Datasheet LTC4002 (Analog Devices) - 10

LTC4002
TEST CIRCUITS Test Circuit 1 Test Circuit 2
15V 15V – – 1.5V 1.5V LT1006 LT1006 + + 0V 0V SENSE LTC4002 – SENSE 100µA COMP – R 100 SENSE µA CA COMP BAT 10Ω RSENSE + CA BAT 10 + Ω 1mA VBAT – 4002 TC01 VA + 4.2V LTC4002 4002 TC02
U OPERATIO
The LTC4002 is a constant current, constant voltage charge mode. In constant current mode, the charge cur- Li-Ion battery charger controller that uses a current mode rent is set by the external sense resistor RSENSE and an PWM step-down (buck) switching architecture. The charge internal 100mV reference; IBAT = 100mV/RSENSE. current is set by an external sense resistor (RSENSE) When the battery voltage approaches the programmed across the SENSE and BAT pins. The final battery float float voltage, the charge current will start to decrease. voltage is internally set to 4.2V per cell. For batteries like When the current drops to 25% (4.2 version) or 10% (8.4 lithium-ion that require accurate final float voltage, the version) of the full-scale charge current, an internal com- internal 2.465V reference, voltage amplifier and the resis- parator turns off the internal pull-down N-channel MOSFET tor divider provide regulation with ±1% accuracy. at the CHRG pin, and connects a weak current source to A charge cycle begins when the voltage at the VCC pin rises ground to indicate a near end-of-charge condition. above the UVLO level and is 250mV or more greater than An internal 3 hour timer determines the total charge time. the battery voltage. At the beginning of the charge cycle, After a time out occurs, the charge cycle is terminated if the battery voltage is less than the trickle charge thresh- and the CHRG pin is forced high impedance. To restart old, 2.9V for the 4.2 version and 5V for the 8.4 version, the the charge cycle, remove and reapply the input voltage or charger goes into trickle charge mode. The trickle charge momentarily shut the charger down. Also, a new charge current is internally set to 10% of the full-scale current. If cycle will begin if the battery voltage drops below the the battery voltage stays low for 30 minutes, the battery recharge threshold voltage of 4.05V per cell. is considered faulty and the charge cycle is terminated. When the input voltage is present, the charger can be shut When the battery voltage exceeds the trickle charge thresh- down (I old, the charger goes into the full-scale constant current CC = 3mA) by pulling the COMP pin low. When the input voltage is not present, the charger goes into sleep 4002f 10