Example 1). Reducing the duty cycle of the load

pulse will allow operation with less input energy.

The VSTORE capacitor may be of very large value (thou-

sands of microfarads or even Farads), to provide energy

storage at times when the input voltage is lost. Note that

this capacitor can charge all the way to the VAUX clamp

voltage of 5.25V typical (regardless of the settings for

VOUT), so be sure that the holdup capacitor has a work-

ing voltage rating of at least 5.5V at the temperature that

it will be used.

The VSTORE input is not designed to provide high pulse

load currents to VOUT

. The current path from VSTORE to

VOUT is limited to about 26mA max.

The VSTORE capacitor can be sized using the following

formula:

CSTORE ≥7μA +IQ+ILDO +IPULSE •t

PULSE •f

()

•t

STORE

5.25 – V

OUT

where 7μA is the quiescent current of the LTC3109, IQ is

the load on VOUT in between pulses, ILDO is the load on

the LDO between pulses, IPULSE is the total load during the

pulse, tPULSE is the duration of the pulse, f is the frequency

of the pulses, tSTORE is the total storage time required

and VOUT is the output voltage required. Note that for a

programmed output voltage of 5V, the VSTORE capacitor

cannot provide any beneﬁ cial storage time to VOUT

To minimize losses and capacitor charge time, all capaci-

tors used for VOUT and VSTORE should be low leakage.

See Table 6 for recommended storage capacitors.

Table 6. Recommended Storage Capacitors

VENDOR PART NUMBER/SERIES

AVX

www.avx.com

BestCap Series

TAJ and TPS Series Tantalum

Cap-XX

www.cap-xx.com

GZ Series

Cooper/Bussman

www.bussmann.com/3/PowerStor.html

KR Series

P Series

Vishay/Sprague

www.vishay.com/capacitors

Tantamount 592D

595D Tantalum

Note that storage capacitors requiring voltage balancing

resistors are not recommended due to the steady-state

current draw of the resistors.

PCB LAYOUT GUIDELINES

Due to the rather low switching frequency of the resonant

converter and the low power levels involved, PCB layout

is not as critical as with many other DC/DC converters.

There are however, a number of things to consider.

Due to the very low input voltages the circuit operates from,

the connections to VIN, the primary of the transformers

and the SW, VIN and GND pins of the LTC3109 should be

designed to minimize voltage drop from stray resistance,

and able to carry currents as high as 500mA. Any small

voltage drop in the primary winding conduction path will

lower efﬁ ciency and increase start-up voltage and capaci-

tor charge time.

Also, due to the low charge currents available at the out-

puts of the LTC3109, any sources of leakage current on

the output voltage pins must be minimized. An example

board layout is shown in Figure 4.

Figure 4. Example Component Placement for 2-Layer PC Board

(QFN Package). Note That VSTORE and VOUT Capacitor Sizes

are Application Dependent

LTC3109

3109fa

APPLICATIONS INFORMATION

DESIGN EXAMPLE 1

This design example will explain how to calculate the

necessary reservoir capacitor value for VOUT in pulsed-

load applications, such as a wireless sensor/transmitter.

In these types of applications, the load is very small for a

majority of the time (while the circuitry is in a low power

sleep state), with pulses of load current occurring periodi-

cally during a transmit burst.

The reservoir capacitor on VOUT supports the load during

the transmit pulse; the long sleep time between pulses

allows the LTC3109 to accumulate energy and recharge

the capacitor (either from the input voltage source or the

storage capacitor). A method for calculating the maximum

rate at which the load pulses can occur for a given output

current from the LTC3109 will also be shown.

In this example, VOUT is set to 3.3V, and the maximum

allowed voltage droop during a transmit pulse is 10%, or

0.33V. The duration of a transmit pulse is 5ms, with a total

average current requirement of 20mA during the pulse.

Given these factors, the minimum required capacitance

on VOUT is:

COUT μF

()

≥20mA • 5ms

0.33V =303μF

Note that this equation neglects the effect of capacitor ESR

on output voltage droop. For ceramic capacitors and low

ESR tantalum capacitors, the ESR will have a negligible

effect at these load currents. However, beware of the voltage

coefﬁ cient of ceramic capacitors, especially those in small

case sizes. This greatly reduces the effective capacitance

when a DC bias is applied.

A standard value of 330μF could be used for COUT in

this case. Note that the load current is the total current

draw on VOUT

, VOUT2 and VLDO, since the current for all

of these outputs must come from VOUT during a pulse.

Current contribution from the capacitor on VSTORE is not

considered, since it may not be able to recharge between

pulses. Also, it is assumed that the harvested charge

current from the LTC3109 is negligible compared to the

magnitude of the load current during the pulse.

To calculate the maximum rate at which load pulses can

occur, you must know how much charge current is avail-

able from the LTC3109 VOUT pin given the input voltage

source being used. This number is best found empirically,

since there are many factors affecting the efﬁ ciency of the

converter. You must also know what the total load cur-

rent is on VOUT during the sleep state (between pulses).

Note that this must include any losses, such as storage

capacitor leakage.

Let’s assume that the charge current available from the

LTC3109 is 150μA and the total current draw on VOUT and

VLDO in the sleep state is 17μA, including capacitor leakage.

We’ll also use the value of 330μF for the VOUT capacitor.

The maximum transmit rate (neglecting the duration of

the transmit pulse, which is very short compared to the

period) is then given by:

T=330μF • 0.33V

150μA – 17μA =0.82sec or fMAX =1.2Hz

Therefore, in this application example, the circuit can sup-

port a 5ms transmit pulse of 20mA every 0.82 seconds.

It can be seen that for systems that only need to transmit

every few seconds (or minutes or hours), the average

charge current required is extremely small, as long as

the sleep or standby current is low. Even if the available

charge current in the example above was only 21μA, if the

sleep current was only 5μA, it could still transmit a pulse

every seven seconds.

The following formula will allow you to calculate the time

it will take to charge the LDO output capacitor and the

VOUT capacitor the ﬁ rst time, from zero volts. Here again,

the charge current available from the LTC3109 must be

known. For this calculation, it is assumed that the LDO

output capacitor is 2.2μF:

tLDO =2.2V • 2.2μF

ICHG –I

LDO

If there was 150μA of charge current available and a 5μA

load on the LDO (when the processor is sleeping), the time

for the LDO to reach regulation would be only 33ms.

LTC3109

3109fa

APPLICATIONS INFORMATION

The time for VOUT to charge and reach regulation can be

calculated by the formula below, which assumes VOUT is

programmed to 3.3V and COUT is 330μF:

tVOUT =3.3V • 330μF

ICHG –I

VOUT –I

LDO

+tLDO

With 150μA of charge current available and 5μA of load on

both VOUT

and VLDO, the time for VOUT to reach regula-

tion after the initial application of power would be 7.81

seconds.

DESIGN EXAMPLE 2

In most pulsed-load applications, the duration, magnitude

and frequency of the load current pulses are known and

ﬁ xed. In these cases, the average charge current required

from the LTC3109 to support the average load must be

calculated, which can be easily done by the following:

ICHG ≥IQ+IPULSE •t

PULSE

where IQ is the sleep current supplied by VOUT and VLDO

to the external circuitry in-between load pulses, including

output capacitor leakage, IPULSE is the total load current

during the pulse, tPULSE is the duration of the load pulse

and T is the pulse period (essentially the time between

load pulses).

In this example, IQ is 5μA, IPULSE is 100mA, tPULSE is 5ms

and T is one hour. The average charge current required

from the LTC3109 would be:

ICHG ≥5μA +100mA • 0.005sec

3600sec =5.14μA

Therefore, if the LTC3109 has an input voltage that allows

it to supply a charge current greater than just 5.14μA, the

application can support 100mA pulses lasting 5ms every

hour. It can be seen that the sleep current of 5μA is the

dominant factor in this example, because the transmit

duty cycle is so small (0.00014%). Note that for a VOUT

of 3.3V, the average power required by this application is

only 17μW (not including converter losses).

Keep in mind that the charge current available from the

LTC3109 has no effect on the sizing of the VOUT capacitor,

and the VOUT capacitor has no effect on the maximum

allowed pulse rate.

LTC3109

3109fa

TYPICAL APPLICATIONS

Energy Harvester Operates from Small Temperature Differentials of Either Polarity

GND 1μF

5.25V

2.2V

LTC3109

3.3V

CSTORE

3109 TA02

C1A

1nF

2.2μF

470pF

1nF

470pF

1:100

TEG

(THERMOELECTRIC GENERATOR)

±30mV TO ±500mV

••

1:100

••

VOUT2

C2A

C1B

C2B

SWB

VINB

VS1

VS2

T1, T2: COILCRAFT LPR6235-752SML

SWA

VINA

VOUT

VLDO

PG00D

VOUT2_EN

VSTORE

VAUX +

470μF

OPTIONAL SWITCHED OUTPUT FOR SENSORS

μP

LOW POWER

RADIO

SENSOR(S)

Li-Ion Battery Charger and LDO Operates from a Low Level AC Input

GND 1μF

2.2V

LTC3109

3109 TA03

C1A

1nF

Li-Ion

BATTERY

*THE LTC4070 IS A PRECISION BATTERY

CHARGER OFFERING UNDERVOLTAGE

PROTECTION, WITH A TYPICAL SUPPLY

CURRENT OF ONLY 0.45μA

FAIRCHILD

FDG328P

470pF

60Hz

1nF

470pF

1:100

50mV TO

300mV RMS

1:100

••

VOUT2

C2A

C1B

C2B

SWB

VINB

T1, T2: COILCRAFT

LPR6235-752SML

VS1

VS2

SWA

VINA

VOUT

VLDO VLDO

TO LOAD

4.1V

2.2μF

PG00D

VOUT2_EN

VSTORE

VAUX

LBO

NTC

VCC

ADJ

HBO

DRV

NTCBIAS

LTC4070*

GND

LTC3109

3109fa

TYPICAL APPLICATIONS

Dual-Input Energy Harvester Generates 5V and 2.2V from Either or Both TEGs,

Operating at Different Temperatures of Fixed Polarity

GND 1μF

2.2V

LTC3109

5V VOUT

VLDO

3109 TA04

C1A

1nF

–

2.2μF

470pF

THERMOELECTRIC

GENERATOR

25mV TO 500mV

THERMOELECTRIC

GENERATOR OR

THERMOPILE

35mV TO 1000mV

4.7nF

470pF

COILCRAFT

LPR6235-752SML

1:100

••

COILCRAFT

LPR6235-123QML

1:50

••

VOUT2

C2A

C1B

C2B

SWB

VINB

VS1

VS2

SWA

VINA

VOUT

VLDO

PG00D PG00D

*THE VALUE OF THE COUT CAPACITOR IS

DETEMINED BY THE LOAD CHARACTERISTICS

VOUT2_EN

VSTORE

VAUX

COUT*

Unipolar Energy Harvester Charges Battery Backup

GND 1μF

LTC3109

3109 TA06a

C1A

33nF

Li-Ion

BATTERY

FAIRCHILD

FDG328P

1nF

330k

1:50

–•• VOUT2

C2A

C1B

C2B

SWB

VINB

T1: COILCRAFT

LPR6235-123QML

VS1

VS2

SWA

VINA

VOUT

VLDO VLDO

PGOOD

VOUT

3.3V

4.1V

2.2μF

47μF

THERMOELECTIC

GENERATOR

FERROTEC 9500/127/100B

330μF

2.2V

PG00D

VOUT2_EN

VSTORE

VAUX

LBO

NTC

VCC

ADJ

HBO

DRV

NTCBIAS

LTC4070

GND

dT (°K)

POUT (mW)

3.0

4.0

5.0

3109 TA06b

2.0

1.0

2.5

3.5

4.5

1.5

0.5

021 43 67 9

510

FERROTEC 9500/127/100B

C1 = 33nF

T1 = COILCRAFT LPR6235-123QML

1:50 RATIO

VOUT = 3.3V

Typical PVOUT vs dT for Unipolar

Conﬁ guration

LTC3109

3109fa

PACKAGE DESCRIPTION

4.00 ±0.10

NOTE:

1. DRAWING IS PROPOSED TO BE MADE A JEDEC PACKAGE OUTLINE MO-220

VARIATION (WGGD-1)—TO BE APPROVED

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

PIN 1

TOP MARK

(NOTE 6)

0.40 ±0.10

2019

BOTTOM VIEW—EXPOSED PAD

2.00 REF

2.45 ±0.10

0.75 ±0.05 R = 0.115

TYP

R = 0.05

TYP

0.25 ±0.05

0.50 BSC

0.200 REF

0.00 – 0.05

(UF20) QFN 01-07 REV A

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

0.70 ±0.05

0.25 ±0.05

0.50 BSC

2.00 REF 2.45 ±0.05

3.10 ±0.05

4.50 ±0.05

PACKAGE OUTLINE

PIN 1 NOTCH

R = 0.20 TYP

OR 0.35 w 45°

CHAMFER

2.45 ±0.10

2.45 ±0.05

UF Package

20-Lead Plastic QFN (4mm w 4mm)

(Reference LTC DWG # 05-08-1710 Rev A)

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

LTC3109

3109fa

PACKAGE DESCRIPTION

.337 – .344*

(8.560 – 8.738)

GN20 REV B 0212

345678910

.229 – .244

(5.817 – 6.198)

.150 – .157**

(3.810 – 3.988)

1617181920 15 14 13 12 11

.016 – .050

(0.406 – 1.270)

.015 ±.004

(0.38 ±0.10) w 45s

0° – 8° TYP

.0075 – .0098

(0.19 – 0.25)

.0532 – .0688

(1.35 – 1.75)

.008 – .012

(0.203 – 0.305)

TYP

.004 – .0098

(0.102 – 0.249)

.0250

(0.635)

BSC

.058

(1.473)

REF

.254 MIN

RECOMMENDED SOLDER PAD LAYOUT

.150 – .165

.0250 BSC.0165 ±.0015

.045 ±.005

* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

INCHES

(MILLIMETERS)

NOTE:

1. CONTROLLING DIMENSION: INCHES

2. DIMENSIONS ARE IN

3. DRAWING NOT TO SCALE

4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE

GN Package

20-Lead Plastic SSOP (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1641 Rev B)

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

LTC3109

3109fa

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-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

A 06/12 Added vendor Information to Table 5 15

LTC3109

3109fa

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

LT 0612 REV A • PRINTED IN USA

RELATED PARTS

TYPICAL APPLICATION

Unipolar TEG Energy Harvester for Low Resistance/High Current Inputs,

Using External Charge Pump Rectiﬁ ers

GND 10μF

2.2V

LTC3109

3.3V VOUT

VOUT2

SWITCHED VOUT GOES HIGH

WHEN PGOOD IS HIGH

VLDO

3109 TA05

C1A

VAUX

BAS31

1.0μF

1nF

2.2μF

0.1μF

70mV TO 1V

COILCRAFT

LPR6235-253PML

1:20

•• VOUT2

C2A

C1B

C2B

SWB

VINB

VS1

VS2

SWA

VINA

VOUT

VLDO

PG00D PG00D

VOUT2_EN

VSTOREVAUX

VAUX

COUT

CSTORE

PART NUMBER DESCRIPTION COMMENTS

LTC3108/

LTC3108-1

Ultralow Voltage Step-Up Converter and

Power Manager

VIN: 0.02V to 1V, VOUT = 2.2V, 2.35V, 3.3V, 4.1V, 5V, IQ = 6μA,

4mm × 3mm DFN-12, SSOP-16; LTC3108-1 VOUT = 2.2V, 2.5V, 3V, 3.7V, 4.5V

LTC4070 Micropower Shunt Battery Charger 1% Float Voltage Accuracy, 50mA Max Shunt Current, VOUT = 4.0V, 4.1V, 4.2V,

IQ = 450nA, 2mm × 3mm DFN-8, MSOP-8

LTC1041 Bang-Bang Controller VIN: 2.8V to 16V; VOUT(MIN) = Adj; IQ = 1.2mA; ISD < 1μA; SO-8 Package

LTC1389 Nanopower Precision Shunt Voltage Reference VOUT(MIN) = 1.25V; IQ = 0.8μA; SO-8 Package

LT1672/LT1673/

LT1674

Single-/Dual-/Quad-Precision 2μA Rail-to-Rail

Op Amps

SO-8, SO-14 and MSOP-8 Packages

LT3009 3μA IQ, 20mA Linear Regulator VIN: 1.6V to 20V; VOUT(MIN): 0.6V to Adj, 1.2V, 1.5V, 1.8V, 2.5V, 3.3V,

5V to Fixed; IQ = 3μA; ISD < 1μA; 2mm × 2mm DFN-8 and SC70 Packages

LTC3588-1 Piezoelectric Energy Generator with Integrated

High Efﬁ ciency Buck Converter

VIN: 2.7V to 20V; VOUT(MIN): Fixed to 1.8V, 2.5V, 3.3V, 3.6V; IQ = 0.95μA;

3mm × 3mm DFN-10 and MSOP-10E Packages

LT8410/LT8410-1 Micropower 25mA/8mA Low Noise Boost Converter

with Integrated Schottky Diode and Output

Disconnect

VIN: 2.6V to 16V; VOUT(MIN) = 40VMAX; IQ = 8.5μA; ISD < 1μA;

2mm × 2mm DFN-8 Package

IVOUT vs VIN

VIN (mV)

IVOUT (mA)

800

3109 TA05b

0200 400 600

100 300 500 700

1:20 RATIO

C1 = 1μF

EXTERNAL DIODES

TYPICAL

VIN (mV)

EFFICIENCY (%)

100 1000

3109 TA05c

Efﬁ ciency vs VIN