LTC4009

LT3651-8.2 LINER

Document overview

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Technical content

LT3651-8.2/LT3651-8.4 36518284f TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Monolithic 4A High Voltage 2-Cell Li-Ion Battery Charger n Industrial Handheld Instruments n 12V to 24V Automotive and Heavy Equipment n Desktop Cradle Chargers n Notebook Computers 9V to 32V 2-Cell 4A Charger Efficiency, Power Loss vs VIN n Wide Input Voltage Range: 9V to 32V (40V Absolute Maximum) n Programmable Charge Current Up to 4A n Selectable C/10 or Onboard Timer Termination n Dynamic Charge Rate Programming/Soft-Start n Programmable Input Current Limit n ±0.5% Float Voltage Accuracy n ±7.5% Charge Current Accuracy n ±4% C/10 Detection Accuracy n NTC Resistor Temperature Monitor n Auto-Recharge at 97.5% Float Voltage n Auto-Precondition at <70% Float Voltage n Bad Battery Detection with Auto-Reset n Average Current Mode, Synchronous Switcher n User Programmable Frequency n Low Profile (0.75mm) 5mm × 6mm 36-Lead The LT®3651-8.2/LT3651-8.4 are 2-cell, 4A Li-Ion/Poly- mer battery chargers that operate over a 9V to 32V input voltage range. An efficient monolithic average current mode synchronous switching regulator provides constant current, constant voltage charging with programmable maximum charge current. A charging cycle starts with battery insertion or when the battery voltage drops 2.5% below the float voltage. Charger termination is selectable as either charge current or internal safety timer timeout. Charge current termination occurs when the charge cur- rent falls to one-tenth the programmed maximum current (C/10). Timer based termination is typically set to three hours and is user programmable (charging continues below C/10 until timeout). Once charging is terminated, the LT3651-8.2/LT3651-8.4 supply current drops to 85µA into a standby mode. The LT3651-8.2/LT3651-8.4 offer several safety features. A discharged battery is preconditioned with a small trickle charge and generates a signal if unresponsive. A thermistor monitors battery temperature, halting charging if out of range. Excessive die temperature reduces charge current. Charge current is also reduced to maintain constant input current to prevent excessive input loading. The LT3651-8.2/LT3651-8.4 are available in a 5mm × 6mm 36-lead QFN package. L, LT, LT C, LT M, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. RT TIMER BOOST SENSE BAT ILIM RNG/SS GND NTC CLP CLN 1µF 100µF 2-CELL Li-Ion BATTERY

365188284 TA01a

10µH TDK SLP12575T-100M5R4 TO SYSTEM LOAD 24m/uni03A9 301k V IN 9V TO 32V CMPSH1-4 10V Si7611DN 100k 10k L T3651-8.2/L T3651-8.4 VIN 22µF FAUL T CHRG ACPR SHDN SW VIN (V) EFFICIENCY (%) POWER LOSS (W) 3.5 4.0 4.5 5.0 5.5 6.0 15 20 25 30

1635 G07

VBAT = 7.8V IBAT = 4A

LT3651-8.2/LT3651-8.4 36518284f PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS (Note 1) 11 12 13 14 TOP VIEW GND SW UHE PACKAGE 36-LEAD (5mm × 6mm) PLASTIC QFN 15 16 17 18 36 35 34 33 32 31 30 29

1 NTC

V IN VIN VIN GND CLN CLP SW SW SW SW SW SW SW SW TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 37) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 38) IS SW, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3651EUHE-8.2#PBF LT3651EUHE-8.2#TRPBF 365182 36-Lead (5mm × 6mm) Plastic QFN –40°C to 125°C LT3651IUHE-8.2#PBF LT3651IUHE-8.2#TRPBF 365182 36-Lead (5mm × 6mm) Plastic QFN –40°C to 125°C LT3651EUHE-8.4#PBF LT3651EUHE-8.4#TRPBF 365184 36-Lead (5mm × 6mm) Plastic QFN –40°C to 125°C LT3651IUHE-8.4#PBF LT3651IUHE-8.4#TRPBF 365184 36-Lead (5mm × 6mm) Plastic QFN –40°C to 125°C Consult LT C Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.Consult LT C 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/ CLN, CLP, SHDN, CHRG, Operating Junction Temperature Range

LT3651-8.2/LT3651-8.4 36518284f The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 20V, SHDN = 2V, SENSE = BAT = VBAT(F LT), CTIMER = 0.68µF, RT = 50k, CLP = CLN = VIN, BOOST – SW = 4V.

ELECTRICAL CHARACTERISTICS

PARAMETER CONDITIONS MIN TYP MAX UNITS VIN Operating Range l 9.0 32 V VIN OVLO Threshold VIN Rising 32 35 40 V VIN OVLO Hysteresis 1.1 V VIN UVLO Threshold VIN Rising l 8.7 9.0 V VIN UVLO Hysteresis 0.2 V Battery Float Voltage, VBAT(F LT) LT3651-8.2 l 8.16 8.12 8.2 8.24 8.28 V V LT3651-8.4 l 8.36 8.32 8.4 8.44 8.48 V V Battery Recharge Voltage Hysteresis Threshold Voltage Relative to V BAT(F LT) –200 mV Battery Precondition Threshold Voltage, VBAT(PRE) LT3651-8.2, VBAT Rising LT3651-8.4, VBAT Rising 5.65 5.80 V V Battery Precondition Threshold Hysteresis Threshold Voltage Relative to V BAT(PRE) 90 mV Operating VIN Supply Current CC/CV Mode, Top Switch On, ISW = 0 Standby Mode Shutdown (SHDN = 0) 8.6 mA µA µA Top Switch On Voltage V IN – VSW , ISW = 4A 480 mV Bottom Switch On Voltage VSW , ISW = 4A –140 mV BOOST Supply Current Switch High, ISW = 0, 2.5V < (VBOOST – VSW) < 8.5V 40 mA BOOST Switch Drive IBOOST/ISW , ISW = 4A 25 mA/A Precondition Current Sense Voltage VSENSE – VBAT , VBAT = 5.0V 14 mV Input Current Limit Voltage VCLP – VCLN, ILIM Open l 70 95 115 mV CLP Input Bias Current 120 nA CLN Input Bias Current 36 µA ILIM Bias Current l 43 50 57 µA System Current Limit Programming Gain VILIM/(VCLP – VCLN), VILIM = 0.5V 11.5 V/V Maximum Charge Current Sense Voltage VSENSE – VBAT , VBAT = 7.5V, VRNG/SS > 1.1V l 88 95 103 mV C/10 T rigger Sense Voltage VSENSE – VBAT l 4.5 8.6 12.3 mV BAT Input Bias Current Charging Terminated 0.1 1 µA SENSE Input Bias Current Charging Terminated 0.1 1 µA RNG/SS Bias Current l 44 50 56 µA Charge Current Limit Programming Gain VRNG/SS/(VSENSE – VBAT), VRNG/SS = 0.5V l 8.5 10.8 12.5 V/V NTC Range Limit (High) VNTC Rising l 1.25 1.36 1.45 V NTC Range Limit (Low) VNTC Falling l 0.27 0.29 0.31 V NTC Threshold Hysteresis % of Threshold 10 % NTC Disable Impedance Minimum External Impedance to GND l 150 470 kΩ NTC Bias Current VNTC = 0.75V l 46.5 50 53.5 µA Shutdown Threshold VSHDN Rising l 1.15 1.20 1.23 V Shutdown Hysteresis 95 mV SHDN Input Bias Current –10 nA Status Low Voltage VCHRG, VFAUL T , VACPR, Load = 10mA l 0.45 V

LT3651-8.2/LT3651-8.4 36518284f 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 LT3651-8.2/LT3651-8.4 are tested under pulse loaded conditions such that T J = TA. The LT3651-8.2E/LT3651-8.4E are guaranteed to meet performance specifications from 0°C to 85°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3651-8.2I/LT3651-8.4I are guaranteed over the full –40°C to 125°C operating junction temperature range. The junction temperature (T J in °C) is calculated from the ambient temperature (TA in °C) and power dissipation (PD in Watts) according to the formula: TJ = TA + PD • θJA where θJA (in °C/W) is the package thermal impedance. Note 3: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. The maximum rated junction temperature will be exceeded when this protection is active. Continuous operation above the specified absolute maximum operating junction temperature may impair device reliability or permanently damage the device. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 20V, SHDN = 2V, SENSE = BAT = VBAT(F LT), CTIMER = 0.68µF, RT = 50k, CLP = CLN = VIN, BOOST – SW = 4V. PARAMETER CONDITIONS MIN TYP MAX UNITS TIMER Charge/Discharge Current 25 µA TIMER Disable Threshold l 0.1 0.25 V Full Charge Cycle Time-Out 3 Hour Precondition Timeout 22.5 Minute Timer Accuracy l –13 13 % Switcher Operating Frequency, fO RT = 50kΩ RT = 250kΩ 1.1 250 MHz kHz Minimum SW On-Time, tON(MIN) 150 ns

LT3651-8.2/LT3651-8.4 36518284f Battery Float Voltage vs Temperature VIN Standby Mode Current vs Temperature SENSE and BAT Pin Currents vs BAT Voltage (VSENSE = VBAT) C/10 Threshold (VSENSE – VBAT) vs Temperature Maximum Charge Current vs V RNG/SS as a Percentage of Programmed IIN(MAX) Maximum Input Current vs V ILIM as a Percentage of Programmed IIN(MAX) TYPICAL PERFORMANCE CHARACTERISTICS ICHG Current Limit (VSENSE – VBAT) vs Temperature Charge Current vs VBAT as a Percentage of Programmed I CHG(MAX) TEMPERATURE (°C) –50 –25 ∆VBAT(FL T) (%) 0.5 125

36518284 G01

–0.5 –1.0 0 100 75 50 25 1.0 TEMPERATURE (°C) –50 IVIN (µA) –25 0 25 50

36518284 G02

VBAT (V) –350 CURRENT (µA) –300 –200 –150 –100 150 2 4 5 9

36518284 G03

–250 100 –50 1 3 6 7 8 ISENSE IBAT LT3651-8.4 TEMPERATURE (°C) –50 VSENSE – VBAT (mV) –25 0 25 50

36518284 G04

VRNG/SS (V) ICHG(MAX) (%) 120 0.2 0.4 0.6 0.8

36518284 G05

1.0 1.2 100 TEMPERATURE (°C) –50 99.0 VSENSE – VBAT (mV) 99.5 100.0 100.5 101.0 –25 0 25 50

36518284 G06

VBAT (V) ICHG (%) 100 120 6 7 8 9

36518284 G07

L T3651-8.4 VILIM (V) IIN(MAX) (%) 120 0.2 0.4 0.6 0.8

36518284 G08

1.0 1.2 100

LT3651-8.2/LT3651-8.4 36518284f Topside Switch VON vs Temperature Boost Drive vs Boost Voltage Bottom Side Switch VON vs Temperature Boost Switch Drive vs Switch Current Timer Resistor (RT) vs Period and Frequency Switch Drive (IBST/ISW) vs Temperature Oscillator Frequency vs Temperature TYPICAL PERFORMANCE CHARACTERISTICS TEMPERATURE (˚C) –50 VIN – VSW (mV) 600 650 700 25 75

36518284 G10

–25 0 50 100 125 450 400 ISW = 4A TEMPERATURE (°C) –50 –250 VSW (mV) –200 –150 –100 –50 –25 0 25 50

26518284 G11

ISW = 4A TEMPERATURE (°C) –50 IBST/ISW (mA/A) –25 0 25 50

26518284 G12

ISW = 4A VBST – VIN = 4V ISW (A) IBST/ISW (mA/A) 1 2 3 4

36518284 G14

TEMPERATURE (°C) –50 –1.0 FREQUENCY DEVIATION (%)–0.5 0.5 1.0 –25 0 25 50

26518284 G15

RT = 54.9k PERIOD (µs) FREQUENCY (kHz) 1000 300 350 400 200

36518284 G16

RT (k/uni03A9) Input Current Limit Voltage Threshold vs Temperature TEMPERATURE (°C) –50 ∆(VCLP – VCLN) (mV) 1.5

36518284 G09

–1.0 –25 0 50 –1.5 –2.0 2.0 1.0 0.5 –0.5 75 100 125 RILIM OPEN RILIM = 10k VBST – VIN (V) 2.5 IBST/ISW (mA/A) 6.5

36518284 G13

3.5 4.5 5.5 7.5 ISW = 4A

LT3651-8.2/LT3651-8.4 36518284f PIN FUNCTIONS NTC (Pin 1): Battery Temperature Monitor Pin. This pin is used to monitor battery temperature. Typically a 10kΩ NTC (negative temperature coefficient) thermistor (B = 3380) is embedded with the battery and connected from the NTC pin to ground. The pin sources 50µA into the resistor and monitors the voltage across the therm- istor, regulating charging based on the voltage. If this function is not desired, leave the NTC pin unconnected. ACPR (Pin 2): Open-Collector AC Present Status Pin. This pin sinks current to indicate that VIN is valid and the charger is on. Typically a resistor pull-up is used on this pin. This pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. BAT (Pin 3): Battery Voltage Monitor Pin. This pin moni- tors battery voltage. A Kelvin connection is made to the battery from this pin and a decoupling capacitor (CBAT) is placed from this pin to ground. The charge function operates to achieve the final float voltage at this pin. The auto-restart feature initiates a new charging cycle when the voltage at the BAT pin falls 2.5% below this float voltage. Once the 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 4): Charge Current Sense Pin. The charge current is monitored with a sense resistor (R SENSE) con- nected between this pin and the BAT pin. The inductor current flows through RSENSE to the battery. The voltage across this resistor sets the average charge current. The maximum average charge current (IMAX) corresponds to 95mV across the sense resistor. BOOST (Pin 5): Bootstrapped Supply Rail for Switch Drive. This pin facilitates saturation of the high side switch transistor. Connect a 1µF or greater capacitor from the BOOST pin to the SW pin. The operating range of this pin is 0V to 8.5V, referenced to the SW pin when the switch is high. 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. GND (Pins 6, 23, 31, 37): Ground. These pins are the ground pins for the part. Pins 31, 34 and 37 must be connected together. Pins 6 and 23 are connected via the leadframe to the exposed backside Pin 37. Solder the exposed backside to the PCB for good thermal and electrical connection. SW (Pins 7, 11-18, 22, 38): Switch Output Pin. These pins are the output of the charger switches. An inductor is connected between these pins and the SENSE pin. When the switcher is active, the inductor is charged by the high side switch from V IN and discharged by the bottom side switch to GND. Solder the exposed backside, Pin 38, to the PCB for good thermal connection. NC (Pins 8-10,19-21): No Connect. These pins can be left floating (not connected). TIMER (Pin 24): End-Of-Cycle Timer Programming Pin. A capacitor on this pin to ground determines the full charge end-of-cycle time. Full charge end-of-cycle time is programmed with this capacitor. A 3 hour charge cycle is obtained with a 0.68µF capacitor. This timer also controls the bad battery fault that is generated if the battery does not reach the precondition threshold voltage within one-eighth of a full cycle (22.5 minutes for a 3 hour charge cycle). The timer based termination 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 rate, or approximately 10% of maximum charge rate. FAULT (Pin 25): Open-Collector Fault Status Output. This pin indicates charge cycle fault conditions during a battery charging cycle. Typically a resistor pull-up is used on this pin. This status pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. A temperature fault causes this pin to be pulled low. If the internal timer is used for termination, a bad battery fault also causes this pin to be pulled low. If no fault conditions exist, the FAUL T pin remains high impedance. CHRG (Pin 26): Open-Collector Charger Status Output.

LT3651-8.2/LT3651-8.4 36518284f PIN FUNCTIONS This pin indicates the battery charging status. Typically a resistor pull-up is used on this pin. This status pin can be pulled up to voltages as high as VIN when disabled, and can sink currents up to 10mA when enabled. CHRG is pulled low during a battery charging cycle. When the charge cycle is terminated, the CHRG pin becomes high impedance. If the internal timer is used for termination, the pin stays low during the charging cycle until the charge current drops below a C/10 rate, or approximately 10% of the maximum charge current. A temperature fault also causes this pin to be pulled low. SHDN (Pin 27): Shutdown Pin. This pin can be used for precision UVLO functions. When this pin rises above the 1.20V threshold, the part is enabled. The pin has 95mV of voltage hysteresis. When in shutdown mode, all charging functions are disabled. When the SHDN pin is pulled below 0.4V, the IC enters a low current shutdown mode where the VIN pin current is reduced to 17µA. Typical SHDN pin input bias current is 10nA. Connect the pin to VIN if the shutdown function is not desired. I LIM (Pin 28): Input Current Limit Programming. This pin allows for setting and dynamic adjustment of the system input current limit, and can be used to employ a soft-start function. The voltage on this pin sets the maximum input current by setting the maximum voltage across the input current sense resistor, placed between CLP and CLN. The effective range on the pin is 0V to 1V. 50µA is sourced from this pin usually to a resistor (RILIM) to ground. VIILIM represents approximately 11 times the maximum voltage across the input current sense resistor. If no RILIM is used the part will default to maximum input current. Soft-start functionality for input current can be imple- mented with a capacitor (C ILIM) from ILIM to ground. The soft-start capacitor and the programming resistor can be implemented in parallel. CLP/CLN (Pin 29/Pin 30): System Current Limit Positive and Negative Input. System current levels are monitored by connecting a sense resistor from the input power sup- ply to the CLP pin, connecting a sense resistor from the CLP pin to the CLN pin and then connecting CLN to VIN. The system load is then delivered from the CLN pin. The LT3651-8.2/LT3651-8.4 servo the maximum charge cur- rent required to maintain programmed maximum system current. The system current limit is set as a function of the voltage on the ILIM pin and the input current sense resistor. This function is disabled by shorting CLP, CLN and VIN together. VIN (Pins 32, 33, 34): Charger Input Supply. These pins provide power for the LT3651-8.2/LT3651-8.4. Charge current for the battery flows into these pins. IVIN is less than 100µA after charge termination. Connect the pins together. RNG/SS (Pin 35): Charge Current Range and Soft-Start Pin. This pin allows for setting and dynamic adjustment of the maximum charge current, and can be used to em- ploy a soft-start function. The voltage on this pin sets the maximum charge current by setting the maximum voltage across the charge current sense resistor, RSENSE , placed between SENSE and BAT. The effective range on the pin is 0V to 1V. 50µA is sourced from this pin usually to a resistor (RRNG/SS) to ground. VRNG/SS represents approximately 10 times the maximum voltage across the charge current sense resistor. If no RRNG/ SS is used the part will default to maximum charge current. Soft-start functionality for charge current can be imple- mented by connecting a capacitor (CRNG/SS) from RNG/SS to ground. The soft-start capacitor and the programming resistor can be implemented in parallel. The RNG/SS pin is pulled low during fault conditions, allowing graceful recovery from faults if CRNG/SS is used. RT (Pin 36): Switcher Oscillator Timer Set Pin. A resis- tor from this pin to ground sets the switcher oscillator frequency. Typically this is 54.9k for fOSC = 1MHz.

LT3651-8.2/LT3651-8.4 36518284f BLOCK DIAGRAM ILIM 50µA

30 CLN

0.2V A14 0.3V A10 C-EA VC 125°C STANDBY TJ ITH A13 VIN REV CUR INHIBIT OVLO UVLOSTANDBY OSC

29 CLP

24 TIMER

26 CHRG

25 FAULT

(TIMER OR C/10) TERMINATE SS/RESET COUNT STATUS CONTROL LOGIC COUNT RESET COUNT RIPPLE COUNTER TIMER OSC LATCH R Q S 35V 8.7V 0.1V 1V 0.15V 5.65V† C/10 NTC PRECONDITION V-EA 10RS RS RS 50µA SS/RESET + + 8.2V* 8.0V** 2.4V 365148284 BD TERMINATE 1.2V + + ACPR 1.36V 0.29V 0.7V GND 6, 23, 31, 37 VBAT(FL T): 8.2V FOR L T3651-8.2, 8.4V FOR L T3651-8.4 VBAT(FL T) – ∆VRECHRG: 8V FOR L T3651-8.2, 8.2V FOR L T3651-8.4 VBAT(PRE): 5.65V FOR L T3651-8.2, 5.8V FOR L T3651-8.4 1.3V STANDBY VINT 2.7V ×2.25 + – 46µA 50µA SHDN RNG/SS BAT SENSE BOOST SW 7, 11-18, 22, 38 VIN 32, 33, 34

LT3651-8.2/LT3651-8.4 36518284f OPERATION Overview The LT3651-8.2/LT3651-8.4 are complete Li-Ion battery chargers, addressing wide input voltage and high currents (up to 4A). High charging efficiency is produced with a constant frequency, average current mode synchronous step-down switcher architecture. The charger includes the necessary circuitry to allow for programming and control of constant current, constant voltage (CC/CV) charging with both current only and timer termination. High charging efficiency is achieved by the switcher by using a bootstrapped supply for low switch drop for the high side driver and a MOSFET for the low side (synchronous) switch. Maximum charge current is set with an external sense re- sistor in series with the inductor and is adjustable through the RNG/SS pin. Total system input current is monitored with an input sense resistor and is used to maintain con- stant input current by regulating battery charge current. It is adjustable through the ILIM pin. If the battery voltage is low, charge current is automatically reduced to 15% of the programmed current to provide safe battery preconditioning. Once the battery voltage climbs above the battery precondition threshold, the IC automatically increases the maximum charge current to the full programmed value. Charge termination can occur when charge current de- creases to one-tenth the programmed maximum charge current (C/10 termination). Alternately, termination can be time based through the use of an internal program- mable charge cycle control timer. When using the timer termination, charging continues beyond the C/10 level to “top-off” a battery. Charging typically terminates three hours after initiation. When the timer-based scheme is used, bad battery detection is also supported. A system fault is triggered if a battery stays in precondition mode for more than one-eighth of the total charge cycle time. Once charging is terminated and the LT3651 -8.2/ LT3651 -8.4 are not actively charging, the IC automatically enters a low current standby mode in which supply bias currents are reduced to <85µA. If the battery voltage drops 2.5% from the full charge float voltage, the LT3651-8.2/ LT3651-8.4 engage an automatic charge cycle restart. The IC also automatically restarts a new charge cycle after a bad battery fault once the failed battery is removed and replaced with another battery. After charging is completed the input bias currents on the pins connecting to the battery are reduced to minimize battery discharge. The LT3651-8.2/LT3651-8.4 contain provisions for a bat- tery temperature monitoring circuit. Battery temperature is monitored by using a NTC thermistor located with the battery. If the battery temperature moves outside a safe charging range of 0°C to 40°C the charging cycle suspends and signals a fault condition. The LT3651-8.2/LT3651-8.4 contain 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. A precision undervoltage lockout is possible by using a resistor divider on the shutdown pin (SHDN). The input supply current is 17µA when the IC is in shutdown. General Operation (See Block Diagram) The LT3651-8.2/LT3651-8.4 use an average current mode control loop architecture to control average charge current. The LT3651-8.2/LT3651-8.4 sense charger output voltage via the BAT pin. The difference between this voltage and the internal float voltage reference is integrated by the voltage error amplifier (V -EA). The amplifier output voltage (ITH) corresponds to the desired average voltage across the inductor sense resistor, RSENSE, connected between the SENSE and BAT pins. The ITH voltage is divided down by a factor of 10, and provides a voltage offset on the input of the current error amplifier (C-EA). The difference be- tween this imposed voltage and the current sense resistor voltage is integrated by C-EA. The resulting voltage (VC) provides a voltage that is compared against an internally generated ramp and generates the switch duty cycle that controls the charger’s switches.

LT3651-8.2/LT3651-8.4 36518284f OPERATION The ITH error voltage corresponds linearly to average cur- rent sensed across the inductor current sense resistor. Maximum charge current is controlled by clamping the maximum voltage of ITH to 1V. This limits the maximum current sense voltage (voltage across RSENSE) to 95mV setting the maximum charge current. Manipulation of maximum charge current is possible through the RNG/SS and ILIM pins (see the RNG/SS: Dynamic Charge Current Adjust, RNG/SS: Soft-Start and ILIM Control sections). If the voltage on the BAT pin (VBAT) is below VBAT(PRE), A7 initiates the precondition mode. During the precondition interval, the charger continues to operate in constant cur- rent mode, but the ITH clamp is reduced to 0.15V reducing charge current to 15% of the maximum programmed value. As VBAT approaches the float voltage (VFLOAT) the voltage error amp V-EA takes control of ITH and the charger transi- tions into constant voltage (CV) mode. As this occurs, the ITH voltage falls from the limit clamp and charge current is reduced from the maximum value. When the ITH voltage falls below 0.1V, A8 signals C/10. If the charger is config- ured for C/10 termination the charge cycle is terminated. Once the charge cycle is terminated, the CHRG status pin becomes high impedance and the charger enters low current standby mode. The LT3651-8.2/LT3651-8.4 contain an internal charge cycle timer that terminates a successful charge cycle af- ter a programmed amount of time. This timer is typically programmed to achieve end-of-cycle in three hours, but can be configured for any amount of time by setting an appropriate timing capacitor value (CTIMER). When timer termination is used, the charge cycle does not terminate after C/10 is achieved. Because the CHRG status pin re- sponds to the C/10 current level, the IC will indicate a fully charged battery status, but the charger will continue to source low currents. At the programmed end of the cycle time the charge cycle stops and the part enters standby mode. If the battery did not achieve at least 97.5% of the full float voltage at the end-of-cycle, charging is deemed unsuccessful and another full-timer cycle is initiated. Use of the timer function also enables bad battery detec- tion. This fault condition is achieved if the battery does not respond to preconditioning and the charger remains in (or enters) precondition mode after one-eighth of the programmed charge cycle time. A bad battery fault halts the charging cycle, the CHRG status pin goes high imped- ance and the FAUL T pin is pulled low. When the LT3651-8.2/LT3651-8.4 terminate a charging cycle, whether through C/10 detection or by reaching timer end-of-cycle, 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 er- ror amp detects an overvoltage condition and rails low. When the voltage error amp output drops below 0.3V, the IC enters standby mode, where most of the internal circuitry is disabled and the VIN bias current is reduced to <100µA. When the voltage on the BAT 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. The system current limit allows charge current to be reduced in order to maintain a constant input current. Input current is measured via a resistor (R CL) that is placed between the CLP and CLN pins. Power is applied through this resistor and is used to supply both VIN of the chip and other system loads. An offset produced on the inputs of A12 sets the threshold. When that threshold is achieved, ITH is reduced, lowering the charge current thus maintaining the maximum input current. 50µA of current is sourced from I LIM to a resistor (RILIM) that is placed from that pin to ground. The voltage on ILIM determines the regulating voltage across RCL. 1V on ILIM corresponds to 95mV across RCL. The ILIM pin clamps internally to 1V maximum. If the junction temperature of the die becomes excessive, A10 activates decreasing I TH and reduces charge current. This reduces on-chip power dissipation to safe levels but continues charging.

LT3651-8.2/LT3651-8.4 36518284f APPLICATIONS INFORMATION OSC Frequency A precision resistor to ground sets the LT3651-8.2/ LT3651-8.4 switcher oscillator frequency, fOSC, permit- ting user adjustability of the frequency value. Typically this frequency is in the 200kHz to 1MHz range. Power consideration may necessitate lower frequency operation especially if the charger is operated with very high voltages. Adjustability also allows the user to position switching harmonics if their system requires. The timing resistor, R T , value is set by the following: RT = 54.9 fOSC MHz( ) kΩ( ) Set RT to 54.9k for 1MHz operation. VIN Input Supply The LT3651-8.2/LT3651-8.4 are 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 required to minimize volt- age glitches on VIN. The VIN decoupling capacitor (CVIN) absorbs all input switching ripple current in the charger. Size is determined by input ripple voltage with the fol- lowing equation: CIN(BULK) ICHG(MAX) •VBAT fOSC MHz( ) •∆VIN •VIN µF( ) where ∆VIN is the input ripple, ICHG(MAX) is the maximum charge current and f is the oscillator frequency. A good starting point for ∆VIN is 0.1V. Worst-case conditions are with VBAT high and VIN at minimum. So for a 15V VIN(MIN), IMAX = 4A and a 1MHz oscillator frequency: CIN(BULK) = 4 •8.2 1•0.1•15 = 22µF The capacitor must have an adequate ripple current rating. RMS ripple current, ICVIN(RMS) is approximated by: ICVIN(RMS) ≈ ICHG(MAX) • VBAT VIN  • VIN VBAT – 1 which has a maximum at VIN = 2 • VBAT , where ICVIN(RMS) = ICHG(MAX)/2. In the example above that requires a capaci- tor RMS rating of 2A. Boost Supply The BOOST bootstrapped supply rail drives the internal switch and facilitates saturation of the high side switch transistor. The BOOST voltage is normally created by connecting a 1µF capacitor from the BOOST pin to the SW pin. Operating range of the BOOST pin is 2V to 8.5V, as referenced to the SW pin. The boost capacitor is normally charged via a diode con- nected from the battery or an external source through the low side switch. Rate the diode average current greater than 0.1A and its reverse voltages greater than V IN(MAX). If an external supply that is greater than the input is avail- able (VBOOST – VIN > 2V), it may be used in place of the bootstrap capacitor and diode. VIN ,VBOOST Start-Up Requirement The LT3651-8.2/LT3651-8.4 operate with a VIN range of 9V to 32V. The charger begins a charging cycle when the detected battery voltage is below the auto-restart float voltage and the part is enabled.

potential after a few cycles. charge at average currents as high as 4A (see Figure 1). where ICHG(MAX) is the maximum average charge current. RSENSE is 24mΩ for a 4A charger. Figure 1. Programming Maximum Charge Current Using RSENSE

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promise between losses due to ripple and inductor size. inductor. Peak current is ICHG(MAX) + ∆ICHG(MAX)/2.

• 1– VBAT VIN(MAX)  V •µs( ) Acceptable power inductors are available from several manufacturers such a Würth Elektronik, Vishay, Coilcraft and TDK. System Input Current Limit The LT3651-8.2/LT3651-8.4 contain a PowerPath control feature to help manage supply load currents. The charger adjusts charger output current in response to a system load so as to maintain a constant input supply load. If overall input supply current exceeds the programmed maximum value the charge current is diminished in an attempt to keep supply current constant. One application where this is helpful is if you have a current limited input supply. Setting the maximum input current limit below the supply limit prevents supply collapse. A resistor, R CL, is placed between the input supply and the system and charger loads as shown in Figure 3. APPLICATIONS INFORMATION

Figure 2. Inductance (L) vs Maximum VIN Figure 3. Input Current Limit Configuration

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Figure 4. Input Current Limit for 4A Maximum Charger if RILIM is greater than 20k or if the pin is left open. across RCL is 95mV. So RCL is set at 95mV/2A = 48mΩ. at 2A. When the system load is 2A the charge current is 0. the internal system timer if used. See Figure 4.

IMAX(RNG/SS) is the maximum charge current. (50% of 1V), imposing a 46mV maximum sense voltage. adjustable then Figure 5 shows one method. RNG/SS pin. An example is shown in Figure 6. from these faults is possible. Figure 5. Using the RNG/SS Pin for Figure 6. Driving the RNG/SS Pin Figure 7. Using the RNG/SS Pin for Soft-Start

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two open-collector outputs, the CHRG and FAUL T pins. sink up to 10mA when enabled. the pin pulled low, and Off indicates pin high impedance. Table 1. Status Pins State Table by shorting the TIMER pin to ground. cycle and enters standby mode.

LT3651-8.2/LT3651-8.4 36518284f APPLICATIONS INFORMATION charge cycle was successful. A successful charge cycle occurs when the battery is charged to within 2.5% of the full-charge float voltage. If a charge cycle is not success- ful at end-of-cycle, 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 re-engages and starts charging. Precondition and Bad Battery Fault A LT3651-8.2/LT3651-8.4 charger has a precondition mode, in which charge current is limited to 15% of the programmed IMAX, as set by RSENSE. The precondition current corresponds to 14mV across RSENSE. Precondition mode is engaged while the voltage on the BAT pin is below the precondition threshold (VBAT(PRE)). Once the BAT voltage rises above the precondition thresh- old, normal full-current charging can commence. The LT3651-8.2/LT3651-8.4 incorporate 2.5% of threshold for hysteresis to prevent mode glitching. When the internal timer is used for termination, bad bat- tery detection is engaged. This fault detection feature is designed to identify failed cells. A bad battery fault is triggered when the voltage on BAT remains below the precondition threshold for greater than one-eighth of a full timer cycle (one-eighth end-of-cycle). A bad battery fault is also triggered if a normally charging battery re-enters precondition mode after one-eighth end-of-cycle. When a bad battery fault is triggered, the charge cycle is suspended, so the CHRG status pin becomes high impedance. The FAUL T pin is pulled low to signal a fault detection. The RNG/SS pin is also pulled low during this fault, to accommodate a graceful restart, in the event that a soft-start function is incorporated (see the RNG/SS: Soft-Start section). Cycling the charger’s power or SHDN function initiates a new charge cycle, but a LT3651-8.2/LT3651-8.4 charger does not require a reset. Once a bad battery fault is de- tected, a new timer charge cycle initiates when the BAT pin exceeds the precondition threshold voltage. During a bad battery fault, 1mA is sourced from the charger. Removing the failed battery allows the charger output voltage to rise and initiate a charge cycle reset. In that way removing a bad battery resets the LT3651-8.2/LT3651-8.4. A new charge cycle is started by connecting another battery to the charger output.

LT3651-8.2/LT3651-8.4 36518284f APPLICATIONS INFORMATION Battery Temperature Fault: NTC The LT3651-8.2/LT3651-8.4 can accommodate battery tem- perature monitoring by using an NTC (negative temperature coefficient) thermistor close to the battery pack. The temper- ature 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 LT3651-8.2/ LT3651-8.4 trigger 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 corresponds to 2.5°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 condition is relieved. The RNG/SS pin is also pulled low during this fault, to accommodate a graceful restart in the event that a soft-start function is being incorporated (see the RNG/ SS: Soft- Start section). 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 (0TC) resistor will increase the effective temperature threshold to 45°C. Thermal Foldback The LT3651-8.2/LT3651-8.4 contain a thermal foldback protection feature that reduces maximum charger output current if the internal IC junction temperature approaches 125°C. In most cases, on-chip temperature servos such that any overtemperature conditions are relieved with only slight reductions in maximum charge current. In some cases, the thermal foldback protection feature can reduce charge currents below the C/10 threshold. In applications that use C/10 termination (TIMER = 0V), the LT3651-8.2/LT3651-8.4 suspend charging and enters standby mode until the overtemperature condition is relieved. Layout Considerations The LT3651-8.2/LT3651-8.4 switch node has rise and fall times that are typically less than 10ns to maximize conver- sion efficiency. These fast switch times require care in the board layout to minimize noise problems. The philosophy is to keep the physical area of high current loops small (the inductor charge/discharge paths) to minimize magnetic radiation. Keep traces wide and short to minimize parasitic inductance and resistance and shield fast switching volt- age nodes (SW, BOOST) to reduce capacitive coupling.

LT3651-8.2/LT3651-8.4 36518284f The switched node (SW pin) trace should be kept as short as possible to minimize high frequency noise. The VIN capacitor (CIN) should be placed close to the IC to minimize this switching noise. Short, wide traces on these nodes minimize stray inductance and resistance. Keep the BOOST decoupling capacitor in close proximity to the IC to minimize ringing from trace inductance. Route the SENSE and BAT traces together and keep the traces as short as possible. Shielding these signals from switching noise with ground is recommended. Make Kelvin connections to the battery and sense resistor. Keep high current paths and transients isolated from battery ground, to assure an accurate output voltage reference. Effective grounding is achieved by considering switched current in the ground plane, and careful compo- nent placement and orientation can effectively steer these high currents such that the battery reference does not get corrupted. Figure 8 illustrates the high current, high speed current loops. When the top switch is enabled (charge loop), current flows from the input bypass capacitor (CIN) through the switch and inductor to the battery positive terminal. When the top switch is disabled (discharge loop), current to the battery positive terminal is provided from ground through the synchronous switch. In both cases, these switched currents return to ground via the output bypass capacitor (CBAT). Power Considerations The LT3651-8.2/LT3651-8.4 packaging is designed to efficiently remove heat from the IC via the exposed pad on the backside of the package, which is soldered to a copper footprint on the PCB. This footprint should be made as large as possible to reduce the thermal resistance of the IC case to ambient air. Consideration should be given for power dissipation and overall efficiency in a LT3651-8.2/LT3651-8.4 charger. A detailed analysis is beyond the scope of the data sheet, however following are general guidelines. The major components of power loss are: conduction and transition losses of the LT3651-8.2/LT3651-8.4 switches; losses in the inductor and sense resistors; and AC losses in the decoupling capacitors. Switch conduction loss is fixed. T ransition losses are adjustable by changing switcher frequency. Higher input voltages cause an increase in transition losses, decreasing overall efficiency. However transition losses are inversely proportional to switcher oscillator frequency so lowering operating frequency reduces these losses. But lower operating frequency usually requires higher inductance to maintain inductor ripple current (inversely proportional). Inductors with larger values typically have more turns, increasing ESR unless you increase wire diameter making them physically Figure 8 VIN BOOST SW

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L T3651-8.2 L T3651-8.4 APPLICATIONS INFORMATION

LT3651-8.2/LT3651-8.4 36518284f larger. So there is an efficiency and board size trade-off. Secondarily, inductor AC losses increase with frequency and lower ripple reduces AC capacitor losses. The following simple rules of thumb assume a charge current of 4A and battery voltage of 7.5V, with 1MHz os- cillator, 24mΩ sense resistor and 3.3µH/20mΩ inductor. A 1% increase in efficiency represents a 0.35W reduction in power loss at 85% overall efficiency. One way to do this is to decrease resistance in the high current path. A reduction of 0.2W at 4A requires a 22mΩ reduction in resistance. This can be done by reducing inductor ESR. It is also possible to lower the sense resistance (with a reduction in RRNG/SS as well), with a trade-off of slightly less accurate current accuracy. All high current board traces should have the lowest resistance possible. Addition of input current limit sense resistance reduces efficiency. Charger efficiency drops approximately linearly with in- creasing frequency all other things constant. At 15V VIN there is a 1% improvement in efficiency for every 200kHz reduction in frequency (100kHz to 1MHz); At 28V VIN, 1% for every 100kHz. Of course all of these must be experimentally confirmed in the actual charger. TYPICAL APPLICATIONS 9V to 32V 4A Charger with High Voltage Current Foldback SHDN ACPR FAULT CHRG SW BOOST SENSE BAT I LIM RNG/SS GND NTC NC CLP RIL CLN 1µF CBAT 100µF

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3.3µH VIN SBM540 RSENSE 24m/uni03A9RT 54.9k SMAZ24 18.2V 120k 1N5819L T3651-8.2/L T3651-84 VIN CIN 22µF RT TIMER + 2-CELL Li-Ion BATTERY Maximum Charge Current vs VIN VIN (V) MAXIMUM CHARGE CURRENT (A)1 10 15 20 25

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LT3651-8.2/LT3651-8.4 36518284f TYPICAL APPLICATIONS 12V to 32V 4A Charger with Low Voltage Current Foldback Using the RNG/SS Pin Maximum Charge Current vs VIN SHDN ACPR FAULT CHRG SW BOOST SENSE BAT I LIM RNG/SS GND NTC CLP SBM540 CLN 1µF NC 1µF5.1k 68k SMAZ9V1 9.1V CBAT 100µF

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3.3µH TO SYSTEM LOAD R SENSE 24m/uni03A9RT 54.9k VIN 1N5819L T3651-82/L T3651-84 VIN CIN 22µF RT TIMER + 2-CELL Li-Ion BATTERY VIN (V) MAXIMUM CHARGE CURRENT (A)

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9V to 32V 4A Charger with Approximately Constant Input Power SHDN ACPR FAULT CHRG SW BOOST SENSE BAT I LIM RNG/SS GND NTC CLP RSENSE 50m/uni03A9 CLN 1µF 0.1µF 22k 180k 180k 20k 8.2V CBAT 100µF

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3.3µH TO SYSTEM LOAD R SENSE 24m/uni03A9RT 54.9k VIN 1N5819 NC L T3651-8.2/L T3651-8.4 VIN CIN 22µF 6.2V RT TIMER SBM540 + 2-CELL Li-Ion BATTERY Input Power vs VIN VIN (V) INPUT POWER (W) 10 15 20 25

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LT3651-8.2/LT3651-8.4 36518284f 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. PACKAGE DESCRIPTION Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. 5.00 ±0.10 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS PIN 1 TOP MARK (SEE NOTE 6) BOTTOM VIEW—EXPOSED PAD 4.50 REF6.00 ±0.10 R = 0.125 TYP 0.25 ±0.05 2.54 ±0.10 3.45 ±0.10 (UHE36MA) QFN 0410 REV A

0.50 BSC

3.45 ±0.10 1.52 ±0.10 2.54 ±0.05 1.52 ±0.05 0.75 ±0.05 0.00 – 0.05

0.200 REF

RECOMMENDED SOLDER PAD LAYOUT APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

3.50 REF

0.40 ±0.10 0.70 ±0.05

4.50 REF

4.10 ±0.05 5.50 ±0.05 5.10 ±0.05 6.50 ±0.05 0.25 ±0.05 PACKAGE OUTLINE 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm 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 PIN 1 NOTCH R = 0.30 TYP OR 0.35 × 45° CHAMFER R = 0.10 TYP Variation: UHE36MA 36-Lead Plastic QFN (5mm × 6mm) (Reference LTC DWG # 05-08-1753 Rev A) 0.25 ±0.05 0.76 ±0.05

LT3651-8.2/LT3651-8.4 36518284f Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear .com  LINEAR TECHNOLOGY CORPORATION 2012 LT 1212 • PRINTED IN USA PART NUMBER DESCRIPTION COMMENTS LT3651-4.1/LT3651-4.2 Monolithic 4A Switch Mode Synchronous 1-Cell Li-Ion Battery Charger Standalone, 4.75 ≤ VIN ≤ 32V (40V Abs Max), 1MHz, 4A, Programmable Charge Current Timer or V/10 Termination 5mm × 6mm QFN-36 Package LT3650 2A Monolithic Li-Ion Battery Charger High Efficiency, Wide Input Voltage Range Charger, Time or Charge Current Termination, Automatic Restart, Temperature Monitoring, Programmable Charge Current, Input Current Limit, 12-Lead DFN and MSOP Packages LT3652/LT3652HV Power T racking 2A Battery Charger Input Supply Voltage Regulation Loop for Peak Power T racking in (MPPT) Solar Applications, Standalone, 4.95V ≤ V IN ≤ 32V (40V Abs Max), 1MHz, 2A Programmable Charge Current, Timer or C/10 Termination, 3mm × 3mm DFN-12 IN = 34V LTC4000 High Voltage High Current Controller for Battery Charging and Power Management Complete High Performance Battery Charger When Paired with a DC/DC Converter Wide Input and Output Voltage Range: 3V to 60V ±0.25% Accurate Programmable Float Voltage, Programmable C/X or Timer Based Charge Termination NTC Input for Temperature Qualified Charging, 28-Lead 4mm × 5mm QFN or SSOP Packages LTC4002 Standalone Li-Ion Switch Mode Battery Charger Complete Charger for 1- or 2-Cell Li-Ion Batteries, Onboard Timer Termination, Up to 4A Charge Current, 10-Lead DFN and SO-8 Packages LTC4006 Small, High Efficiency, Fixed Voltage Li-Ion Battery Charger with Termination Complete Charger for 2-, 3- or 4-Cell Li-Ion Batteries, AC Adapter Current Limit and Thermistor Sensor, 16-Lead 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, 24-Lead SSOP Package LTC 4008 4A, High Efficiency, Multi-Chemistry Battery Charger Complete Charger for 2- to 6-Cell Li-Ion Batteries or 4- to 18-Cell Nickel Batteries, Up to 96% Efficiency, 20-Lead SSOP Package LTC4009/LTC4009-1 LTC4009-2 High Efficiency, Multi-Chemistry Battery Charger Complete Charger for 1- to 4-Cell Li-Ion Batteries or 4- to 18-Cell Nickel Batteries, Up to 93% Efficiency, 20-Lead (4mm × 4mm) QFN Package, LTC4009-1 for 4.1V Float Voltage, LTC4009 -2 for 4.2V Float Voltage 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; LTC4012-1 Version for 4.1V Li Cells, LTC4012 -2 Version for 4.2V Li Cells, LTC4012-3 Version Has Extra GND Pin RELATED PARTS TYPICAL APPLICATION 9V to 32V 4A Charger with 3-Hour Charge Timeout, 6.3A Input Current Limit, 10ms Soft-Start and Battery Temperature Monitoring ACPR FAULT CHRG RT TIMER BOOST SENSE BAT I LIM GNDRNG/SS NTC CLP SHDN SW RIL 16m/uni03A9 CLN 1µFNC CTIMER 0.68µF CBAT 100µF 0.47µF NTC B 10k

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3.3µH TO SYSTEM LOAD R SENSE 24m/uni03A9RT 54.9k VIN VLOGIC TO CONTROLLER 1N5819 L T3651-8.2 L T3651-8.4 V IN CIN 22µF1µF 50k50k50k50k SBM540 + 2-CELL Li-Ion BATTERY