LT3652

LT3652 - Power Tracking 2A Battery Charger for Solar Power

Document overview

• Manufacturer or author: Linear Technology Corporation
• PDF pages: 26

Technical content

3652feFor more information www.linear.com/LT3652 TYPICAL APPLICATION

DESCRIPTION

The LT®3652 is a complete monolithic step-down bat - tery charger that operates over a 4.95V to 32V input voltage range. The LT3652 provides a constant-current/ constant-voltage charge characteristic, with maximum charge current externally programmable up to 2A. The charger employs a 3.3V float voltage feedback reference, so any desired battery float voltage up to 14.4V can be programmed with a resistor divider. The LT3652 employs an input voltage regulation loop, which reduces charge current if the input voltage falls below a programmed level, set with a resistor divider. When the LT3652 is powered by a solar panel, the input regulation loop is used to maintain the panel at peak output power. The LT3652 can be configured to terminate charging when charge current falls below 1/10 of the programmed maximum (C/10). Once charging is terminated, the LT3652 enters a low-current (85µA) standby mode. An auto-re charge feature starts a new charging cycle if the battery voltage falls 2.5% below the programmed float voltage. The LT3652 also contains a programmable safety timer, used to terminate charging after a desired time is reached. This allows top-off charging at currents less than C/10. 2A Solar Panel Power Manager With 7.2V LiFePO 4 Battery and 17V Peak Power Tracking

FEATURES

APPLICATIONS

n Input Supply Voltage Regulation Loop for Peak Power T racking in (MPPT) Solar Applications n Wide Input Voltage Range: 4.95V to 32V (40V Abs Max) n Programmable Charge Rate Up to 2A n User Selectable Termination: C/10 or On-Board Termination Timer n Resistor Programmable Float Voltage Up to 14.4V Accommodates Li-Ion/Polymer , LiFePO 4, SLA Chemistries n No VIN Blocking Diode Required for Battery Voltages ≤ 4.2V n 1MHz Fixed Frequency n 0.5% Float Voltage Reference Accuracy n 5% Charge Current Accuracy n 2.5% C/10 Detection Accuracy n Binary-Coded Open-Collector Status Pins n Thermally Enhanced 12-Lead 3mm × 3mm DFN and MSE Packages n Solar Powered Applications n Remote Monitoring Stations n LiFePO 4 (Lithium Phosphate) Applications n Portable Handheld Instruments n 12V to 24V Automotive Systems Solar Panel Input Voltage Regulation, Tracks Max Power Point to Greater Than 98% SWVIN SOLAR PANEL INPUT (<40V OC VOL TAGE) VIN_REG VFB BOOST SENSE BAT NTC TIMER CMSH3-40MA SYSTEM LOAD 1µF 542k 459k

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B = 3380 2-CELL LiFePO4 (2 × 3.6V) BATTERY PACK 10µF CMSH1-40MA 10µF 10µH 0.05 L T3652 530k 100k SHDN CHRG FAULT CMSH3-40MA CHARGER OUTPUT CURRENT (A) 0.2 INPUT REGULATION VOLTAGE (V) 0.6 1 1.2

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100% TO 98% PEAK POWER 98% TO 95% PEAK POWER TA = 25°C L, L T , L TC, L TM, Linear Technology and the Linear logo are registered trademarks and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.

3652fe For more information www.linear.com/LT3652 PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Voltages: (Note 1) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3652EDD#PBF LT3652EDD#TRPBF LFHT 12-Lead Plastic DFN 3mm × 3mm –40°C to 125°C LT3652IDD#PBF LT3652IDD#TRPBF LFHT 12-Lead Plastic DFN 3mm × 3mm –40°C to 125°C LT3652EMSE#PBF LT3652EMSE#TRPBF 3652 12-Lead Plastic MSOP –40°C to 125°C LT3652IMSE#PBF LT3652IMSE#TRPBF 3652 12-Lead Plastic MSOP –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. TOP VIEW DD PACKAGE 12-LEAD (3mm × 3mm) PLASTIC DFN 1 SW BOOST SENSE BAT NTC V FB VIN VIN_REG SHDN CHRG FAULT TIMER 6 7 GND V IN VIN_REG SHDN CHRG FAULT TIMER SW BOOST SENSE BAT NTC V FB TOP VIEW GND MSE PACKAGE 12-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 43°C/W , θJC = 3°C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB TJMAX = 125°C, θJA = 43°C/W , θJC = 3°C/W EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB Operating Junction Temperature Range

3652feFor more information www.linear.com/LT3652 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VIN VIN Operating Range VIN Start Voltage VBAT = 4.2 (Notes 3, 4) VBAT = 4.2 (Note 4) l l 4.95 7.5 32 V V VIN(OVLO) OVLO Threshold OVLO Hysteresis VIN Rising l 32 35 40 V V VIN(UVLO) UVLO Threshold UVLO Hysteresis VIN Rising 4.6 0.2 4.95 V V VFB(FL T) Float Voltage Reference (Note 6) l 3.282 3.26 3.3 3.318 3.34 V V ΔVRECHARGE Recharge Reference Threshold Voltage Relative to VFB(FL T) (Note 6) 82.5 mV VFB(PRE) Reference Precondition Threshold VFB Rising (Note 6) 2.3 V VFB(PREHYST) Reference Precondition Threshold Hysteresis Voltage Relative to VFB(PRE) (Note 6) 70 mV VIN_REG(TH) Input Regulation Reference VFB = 3V; VSENSE – VBAT = 50mV l 2.65 2.7 2.75 V IIN_REG Input Regulation Reference Bias Current VIN_REG = VIN_REG(TH) l 35 100 nA IVIN Operating Input Supply Current CC/CV Mode, ISW = 0 Standby Mode Shutdown (SHDN = 0) l 2.5 3.5 mA µA µA IBOOST BOOST Supply Current Switch On, ISW = 0, 2.5 < V(BOOST – SW) < 8.5 20 mA IBOOST/ISW BOOST Switch Drive ISW = 2A 30 mA/A VSW(ON) Switch-On Voltage Drop VIN – VSW, ISW = 2A 350 mV ISW(MAX) Switch Current Limit l 2.5 3 A VSENSE(PRE) Precondition Sense Voltage VSENSE – VBAT; VFB = 2V 15 mV VSENSE(DC) Maximum Sense Voltage VSENSE – VBAT; VFB = 3V (Note 7) l 95 100 105 mV VSENSE(C/10) C/10 T rigger Sense Voltage VSENSE – VBAT, Falling l 7.5 10 12.5 mV IBAT BAT Input Bias Current Charging Terminated 0.1 1 µA ISENSE SENSE Input Bias Current Charging Terminated 0.1 1 µA IREVERSE Charger Reverse Current IBAT + ISENSE + ISW VIN = 0; VBAT = VSENSE = VSW = 4.2V 1 µA IVFB VFB Input Bias Current Charging Terminated 65 nA IVFB VFB Input Bias Current CV Operation (Note 5) 110 nA VNTC(H) NTC Range Limit (High) VNTC Rising l 1.25 1.36 1.45 V VNTC(L) NTC Range Limit (Low) VNTC Falling l 0.27 0.29 0.315 V VNTC(HYST) NTC Threshold Hysteresis % of threshold 20 % RNTC(DIS) NTC Disable Impedance Impedance to ground l 250 500 kΩ INTC NTC Bias Current VNTC = 0.8V l 47.5 50 52.5 µA VSHDN Shutdown Threshold Rising l 1.15 1.2 1.25 V VSHDN(HYST) Shutdown Hysteresis 120 mV ISHDN SHDN Input Bias Current –10 nA VCHRG, VFAULT Status Low Voltage 10mA Load l 0.4 V ITIMER Charge/Discharge Current 25 µA VTIMER(DIS) Timer Disable Threshold l 0.1 0.25 V The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 20V, Boost – SW = 4V, SHDN = 2V, VFB = 3.3V, CTIMER = 0.68µF.

ELECTRICAL CHARACTERISTICS

3652fe For more information www.linear.com/LT3652 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS tTIMER Full Charge Cycle Timeout 3 hr Precondition Timeout 22.5 min Timer Accuracy l –10 10 % fO Operating Frequency 1 MHz DC Duty Cycle Range Continuous Operation l 15 90 % The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 20V, Boost – SW = 4V, SHDN = 2V, VFB = 3.3V, CTIMER = 0.68µF. 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 L T3652EDD is guaranteed to meet performance specifications from 0°C to 125°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 L T3652IDD specifications are guaranteed over the full –40°C to 125°C operating junction temperature range. 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: V IN minimum voltages below the start threshold are only supported if (VBOOST-VSW) > 2V . Note 4: This parameter is valid for programmed output battery float voltages ≤ 4.2V . V IN operating range minimum is 0.75V above the programmed output battery float voltage (VBAT(FL T) + 0.75V). VIN Start Voltage is 3.3V above the programmed output battery float voltage (VBAT(FL T) + 3.3V). Note 5: Output battery float voltage (VBAT(FL T)) programming resistor divider equivalent resistance = 250k compensates for input bias current. Note 6: All VFB voltages measured through 250k series resistance. Note 7: VSENSE(DC) is reduced by thermal foldback as junction temperature approaches 125°C.

3652feFor more information www.linear.com/LT3652 TYPICAL PERFORMANCE CHARACTERISTICS Switch Forward Drop (V IN – VSW) vs Temperature CC/CV Charging; SENSE Pin Bias Current vs V SENSE C/10 Threshold (V SENSE –VBAT) vs Temperature VFB Reference Voltage vs Temperature VIN Standby Mode Current vs Temperature Switch Drive (I SW/IBOOST ) vs Switch Current TJ = 25°C, unless otherwise noted. TEMPERATURE (°C) –50 VFB (FLT) 3.296 3.298 3.300 3.302 0 50 75

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3.304 –25 25 100 125 TEMPERATURE (°C) –50 IVIN CURRENT (µA) 100 0 50 75

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–25 25 100 SWITCH CURRENT (A) ISW/IBOOST 1.6

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TEMPERATURE (°C) –50 320 VSW(ON) (mV) 340 360 380 480 420 0 50 75

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–25 25 100 125 ISW = 2A VSENSE (V) –350 ISENSE (µA) –250 –150 –50 100 1 2 2.5 –300 –200 –100 0.5 1.5

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VBAT = VBAT(PRE) VBAT = VBAT(FLT) TEMPERATURE (°C) –50 VSENSE(C/10) (mV) 0 50 75

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–25 25 100 125 TEMPERATURE (°C) –50 VIN_REG(TH) (V) 2.680 2.685 2.690 2.715 2.710 2.705 2.700 2.695 0 50 75

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2.720 –25 25 100 125 VIN_REG Threshold vs Temperature: ICHG at 50%

3652fe For more information www.linear.com/LT3652 TYPICAL PERFORMANCE CHARACTERISTICS Maximum Charge Current (VSENSE –VBAT) vs Temperature Thermal Foldback – Maximum Charge Current (V SENSE –VBAT) vs Temperature CC/CV Charging; BAT Pin Bias Current vs V BAT Battery Bias Current with Charger Disabled BAT + ISENSE + IBOOST + ISW) TA = 25°C, unless otherwise noted. TEMPERATURE (°C) –50 99.0 VSENSE(DC) (mV) 99.2 99.6 99.8 100.0 101.0 100.4 0 50 75

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99.4 100.6 100.8 100.2 –25 25 100 125 VFB = 3V TEMPERATURE (°C) VSENSE(DC) (mV) 100 120 45 65 85 105 12535 13525 55 75 95 115

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VBAT (V) –0.4 IBAT (mA) 0.0 0.4 0.8 2.2 1.6 1 2 2.5 2.0 1.2 –0.2 0.2 0.6 1.0 1.8 1.4 0.5 1.5 3

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VBAT(FLT) VIN_REG (V) 2.65 VSENSE(DC) (mV) 2.67 2.69 2.7

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VBAT(FL T) (V) 0 2 IRFB (µA)

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TIME (MINUTES) EFFICIENCY (%) CHARGE CURRENT (A); POWER LOSS (W) 0.5 2.0 2.5 1.5 1.0 40 80 100

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3.0 20 60 140120 160 180 200 CHARGE CURRENT EFFICIENCY POWER LOSS VIN = 20V Maximum Charge Current (VSENSE –VBAT) vs VIN_REG Voltage VFLOAT Programming Resistor Current vs V FLOAT for 2-Resistor Network Charge Current, Efficiency, and Power Loss vs Time CHG(MAX) = 2A; VFLOAT = 8.2V) Charger Efficiency vs Battery Voltage (I CHG = 2A) VBAT (V) EFFICIENCY (%) 5 7 9 11 134 14 153 6 8 10 12

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VIN = 20V WITH INPUT BLOCKING DIODE VBAT (V) BATTERY CURRENT (µA) 4 8 10 VIN = 20V; VSHDN = 0V

3652feFor more information www.linear.com/LT3652 PIN FUNCTIONS VIN (Pin 1): Charger Input Supply. V IN operating range is 4.95V to 32V. VIN must be 3.3V greater than the pro - grammed output battery float voltage (VBAT(FLT)) for reli- able start-up. (V IN – VBAT(FLT)) ≥ 0.75V is the minimum operating voltage, provided (VBOOST – VSW) ≥ 2V. IVIN ~ 85µA after charge termination. VIN_REG (Pin 2): Input Voltage Regulation Reference. Maximum charge current is reduced when this pin is below 2.7V. Connecting a resistor divider from V IN to this pin enables programming of minimum operational VIN voltage. This is typically used to program the peak power voltage for a solar panel. The LT3652 servos the maximum charge current required to maintain the programmed operational V IN voltage, through maintaining the voltage on V IN_REG at or above 2.7V. If the voltage regulation feature is not used, connect the pin to V IN. SHDN (Pin 3): Precision Threshold Shutdown Pin. The enable threshold is 1.2V (rising), with 120mV of input hysteresis. When in shutdown mode, all charging functions are disabled. The precision threshold allows use of the SHDN pin to incorporate UVLO functions. If the SHDN pin is pulled below 0.4V, the IC enters a low current shutdown mode where V IN current is reduced to 15µA. Typical SHDN pin input bias current is 10nA. If the shutdown function is not desired, connect the pin to VIN. CHRG (Pin 4): Open-Collector Charger Status Output; typically pulled up through a resistor to a reference volt age. This status pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. During a battery charging cycle, if required charge current is greater than 1/10 of the programmed maximum current (C/10), CHRG is pulled low. A tem - perature fault also causes this pin to be pulled low. After C/10 charge termination or, if the internal timer is used for termination and charge current is less than C/10, the CHRG pin remains high-impedance. FAULT (Pin 5): Open-Collector Charger Status Output; typically pulled up through a resistor to a reference volt age. This status pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. This pin indicates fault conditions during a battery charging cycle. A temperature fault causes this pin to be pulled low. If the internal timer is used for termina- tion, a bad battery fault also causes this pin to be pulled low. If no fault conditions exist, the FAULT pin remains high-impedance. TIMER (Pin 6): End-Of-Cycle Timer Programming Pin. If a timer-based charge termination is desired, connect a capacitor from this pin to ground. Full charge end-of- cycle time (in hours) is programmed with this capacitor following the equation: t EOC = CTIMER • 4.4 • 106 A bad battery fault is generated if the battery does not achieve the precondition threshold voltage within one- eighth of tEOC, or: t PRE = CTIMER • 5.5 • 105 A 0.68µF capacitor is typically used, which generates a timer EOC at three hours, and a precondition limit time of 22.5 minutes. If a timer-based termination is not desired, the timer function is disabled by connecting the TIMER pin to ground. With the timer function disabled, charging terminates when the charge current drops below a C/10 threshold, or I CHG(MAX) /10 VFB (Pin 7): Battery Float Voltage Feedback Reference. The charge function operates to achieve a final float voltage of 3.3V on this pin. Output battery float voltage (V BAT(FLT)) is programmed using a resistor divider. VBAT(FLT) can be programmed up to 14.4V. The auto-restart feature initiates a new charging cycle when the voltage at the VFB pin falls 2.5% below the float voltage reference. The VFB pin input bias current is 110nA. Using a resistor divider with an equivalent input resistance at the VFB pin of 250k compensates for input bias current error. Required resistor values to program desired V BAT(FLT) follow the equations: R1 = (V R1 is connected from BAT to V FB, and R2 is connected from VFB to ground.

3652fe For more information www.linear.com/LT3652 NTC (Pin 8): Battery Temperature Monitor Pin. This pin is the input to the NTC (Negative Temperature Coefficient) thermistor temperature monitoring circuit. This function is enabled by connecting a 10kΩ, B = 3380 NTC thermistor from the NTC pin to ground. The pin sources 50µA, and monitors the voltage across the 10kΩ thermistor. When the voltage on this pin is above 1.36 (T < 0°C) or below 0.29V (T > 40°C), charging is disabled and the CHRG and FAULT pins are both pulled low. If internal timer termina tion is being used, the timer is paused, suspending the charging cycle. Charging resumes when the voltage on NTC returns to within the 0.29V to 1.36V active region. There is approximately 5°C of temperature hysteresis associated with each of the temperature thresholds. The temperature monitoring function remains enabled while the thermistor resistance to ground is less than 250k, so if this function is not desired, leave the NTC pin unconnected. BAT (Pin 9): Charger Output Monitor Pin. Connect a 10µF decoupling capacitance (C BAT) to ground. Depend- ing on application requirements, larger value decoupling capacitors may be required. The charge function operates to achieve the programmed output battery float voltage BAT(FLT)) at this pin. This pin is also the reference for the current sense voltage. Once a charge cycle is termi - nated, the input bias current of the BAT pin is reduced to < 0.1µA, to minimize battery discharge while the charger remains connected. SENSE (Pin 10): Charge Current Sense Pin. Connect the inductor sense resistor (R SENSE) from the SENSE pin to the BAT pin. The voltage across this resistor sets the average charge current. The maximum charge current (ICHG(MAX)) corresponds to 100mV across the sense resistor. This resistor can be set to program maximum charge cur rent as high as 2A. The sense resistor value follows the relation: R SENSE = 0.1/ICHG(MAX) (Ω) Once a charge cycle is terminated, the input bias current of the SENSE pin is reduced to < 0.1µA, to minimize battery discharge while the charger remains connected. BOOST (Pin 11): Bootstrapped Supply Rail for Switch Drive. This pin facilitates saturation of the switch transistor. Connect a 1µF or greater capacitor from the BOOST pin to the SW pin. Operating range of this pin is 0V to 8.5V, referenced to the SW pin. The voltage on the decoupling capacitor is refreshed through a rectifying diode, with the anode connected to either the battery output voltage or an external source, and the cathode connected to the BOOST pin. SW (Pin 12): Switch Output Pin. This pin is the output of the charger switch, and corresponds to the emitter of the switch transistor. When enabled, the switch shorts the SW pin to the V IN supply. The drive circuitry for this switch is bootstrapped above the V IN supply using the BOOST supply pin, allowing saturation of the switch for maximum efficiency. The effective on-resistance of the boosted switch is 0.175Ω. GND (Pin 13): Ground Reference and Backside Exposed Lead Frame Thermal Connection. Solder the exposed lead frame to the PCB ground plane. PIN FUNCTIONS

3652feFor more information www.linear.com/LT3652 BLOCK DIAGRAM 3652 BD TIMER 10m/uni03A9 35V 0.1V OFFSET 2.3V 4.6V RESET ENABLE COUNT RESET C/10 PRECONDITION 1.36V 0.29V 46µA VIN_REG BOOST VIN SW SENSE BAT VFB NTC VINT 2.7V 1.3V 1V 0.15V 1.2V 3.3V 3.218V TERMINATE50µA 0.7V CONTROL LOGIC RIPPLE COUNTER STATUS TIMER OSC. NTC 0.2V 125°C COUNT COUNT OSC 1MHz LATCH RS RS C-EA 30mV x2.25 10 × RS 0.3V VC TDIE ITH MODE (TIMER OR C/10) TERMINATE R QS 2.7VUVLO OVLO FAULT CHRG STANDBY SHDN V-EA STANDBY STANDBY

3652fe For more information www.linear.com/LT3652 APPLICATIONS INFORMATION Overview L T3652 is a complete monolithic, mid-power , multi-chem- istry buck battery charger , addressing high input voltage applications with solutions that require a minimum of exter- nal components. The IC uses a 1MHz constant frequency, average-current mode step-down architecture. The L T3652 incorporates a 2A switch that is driven by a bootstrapped supply to maximize efficiency during charging cycles. Wide input range allows operation to full charge from voltages as high as 32V . A precision threshold shutdown pin allows incorporation of UVLO functionality using a simple resistor divider . The IC can also be put into a low-current shutdown mode, in which the input supply bias is reduced to only 15µA. The L T3652 employs an input voltage regulation loop, which reduces charge current if a monitored input volt age falls below a programmed level. When the L T3652 is powered by a solar panel, the input regulation loop is used to maintain the panel at peak output power . The L T3652 automatically enters a battery precondition mode if the sensed battery voltage is very low. In this mode, the charge current is reduced to 15% of the programmed maximum, as set by the inductor sense resistor , RSENSE. Once the battery voltage reaches 70% of the fully charged float voltage, the IC automatically increases maximum charge current to the full programmed value. The L T3652 can use a charge-current based C/10 termina- tion scheme, which ends a charge cycle when the battery charge current falls to one tenth of the programmed maximum charge current. The L T3652 also contains an internal charge cycle control timer , for timer-based termina- tion. When using the internal timer , the IC combines C/10 detection with a programmable time constraint, during which the charging cycle can continue beyond the C/10 level to top-off a battery. The charge cycle terminates when a specific time elapses, typically 3 hours. When the timer-based scheme is used, the IC also supports bad battery detection, which triggers a system fault if a battery stays in precondition mode for more than one eighth of the total charge cycle time. Once charging is terminated, the L T3652 automatically enters a low-current standby mode where supply bias currents are reduced to 85µA. The IC continues to monitor the battery voltage while in standby, and if that voltage falls 2.5% from the full-charge float voltage, the L T3652 engages an automatic charge cycle restart. The IC also automatically restarts a new charge cycle after a bad bat tery fault once the failed battery is removed and replaced with another battery. The L T3652 contains provisions for a battery temperature monitoring circuit. This feature monitors battery tempera ture using a thermistor during the charging cycle. If the battery temperature moves outside a safe charging range of 0°C to 40°C, the IC suspends charging and signals a fault condition until the temperature returns to the safe charging range. The L T3652 contains two digital open-collector outputs, which provide charger status and signal fault conditions. These binary-coded pins signal battery charging, standby or shutdown modes, battery temperature faults, and bad battery faults. General Operation (See Block Diagram) The L T3652 uses average current mode control loop architecture, such that the IC servos directly to average charge current. The L T3652 senses charger output voltage through a resistor divider via the V FB pin. The difference between the voltage on this pin and an internal 3.3V volt- age reference is integrated by the voltage error amplifier (V-EA). This amplifier generates an error voltage on its output (I TH), which corresponds to the average current sensed across the inductor current sense resistor , RSENSE, which is connected between the SENSE and BAT pins. The I TH voltage is then divided down by a factor of 10, and imposed on the input of the current error amplifier (C-EA). The difference between this imposed voltage and the current sense resistor voltage is integrated, with the resulting voltage (V C) used as a threshold that is compared against an internally generated ramp. The output of this comparison controls the charger’s switch.

3652feFor more information www.linear.com/LT3652 APPLICATIONS INFORMATION The I TH error voltage corresponds linearly to average current sensed across the inductor current sense resistor , allowing maximum charge current control by limiting the effective voltage range of ITH. A clamp limits this voltage to 1V which, in turn, limits the current sense voltage to 100mV . This sets the maximum charge current, or the current delivered while the charger is operating in con - stant-current (CC) mode, which corresponds to 100mV across R SENSE. The ITH voltage is pulled down to reduce this maximum charge current should the voltage on the VIN_REG pin falls below 2.7V (VIN_REG(TH)) or the die tem- perature approaches 125°C. If the voltage on the V FB pin is below 2.3V (V FB(PRE)), the L T3652 engages precondition mode. During the precondition interval, the charger continues to operate in constant-current mode, but the maximum charge current is reduced to 15% of the maximum programmed value as set by R SENSE. When the charger output voltage approaches the float volt- age, or the voltage on the VFB pin approaches 3.3V (VFB(FL T)), the charger transitions into constant-voltage (CV) mode and charge current is reduced from the maximum value. As this occurs, the I TH voltage falls from the limit clamp and servos to lower voltages. The IC monitors the ITH volt- age as it is reduced, and detection of C/10 charge current is achieved when I TH = 0.1V . If the charger is configured for C/10 termination, this threshold is used to terminate the charge cycle. Once the charge cycle is terminated, the CHRG status pin becomes high-impedance and the charger enters low-current standby mode. The L T3652 contains an internal charge cycle timer that terminates a successful charge cycle after a programmed amount of time. This timer is typically programmed to achieve end-of-cycle (EOC) in 3 hours, but can be con figured for any amount of time by setting an appropriate timing capacitor value (CTIMER). When timer termination is used, the charge cycle does not terminate when C/10 is achieved. Because the CHRG status pin responds to the C/10 current level, the IC will indicate a fully-charged battery status, but the charger continues to source low currents into the battery until the programmed EOC time has elapsed, at which time the charge cycle will terminate. At EOC when the charging cycle terminates, if the battery did not achieve at least 97.5% of the full float voltage, charging is deemed unsuccessful, the L T3652 re-initiates, and charging continues for another full timer cycle. Use of the timer function also enables bad-battery detec tion. This fault condition is achieved if the battery does not respond to preconditioning, such that the charger remains in (or enters) precondition mode after 1/8th of the programmed charge cycle time. A bad battery fault halts the charging cycle, the CHRG status pin goes high- impedance, and the FAULT pin is pulled low. When the L T3652 terminates a charging cycle, whether through C/10 detection or by reaching timer EOC, the average current mode analog loop remains active, but the internal float voltage reference is reduced by 2.5%. Because the voltage on a successfully charged battery is at the full float voltage, the voltage error amp detects an over-voltage condition and I TH is pulled low. When the voltage error amp output drops below 0.3V , the IC enters standby mode, where most of the internal circuitry is dis- abled, and the VIN bias current is reduced to 85µA. When the voltage on the VFB pin drops below the reduced float reference level, the output of the voltage error amp will climb, at which point the IC comes out of standby mode and a new charging cycle is initiated. V IN Input Supply The L T3652 is biased directly from the charger input supply through the VIN pin. This supply provides large switched currents, so a high-quality, low ESR decoupling capacitor is recommended to minimize voltage glitches on V IN. The VIN decoupling capacitor (CVIN) absorbs all input switching

Input ripple voltages above 0.1V are not recommended. where ICHG(MAX) is the maximum average charge current. switch and facilitates saturation of the switch transistor . Figure 1. Programming Maximum Charge

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from the BOOST pin to the SW pin.

BOOST supply is available and (VBOOST – VSW) > 2V . exceed the battery float voltage. L T3652 charger is the ripple current created in that inductor . determined by setting 0.25 < ΔIL/ICHG(MAX) < 0.35. Figure 2. Zener Diode Reduces Refresh

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Figure 3. 7.2V at 1.5A Switched Inductor Values

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Figure 4. Feedback Resistors from BAT to VFB

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reverse voltages greater than the maximum VIN voltage. by connecting a resistor divider from the BAT pin to VFB. VBAT(FL T) can be programmed up to 14.4V .

pin falls 2.5% below that float voltage. additional current through the feedback divider .

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Figure 5. A Three-Resistor Feedback Network Can

used to program the peak power voltage for a solar panel. is below the regulation threshold of 2.7V . the voltage on VIN_REG at or above 2.7V . Figure 6. The ratio of R IN1/RIN2 for a desired minimum Figure 6. Resistor Divider Sets Minimum VIN

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Figure 7. Temperature Characteristics for Solar Panel

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nected cells, each cell being a forward-biased p-n junction. for the peak power point is similar to that of VOC. typical panel straight forward.

perature dependent characteristic. Figure 8. MPPT Temperature Compensation Network

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typically specified at –3.3mV/°C per cell.

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Figure 9. Lead-Acid 6-Cell Float Charge Voltage vs

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3652 F10b

Figure 10. Thermistor-Based Temperature Compensation

3652feFor more information www.linear.com/LT3652 Status Pins The L T3652 reports charger status through two open collector outputs, the CHRG and FAULT pins. These pins can accept voltages as high as V IN, and can sink up to 10mA when enabled. The CHRG pin indicates that the charger is delivering current at greater that a C/10 rate, or 1/10th of the pro - grammed maximum charge current. The FAULT pin signals bad battery and NTC faults. These pins are binary coded, and signal following the table below, where ON indicates pin pulled low, and OFF indicates pin high-impedance: STATUS PINS STATE CHARGER STATUSCHRG FAULT OFF OFF Not Charging — Standby or Shutdown Mode OFF ON Bad Battery Fault (Precondition Timeout/EOC Failure) ON OFF Normal Charging at C/10 or Greater ON ON NTC Fault (Pause) If the battery is removed from an L T3652 charger that is configured for C/10 termination, a sawtooth waveform of approximately 100mV appears at the charger output, due to cycling between termination and recharge events, This cycling results in pulsing at the CHRG output. An LED connected to this pin will exhibit a blinking pattern, indicating to the user that a battery is not present. The frequency of this blinking pattern is dependent on the output capacitance. C/10 Termination The L T3652 supports a low-current based termination scheme, where a battery charge cycle terminates when the current output from the charger falls to below one-tenth of the maximum current, as programmed with R SENSE. The C/10 threshold current corresponds to 10mV across RSENSE. This termination mode is engaged by shorting the TIMER pin to ground. APPLICATIONS INFORMATION When C/10 termination is used, a L T3652 charger will source battery charge current as long as the average current level remains above the C/10 threshold. As the full-charge float voltage is achieved, the charge current falls until the C/10 threshold is reached, at which time the charger terminates and the L T3652 enters standby mode. The CHRG status pin follows the charger cycle, and is high impedance when the charger is not actively charging. When V BAT drops below 97.5% of the full-charged float voltage, whether by battery loading or replacement of the battery, the charger automatically re-engages and starts charging. There is no provision for bad battery detection if C/10 termination is used. Timer Termination The L T3652 supports a timer based termination scheme, in which a battery charge cycle is terminated after a specific amount of time elapses. Timer termination is engaged when a capacitor (C TIMER) is connected from the TIMER pin to ground. The timer cycle EOC (TEOC) occurs based on CTIMER following the relation: C TIMER = TEOC • 2.27 x 10–7 (Hours) Timer EOC is typically set to 3 hours, which requires a 0.68µF capacitor . The CHRG status pin continues to signal charging at a C/10 rate, regardless of what termination scheme is used. When timer termination is used, the CHRG status pin is pulled low during a charging cycle until the charger output cur rent falls below the C/10 threshold. The charger continues to top-off the battery until timer EOC, when the L T3652 terminates the charging cycle and enters standby mode. Termination at the end of the timer cycle only occurs if the charging cycle was successful. A successful charge cycle is when the battery is charged to within 2.5% of the

3652fe For more information www.linear.com/LT3652 APPLICATIONS INFORMATION full-charge float voltage. If a charge cycle is not successful at EOC, the timer cycle resets and charging continues for another full timer cycle. When VBAT drops below 97.5% of the full-charge float voltage, whether by battery loading or replacement of the battery, the charger automatically reengages and starts charging. Preconditioning and Bad Battery Fault A L T3652 has a precondition mode, where charge current is limited to 15% of the programmed ICHG(MAX), as set by RSENSE. The precondition current corresponds to 15mV across RSENSE. Precondition mode is engaged while the voltage on the VFB pin is below the precondition threshold (2.3V , or 0.7 • V BAT(FL T)). Once the V FB voltage rises above the precondition threshold, normal full-current charging can commence. The L T3652 incorporates 70mV of threshold hysteresis to prevent mode glitching. When the internal timer is used for termination, bad battery detection is engaged. There is no provision for bad battery detection if C/10 termination is used. A bad battery fault is triggered when the voltage on V FB remains below the precondition threshold for greater than 1/8 of a full timer cycle (1/8 EOC). A bad battery fault is also triggered if a normally charging battery re-enters precondition mode after 1/8 EOC. When a bad battery fault is triggered, the charging cycle is suspended, so the CHRG status pin becomes high- impedance. The FAULT pin is pulled low to signal a fault detection. Cycling the charger’s power or SHDN function initiates a new charging cycle, but a L T3652 charger does not re quire a reset. Once a bad battery fault is detected, a new timer charging cycle initiates when the V FB pin exceeds the precondition threshold voltage. During a bad battery fault, 0.5mA is sourced from the charger , so removing the failed battery allows the charger output voltage to rise and initiate a charge cycle reset. As such, removing a bad battery resets the L T3652, so a new charge cycle is started by connecting another battery to the charger output. Battery Temperature Monitor and Fault The L T3652 can accommodate battery temperature moni toring by using an NTC (negative temperature co-efficient) thermistor close to the battery pack. The temperature monitoring function is enabled by connecting a 10kΩ, B = 3380 NTC thermistor from the NTC pin to ground. If the NTC function is not desired, leave the pin unconnected. The NTC pin sources 50µA, and monitors the voltage dropped across the 10kΩ thermistor . When the voltage on this pin is above 1.36V (0°C) or below 0.29V (40°C), the battery temperature is out of range, and the L T3652 triggers an NTC fault. The NTC fault condition remains until the voltage on the NTC pin corresponds to a temperature within the 0°C to 40°C range. Both hot and cold thresholds incorporate hysteresis that correspond to 5°C. If higher operational charging temperatures are desired, the temperature range can be expanded by adding series resistance to the 10k NTC resistor . Adding a 0.91k resistor will increase the effective hot temperature to 45°C. During an NTC fault, charging is halted and both status pins are pulled low. If timer termination is enabled, the timer count is suspended and held until the fault condi tion is relieved. Thermal Foldback The L T3652 contains a thermal foldback protection feature that reduces maximum charger output current if the IC junction temperature approaches 125°C. In most cases, on-chip temperatures servo such that any excessive tem perature conditions are relieved with only slight reductions in maximum charger current.

until the excessive temperature condition is relieved. typically less than 10nS to maximize conversion efficiency. also help to avoid voltage stress from inductive ringing. a ground plane is recommended.

3652 F11

Figure 11. Component Orientation Isolates High Current Paths

3652fe For more information www.linear.com/LT3652 TYPICAL APPLICATIONS 2-Cell Li-Ion Charger (8.3V at 2A) With 3 Hour Timer Termination Powered by Inexpensive 12V at 1A Unregulated Wall Adapter; V IN_REG Loop Servos Maximum Charge Current to Prevent AC Adapter Output from Drooping Lower than 12V Basic 2A 1-Cell LiFePO 4 Charger (3.6V Float) With C/10 Termination SWVIN AC ADAPTER INPUT 12V AT 1A SH-DC121000 VIN_REG VFB BOOST SENSE BAT NTC TIMER MBRS340 D3 8.2µHVISHAY 1HLP-2525CZ8R2M11 MBRS340 0.68µF 10k 626k 1µF 1N914 412k SYSTEM LOAD R1 10k B = 3380 REMOVABLE 2-CELL Li-Ion PACK (8.3V FLOAT) 1µF 10µF 0.05 100µF L T3652 10µF SHDN CHRG FAULT 10k 51k 330k 47k

3652 TA02a

5V TO 32V (40V MAX) VIN_REG VFB BOOST SENSE BAT NTC TIMER CMDSH2-4L SYSTEM LOAD 1µF 30k 223k

3652 TA03

10µF 10µF 0.05 5.6µH L T3652 SHDN CHRG FAULT CMSH3-40MA 330k LiFePO4 CELL OUTPUT CURRENT (A) OUTPUT VOLTAGE (V) 0.2 0.6

3652 TA02b

AC Adapter V vs I Characteristics

3652feFor more information www.linear.com/LT3652 PACKAGE DESCRIPTION 3.00 ±0.10 (4 SIDES) NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 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 AND TIE BARS SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.40 ±0.10 BOTTOM VIEW—EXPOSED PAD 1.65 ±0.10 0.75 ±0.05 R = 0.115 TYP 127 PIN 1 TOP MARK (SEE NOTE 6)

0.200 REF

0.00 – 0.05 (DD12) DFN 0106 REV A RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.23 ±0.05 0.25 ±0.05

2.25 REF

2.38 ±0.05 0.70 ±0.05 3.50 ±0.05 PACKAGE OUTLINE PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER 2.38 ±0.10

0.45 BSC

12-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1725 Rev A) Please refer to http://www.linear.com/product/LT3652#packaging for the most recent package drawings.

3652fe For more information www.linear.com/LT3652 PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LT3652#packaging for the most recent package drawings. MSOP (MSE12) 0213 REV G 0.53 ±0.152 (.021 ±.006) SEATING PLANE 0.18 (.007) 1.10 (.043) MAX 0.22 –/uni00A00.38 (.009 – .015) TYP 0.86 (.034) REF 0.650 (.0256) BSC 12 11 10 9 8 7 DETAIL “B” 1 6 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 6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL NOT EXCEED 0.254mm (.010") PER SIDE. 0.254 (.010) 0° – 6° TYP DETAIL “A” DETAIL “A” GAUGE PLANE RECOMMENDED SOLDER PAD LAYOUT BOTTOM VIEW OF EXPOSED PAD OPTION 2.845 ±0.102 (.112 ±.004) 4.039 ±0.102 (.159 ±.004) (NOTE 3) 1.651 ±0.102 (.065 ±.004) 1.651 ±0.102 (.065 ±.004) 0.1016 ±0.0508 (.004 ±.002) 1 2 3 4 5 6 3.00 ±0.102 (.118 ±.004) (NOTE 4) 0.406 ±0.076 (.016 ±.003) REF 4.90 ±0.152 (.193 ±.006) DETAIL “B” CORNER TAIL IS PART OF THE LEADFRAME FEATURE. FOR REFERENCE ONL Y NO MEASUREMENT PURPOSE

0.12 REF

0.35 REF 5.10 (.201) MIN 3.20 – 3.45 (.126 – .136) 0.889 ±0.127 (.035 ±.005) 0.42 ±0.038 (.0165 ±.0015) TYP 0.65 (.0256) BSC 12-Lead Plastic MSOP, Exposed Die Pad (Reference LTC DWG # 05-08-1666 Rev G)

3652feFor more information www.linear.com/LT3652

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER B 2/10 Add MSOP-12 Package 1, 2, 24 C 5/10 Corrected SHDN Pin Labels 3, 4 D 12/12 Removed reference to Nickel cell charging capability Added new Battery Bias Current curve E 12/15 Enhanced Pin Configuration Added Note 2 to top of Electrical Characteristics Enhanced Note 2 Changed name of Pin 13 Modified Inductor Selection section Modified Battery Float Voltage Programming equations 3, 4 (Revision history begins at Rev B) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

3652fe For more information www.linear.com/LT3652 RELATED PARTS TYPICAL APPLICATION PART NUMBER DESCRIPTION COMMENTS LT3650-8.2/LT3650-8.4 Monolithic 2A Switch Mode 2-Cell Li-Ion Battery Charger Standalone, 9V ≤ V IN ≤ 32V (40V Absolute Maximum), 1MHz, 2A Programmable Charge Current, Timer or C/10 Termination, Small and Few External Components, 3mm × 3mm DFN12 Package, –8.2 for 2 × 4.1V Float Voltage Batteries, –8.4 for 2 × 4.2V Float Voltage Batteries LTC4001/LTC4001-1 Monolithic 2A Switch Mode Synchronous Li-Ion Battery Charger Standalone, 4V ≤ V IN ≤ 5.5V (6V Absolute Maximum, 7V Transient), 1.5MHz, Synchronous Rectification Efficiency >90%, Adjustable Timer Termination, Small and Few External Components, 4mm × 4mm QFN-16 Package –1 for 4.1V Float Voltage Batteries LTC4002 Switch Mode Lithium-Ion Battery Charger Standalone, 4.7V ≤ V IN ≤ 24V, 500kHz Frequency, 3 Hour Charge Termination LTC4006 Small, High Efficiency, Fixed Voltage, Lithium-Ion Battery Charger with Termination and Thermistor Sensor Complete Charger for 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit, 16-Pin Narrow SSOP Package LTC4007 High Efficiency, Programmable Voltage Battery Charger with Termination Complete Charger for 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit, Thermistor Sensor and Indicator Outputs LTC4008 4A, High Efficiency, Multi-Chemistry Battery Charger Constant-Current/Constant-Voltage Switching Regulator Charger, Resistor Voltage/Current Programming, AC Adapter Current Limit and Thermistor Sensor and Indicator Outputs LTC4012/LTC4012-1/ LTC4012-2/ LTC4012-3 4A, High Efficiency, Multi-Chemistry Battery Charger with PowerPath ™ Control PowerPath Control, Constant-Current/Constant-Voltage Switching Regulator Charger, Resistor Voltage/Current Programming, AC Adapter Current Limit and Thermistor Sensor and Indicator Outputs 1 to 4 Cell Li, Up to 18 Cell Ni, SLA and Supercap Compatible; 4mm × 4mm QFN-20 Package –1 Version for 4.1V Li Cells, –2 Version for 4.2V Li Cells, –3 Version has Extra GND Pin LTC4015 Multichemistry Buck Battery Charger Controller with Digital Telemetry System Multichemistry Li-Ion/Polymer, LiFePO 4, or Lead-Acid Battery Charger with Termination, Digital Telemetry System Monitors V BAT, IBAT, RBAT, NTC Ratio (Battery Temperature), V IN, IIN, VSYSTEM , Die Temperature, Coulomb Counter and Integrated 14-Bit ADC, Maximum Power Point Tracking, Wide Charging Input Voltage Range: 4.5V to 35V, Wide Battery Voltage Range: Up to 35V, 5mm × 7mm QFN-38 Package LTC4020 55V Buck-Boost Multi-Chemistry Battery Charger Wide Voltage Range: 4.5V to 55V Input, Up to 55V Output (60V Absolute Maximums), Synchronous Buck-Boost DC/DC Controller, Li-Ion and Lead-Acid Charge Algorithms, Input Voltage Regulation for High Impedance Input Supplies and Solar Panel Peak Power Operation, Low Profile (0.75mm) 38-Pin 5mm × 7mm QFN Package 1A Solar Panel Powered 3-Stage 12V Lead-Acid Fast/Float Charger; 1A Charger Fast Charges with CC/CV Characteristics Up to 14.4V; When Charge Current Falls to 0.1A Charger Switches to 13.5V Float Charge Mode; Charger Re-Initiates 14.4V Fast Charge Mode if Battery Voltage Falls Below 13.2V and Trickle Charges at 0.15A if Battery Voltage is Below 10V; 0°C to 45°C Battery Temperature Charging Range SWVIN SOLAR PANEL INPUT <40V OC VOL TAGE 16V PEAK POWER VOL TAGE VIN_REG VFB BOOST SENSE BAT NTC TIMER 22µH MBRS340 309k 100k 1µF 1N914 BZX84C6V2L 910 174k 1N41481M SYSTEM LOAD WURTH 7447779122 12V LEAD ACID BATTERY 10k B = 3380 muRata NCP18XH103 10µF 0.1 100µF L T3652 10µF 4.7µF SHDN CHRG FAULT 499k 100k

3652 TA04

 LINEAR TECHNOLOGY CORPORATION 2010 LT 1215 REV E • PRINTED IN USA Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT3652