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LTC3105 400mA Step-Up DC/DC Converter with Maximum Power Point Control and 250mV Start-Up FEATURES
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DESCRIPTION
The LTC(R)3105 is a high efficiency step-up DC/DC converter that can operate from input voltages as low as 225mV. A 250mV start-up capability and integrated maximum power point controller (MPPC) enable operation directly from low voltage, high impedance alternative power sources such as photovoltaic cells, TEGs (thermoelectric generators) and fuel cells. A user programmable MPPC set point maximizes the energy that can be extracted from any power source. Burst Mode operation, with a proprietary self adjusting peak current, optimizes converter efficiency and output voltage ripple over all operating conditions. The AUX powered 6mA LDO provides a regulated rail for external microcontrollers and sensors while the main output is charging. In shutdown, IQ is reduced to 10A and integrated thermal shutdown offers protection from overtemperature faults. The LTC3105 is offered in 10-lead 3mm x 3mm x 0.75mm DFN and 12-lead MSOP packages.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Low Start-Up Voltage: 250mV Maximum Power Point Control Wide VIN Range: 225mV to 5V Auxiliary 6mA LDO Regulator Burst Mode(R) Operation: IQ = 24A Output Disconnect and Inrush Current Limiting VIN > VOUT Operation Antiringing Control Soft Start Automatic Power Adjust Power Good Indicator 10-Lead 3mm x 3mm x 0.75mm DFN and 12-Lead MSOP Packages
APPLICATIONS
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Solar Powered Battery/Supercapacitor Chargers Energy Harvesting Remote Industrial Sensors Low Power Wireless Transmitters Cell Phone, MP3, PMP and GPS Accessory Chargers
TYPICAL APPLICATION
Single Photovoltaic Cell Li-Ion Trickle Charger
10H 225mV TO 5V PHOTOVOLTAIC CELL 80 70 VOUT 4.1V 1020k FB MPPC OFF ON 40.2k 1F SHDN AUX GND PGOOD LDO FBLDO 4.7F
3105 TA01a
Output Current vs Input Voltage
MPPC DISABLED VOUT = 3.3V
-
10F LTC3105
VOUT
OUTPUT CURRENT (mA)
+
VIN
SW
60 50 40 30 20 10 0 0.2 0.3 VOUT = 4.2V
Li-Ion 332k 2.2V 10F
VOUT = 5V
0.4 0.5 0.6 0.7 0.8 INPUT VOLTAGE (V)
0.9
1.0
3105 TA01b
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LTC3105 ABSOLUTE MAXIMUM RATINGS
(Note 1)
SW Voltage DC............................................................ -0.3V to 6V Pulsed (<100ns) ...........................................-1V to 7V Voltage, All Other Pins ................................. -0.3V to 6V Operating Junction Temperature Range (Note 2).........................................-40C to 85C
Maximum Junction Temperature (Note 4) ............ 125C Storage Temperature.............................. -65C to 150C Lead Temperature (Soldering, 10 sec.) MS Package ...................................................... 300C
PIN CONFIGURATION
TOP VIEW FB LDO FBLDO SHDN MPPC 1 2 3 4 5 11 GND 10 AUX 9 VOUT 8 PGOOD 7 SW 6 VIN FB LDO FBLDO SHDN MPPC GND 1 2 3 4 5 6 TOP VIEW 12 11 10 9 8 7 AUX VOUT PGOOD SW VIN GND
DD PACKAGE 10-LEAD (3mm x 3mm) PLASTIC DFN TJMAX = 125C, JA = 43C/W, JC = 3C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
MS PACKAGE 12-LEAD PLASTIC MSOP TJMAX = 125C, JA = 130C/W, JC = 21C/W
ORDER INFORMATION
LEAD FREE FINISH LTC3105EDD#PBF LTC3105EMS#PBF TAPE AND REEL LTC3105EDD#TRPBF LTC3105EMS#TRPBF PART MARKING LFQC 3105 PACKAGE DESCRIPTION 10-Lead (3mm x 3mm) Plastic DFN 12-Lead Plastic MSOP TEMPERATURE RANGE -40C to 85C -40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
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LTC3105 ELECTRICAL CHARACTERISTICS
PARAMETER Step-Up Converter Input Operating Voltage Input Start-Up Voltage Output Voltage Adjust Range Feedback Voltage (FB Pin) VOUT IQ in Operation VOUT IQ in Shutdown MPPC Pin Output Current SHDN Input Logic High Voltage SHDN Input Logic Low Voltage N-Channel SW Pin Leakage Current P-Channel SW Pin Leakage Current N-Channel On-Resistance: SW to GND P-Channel On-Resistance: SW to VOUT Peak Current Limit Valley Current Limit PGOOD Threshold (% of Feedback Voltage) LDO Regulator LDO Output Adjust Range LDO Output Voltage Feedback Voltage (FBLDO Pin) Load Regulation Line Regulation Dropout Voltage LDO Current Limit LDO Reverse-Blocking Leakage Current External Feedback Network, VAUX > VLDO VFBLDO = 0V External Feedback Network ILDO = 1mA to 6mA VAUX = 2.5V to 5V ILDO = 6mA, VOUT = VAUX = 2.2V VLDO 0.5V Below Regulation Voltage VIN = VAUX = VOUT = 0V, VSHDN = 0V
l l l l l
The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25C (Note 2). VAUX = VOUT = 3.3V, VLDO = 2.2V, VIN = 0.6V, unless otherwise noted.
CONDITIONS MIN 0.225 0.25 1.5 0.984 1.004 24 10 9.72
l l
TYP
MAX 5 0.4 0.36 5.25 1.024
UNITS V V V V V A A
(Note 5) TJ = 0C to 85C (Note 5)
l l l
VFB = 1.10V SHDN = 0V VMPPC = 0.6V 1.1
10
10.28 0.3
A V V A A A A
VIN = VSW = 5V, VSHDN = 0V VIN = VSW = 0V, VOUT = VAUX = 5.25V
1 1 0.5 0.5
10 10
VFB = 0.90V, VMPPC = 0.4V (Note 3) VFB = 0.90V, VMPPC = 0.4V (Note 3) VOUT Falling
0.4 0.275 85 1.4 2.148 0.984
0.5 0.35 90 95 5 2.2 1.004 0.40 0.15 105 2.236 1.024
% V V V % % mV mA A
6
12 1
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 LTC3105 is tested under pulsed load conditions such that TJ TA. The LTC3105E is guaranteed to meet specifications from 0C to 85C junction temperature. Specifications over the -40C to 85C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors.
Note 3: Current measurements are performed when the LTC3105 is not switching. The current limit values measured in operation will be somewhat higher due to the propagation delay of the comparators. Note 4: This IC includes over temperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 5: The LTC3105 has been optimized for use with high impedance power sources such as photovoltaic cells and thermoelectric generators. The input start-up voltage is measured using an input voltage source with a series resistance of approximately 200m and MPPC enabled. Use of the LTC3105 with lower resistance voltage sources or with MPPC disabled may result in a higher input start-up voltage.
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LTC3105 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 0.6V, unless otherwise noted. Minimum Input Start-Up Voltage vs Temperature
340 320 THRESHOLD VOLTAGE (mV) INPUT VOLTAGE (mV) 300 280 260 240 220 200 -45 -30 -15 1000 900 800 700 600 500 400 300 200 100 0 15 30 45 60 TEMPERATURE (C) 75 90
3105 G01
TA = 25C, VAUX = VOUT = 3.3V, VLDO = 2.2V,
Shutdown Thresholds vs Input Voltage
IC ENABLE
120
IC Enable Delay vs Input Voltage
100 IC DISABLE DELAY TIME (s)
80
60
0 1.25
2.25 4.25 3.25 SUPPLY VOLTAGE, VIN OR VAUX (V)
5.25
3105 G02
40 1.25
2.25 4.25 3.25 SUPPLY VOLTAGE, VIN OR VAUX (V)
5.25
3105 G03
MPPC Current Variation vs Temperature
2.5 2.0 CHANGE FROM 25C (%) SOFT-START TIME (ms) 0 15 30 45 60 TEMPERATURE (C) 75 90
3105 G05
LDO Soft-Start Duration vs LDO Load
1.25 1.20 1.15 1.10 1.05 1.00 0.95
1.5 1.0 0.5 0 -0.5 -1.0 -1.5 -45 -30 -15
1
3 4 5 2 LDO LOAD CURRENT (mA)
6
3105 G06
VOUT IQ vs Temperature During Shutdown
22 20 18 16 IQ (A) 14 12 10 8 6 4 -45 -30 -15 0 15 30 45 60 TEMPERATURE (C) 75 90
3105 G07
VIN for Synchronous Operation
5.0 4.5 MAXIMUM INPUT VOLTAGE (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 OUTPUT VOLTAGE (V) 5.0 5.5
3105 G09
SHDN = 0V
NONSYNCHRONOUS OPERATION
SYNCHRONOUS OPERATION
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LTC3105 TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 0.6V, unless otherwise noted. Exiting MPPC Control on Input Voltage Step
VIN VOLTAGE 200mV/DIV VMPPC = 400mV 1.0 0.5 CHANGE FROM 25C (%) 0 -0.5 -1.0 -1.5 -2.0 15s/DIV -2.5 -45 -30 -15 IVALLEY EFFICIENCY (%) IPEAK 90 80 70 60 50 40 0.25
TA = 25C, VAUX = VOUT = 3.3V, VLDO = 2.2V,
IPEAK and IVALLEY Current Limit Change vs Temperature
100
Efficiency vs VIN
VOUT = 3V ILOAD = 10mA LDO = 2.2V
INDUCTOR CURRENT 100mA/DIV MPPC VOLTAGE 200mV/DIV
3105 G10
0 15 30 45 60 TEMPERATURE (C)
75 90
3105 G11
1.25
2.25 3.25 4.25 INPUT VOLTAGE (V)
5.25
3105 G12
Input and Output Burst Ripple
VIN = 0.6V CIN = 470F OUTPUT VOLTAGE 50mV/DIV SW CURRENT 200mA/DIV VOUT = 3.3V IOUT = 15mA COUT = 10F EFFICIENCY (%) 90 80 70 60 50 40 30 20 10 50s/DIV
Efficiency vs Output Current and Power Loss, VOUT = 3.3V
VIN = 0.6V VIN = 0.8V VIN = 1V EFFICIENCY
1000
100
POWER LOSS (mW)
10 POWER LOSS 1
INPUT VOLTAGE 5mV/DIV
3105 G13
0 0.01
0.1
1
10
0.1 100
3105 G14
OUTPUT CURRENT (mA)
Efficiency vs Output Current and Power Loss, VOUT = 5V
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 0.01 1 10 0.1 OUTPUT CURRENT (mA) 0.1 100
3105 G15
No-Load Input Current vs Input Voltage
1000 800 700 INPUT CURRENT (A) 100 600 500 400 300 200 100 0 0.2 0.4 0.6 0.8 INPUT VOLTAGE (V) 1.0 1.2
3105 G16
VIN = 3V VIN = 2V VIN = 1.5V EFFICIENCY
VOUT = 3.3V
POWER LOSS (mW)
10
POWER LOSS
1
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LTC3105 PIN FUNCTIONS
(DFN/MSOP)
FB (Pin 1/Pin 1): Step-Up Converter Feedback Input. Connect the VOUT resistor divider tap to this input. The output voltage can be adjusted between 1.5V and 5.25V. LDO (Pin 2/Pin 2): LDO Regulator Output. Connect a 4.7F or larger capacitor between LDO and GND. FBLDO (Pin 3/Pin 3): LDO Feedback Input. Connect the LDO resistive divider tab to this input. Alternatively, connecting FBLDO directly to GND will configure the LDO output voltage to be internally set at 2.2V (nominal). SHDN (Pin 4/Pin 4): Logic Controlled Shutdown Input. With SHDN open, the converter is enabled by an internal 2M pull-up resistor. The SHDN pin should be driven with an open-drain or open-collector pull-down and floated until the converter has entered normal operation. Excessive loading on this pin may cause a failure to complete start-up. SHDN = Low: IC Disabled SHDN = High: IC Enabled MPPC (Pin 5/Pin 5): Set Point Input for Maximum Power Point Control. Connect a resistor from MPPC to GND to program the activation point for the MPPC loop. To disable the MPPC circuit, connect MPPC directly to GND. VIN (Pin 6/Pin 8): Input Supply. Connect a decoupling capacitor between this pin and GND. The PCB trace length from the VIN pin to the decoupling capacitor should be as short and wide as possible. When used with high impedance sources such as photovoltaic cells, this pin should have a 10F or larger decoupling capacitor.
GND (Exposed Pad Pin 11/Pins 6, 7) : Small Signal and Power Ground for the IC. The GND connections should be soldered to the PCB ground using the lowest impedance path possible. SW (Pin 7/Pin 9): Switch Pin. Connect an inductor between SW and VIN. PCB trace lengths should be as short as possible to reduce EMI. While the converter is sleeping or is in shutdown, the internal antiringing switch connects the SW pin to the VIN pin in order to minimize EMI. PGOOD (Pin 8/Pin 10): Power Good Indicator. This is an open-drain output. The pull-down is disabled when VOUT has achieved the voltage defined by the feedback divider on the FB pin. The pull-down is also disabled while the IC is in shutdown or start-up mode. VOUT (Pin 9/Pin 11): Step-Up Converter Output. This is the drain connection of the main output internal synchronous rectifier. A 10F or larger capacitor must be connected between this pin and GND. The PCB trace length from the VOUT pin to the output filter capacitor should be as short and wide as possible. AUX (Pin 10/Pin 12): Auxiliary Voltage. Connect a 1F capacitor between this pin and GND. This pin is used by the start-up circuitry to generate a voltage rail to power internal circuitry until the main output reaches regulation. AUX and VOUT are internally connected together once VOUT exceeds VAUX.
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LTC3105 BLOCK DIAGRAM
L1 10H 7 SHUTDOWN SLEEP OR SW WELL CONTROL AUX SHORT CONTROL LOW VOLTAGE START-UP CURRENT ADJUST VAUX 10 CAUX 1F 1.5V TO 5.25V COUT 10F
(Pin Numbers for DFN Package Only)
225mV TO 5V
6 CIN 10F
VIN
VOUT
9
SHUTDOWN VCC MPPC 10A VIN VCC SHDN 2M
LDO
2 CLDO 4.7F
-+
-+
PEAK CURRENT LIMIT VALLEY CURRENT LIMIT LOGIC USER SHUTDOWN
5 RMPPC
- gm +
SHUTDOWN SLEEP BURST CONTROL
4
1.004V
VIN VAUX VCC EXPOSED PAD 11
FB 0.9V
+ -
- +
1.004V
-+
FBLDO FB PGOOD 3 1 8 SLEEP
3105 BD
R3
R1
R4
R2
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LTC3105 OPERATION
Introduction The LTC3105 is a unique, high performance, synchronous boost converter that incorporates maximum power point control, 250mV start-up capability and an integrated LDO regulator. This part operates over a very wide range of input voltages from 225mV to 5V. Its Burst Mode architecture and low 24A quiescent current optimize efficiency in low power applications. An integrated maximum power point controller allows for operation directly from high impedance sources such as photovoltaic cells by preventing the input power source voltage from collapsing below the user programmable MPPC threshold. Peak current limits are automatically adjusted with proprietary techniques to maintain operation at levels that maximize power extraction from the source. The 250mV start-up voltage and 225mV minimum operating voltage enable direct operation from a single photovoltaic cell and other very low voltage, high series impedance power sources such as TEGs and fuel cells. Synchronous rectification provides high efficiency operation while eliminating the need for external Schottky diodes. The LTC3105 provides output disconnect which prevents large inrush currents during start-up. This is particularly important for high internal resistance power sources like photovoltaic cells and thermoelectric generators which can become overloaded if inrush current is not limited during start-up of the power converter. In addition, output disconnect isolates VOUT from VIN while in shutdown. VIN > VOUT Operation The LTC3105 includes the ability to seamlessly maintain regulation if VIN becomes equal to or greater than VOUT . With VIN greater than or equal to VOUT , the synchronous rectifiers are disabled which may result in reduced efficiency. Shutdown Control The SHDN pin is an active low input that places the IC into low current shutdown mode. This pin incorporates an internal 2M pull-up resistor which enables the converter if the SHDN pin is not controlled by an external circuit. The SHDN pin should be allowed to float while the part is in start-up mode. Once in normal operation, the SHDN pin may be controlled using an open-drain or open-collector pull-down. Other external loads on this pin should be avoided, as they may result in the part failing to reach regulation. In shutdown, the internal switch connecting AUX and VOUT is enabled. When the SHDN pin is released, the LTC3105 is enabled and begins switching after a short delay. When either VIN or VAUX is above 1.4V, this delay will typically range between 20s and 100s. Refer to the Typical Performance Characteristics section for more details. Start-Up Mode Operation The LTC3105 provides the capability to start with voltages as low as 250mV. During start-up the AUX output initially is charged with the synchronous rectifiers disabled. Once VAUX has reached approximately 1.4V, the converter leaves start-up mode and enters normal operation. Maximum power point control is not enabled during start-up, however, the currents are internally limited to sufficiently low levels to allow start-up from weak input sources. While the converter is in start-up mode, the internal switch between AUX and VOUT remains disabled and the LDO is disabled. Refer to Figure 1 for an example of a typical start-up sequence. The LTC3105 is optimized for use with high impedance power sources such as photovoltaic cells. For operation from very low impedance, low input voltage sources, it may be necessary to add several hundred milliohms of series input resistance to allow for proper low voltage start-up. Normal Operation When either VIN or VAUX is greater than 1.4V typical, the converter will enter normal operation. The converter continues charging the AUX output until the LDO output enters regulation. Once the LDO output is in regulation, the converter begins charging the VOUT pin. VAUX is maintained at a level sufficient to ensure the LDO remains in regulation. If VAUX becomes higher than required to maintain LDO regulation, charge is transferred from the AUX output to the VOUT output. If VAUX falls too low, current is redirected to the AUX output instead of being used to charge the VOUT output. Once VOUT rises
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LTC3105 OPERATION
INDUCTOR CURRENT
TIME
OUTPUT VOLTAGE
VAUX
VLDO
VOUT
1.4V
LDO IN REGULATION START-UP MODE NORMAL OPERATION VOUT SYNCHRONOUS RECTIFIER ENABLED
VOUT IN REGULATION VOUT = VAUX
TIME
3105 F01
Figure 1. Typical Converter Start-Up Sequence
above VAUX , an internal switch is enabled to connect the two outputs together. If VIN is greater than the voltage on the driven output (VOUT or VAUX), or the driven output is less than 1.2V (typical), the synchronous rectifiers are disabled. With the synchronous rectifiers disabled, the converter operates in critical conduction mode. In this mode, the N-channel MOSFET between SW and GND is enabled and remains on until the inductor current reaches the peak current limit. It is then disabled and the inductor current discharges completely before the cycle is repeated. When the output voltage is greater than the input voltage and greater than 1.2V, the synchronous rectifier is enabled. In this mode, the N-channel MOSFET between SW and GND is enabled until the inductor current reaches the peak current limit. Once current limit is reached, the N-channel MOSFET turns off and the P-channel MOSFET between SW and the driven output is enabled. This switch remains on until the inductor current drops below the valley current limit and the cycle is repeated.
When VOUT reaches the regulation point, the N- and Pchannel MOSFETs connected to the SW pin are disabled and the converter enters sleep. Auxiliary LDO The integrated LDO provides a regulated 6mA rail to power microcontrollers and external sensors. When the input voltage is above the minimum of 225mV, the LDO is powered from the AUX output allowing the LDO to attain regulation while the main output is still charging. The LDO has a 12mA current limit and an internal 1ms soft-start to eliminate inrush currents. The LDO output voltage is set by the FBLDO pin. If a resistor divider is connected to this pin, the ratio of the resistors determines the LDO output voltage. If the FBLDO pin is connected directly to GND, the LDO will use a 2M internal divider network to program a 2.2V nominal output voltage. The LDO should be programmed for an output voltage less than the programmed VOUT .
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LTC3105 OPERATION
When the converter is placed in shutdown mode, the LDO is forced into reverse-blocking mode with reverse current limited to under 1A. After the shutdown event has ended, the LDO remains in reverse-blocking mode until VAUX has risen above the LDO voltage. MPPC Operation The maximum power point control circuit allows the user to set the optimal input voltage operating point for a given power source. The MPPC circuit dynamically regulates the average inductor current to prevent the input voltage from dropping below the MPPC threshold. When VIN is greater than the MPPC voltage, the inductor current is increased until VIN is pulled down to the MPPC set point. If VIN is less than the MPPC voltage, the inductor current is reduced until VIN rises to the MPPC set point. Automatic Power Adjust The LTC3105 incorporates a feature that maximizes efficiency at light load while providing increased power capability at heavy load by adjusting the peak and valley of the inductor current as a function of load. Lowering the peak inductor current to 100mA at light load optimizes efficiency by reducing conduction losses. As the load increases, the peak inductor current is automatically increased to a maximum of 500mA. At intermediate loads, the peak inductor current can vary between 100mA to 500mA. This function is overridden by the MPPC function and will only be observed when the power source can deliver more power than the load requires. PGOOD Operation The power good output is used to indicate that VOUT is in regulation. PGOOD is an open-drain output, and is disabled in shutdown. PGOOD will indicate that power is good at the beginning of the first sleep event after the output voltage has risen above 90% of its regulation value. PGOOD remains asserted until VOUT drops below 90% of its regulation value at which point PGOOD will pull low.
APPLICATIONS INFORMATION
Component Selection Low DCR power inductors with values between 4.7H and 30H are suitable for use with the LTC3105. For most applications, a 10H inductor is recommended. In applications where the input voltage is very low, a larger value inductor can provide higher efficiency and a lower start-up voltage. In applications where the input voltage is relatively high (VIN > 0.8V), smaller inductors may be used to provide a smaller overall footprint. In all cases, the inductor must have low DCR and sufficient saturation current rating. If the DC resistance of the inductor is too high, efficiency will be reduced and the minimum operating voltage will increase. Input capacitor selection is highly important in low voltage, high source resistance systems. For general applications, a 10F ceramic capacitor is recommended between VIN and GND. For high impedance sources, the input capacitor should be large enough to allow the converter to complete start-up mode using the energy stored in the input capacitor. When using bulk input capacitors that have high ESR, a small valued parallel ceramic capacitor should be placed between VIN and GND as close to the converter pins as possible. A 1F ceramic capacitor should be connected between AUX and GND. Larger capacitors should be avoided to minimize start-up time. A low ESR output capacitor should be connected between VOUT and GND. The main output capacitor should be 10F or larger. The main output can also be used to charge energy storage devices including tantalum capacitors, supercapacitors and batteries. When using output bulk storage devices with high ESR, a small valued ceramic capacitor should be placed in parallel and located as close to the converter pins as possible.
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LTC3105 APPLICATIONS INFORMATION
Step-Up Converter Feedback Configuration A resistor divider connected between the VOUT and FB pins programs the step-up converter output voltage, as shown in Figure 2. An optional 22pF feedforward capacitor, CFF1, can be used to reduce output ripple and improve load transient response. The equation for VOUT is: R1 VOUT = 1.004V * +1 R2 LDO Regulator Feedback Configuration Two methods can be used to program the LDO output voltage, as shown in Figure 3. A resistor divider connected between the LDO and FBLDO pins can be used to program the LDO output voltage. The equation for the LDO output voltage is: R3 VLDO = 1.004V * +1 R4 Alternatively, the FBLDO pin can be connected directly to GND. In this configuration, the LDO is internally set to a nominal 2.2V output.
VOUT CFF1 R1 FB R2 LTC3105 10A RMPPC
MPPC Threshold Configuration The MPPC circuit controls the inductor current to maintain VIN at the voltage on the MPPC pin. The MPPC pin voltage is set by connecting a resistor between the MPPC pin and GND, as shown in Figure 4. The MPPC voltage is determined by the equation: VMPPC = 10A * RMPPC In photovoltaic cell applications, a diode can be used to set the MPPC threshold so that it tracks the cell voltage over temperature, as shown in Figure 5. The diode should be thermally coupled to the photovoltaic cell to ensure proper tracking. A resistor placed in series with the diode can be used to adjust the DC set point to better match the maximum power point of a particular source if the selected diode forward voltage is too low. If the diode is located far from the converter inputs, a capacitor may be required to filter noise that may couple onto the MPPC pin, as shown in Figure 5. This method can be extended to stacked cell sources through use of multiple series connected diodes.
MPPC LTC3105
3105 F02 3105 F04
Figure 2. FB Configuration
Figure 4. MPPC Configuration
LDO R3 LTC3105 FBLDO R4
2.2V
LDO LTC3105 FBLDO VFWD RMPPC
10A
MPPC LTC3105
+
-
C6 10nF
3105 F03
3105 F05
Figure 3. FBLDO Configuration
Figure 5. MPPC Configuration with Temperature Adjustment
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LTC3105 APPLICATIONS INFORMATION
Industrial Current Loops The low 250mV start-up and low voltage operation of the LTC3105 allow it to be supplied by power from a diode placed in an industrial sensor current loop, as shown in Figure 6. In this application, a large input capacitor is required due to the very low available supply current (less than 4mA). The loop diode should be selected for a minimum forward drop of 300mV. The MPPC pin voltage should be set for a value approximately 50mV below the minimum diode forward voltage.
4mA TO 20mA CURRENT LOOP VFWD
+
VIN CIN LTC3105 GND RMPPC MPPC
3105 F06
-
Figure 6. Current Loop Power Tap
TYPICAL APPLICATIONS
3.3V from a Single-Cell Photovoltaic Source with Temperature Tracking
L1** 10H
+ -
THERMALLY COUPLED
VIN CIN 10F
SW VOUT LTC3105 FB R1 2.26M R2 1M VOUT 3.3V
MPPC RMPPC OFF ON 9.09k SHDN AUX GND
PGOOD LDO FBLDO CLDO 4.7F 2.2V
COUT 10F
D1*
CMPPC 10nF
CAUX 1F
* MRA4003T3 ** COILCRAFT MSS5131-103MX
3105 TA02
VMPPC vs Temperature
0.7 0.6 MPPC VOLTAGE (V) 0.5 0.4 0.3 0.2 0.1 0 -45 -30 -15
MPPC Response to Input Source Current Step
VOUT = 2.8V VMPPC = 0.4V VFB = 0.94V
INPUT VOLTAGE 50mV/DIV INPUT CURRENT 25mA/DIV OUTPUT CURRENT 5mA/DIV 0 15 30 45 60 TEMPERATURE (C) 75 90
3105 TA02a
0.38V 10mA 0.7mA
25s/DIV
3105 TA02b
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LTC3105 TYPICAL APPLICATIONS
3.3V from Multiple Stacked-Cell Photovoltaic with Source Temperature Tracking
L1** 6.8H
+ - + -
THERMALLY COUPLED D1* D2* RMPPC 4.99k MPPC OFF ON CMPPC 10nF CAUX 1F SHDN AUX GND CIN 10F VIN SW VOUT LTC3105 FB PGOOD LDO FBLDO CLDO 4.7F
3105 TA03
R1 1.37M R2 604k
VOUT 3.3V
COUT 10F
2.2V
* MRA4003T3 ** PANASONIC ELL-VEG6R8N
Thermoelectric Generator to 2.4V Super Capacitor Charger
L1** 10H T 10C
+
TEG*
VIN CIN 100F
SW VOUT LTC3105 FB CFF 22pF R1 1.10M R2 787k VOUT 2.4V COUT 1F
MPPC OFF ON RMPPC 30.1k SHDN AUX CAUX 1F GND
PGOOD LDO FBLDO CLDO 4.7F 2.2V
+
CBULK 1F 2.5V
3105 TA04
* MICROPELT MPG-D751 ** COILCRAFT MSS5131-103MX
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LTC3105 TYPICAL APPLICATIONS
Industrial Sensor 4mA to 20mA Current Loop Power Tap
L1** 10H VIN LTC3105 FB CIN 470F 280mV RMPPC 28k * MBRS190T3 ** COILCRAFT MSS5131-103MX OFF ON CAUX 1F MPPC SHDN AUX GND
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SW VOUT R1 2M EN P VDD CLDO 4.7F R2 1M 10F
4mA TO 20mA CURRENT LOOP
VFWD = 330mV
PGOOD LDO
D1*
RPG 499k 2.2V
+
VOUT, 3V
-
FBLDO
Transient Response to Load Pulse with 4mA Loop Current
VOUT VOLTAGE 250mV/DIV
Start-Up VIN, VOUT , VLDO
VOUT VOLTAGE 500mV/DIV LDO VOLTAGE 500mV/DIV
VIN VOLTAGE 50mV/DIV
0V LOAD CURRENT 2mA/DIV 100mV 2ms/DIV
3105 TA05a
VIN VOLTAGE 200mV/DIV
50ms/DIV
3105 TA05b
Single-Cell Photovoltaic NiMH Trickle Charger
L1, 10H
+ -
VIN CIN 10F
SW VOUT LTC3105 FB R1 1.02M R2 470k 1.8V R3 1M CLDO 4.7F COUT 10F
+ +
NiMH x2
VOUT 3.2V
MPPC OFF ON RMPPC 40.2k CAUX 1F SHDN
PGOOD LDO
AUX GND
FBLDO R4 1.27M
3105 TA06
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14
LTC3105 PACKAGE DESCRIPTION
DD Package DD Package 10-Lead Plastic DFN (3mm x 3mm) 10-Lead Plastic DFN (3mm x (Reference LTC DWG # 05-08-1699 Rev C) 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
0.70 0.05
3.55 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05
0.50 BSC 2.38 0.05 (2 SIDES) R = 0.125 TYP 6 0.40 0.10 10
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 0.10 (4 SIDES) PIN 1 TOP MARK (SEE NOTE 6) 0.200 REF 0.75 0.05
1.65 0.10 (2 SIDES)
PIN 1 NOTCH R = 0.20 OR 0.35 x 45 CHAMFER 5 2.38 0.10 (2 SIDES) 1
(DD) DFN REV C 0310
0.25 0.05 0.50 BSC
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
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15
LTC3105 PACKAGE DESCRIPTION
MS Package 12-Lead Plastic MSOP MS Package (Reference LTC DWG # 05-08-1668 Rev O) 12-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1668 Rev O)
0.889 0.127 (.035 .005)
5.23 (.206) MIN
3.20 - 3.45 (.126 - .136)
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
4.039 0.102 (.159 .004) (NOTE 3) 12 11 10 9 8 7
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP
0.406 0.076 (.016 .003) REF
0.254 (.010)
GAUGE PLANE
4.90 0.152 (.193 .006)
3.00 0.102 (.118 .004) (NOTE 4)
0.53 0.152 (.021 .006)
DETAIL "A"
0.18 (.007)
SEATING PLANE
1.10 (.043) MAX
123456
0.86 (.034) REF
NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.22 - 0.38 (.009 - .015) TYP
0.650 (.0256) BSC
0.1016 0.0508 (.004 .002)
MSOP (MS12) 1107 REV O
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16
LTC3105 REVISION HISTORY
REV A DATE 02/11 DESCRIPTION Added (Note 5) notation to Input Start-Up Voltage conditions Added Note 5 Updated Start-Up Mode Operation section PAGE NUMBER 3 3 8
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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.
17
LTC3105 TYPICAL APPLICATION
Single-Cell Powered Remote Wireless Sensor
L1* 10H
+ -
VIN CIN 10F LTC3105 MPPC
SW VOUT R1 2.32M FB R2 1.02M COUT 100F VOUT 3.3V XMTR
RMPPC 40.2k OFF ON PGOOD SHDN AUX 2N7000 CAUX 1F GND LDO FBLDO
I/O EN 2.2V RPG 499k VDD CLDO 4.7F C A/D SENSOR
GPIO
GND
* COILCRAFT MSS5131-103MX
3105 TA07
RELATED PARTS
PART NUMBER LTC3108/LTC3108-1 LTC3109 LTC4070 LTC4071 LTC3588-1/LTC3588-2 LTC3388-1/LTC3388-3 LTC3225/LTC3225-1 DESCRIPTION Ultralow Voltage Step-Up Converter and Power Manager Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager Li-Ion/Polymer Shunt Battery Charger System Li-Ion/Polymer Shunt Battery Charger System with Low Battery Disconnect Piezoelectric Energy Harvesting Power Supply 20V High Efficiency Nanopower Step-Down Regulator 150mA Super Capacitor Charger COMMENTS VIN : 0.02V to 1V; VOUT = 2.2V, 2.35V, 3.3V, 4.1V, 5V; IQ = 6A; 4mm x 3mm DFN-12, SSOP-16 Packages; LTC3108-1 VOUT = 2.2V, 2.5V, 3V, 3.7V, 4.5V |VIN |: 0.03V to 1V; VOUT = 2.2V, 2.35V, 3.3V, 4.1V, 5V; IQ = 7A; 4mm x 4mm QFN-20, SSOP-20 Packages 450nA IQ; 1% Float Voltage Accuracy; 50mA Shunt Current 4.0V/4.1V/4.2V 550nA IQ; 1% Float Voltage Accuracy; <10nA Low Battery Disconnect; 4.0V/4.1V/4.2V; 8-Lead 2mm x 3mm DFN and MSOP Packages < 1A IQ in Regulation; 2.7V to 20V Input Range; Integrated Bridge Rectifier 860nA IQ in Sleep; 2.7V to 20V Input; VOUT : 1.2V to 5V; Enable and Standby Pins Programmable Charge Current Up to 150mA; Constant-Frequency Charging of Two Series Supercapacitors; No Inductors; 2mm x 3mm DFN Package 95% Efficiency; VIN : 1V to 4.5V; VOUT = 3V, 3.3V or 5V; IQ = 7A; ISD < 1A; SC70 Package; LTC3525L-3 VIN : 0.7V to 4.5V 95% Efficiency; VIN : 0.7V to 5.5V; VOUT(MAX) = 5.25V; IQ = 9A; ISD < 1A; 2mm x 2mm DFN Package VIN : 0.5V to 5V; VOUT : 1.6V to 5.25V; IQ = 12A; ISD < 1A; 3mm x 3mm QFN Package 94% Efficiency; VIN : 0.7V to 5.5V; VOUT(MAX) = 5.25V; IQ = 12A; ISD < 1A; 2mm x 3mm DFN-8 Package VIN : 0.68V to 5V; VOUT : 1.5V to 5.25V; 3mm x 3mm QFN Package 94% Efficiency; VIN : 0.7V to 5V; VOUT(MAX) = 5.25V; IQ = 10A; ISD < 1A; 2mm x 3mm DFN Package
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LTC3525-3/LTC3525-3.3/ 400mA Micropower Synchronous Step-Up LTC3525-5/LTC3525L-3 DC/DC Converter with Output Disconnect LTC3526L/LTC3526L-2/ 550mA, 1MHz/2MHz Synchronous Boost LTC3526LB/LTC3526LB-2 Converter LTC3527 LTC3528/LTC3528-2/ LTC3528B/LTC3528B-2 LTC3537 LTC3539/LTC3539-2 Dual 2.2MHz 800mA/400mA Synchronous StepUp DC/DC Converters 1A (ISW), 1MHz/2MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 2.2MHz, 600mA Synchronous Step-Up DC/DC Converter and 100mA LDO 2A (ISW), 1MHz/2MHz Synchronous Step-Up DC/DC Converter with Output Disconnect
18 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 0211 REV A * PRINTED IN USA
www.linear.com
LINEAR TECHNOLOGY CORPORA TION 2010

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