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 – 2.2V, 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 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 generators) 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 complete 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 quiescent current and high efficiency maximizes the harvested energy available for the application. APPLICATIONS n n n n n n Remote Sensor and Radio Power HVAC Systems Automatic Metering Building Automation Predictive Maintenance Industrial Wireless Sensing The LTC3109 is available in a small, thermally enhanced 20-lead (4mm × 4mm) QFN package and a 20-lead SSOP package. 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. TYPICAL APPLICATION TEG (THERMOELECTRIC GENERATOR) ±30mV TO ±500mV 1:100 • VOUT Current vs TEG Voltage 1nF C1A • VOUT2 OPTIONAL SWITCHED OUTPUT FOR SENSORS 900 1:100 TRANSFORMERS C1A = C1B = 1nF VOUT = 3.3V 470pF C2A VOUT SWA VINA VLDO 800 + 2.2V 1nF 1:100 • 2.2μF LOW POWER RADIO LTC3109 C1B • SENSOR(S) μP 470pF C2B 700 470μF 600 IVOUT (μA) 47μF 3.3V 500 400 300 PG00D 200 VAUX SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND 100 5.25V 1μF 0 –300 + CSTORE 3109 TA01a –200 –100 0 100 VTEG (mV) 200 300 3109 TA01b 3109fa 1 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...................................................... 15mA Into VAUX Operating Junction Temperature Range (Note 2).................................................. –40°C to 125°C Storage Temperature Range .................. –65°C to 125°C PIN CONFIGURATION TOP VIEW GND C2A C1A VS1 VS2 TOP VIEW 20 19 18 17 16 VS1 1 20 C1A VS2 2 19 C2A VSTORE 1 15 SWA VSTORE 3 18 GND VAUX 2 14 VINA VAUX 4 17 SWA 13 VINB VOUT 5 16 VINA 21 GND VOUT 3 VOUT2 4 12 SWB VOUT2 6 15 VINB VOUT2_EN 5 11 GND VOUT2_EN 7 14 SWB PGOOD 8 13 GND VLDO 9 12 C2B GND 10 11 C1B C2B 9 10 C1B 8 GND 7 VLDO PGOOD 6 UF PACKAGE 20-LEAD (4mm s 4mm) PLASTIC QFN GN PACKAGE 20-LEAD PLASTIC SSOP TJMAX = 125°C, θJA = 37°C/W EXPOSED PAD (PIN 21) IS GND (Note 5) TJMAX = 125°C, θJA = 90°C/W 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 specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. 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/ 3109fa 2 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. PARAMETER CONDITIONS MIN TYP MAX ±50 Minimum Start-Up Voltage Using 1:100 Transformer Turns Ratio, VAUX = 0V ±30 No-Load Input Current Using 1:100 Transformer Turns Ratios, VIN = 30mV, VOUT2_EN = 0V, All Outputs Charged and in Regulation 6 Input Voltage Range Using 1:100 Transformer Turns Ratios l VSTARTUP Output Voltage VS1 = VS2 = GND VS1 = VAUX, VS2 = GND VS1 = GND, VS2 = VAUX VS1 = VS2 = VAUX l l l l 2.30 3.234 4.018 4.875 VAUX Quiescent Current No Load, All Outputs Charged VAUX Clamp Voltage Current Into VAUX = 5mA VOUT Quiescent Current VOUT = 3.3V, VOUT2_EN = 0V VOUT Current Limit VOUT = 0V N-Channel MOSFET On-Resistance C2B = C2A = 5V (Note 3) Measured from VINA or SWA, VINB or SWB to GND LDO Output Voltage 0.5mA Load On VLDO l 5.0 l 6 UNITS mV mA ±500 mV 2.350 3.300 4.100 5.000 2.40 3.366 4.182 5.10 V V V V 7 10 μA 5.25 5.55 V 0.2 15 μA 26 mA 0.35 l 2.134 2.2 Ω 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 l 100 200 mV LDO Current Limit VLDO = 0V l VSTORE Leakage Current VSTORE = 5V l VSTORE Current Limit VSTORE = 0V VOUT2 Leakage Current VOUT2 = 0V, VOUT2_EN = 0V VS1, VS2 Input Current VS1 = VS2 = 5V PGOOD Threshold (Rising) Measured Relative to the VOUT Voltage PGOOD Threshold (Falling) Measured Relative to the VOUT Voltage PGOOD VOL Sink Current = 100μA PGOOD VOH Source Current = 0 6 0.4 mA 0.3 μA 15 26 mA nA 0.85 1.2 V 1 50 nA –7.5 % –9 % 0.12 0.3 V 2.1 2.2 2.3 V 0.4 1.0 PGOOD Pull-Up Resistance VOUT2_EN Threshold Voltage 12 0.1 50 l VS1, VS2 Threshold Voltage 5 1 VOUT2_EN Rising l VOUT2_EN Threshold Hysteresis VOUT2_EN Pull-Down Resistance VOUT2 Turn-On Time MΩ 1.3 V 100 mV 5 MΩ 0.5 μs VOUT2 Turn-Off Time (Note 3) VOUT2 Current Limit VOUT = 3.3V VOUT2 Current Limit Response Time (Note 3) 350 ns VOUT2 P-Channel MOSFET On-Resistance VOUT = 5V (Note 3) 1.0 Ω 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 specifications from 0.15 l 0.2 0.3 μs 0.5 A 0°C to 85°C junction temperature. Specifications 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 specific operating conditions in conjunction with 3109fa 3 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. 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: Specification is guaranteed by design and not 100% tested in production. Note 4: Current measurements are made when the output is not switching. TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. IIN vs VIN IVOUT vs VIN PVOUT vs VIN 10000 VOUT = 0V 100 1:100 RATIO, C1 = 1nF 1:50 RATIO, C1 = 4.7nF 1:20 RATIO, C1 = 10nF VOUT = 3.3V NO LOAD ON VLDO 1000 IIN (mA) 100 10 VOUT = 5V 10 IVOUT (μA) 100 1:50 RATIO C1 = 4.7nF PVOUT (mW) 1000 VOUT = 3.3V 1 1:100 RATIO, C1 = 1nF 1:50 RATIO, C1 = 4.7nF 1:20 RATIO, C1 = 10nF 10 1 100 VIN (mV) 0.1 10 1000 100 VIN (mV) Input Resistance vs VIN 6.0 40 5.5 35 EFFICIENCY (%) RIN (Ω) 45 4.5 4.0 90 1:100 RATIO, C1 = 1nF 1:50 RATIO, C1 = 4.7nF 1:20 RATIO, C1 = 10nF VOUT = 0V 80 30 25 20 15 3.5 10 1:100 RATIO, C1 = 1nF 1:50 RATIO, C1 = 4.7nF 1:20 RATIO, C1 = 10nF 2.5 100 VIN (mV) 1000 3109 G03 60 50 40 30 20 0 0 10 70 10 5 2.0 1000 Open-Circuit Start-Up Voltage vs Source Resistance 50 VOUT = 0V 5.0 100 VIN (mV) 3109 G18 Efficiency vs VIN 6.5 3.0 10 3109 G02 3109 G01 7.0 1000 VSTARTUP (OPEN CIRCUIT) (mV) 10 10 100 VIN (mV) 1000 3109 G04 0 1 2 3 4 5 6 7 8 SOURCE RESISTANCE (Ω) 9 10 3109 G05 3109fa 4 LTC3109 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. VAUX Clamp Voltage vs Shunt Current VOUT and VLDO vs Temperature 5.5 1.00 3.0 0.75 2.5 5.4 0.50 FERROTEC 9500/127/100B 40mm VOUT 0 –0.25 PVOUT (mW) VLDO 0.25 VAUX (V) CHANGE (%) (RELATIVE TO 25°C) PVOUT vs dT and TEG Size, 1:100 Ratio, VOUT = 5V 5.3 5.2 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 5.0 125 3 9 12 6 VAUX SHUNT CURRENT (mA) 0 FERROTEC 9501/071/040B 22mm 0 15 0 1 2 4 3 5 6 dT (°K) 8 7 3109 G07 3109 G06 Resonant Switching Waveforms 9 10 3109 G08 LDO Load Regulation LDO Dropout Voltage 0.00 0.20 0.18 C1 A OR B 2V/DIV 0.16 C2 A OR B 2V/DIV DROPOUT VOLTAGE (V) DROP IN VLDO (%) –0.25 –0.50 –0.75 0.12 0.10 0.08 0.06 0.04 3109 G9 20μs/DIV 0.14 0.02 –1.00 0.00 0 0.5 1 1.5 2 2.5 LDO LOAD (mA) 3 3.5 4 0 0.5 1 3109 G10 VIN = 50mV 1:100 RATIO TRANSFORMER COUT = 220μF CSTORE = 470μF CLDO = 2.2μF CH2, VOUT 1V/DIV CH3, VLDO 1V/DIV 10SEC/DIV 3109 G12 3.5 4 VOUT Ripple 50mA LOAD STEP COUT = 220μF CH1 VSTORE 1V/DIV 3 3109 G11 VOUT and PGOOD Response During a Step Load Start-Up Voltage Sequencing 1.5 2 2.5 LDO LOAD (mA) 30μA LOAD COUT = 220μF CH2 VOUT 1V/DIV 20mV/ DIV CH1 PGD 1V/DIV 5ms/DIV 3109 G13 100ms/DIV 3109 G14 3109fa 5 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 3109 G17 5SEC/DIV 10mA LOAD ON VOUT2 COUT = 220μF 0mA TO 3mA LOAD STEP CLDO = 2.2μF PIN FUNCTIONS 3109 G16 1ms/DIV (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 Rectifier Circuit 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): VOUT Select Pin 2. Connect this pin to ground or VAUX to program the output voltage (see Table 1). VS1 (Pin 19/Pin 1): VOUT 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 3109fa 6 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. 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. SWA (Pin 15/Pin 17): Connection to the Internal N-Channel 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-Channel 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). 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. 3109fa 7 LTC3109 BLOCK DIAGRAM SYNC RECTIFY C1B REFERENCE VREF 1.2V VOUT2 1Ω SYNC RECTIFY VOUT2_EN VOUT C1A • VOUT2 • 5.25V COUT + C2A VIN C2B VOUT VINA • SWB VS1 VOUT PROGRAM VS2 CHARGE CONTROL – VLDO VSTORE SWA • VOUT + POWER SWITCHES VREF 1M + PG00D PG00D – VSTORE VINB VOUT + CSTORE LDO VREF VAUX CAUX 1μF VLDO GND 3109 BD 2.2V CLDO 2.2μF 3109fa 8 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. 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 measurements 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 resonant 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 Rectifier The AC voltage produced on the secondary winding of the transformer is boosted and rectified using an external charge pump capacitor (from the secondary winding to pin C1A or C1B) and the rectifiers internal to the LTC3109. The rectifier circuit feeds current into the VAUX pin, providing 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 allowed 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 Rectifiers Once VAUX exceeds 2V, synchronous rectifiers in parallel with each of the internal rectifier diodes take over the job of rectifying the input voltage at pins C1A and C1B, improving efficiency. Low Dropout Linear Regulator (LDO) The LTC3109 includes a low current LDO to provide a regulated 2.2V output for powering low power processors 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 3109fa 9 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. 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, according 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 pullup (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 configuration 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 connected 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 amplifiers, that don’t have a low power “sleep” or shutdown capability. 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, allowing 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 circuitry for VOUT2 draws an extra 8μA of quiescent current from VOUT . This added current draw has a negligible effect 3109fa 10 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). 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. VOLTAGE (V) If VAUX drops below VSTORE, the LTC3109 will automatically 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. 5.0 2.5 0 3.0 2.0 1.0 0 5.0 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. VSTORE PGOOD 2.5 VOUT 0 3.0 2.0 1.0 0 5.0 2.5 0 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. VLDO VAUX 0 10 20 30 40 TIME (ms) 50 60 70 80 3109 F01 Figure 1. Output Voltage Sequencing (with VOUT Programmed for 3.3V). Time Not to Scale 3109fa 11 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. 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 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 PELTIER CELL (THERMOELECTRIC GENERATOR) A Peltier cell is made up of a large number of series-connected 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 thermoelectric 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 voltage 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 harvesting 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). 1000 100 TEG: 30mm SQUARE 127 COUPLES R = 2Ω 100 10 VOC MAX POUT (IDEAL) 10 1 1 1 10 dT (°C) TEG MAXIMUM POUT – IDEAL (mW) 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. 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. TEG VOPEN-CIRCUIT (mV) INTRODUCTION 0.1 100 3109 F02 Figure 2. Typical Performance of a Peltier Cell Acting as a Power Generator (TEG) 3109fa 12 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. 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. The LTC3109 can also be configured to operate from two independent unipolar voltage sources, such as two TEGs in different locations. In this configuration, energy can be harvested from either or both sources simultaneously. See the Typical Applications for an example. The LTC3109 can also be configured 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 configuration, along with the performance curves. Table 3. Peltier Cell Manufacturers PELTIER CELL (TEG) SUPPLIERS 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 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. Kryotherm www.kryotherm COMPONENT SELECTION Laird Technologies www.lairdtech.com Step-Up Transformer Micropelt www.micropelt.com Nextreme www.nextreme.com TE Technology www.tetech.com/Peltier-Thermoelectric-Cooler-Modules.html Tellurex www.tellurex.com/ 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 significantly different in one polarity, in which case the ratios may be different. Table 4. Recommended TEG Part Numbers by Size MANUFACTURER CUI Inc. (Distributor) 15mm 20mm 30mm 40mm 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 Tellurex TE Technology RC3-8-01 RC6-6-01 RC12-8-01LS C2-15-0405 C2-20-0409 C2-30-1505 C2-40-1509 TE-31-1.0-1.3 TE-31-1.4-1.15 TE-71-1.4-1.15 TE-127-1.4-1.05 3109fa 13 LTC3109 APPLICATIONS INFORMATION C1 VIN T1 • + C1A • 1nF CIN VOUT2 VOUT2 LTC3109 330k VOUT SET C2A VOUT VOUT + VLDO SWA VINA C1B C2B PG00D SWB VINB VOUT2_EN VS1 VSTORE VAUX VS2 GND COUT VLDO 2.2μF PG00D VOUT2_ENABLE 10μF NOTE: VALUES FOR CIN, T1, C1 AND COUT ARE DETERMINED BY THE APPLICATION 3109 F03a Figure 3. Unipolar Application Typical PVOUT vs dT for Unipolar Configuration 10000 FERROTEC 9500/127/100B, 40mm TEG C1 = 33nF, T1 = COILCRAFT LPR6235-123QML 1:50 RATIO VOUT = 5V 60 VOUT = 3.3V 55 50 45 EFFICIENCY (%) 1000 IVOUT (μA) POUT (mW) 10 Typical Efficiency vs VIN for Unipolar Configuration Typical IVOUT vs VIN for Unipolar Configuration VOUT = 3.3V 1 100 40 35 30 25 20 15 1:100, C1 = 6.8nF 1:50, C1 = 33nF 1:20, C1 = 68nF 0.1 100 10 10 100 VIN (mV) 10 dT (°K) 1000 600 10 100 VIN (mV) 1000 3109 F03c 4.0 1:100, C1 = 6.8nF 1:50, C1 = 33nF 1:20, C1 = 68nF 3.5 450 INPUT RESISTANCE (Ω) INPUT CURRENT (mA) 0 Typical RIN vs VIN for Unipolar Configuration Typical Input Current vs VIN for Unipolar Configuration 500 5 3109 F03b 3109 F03f 550 1:100, C1 = 6.8nF 1:50, C1 = 33nF 1:20, C1 = 68nF 10 400 350 300 250 200 150 100 3.0 2.5 2.0 1.5 1.0 1:100, C1 = 6.8nF 1:50, C1 = 33nF 1:20, C1 = 68nF 0.5 50 0 0 10 100 VIN (mV) 1000 3109 F03d 10 100 VIN (mV) 1000 3109 F03e 3109fa 14 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. Freq = 1 Hz 2 • π • LSEC • C where LSEC is the inductance of one of the secondary windings and C is the load capacitance on the secondary 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 STARTUP 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) 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 resistance 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 performance 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 efficiency. Note that the C1 and C2 capacitors must have a voltage rating greater than the maximum input voltage times the transformer turns ratio. USING EXTERNAL CHARGE PUMP RECTIFIERS VOUT AND VSTORE CAPACITOR The synchronous rectifiers 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 rectifiers (1N4148 or 1N914 or equivalent) is recommended. See the Typical Application circuits for an example. Avoid the use of Schottky rectifiers, as their low forward voltage increases the minimum start-up voltage. 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 application can tolerate (ΔVOUT). The capacitor must be rated for whatever voltage has been selected for VOUT by VS1 and VS2: COUT (μF) ≥ ILOAD(mA)• tPULSE(ms) ΔVOUT (V) 3109fa 15 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. The VSTORE capacitor may be of very large value (thousands 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 working voltage rating of at least 5.5V at the temperature that it will be used. 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. 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 • tPULSE • f)) • tSTORE 5.25 – VOUT PCB LAYOUT GUIDELINES 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 efficiency and increase start-up voltage and capacitor charge time. Also, due to the low charge currents available at the outputs 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. 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 beneficial storage time to VOUT . To minimize losses and capacitor charge time, all capacitors 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 Figure 4. Example Component Placement for 2-Layer PC Board (QFN Package). Note That VSTORE and VOUT Capacitor Sizes are Application Dependent Cooper/Bussman KR Series www.bussmann.com/3/PowerStor.html P Series Vishay/Sprague www.vishay.com/capacitors Tantamount 592D 595D Tantalum 3109fa 16 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. 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 = 303μF 0.33V 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 coefficient 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 available 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 efficiency of the converter. You must also know what the total load current 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 = 0.82sec or fMAX = 1.2Hz 150μA – 17μA Therefore, in this application example, the circuit can support 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 first 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 – ILDO 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. 3109fa 17 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 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. DESIGN EXAMPLE 2 In most pulsed-load applications, the duration, magnitude and frequency of the load current pulses are known and fixed. 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 + 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 = 5.14μA 3600sec 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. IPULSE • tPULSE T 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). 3109fa 18 LTC3109 TYPICAL APPLICATIONS Energy Harvester Operates from Small Temperature Differentials of Either Polarity TEG (THERMOELECTRIC GENERATOR) T1 ±30mV TO ±500mV 1:100 • 1nF • C1A VOUT2 C2A VOUT SWA VINA VLDO OPTIONAL SWITCHED OUTPUT FOR SENSORS 470pF 3.3V + 2.2V T2 1:100 • 1nF 470μF 2.2μF LOW POWER RADIO LTC3109 C1B • SENSOR(S) μP 470pF C2B PG00D SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND 5.25V 1μF + CSTORE 3109 TA02 T1, T2: COILCRAFT LPR6235-752SML Li-Ion Battery Charger and LDO Operates from a Low Level AC Input 50mV TO 300mV RMS T1 1:100 • 1nF • C1A VOUT2 C2A VOUT 470pF AC 60Hz TO LOAD 2.2V 1nF T2 1:100 • SWA VINA VLDO VLDO FAIRCHILD 2.2μF FDG328P LTC3109 4.1V C1B • + 470pF C2B T1, T2: COILCRAFT LPR6235-752SML PG00D SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND 1μF NC Li-Ion BATTERY LTC4070* HBO LBO NC NTC DRV NC VCC NTCBIAS NC ADJ GND *THE LTC4070 IS A PRECISION BATTERY CHARGER OFFERING UNDERVOLTAGE PROTECTION, WITH A TYPICAL SUPPLY CURRENT OF ONLY 0.45μA 3109 TA03 3109fa 19 LTC3109 TYPICAL APPLICATIONS Unipolar Energy Harvester Charges Battery Backup THERMOELECTIC GENERATOR FERROTEC 9500/127/100B T1 1:50 + 47μF – • 33nF • C1A VOUT2 C2A VOUT 1nF 330k 5.0 FERROTEC 9500/127/100B C1 = 33nF T1 = COILCRAFT LPR6235-123QML 1:50 RATIO VOUT = 3.3V 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 4.0 330μF 4V LTC3109 T1: COILCRAFT LPR6235-123QML 4.5 + VOUT 3.3V VLDO 2.2μF PGOOD FAIRCHILD FDG328P 1μF 4.1V + 3.0 NC Li-Ion BATTERY LTC4070 HBO LBO NC NTC DRV NC VCC NTCBIAS NC ADJ GND 3109 TA06a 2.5 2.0 1.5 1.0 0.5 0 0 1 2 3 4 5 6 dT (°K) 7 8 9 10 3109 TA06b Dual-Input Energy Harvester Generates 5V and 2.2V from Either or Both TEGs, Operating at Different Temperatures of Fixed Polarity COILCRAFT LPR6235-752SML 1:100 THERMOELECTRIC GENERATOR 25mV TO 500mV + • 1nF C1A • 470pF – VOUT2 LTC3109 C2A VOUT 5V COILCRAFT LPR6235-123QML 4.7nF 1:50 THERMOELECTRIC GENERATOR OR THERMOPILE 35mV TO 1000mV + – • • VOUT + SWA VINA COUT* VLDO 2.2V VLDO 2.2μF C1B 470pF C2B PG00D SWB VOUT2_EN VINB VS1 VS2 PG00D VSTORE VAUX 1μF GND 3109 TA04 *THE VALUE OF THE COUT CAPACITOR IS DETEMINED BY THE LOAD CHARACTERISTICS 3109fa 20 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 w 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 0.75 ±0.05 4.00 ±0.10 R = 0.05 TYP R = 0.115 TYP 19 20 0.40 ±0.10 PIN 1 TOP MARK (NOTE 6) 1 2.45 ±0.10 4.00 ±0.10 PIN 1 NOTCH R = 0.20 TYP OR 0.35 w 45° CHAMFER BOTTOM VIEW—EXPOSED PAD 2 2.00 REF 2.45 ±0.10 (UF20) QFN 01-07 REV A 0.200 REF 0.00 – 0.05 0.25 ±0.05 0.50 BSC 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 3109fa 21 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 w 45s (0.38 ±0.10) .0075 – .0098 (0.19 – 0.25) 2 3 4 5 6 7 8 .0532 – .0688 (1.35 – 1.75) 9 10 .004 – .0098 (0.102 – 0.249) 0° – 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) .008 – .012 (0.203 – 0.305) TYP .0250 (0.635) BSC GN20 REV B 0212 3. DRAWING NOT TO SCALE 4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE *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 3109fa 22 LTC3109 REVISION HISTORY REV DATE DESCRIPTION A 06/12 Added vendor Information to Table 5 PAGE NUMBER 15 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 23 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 + • VAUX BAS31 C1A • 1nF 70mV TO 1V 12 IVOUT (mA) COILCRAFT LPR6235-253PML 1.0μF 1:20 VOUT2 SWITCHED VOUT GOES HIGH WHEN PGOOD IS HIGH VOUT2 0.1μF C1B VOUT 3.3V 8 6 2 0 VOUT + 10 4 LTC3109 C2A SWA VINA TYPICAL 0 COUT 100 200 300 400 500 600 700 800 VIN (mV) 3109 TA05b VLDO 2.2V Efficiency vs VIN VLDO 2.2μF 50 VAUX PG00D SWB VOUT2_EN VINB VS1 VSTORE VAUX VS2 GND 45 PG00D 40 + 10μF CSTORE 3109 TA05 EFFICIENCY (%) C2B 35 30 25 20 15 10 5 0 100 VIN (mV) 10 1000 3109 TA05c RELATED PARTS 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 Efficiency 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 VIN: 2.6V to 16V; VOUT(MIN) = 40VMAX; IQ = 8.5μA; ISD < 1μA; with Integrated Schottky Diode and Output 2mm × 2mm DFN-8 Package Disconnect 3109fa 24 Linear Technology Corporation LT 0612 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2010