LT3651-4.1

LT3651-4.1/LT3651-4.2 Monolithic 4A High Voltage 1 Cell Li-Ion Battery Charger FEATURES n n n n n n n n n n n n n n n DESCRIPTION The LT®3651 is a 1 cell 4A Li-Ion/Polymer battery charger that operates over a 4.8V 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 current falls to onetenth 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 supply current drops to 85μA into a standby mode. The LT3651 offers 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 is available in a 5mm × 6mm 36-pin QFN package. Wide Input Voltage Range: 4.8V to 32V (40V Absolute Maximum) Programmable Charge Current Up to 4A Selectable C/10 or Onboard Timer Termination Dynamic Charge Rate Programming/Soft-Start Programmable Input Current Limit 0.5% Float Voltage Accuracy 7.5% Charge Current Accuracy 4% C/10 Detection Accuracy NTC Resistor Temperature Monitor Auto-Recharge at 97.5% Float Voltage Auto-Precondition 1.1V VSENSE – VBAT Charging Terminated Charging Terminated l l l 44 8.5 1.25 0.27 150 46.5 1.16 50 10.8 1.36 0.29 10 470 50 1.20 95 –10 VRNG/SS/(VSENSE – VBAT), VRNG/SS = 0.5V VNTC Rising VNTC Falling % of Threshold Minimum External Impedance to GND VNTC = 0.75V VSHDN Rising l l l l l l 53.5 1.23 μA V mV nA VCHRG, VFAULT , VACPR, Load = 10mA l 0.45 V 365142fb 3 LT3651-4.1/LT3651-4.2 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(FLT), CTIMER = 0.68μF RT = 50k, CLP = CLN = VIN, BOOST – SW = 4V. , PARAMETER TIMER Charge/Discharge Current TIMER Disable Threshold Full Charge Cycle Time-Out Precondition Timeout Timer Accuracy Switcher Operating Frequency, fO Minimum SW On-Time, tON(MIN) 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 is tested under pulse loaded conditions such that TJ = TA. The LT3651E is 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 LT3651I is guaranteed over the full –40°C to 125°C operating junction RT = 50kΩ RT = 250kΩ l l ELECTRICAL CHARACTERISTICS CONDITIONS MIN 0.1 TYP 25 0.25 3 22.5 MAX UNITS μA V Hour Minute –13 1.1 250 150 13 % MHz kHz ns temperature range. The junction temperature (TJ 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. 365142fb 4 LT3651-4.1/LT3651-4.2 TYPICAL PERFORMANCE CHARACTERISTICS Battery Float Voltage vs Temperature 1.0 100 95 0.5 ΔVBAT(FLT) (%) IVIN (μA) 90 85 CURRENT (μA) 80 75 70 65 60 55 –1.0 –50 –25 25 50 75 0 TEMPERATURE (°C) 100 125 50 –50 –25 25 50 0 TEMPERATURE (°C) 75 100 VIN Standby Mode Current vs Temperature 150 100 50 0 –50 –100 –150 –200 –250 –300 –350 SENSE and BAT Pin Current vs BAT Voltage, VSENSE = VBAT LT3651-4.2 ISENSE IBAT 0 –0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 VBAT (V) 365142 G03 365142 G01 365142 G02 Maximum Charge Current vs VRNG/SS as a Percentage of Programmed IMAX 120 100 100.5 ICHG(MAX) (%) 80 60 40 20 0 VSENSE – VBAT (mV) 101.0 IMAX Current Limit (VSENSE – VBAT) vs Temperature 120 100 80 60 40 20 99.0 –50 Thermal Foldback–Charge Current vs Temperature as a Percentage of Programmed ICHG(MAX) 100.0 99.5 ICHG(MAX) (%) 0 0.2 0.4 0.6 VRNG/SS (V) 0.8 1.0 1.2 –25 75 0 25 50 TEMPERATURE (°C) 100 125 0 100 110 120 130 TEMPERATURE (°C) 140 365142 G06 365142 G04 365142 G05 Maximum Input Current vs VILIM as a Percentage of Programmed IIN(MAX) 120 100 80 60 40 20 0 Δ(VCLP – VCLN) (mV) 2.0 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 0 0.4 0.6 0.8 VILIM (V) 1.0 1.2 Input Current Limit Voltage Threshold vs Temperature 120 100 RILIM OPEN 80 RILIM = 10k ICHG (%) 60 40 20 0 Charge Current vs VBAT as a Percentage of Programmed ICHG(MAX) LT3651-4.2 IIN(MAX) (%) 0.2 –2.0 –50 –25 0 75 50 25 TEMPERATURE (°C) 100 125 2.5 3.0 3.5 VBAT (V) 4.0 4.5 365142 G09 365142 G07 365142 G08 365142fb 5 LT3651-4.1/LT3651-4.2 TYPICAL PERFORMANCE CHARACTERISTICS C/10 Threshold (VSENSE –VBAT) vs Temperature 11 700 ISW = 4A 650 10 VSENSE – VBAT (mV) VIN – VSW (mV) 600 VSW (mV) 550 500 –200 450 7 –50 400 –50 –25 –250 –50 –150 –100 Top Side Switch VON vs Temperature –50 Bottom Side VON vs Temperature ISW = 4A 9 8 –25 75 0 25 50 TEMPERATURE (°C) 100 125 50 25 75 0 TEMPERATURE (˚C) 100 125 –25 75 0 25 50 TEMPERATURE (°C) 100 125 365142 G10 365142 G11 365142 G12 Switch Drive (IBST/ISW) vs Temperature 35 60 ISW = 4A 50 IBST/ISW (mA/A) Boost Drive vs Boost Voltage 70 ISW = 4A 60 IBST/ISW (mA/A) 3.5 5.5 6.5 4.5 VBST – VIN (V) 50 40 30 20 10 7.5 365142 G14 Boost Switch Drive vs Switch Current 30 IBST/ISW (mA/A) 40 25 30 20 20 15 –50 –25 75 0 25 50 TEMPERATURE (°C) 100 125 10 2.5 0 1 2 ISW (A) 3 4 5 365142 G15 365142 G13 Oscillator Frequency vs Temperature 1.0 400 RT = 54.9k 350 FREQUENCY DEVIATION (%) 0.5 RT (kΩ) 300 250 200 150 100 –1.0 –50 50 –25 75 0 25 50 TEMPERATURE (°C) 100 125 Timer Resistor (RT) vs Period and Frequency 0 –0.5 1 1000 2 500 365142 G16 3 4 333 250 PERIOD (μs) FREQUENCY (kHz) 5 200 6 167 365142 G17 365142fb 6 LT3651-4.1/LT3651-4.2 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 thermistor, 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 monitors 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 terminated, the input bias current of the BAT pin is reduced to