Datasheet

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LTC3109

3109fb

For more information www.linear.com/LTC3109

Typical applicaTion

FeaTures DescripTion

Auto-Polarity, Ultralow

Voltage Step-Up Converter

and Power Manager

The LT C

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 ﬁxed 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 efﬁciency 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.

OUT

Current vs TEG Voltage

applicaTions

Operates from Inputs as Low as ±30mV

Less Than ±1°C Needed Across TEG to Harvest

Energy

Proprietary Auto-Polarity Architecture

Complete Energy Harvesting Power Management

System

– Selectable V

OUT

of 2.35V, 3.3V, 4.1V or 5V

– 2.2V, 5mA LDO

– Logic-Controlled Output

– Energy Storage Capability for Operation During

Power Interruption

Power Good Indicator

Uses Compact Step-up Transformers

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

20-Lead SSOP

Remote Sensor and Radio Power

HVAC Systems

Automatic Metering

Building Automation

Predictive Maintenance

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

STORE

3109 TA01a

C1A

1nF

2.2µF

470pF

47µF

1nF

470pF

1:100

TEG

(THERMOELECTRIC GENERATOR)

±30mV TO ±500mV

• •

1:100

• •

OUT2

C2A

C1B

C2B

SWB

INB

VS1

VS2

SWA

INA

OUT

VLDO

PG00D

OUT2_EN

VSTOREVAUX

VAUX

470µF

OPTIONAL SWITCHED OUTPUT FOR SENSORS

µP

LOW POWER

RADIO

SENSOR(S)

TEG

(mV)

–300

VOUT

(µA)

100

300

400

500

100

900

3109 TA01b

200

–100

–200

200

0 300

600

700

800

1:100 TRANSFORMERS

C1A = C1B = 1nF

OUT

= 3.3V

Summary of content (24 pages)

PAGE 1
LTC3109 Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager Description Features n n n n n n n Operates from Inputs as Low as ±30mV Less Than ±1°C Needed Across TEG to Harvest Energy Proprietary Auto-Polarity Architecture Complete Energy Harvesting Power Management System – Selectable VOUT of 2.35V, 3.3V, 4.1V or 5V – 2.
PAGE 2
LTC3109 Absolute Maximum Ratings (Note 1) 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 VLDO, VSTORE............................................. –0.3V to 6V VAUX.......................................................
PAGE 3
LTC3109 Electrical Characteristics The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are for TA = 25°C (Note 2). VAUX = 5V unless otherwise noted.
PAGE 4
LTC3109 Electrical Characteristics 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.
PAGE 5
LTC3109 Typical Performance Characteristics TA = 25°C, unless otherwise noted. 5.5 3.0 0.75 VLDO VOUT 0 5.3 –0.25 PVOUT (mW) 0.25 PVOUT vs dT and TEG Size, 1:100 Ratio, VOUT = 5V 2.5 5.4 0.50 VAUX (V) CHANGE (%) (RELATIVE TO 25°C) 1.00 VAUX Clamp Voltage vs Shunt Current VOUT and VLDO vs Temperature 5.2 FERROTEC 9500/127/100B 40mm 2.0 1.5 1.0 –0.50 5.1 0.5 –0.75 –1.00 –50 –25 75 50 25 TEMPERATURE (°C) 0 100 5.
PAGE 6
LTC3109 Typical Performance Characteristics TA = 25°C, unless otherwise noted. LDO Step Load Response Enable Input and VOUT2 Running on Storage Capacitor CSTORE = 470µF VOUT LOAD = 100µA VLDO 20mV/DIV CH3 VSTORE 1V/DIV CH2 VOUT2 1V/DIV ILDO 5mA/DIV CH2, VOUT 1V/DIV CH4, VLDO 1V/DIV CH1, VIN 50mV/DIV CH1 VOUT2_EN 1V/DIV 200µs/DIV 3109 G15 (QFN/SSOP) VSTORE (Pin 1/Pin 3): Output for the Storage Capacitor or Battery.
PAGE 7
LTC3109 Pin Functions (DFN/SSOP) C1B (Pin 9/Pin 11): Input to the Charge Pump and Rectifier 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 Rectifier Circuit for Channel A. Connect a capacitor from this pin to the secondary winding of the “A” step-up transformer.
PAGE 8
LTC3109 Block Diagram SYNC RECTIFY C1B REFERENCE VREF 1.2V VOUT2 1Ω SYNC RECTIFY • • VOUT2_EN VOUT C1A 5.25V + C2A VIN C2B VOUT VINA • • SWB + – POWER SWITCHES VREF COUT VOUT PROGRAM VS2 CHARGE CONTROL VOUT VS1 VLDO VSTORE SWA VOUT2 1M + PG00D PG00D – VINB VSTORE VOUT VREF VAUX CAUX 1µF 8 + LDO VLDO CSTORE GND 3109 BD 2.2V CLDO 2.2µF 3109fb For more information www.linear.
PAGE 9
LTC3109 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.
PAGE 10
LTC3109 Operation (Refer to the Block Diagram) 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.
PAGE 11
LTC3109 Operation (Refer to the Block Diagram) 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).
PAGE 12
LTC3109 Applications Information The LTC3109 is designed to gather energy from very low input voltage sources and convert it to usable output voltages to power microprocessors, wireless transmitters and analog sensors. Its architecture is specifically 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.
PAGE 13
LTC3109 Applications Information TEG Load Matching Unipolar Applications The LTC3109 was designed to present an input resistance (load) in the range of 2Ω to 10Ω, depending on input voltage, 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.
PAGE 14
LTC3109 Applications Information VIN + • T1 CIN C1 • C1A 1nF VOUT2 VOUT2 LTC3109 330k VOUT SET C2A VOUT + VLDO SWA VINA C1B C2B PG00D SWB VINB VOUT2_EN VS1 VSTORE VAUX VS2 GND VLDO 2.2µF VOUT COUT PG00D VOUT2_ENABLE 10µF NOTE: VALUES FOR CIN, T1, C1 AND COUT ARE DETERMINED BY THE APPLICATION 3109 F03a Figure 3.
PAGE 15
LTC3109 Applications Information Using a 1:100 primary-secondary ratio yields start-up voltages as low as 30mV. Other factors that affect performance are the resistance of the transformer windings and the inductance of the windings. Higher DC resistance will result in lower efficiency and higher start-up voltages. The secondary winding inductance will determine the resonant frequency of the oscillator, according to the formula below.
PAGE 16
LTC3109 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. Note that storage capacitors requiring voltage balancing resistors are not recommended due to the steady-state current draw of the resistors.
PAGE 17
LTC3109 Applications Information Design example 1 This design example will explain how to calculate the necessary reservoir capacitor value for VOUT in pulsedload 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 periodically during a transmit burst.
PAGE 18
LTC3109 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: t VOUT = 3.3V • 330µF + tLDO ICHG – IVOUT – ILDO ICHG ≥ 5µA + With 150µA of charge current available and 5µA of load on both VOUT and VLDO, the time for VOUT to reach regulation after the initial application of power would be 7.81 seconds.
PAGE 19
LTC3109 Typical Applications Energy Harvester Operates from Small Temperature Differentials of Either Polarity TEG (THERMOELECTRIC GENERATOR) T1 ±30mV TO ±500mV 1:100 • • T2 1:100 1nF • C1A VOUT2 C2A VOUT SWA VINA VLDO 470pF 1nF OPTIONAL SWITCHED OUTPUT FOR SENSORS 3.3V + 2.2V LOW POWER RADIO LTC3109 C1B • 470µF 2.2µF SENSOR(S) µP 470pF C2B PG00D SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND 5.
PAGE 20
LTC3109 Typical Applications Unipolar Energy Harvester Charges Battery Backup THERMOELECTIC GENERATOR FERROTEC 9500/127/100B + – 47µF • T1 1:50 33nF • C1A VOUT2 C2A VOUT 1nF 330k FERROTEC 9500/127/100B C1 = 33nF T1 = COILCRAFT LPR6235-123QML 1:50 RATIO VOUT = 3.3V 4.0 POUT (mW) 3.5 2.2V VLDO SWA VINA C1B C2B PG00D SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND Typical PVOUT vs dT for Unipolar Configuration 4.5 330µF 4V LTC3109 T1: COILCRAFT LPR6235-123QML 5.0 + VOUT 3.3V VLDO 2.
PAGE 21
LTC3109 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. UF Package 20-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1710 Rev A) 0.70 ±0.05 4.50 ±0.05 3.10 ±0.05 2.00 REF 2.45 ±0.05 2.45 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ±0.10 0.75 ±0.05 R = 0.05 TYP R = 0.115 TYP 19 20 0.40 ±0.10 PIN 1 TOP MARK (NOTE 6) 4.00 ±0.
PAGE 22
LTC3109 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. GN Package 20-Lead Plastic SSOP (Narrow .150 Inch) (Reference LTC DWG # 05-08-1641 Rev B) .337 – .344* (8.560 – 8.738) .045 ±.005 20 19 18 17 16 15 14 13 12 .254 MIN .150 – .165 .0165 ±.0015 11 .229 – .244 (5.817 – 6.198) .058 (1.473) REF .150 – .157** (3.810 – 3.988) .0250 BSC 1 RECOMMENDED SOLDER PAD LAYOUT .015 ±.004 × 45° (0.38 ±0.10) .0075 – .0098 (0.19 – 0.
PAGE 23
LTC3109 Revision History REV DATE DESCRIPTION A 06/12 Added vendor Information to Table 5 PAGE NUMBER 15 B 08/13 Changed Würth transformer part numbers 15 3109fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. For more information www.
PAGE 24
LTC3109 Typical Application IVOUT vs VIN 16 1:20 RATIO C1 = 1µF EXTERNAL DIODES 14 Unipolar TEG Energy Harvester for Low Resistance/High Current Inputs, Using External Charge Pump Rectifiers • C1A • 1nF 70mV TO 1V VOUT2 LTC3109 C2A SWA VINA C1B VOUT VLDO SWITCHED VOUT GOES HIGH WHEN PGOOD IS HIGH VOUT2 0.1µF 3.3V + PG00D SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND VAUX 8 6 2 0 VOUT 0 COUT 100 200 300 400 500 600 700 800 VIN (mV) 3109 TA05b 2.2V C2B 10 4 2.