Low Power Energy Harvester IC From Linear Technologies - LTC3108
Low Power Energy Harvester IC From Linear Technologies - LTC3108
Low Power Energy Harvester IC From Linear Technologies - LTC3108
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DESCRIPTION
The LTC3108 is a highly integrated DC/DC converter ideal for harvesting and managing surplus energy from extremely low input voltage sources such as TEGs (thermoelectric generators), thermopiles and small solar cells. The step-up topology operates from input voltages as low as 20mV. The LTC3108 is functionally equivalent to the LTC3108-1 except for its unique xed VOUT options. Using a small step-up transformer, the LTC3108 provides a complete power management solution for wireless sensing and data acquisition. The 2.2V LDO powers an external microprocessor, while the main output is programmed to one of four xed voltages to power a wireless transmitter or sensors. The power good indicator signals that the main output voltage is within regulation. A second output can be enabled by the host. A storage capacitor provides power when the input voltage source is unavailable. Extremely low quiescent current and high efciency design ensure the fastest possible charge times of the output reservoir capacitor. The LTC3108 is available in a small, thermally enhanced 12-lead (3mm 4mm) DFN package and a 16-lead SSOP package.
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Operates from Inputs of 20mV Complete Energy Harvesting Power Management System - Selectable VOUT of 2.35V, 3.3V, 4.1V or 5V - LDO: 2.2V at 3mA - Logic Controlled Output - Reserve Energy Output Power Good Indicator Uses Compact Step-Up Transformers Small 12-Lead (3mm 4mm) DFN or 16-Lead SSOP Packages
APPLICATIONS
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Remote Sensors and Radio Power Surplus Heat Energy Harvesting HVAC Systems Industrial Wireless Sensing Automatic Metering Building Automation Predictive Maintenance
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.
TYPICAL APPLICATION
Wireless Remote Sensor Application Powered From a Peltier Cell
1nF 1:100 + THERMOELECTRIC GENERATOR 20mV TO 500mV
+
220F 330pF
VS2
VOUT
3.3V
+
470F
RF LINK
1 1:100 Ratio 1:50 Ratio 1:20 Ratio 0 50 100 150 200 250 300 350 400 VIN (mV)
3108 TA01b
3108 TA01a
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SW Voltage ..................................................0.3V to 2V C1 Voltage....................................................0.3V to 6V C2 Voltage (Note 5).........................................8V to 8V VOUT2, VOUT2_EN ...........................................0.3V to 6V VAUX....................................................15mA into VAUX
VS1, VS2, VAUX, VOUT, PGD ........................0.3V to 6V VLDO, VSTORE ............................................0.3V to 6V Operating Junction Temperature Range (Note 2)................................................. 40C to 125C Storage Temperature Range.................. 65C to 125C
PIN CONFIGURATION
TOP VIEW GND VAUX VSTORE VOUT VOUT2 VLDO PGD 1 2 3 4 5 6 13 GND 12 SW 11 C2 10 C1 9 8 7 VOUT2_EN VS1 VS2 VAUX VSTORE VOUT VOUT2 VLDO PGD GND 1 2 3 4 5 6 7 8 TOP VIEW 16 GND 15 SW 14 C2 13 C1 12 VOUT2_EN 11 VS1 10 VS2 9 GND
DE PACKAGE 12-LEAD (4mm 3mm) PLASTIC DFN TJMAX = 125C, JA = 43C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB (NOTE 4)
ORDER INFORMATION
LEAD FREE FINISH LTC3108EDE#PBF LTC3108IDE#PBF LTC3108EGN#PBF LTC3108IGN#PBF TAPE AND REEL LTC3108EDE#TRPBF LTC3108IDE#TRPBF LTC3108EGN#TRPBF LTC3108IGN#TRPBF PART MARKING* 3108 3108 3108 3108 PACKAGE DESCRIPTION 12-Lead (4mm 3mm) Plastic DFN 12-Lead (4mm 3mm) Plastic DFN 16-Lead Plastic SSOP 16-Lead Plastic SSOP TEMPERATURE RANGE 40C to 125C 40C to 125C 40C to 125C 40C to 125C
Consult LTC Marketing for parts specied for other xed output voltages or wider operating temperature ranges. *The temperature grade is identied by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Start-Up Voltage No-Load Input Current Input Voltage Range CONDITIONS
The l denotes the specications which apply over the full operating junction temperature range, otherwise specications are for TA = 25C (Note 2). VAUX = 5V, unless otherwise noted.
MIN TYP 20 3
l
MAX 50
UNITS mV mA
Using 1:100 Transformer Turns Ratio, VAUX = 0V Using 1:100 Transformer Turns Ratio; VIN = 20mV, VOUT2_EN = 0V; All Outputs Charged and in Regulation Using 1:100 Transformer Turns Ratio VSTARTUP
500
mV
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The l denotes the specications which apply over the full operating junction temperature range, otherwise specications are for TA = 25C (Note 2). VAUX = 5V, unless otherwise noted.
MIN 2.30 3.234 4.018 4.90 TYP 2.350 3.300 4.100 5.000 0.2 6 2.134 2.2 0.5 0.05 100 4 2.8 2.8 5 11 4.5 4.5 5.25 0.1 0.1 0.4 0.85 0.01 7.5 9 0.15 2.1
l
MAX 2.40 3.366 4.182 5.10 9 2.266 1 0.2 200 7 7 5.55 0.3 1.2 0.1
UNITS V V V V A A V % % mV mA mA mA V A A V A % %
VOUT Quiescent Current VAUX Quiescent Current LDO Output Voltage LDO Load Regulation LDO Line Regulation LDO Dropout Voltage LDO Current Limit VOUT Current Limit VSTORE Current Limit VAUX Clamp Voltage VSTORE Leakage Current VOUT2 Leakage Current VS1, VS2 Threshold Voltage VS1, VS2 Input Current PGOOD Threshold (Rising) PGOOD Threshold (Falling) PGOOD VOL PGOOD VOH PGOOD Pull-Up Resistance VOUT2_EN Threshold Voltage VOUT2_EN Pull-Down Resistance VOUT2 Turn-On Time VOUT2 Turn-Off Time VOUT2 Current Limit VOUT2 Current Limit Response Time VOUT2 P-Channel MOSFET On-Resistance N-Channel MOSFET On-Resistance
VS1 = VS2 = 5V Measured Relative to the VOUT Voltage Measured Relative to the VOUT Voltage Sink Current = 100A Source Current = 0 VOUT2_EN Rising
V V M V M s s
2.2 1 1 5 5
0.4
A ns
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 LTC3108 is tested under pulsed load conditions such that TJ TA. The LTC3108E is guaranteed to meet specications from 0C to 85C junction temperature. Specications over the 40C to 125C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC3108I is guaranteed over the full 40C to 125C operating junction temperature range. Note that the maximum ambient temperature is determined by specic operating conditions in conjunction with 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 JAC/W), where JA is the package thermal impedance. Note 3: Specication is guaranteed by design and not 100% tested in production. Note 4: Failure to solder the exposed backside of the package to the PC board ground plane will result in a thermal resistance much higher than 43C/W. Note 5: The absolute maximum rating is a DC rating. Under certain conditions in the applications shown, the peak AC voltage on the C2 pin may exceed 8V. This behavior is normal and acceptable because the current into the pin is limited by the impedance of the coupling capacitor.
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TA = 25C, unless otherwise noted. IVOUT and Efciency vs VIN, 1:20 Ratio Transformer
C1 = 10nF IVOUT (VOUT = 0V) 80 70 60 EFFICIENCY (%) 50 EFFICIENCY (VOUT = 4.5V) IVOUT (VOUT = 4.5V) 40 30 20 10 0 100 200 300 400 0 500
3108 G01
10
VIN (mV)
C1 = 4.7nF
60 50 40
30 20 10 0 500
1:50 RATIO
100
1:100 RATIO
10
0 0
1 2 5 10 100 200 300 400 500 600 700 800 VIN OPEN-CIRCUIT (mV)
3108 G05
VIN (mV)
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TA = 25C, unless otherwise noted. IVOUT vs VIN and Source Resistance, 1:100 Ratio
C1 = 1nF
100
100
10
0 0
1 2 5 10 100 200 300 400 500 600 700 800 VIN OPEN-CIRCUIT (mV)
3108 G06
1 2 5 10 500
3108 G07
10
0 0.1
1:50 RATIO 1:100 RATIO 1:50 RATIO 1:100 RATIO 10 1 dT ACROSS TEG (C) 100
3108 G08
10s/DIV
3108 G09
0.50
0.75
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10sec/DIV
3108 G12
5ms/DIV
3108 G13
VOUT Ripple
30A LOAD COUT = 220F VLDO 20mV/DIV
20mV/ DIV
3108 G15
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VAUX (Pin 1/Pin 2): Output of the Internal Rectier Circuit and VCC for the IC. Bypass VAUX with at least 1F of capacitance. An active shunt regulator clamps VAUX to 5.25V (typical). VSTORE (Pin 2/Pin 3): Output for the Storage Capacitor or Battery. A large 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. VOUT (Pin 3/Pin 4): 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 an energy storage capacitor or to a rechargeable battery. VOUT2 (Pin 4/Pin 5): Switched Output of the Converter. Connect this pin to a switched load. This output is open until VOUT2_EN is driven high, then it is connected to VOUT through a 1.3 P-channel switch. If not used, this pin should be left open or tied to VOUT. The peak current in this output is limited to 0.3A typical. VLDO (Pin 5/Pin 6): Output of the 2.2V LDO. Connect a 2.2F or larger ceramic capacitor from this pin to GND. If not used, this pin should be tied to VAUX. PGD (Pin 6/Pin 7): Power Good Output. When VOUT is within 7.5% of its programmed value, PGD will be pulled up to VLDO through a 1M resistor. If VOUT drops 9% below its programmed value PGD will go low. This pin can sink up to 100A. VS2 (Pin 7/Pin 10): VOUT Select Pin 2. Connect this pin to ground or VAUX to program the output voltage (see Table 1).
VS1 (Pin 8/Pin 11): VOUT Select Pin 1. Connect this pin to ground or VAUX to program the output voltage (see Table 1). VOUT2_EN (Pin 9/Pin 12): 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. C1 (Pin 10/Pin 13): Input to the Charge Pump and Rectier Circuit. Connect a capacitor from this pin to the secondary winding of the step-up transformer. C2 (Pin 11/Pin 14): Input to the N-Channel Gate Drive Circuit. Connect a capacitor from this pin to the secondary winding of the step-up transformer. SW (Pin 12/Pin 15): Drain of the Internal N-Channel Switch. Connect this pin to the primary winding of the transformer. GND (Pins 1, 8, 9, 16) SSOP Only: Ground GND (Exposed Pad Pin 13) DFN Only: Ground. The DFN exposed pad must be soldered to the PCB ground plane. It serves as the ground connection, and as a means of conducting heat away from the die.
Table 1. Regulated Voltage Using Pins VS1 and VS2
VS2 GND GND VAUX VAUX VS1 GND VAUX GND VAUX VOUT 2.35V 3.3V 4.1V 5V
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OFF ON
+
VAUX 1F VOUT GND (SSOP) VBEST VREF LDO VLDO
2.2V 2.2F
OPERATION
The LTC3108 is designed to use a small external step-up transformer to create an ultralow input voltage step-up DC/DC converter and power manager. 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 LTC3108 is designed to manage the charging and regulation of multiple outputs in a system in which the
average power draw is very low, but there may be periodic pulses of higher load current required. This is typical of wireless sensor applications, where the quiescent power draw is extremely low most of the time, except for transmit bursts when circuitry is powered up to make measurements and transmit data. The LTC3108 can also be used to trickle charge a standard capacitor, supercapacitor or rechargeable battery, using energy harvested from a Peltier or photovoltaic cell.
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LTC3108 OPERATION
Oscillator The LTC3108 utilizes a MOSFET switch to form a resonant step-up oscillator using an external step-up transformer and a small coupling capacitor. This allows it to boost input voltages as low as 20mV 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 20mV, a primary-secondary turns ratio of about 1:100 is recommended. For higher input voltages, this ratio can be lower. See the Applications Information section for more information on selecting the transformer. Charge Pump and Rectier The AC voltage produced on the secondary winding of the transformer is boosted and rectied using an external charge pump capacitor (from the secondary winding to pin C1) and the rectiers internal to the LTC3108. The rectier circuit feeds current into the VAUX pin, providing charge to the external VAUX capacitor and the other outputs. VAUX The active circuits within the LTC3108 are powered from VAUX, which should be bypassed with a 1F capacitor. Larger capacitor values are recommended when using turns ratios of 1:50 or 1:20 (refer to the Typical Application examples). 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 GND 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. Voltage Reference The LTC3108 includes a precision, micropower reference, for accurate regulated output voltages. This reference becomes active as soon as VAUX exceeds 2V. Synchronous Rectiers Once VAUX exceeds 2V, synchronous rectiers in parallel with each of the internal diodes take over the job of rectifying the input voltage, improving efciency. Low Dropout Linear Regulator (LDO) The LTC3108 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 VOUT storage capacitor is still charging. In the event of a step load on the LDO output, current can come from the main VOUT capacitor if VAUX drops below VOUT. The LDO requires a 2.2F 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 4mA 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. Regulated Voltage Using Pins VS1 and VS2
VS2 GND GND VAUX VAUX VS1 GND VAUX GND VAUX VOUT 2.35V 3.3V 4.1V 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 internal programmable resistor divider sets VOUT, eliminating the need for very high value external resistors that are susceptible to board leakage.
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LTC3108 OPERATION
In a typical application, a storage capacitor (typically a few hundred microfarads) is connected to VOUT. As soon as VAUX exceeds 2.5V, the VOUT capacitor will be allowed 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 4.5mA typical. PGOOD A power good comparator monitors the VOUT voltage. The PGD pin is an open-drain output with a weak pull-up (1M) to the LDO voltage. Once VOUT has charged to within 7.5% of its regulated voltage, the PGD output will go high. If VOUT drops more than 9% from its regulated voltage, PGD will go low. The PGD 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. Pulling PGD up externally to a voltage greater than VLDO will cause a small current to be sourced into VLDO. PGD can be pulled low in a wire-OR conguration 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 1.3 P-channel MOSFET switch. This output, controlled by a host processor, can be used to power external circuits such as sensors and ampliers, that do not 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 will allow it to be switched on and off faster, allowing shorter burst times and, therefore, smaller duty cycles in pulsed 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 soft-start time of about 5s to limit capacitor charging current and minimize glitching of the main output when VOUT2 is enabled. It also 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 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 8A of quiescent current from VOUT. This added current draw has a negligible effect on the application and capacitor sizing, since the load on the VOUT2 output, when enabled, is likely to be orders of magnitude higher than 8A. VSTORE The VSTORE output can be used to charge a large storage capacitor or rechargeable battery after VOUT has reached regulation. Once VOUT has reached regulation, the VSTORE output will be allowed to charge up to the VAUX voltage. The storage element on VSTORE can 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 LTC3108 will automatically draw current from the storage element. Note that it may take a long time to charge a large capacitor, depending on the input energy available and the loading on VOUT and VLDO. Since the maximum current from VSTORE is limited to a few milliamps, it can safely be used to trickle-charge NiCd or NiMH rechargeable batteries for energy storage when the input voltage is lost. Note that the VSTORE capacitor cannot supply large pulse currents to VOUT . Any pulse load on VOUT must be handled by the VOUT capacitor. Short-Circuit Protection All outputs of the LTC3108 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: time not to scale.
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LTC3108 OPERATION
5.0 2.5 0 3.0 2.0 1.0 0 VOLTAGE (V) 5.0 2.5 0 3.0 2.0 1.0 0 5.0 2.5 0 0 10 20 30 40 TIME (ms)
3108 F01a
VSTORE (V)
PGD (V)
VOUT (V)
VLDO (V)
VAUX (V)
50
60
70
80
Figure 1. Output Voltage Sequencing with VOUT Programmed for 3.3V (Time Not to Scale)
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11
1000
10
10 dT (C)
0.1 100
3108 F02
12
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13
these applications the C2 and SW pins are not used and can be grounded or left open. Examples of such input sources would be piezoelectric transducers, vibration energy harvesters, low current generators, a stack of low current solar cells or a 60Hz AC input. A series resistance of at least 100/V should be used to limit the maximum current into the VAUX shunt regulator. COMPONENT SELECTION Step-Up Transformer The step-up transformer turns ratio will determine how low the input voltage can be for the converter to start. Using a 1:100 ratio can yield start-up voltages as low as 20mV. Other factors that affect performance are the DC resistance of the transformer windings and the inductance of the windings. Higher DC resistance will result in lower efciency. The secondary winding inductance will determine the resonant frequency of the oscillator, according to the following formula. Frequency = 1 Hz 2 L(sec) C
Where L is the inductance of the transformer secondary winding and C is the load capacitance on the secondary winding. This is comprised of the input capacitance at pin C2, typically 30pF in parallel with the transformer secondary , windings shunt capacitance. The recommended resonant frequency is in the range of 10kHz to 100kHz. See Table 5 for some recommended transformers.
Table 5. Recommended Transformers
VENDOR Coilcraft www.coilcraft.com Wrth www.we-online PART NUMBER LPR6235-752SML (1:100 Ratio) LPR6235-253PML (1:20 Ratio) LPR6235-123QML (1:50 Ratio) S11100034 (1:100 Ratio) S11100033 (1:50 Ratio) S11100032 (1:20 Ratio)
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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 (to be discussed in the next example). Reducing the duty cycle of the load pulse will allow operation with less input energy.
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Where 6A is the quiescent current of the LTC3108, IQ is the load on VOUT in between bursts, ILDO is the load on the LDO between bursts, IBURST is the total load during the burst, t is the duration of the burst, f is the frequency of the bursts, TSTORE is the 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 benecial storage time. 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 AVX www.avx.com Cap-XX www.cap-xx.com Cooper/Bussmann www.bussmann.com/3/PowerStor.html Vishay/Sprague www.vishay.com/capacitors PART NUMBER/SERIES BestCap Series TAJ and TPS Series Tantalum GZ Series
VAUX VOUT VOUT2 VLDO PGOOD VSTORE VOUT VOUT2 VLDO PGD
1 2 3 4 5 6
12 11 10 9 8 7
GND
3108 FO3
KR Series P Series Tantamount 592D 595D Tantalum 150CRZ/153CRV Aluminum 013 RLC (Low Leakage)
Design Example 1 This design example will explain how to calculate the necessary storage 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 bursts of load current occurring periodically during a transmit burst. The storage capacitor on VOUT supports the load during the transmit burst, and the long sleep time between bursts allows the LTC3108 to recharge the capacitor. A method for calculating the maximum rate
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Storage capacitors requiring voltage balancing are not recommended due to the current draw of the balancing 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.
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Note that this equation neglects the effect of capacitor ESR on output voltage droop. For most ceramic or low ESR tantalum capacitors, the ESR will have a negligible effect at these load currents. A standard value of 150F or larger 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 burst. Current contribution from the holdup capacitor on VSTORE is not considered, since it may not be able to recharge between bursts. Also, it is assumed that the charge current from the LTC3108 is negligible compared to the magnitude of the load current during the burst. To calculate the maximum rate at which load bursts can occur, determine how much charge current is available from the LTC3108 VOUT pin given the input voltage source being used. This number is best found empirically, since there are many factors affecting the efciency of the converter. Also determine what the total load current is on VOUT during the sleep state (between bursts). Note that this must include any losses, such as storage capacitor leakage. Assume, for instance, that the charge current from the LTC3108 is 50A and the total current drawn on VOUT in the sleep state is 17A, including capacitor leakage. In addition, use the value of 150F for the VOUT capacitor. The maximum transmit rate (neglecting the duration of the transmit burst, which is typically very short) is then given by: 150F 0.33V t= = 1.5sec or fMAX = 0.666Hz (50A 17A)
If there were 50A of charge current available and 5A of load on VOUT, the time for VOUT to reach regulation after the initial application of power would be 12.5 seconds. Design Example 2 In many pulsed load applications, the duration, magnitude and frequency of the load current bursts are known and xed. In these cases, the average charge current required from the LTC3108 to support the average load must be calculated, which can be easily done by the following: ICHG IQ + IBURST t T
Where IQ is the sleep current on VOUT required by the external circuitry in between bursts (including cap leakage), IBURST is the total load current during the burst, t is the
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17
Therefore, if the LTC3108 has an input voltage that allows it to supply a charge current greater than 5.14A, the application can support 100mA bursts lasting 5ms every
TYPICAL APPLICATIONS
Peltier-Powered Energy Harvester for Remote Sensor Applications
VSTORE
5V
+
CIN VOUT2 PGD VLDO
COOPER BUSSMAN PB-5ROH104-R OR KR-5R5H104-R CSTORE 0.1F 3.3V 6.3V VOUT2 SENSORS P 2.2F XMTR
PGOOD 2.2V
T = 1C TO 20C
VOUT VS2 VS1 VAUX T1: COILCRAFT LPR6235-752SML *COUT VALUE DEPENDENT ON THE MAGNITUDE AND DURATION OF THE LOAD PULSE VOUT2_EN GND
3.3V
+
COUT*
OFF ON
1F
3108 TA02
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18
+
SOLAR CELL*
+
220F
VLDO 2.2F
VOUT2_EN GND
VSTORE VOUT2 LTC3108 PGD VLDO VOUT 2.35V PGOOD 2.2V VLDO 2.2F
+
220F
VOUT2_EN GND
CAP-XX GZ115F
5V
+
CSTORE AC VIN VIN > 5VP-P - PIEZO - 60Hz VLDO 2.2F
C1
5V
+
CSTORE
VOUT2 PGOOD
VOUT2 PGOOD
2.2V
VLDO VOUT 5V
2.2V
VLDO 2.2F
VOUT COUT
VOUT COUT
VS1 VAUX
VOUT2_EN GND
3108 TA05
VOUT2_ENABLE
VOUT2_EN GND
3108 TA06
VOUT2_ENABLE
2.2F
2.2F
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19
.254 MIN
.150 .165
.0165 .0015
.0250 BSC
1 .015 .004 (0.38 0.10) .007 .0098 (0.178 0.249) .016 .050 (0.406 1.270)
NOTE: 1. CONTROLLING DIMENSION: INCHES INCHES 2. DIMENSIONS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE 4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
2 3
5 6
8
.004 .0098 (0.102 0.249)
45
0 8 TYP
*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
R = 0.115 TYP
0.40 0.10 12
0.200 REF
0.75 0.05
6 0.25 0.05
NOTE: 1. DRAWING PROPOSED TO BE A VARIATION OF VERSION (WGED) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
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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.
21
+
CSTORE
LPR6235-752SML
LPR6235-752SML
3108 TA07
RELATED PARTS
PART NUMBER LTC1041 LTC1389 LT1672/LT1673/ LT1674 LT3009 LTC3108-1 LTC3525L-3/ LTC3525L-3.3/ LTC3525L-5 LTC3588-1 LTC3642 LTC6656 LT8410/ LT8410-1 LTC4O70 DESCRIPTION Bang-Bang Controller Nanopower Precision Shunt Voltage Reference Single-/Dual-/Quad-Precision 2A Rail-to-Rail Op Amps 3A IQ, 20mA Linear Regulator COMMENTS VIN: 2.8V to 16V; IQ = 1A; SO-8 Package VOUT(MIN) = 1.25V; IQ = 0.8A; SO-8 Package SO-8, SO-14 and MSOP-8 Packages 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 = 3A; ISD < 1A; 2mm 2mm DFN-8 and SC70 Packages
Ultralow Voltage Step-Up Converter and Power Manager VIN: 0.02V to 1V; VOUT = 2.5V, 3V, 3.7V, 4.5V Fixed; IQ = 6A; 3mm 4mm DFN-12 and SSOP-16 Packages 400mA (ISW), Synchronous Step-Up DC/DC Converter with Output Disconnect Piezoelectric Energy Generator with Integrated High Efciency Buck Converter 45V, 50mA Synchronous MicroPower Buck Converter 850mA Precision Reference MicroPower 25mA/8mA Low Noise Boost Converter with Integrated Schottky Diode and Output Disconnect Micropower Shunt Li-Ion Charge VIN: 0.7V to 4V; VOUT(MIN) = 5VMAX; IQ = 7A; ISD < 1A; SC70 Package
VIN: 2.7V to 20V; VOUT(MIN): Fixed to 1.8V, 2.5V, 3.3V, 3.6V; IQ = 0.95A; 3mm 3mm DFN-10 and MSOP-10E Packages VIN: 4.5V to 45V, 60VMAX; VOUT(MIN): 0.8V to Adj, 3.3V Fixed, 5V Fixed; IQ = 12A; ISD < 1A; 3mm 3mm DFN-8 and MSOP-8E Packages Series Low Dropout Precision VIN: 2.6V to 16V; VOUT(MIN) = 40VMAX; IQ = 8.5A; ISD < 1A; 2mm 2mm DFN-8 Package Controls Charging with A Source
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