The LTC®4007-1 is a constant-current/constant-voltage charger controller for 3- or 4-cell lithium-ion batteries. The PWM controller uses a synchronous, quasi-constant frequency, constant off-time architecture that will not generate audible noise even when using ceramic capacitors. Charging current is programmable to ±4% accuracy using a programming resistor. Charging current can also be monitored as a voltage across the programming resistor.The output float voltage is pin programmed for cell count (3 cells or 4 cells) and chemistry (4.2V/4.1V). A timer, programmed by an external resistor, sets the total charge time.The LTC4007-1 includes a thermistor input, which suspends charging if an unsafe temperature condition is detected. If the cell voltage is less than 3.25V, a low-battery indicator asserts and can be used to program a trickle charge current to safely charge depleted batteries. The FAULT pin is also asserted and charging terminates if the low-battery condition persists for more than 1/4 of the total charge time.
