USB Battery Charger With LM3622
Description USB Battery Charger With LM3622
The LM3622 is a charge controller for Lithium-Ion batteries. This monolithic integrated circuit accurately controls an external pass transistor for precision Lithium-Ion battery charging. The LM3622 provides a constant voltage or constant current (CVCC) configuration that changes, as necessary, to optimally charge lithium-ion battery cells. Voltage charging versions (4.1V, 4.2V, 8.2V, and 8.4V) are available for one or two cell battery packs and for coke or graphite anode battery chemistry. The LM3622 accepts input voltages from 4.5V to 24V. Controller accuracy over temperature is ±30mV/cell for A grade and ±50mV/cell for the standard grade. No precision external resistors are required. Furthermore, the LM3622’s proprietary output voltage sensing circuit drains less than 200nA from the battery when the input source is disconnected. The LM3622 circuitry includes functions for regulating the charge voltage with a temperature compensated bandgap reference and regulating the current with an external sense resistor. The internal bandgap insures excellent controller performance over the operating temperature and input supply range.
The LM3622 can sink 15mA minimum at the EXT pin to drive the base of an external PNP pass transistor. It also has low-voltage battery threshold circuitry that removes this drive when the cell voltage drops below a preset limit. The LVSEL pin programs this threshold voltage to either 2.7V/cell or 2.15V/cell. The low-voltage detection, which is a user enabled feature, provides an output signal that can be used to enable a “wake up charge” source automatically to precondition a deeply discharged pack.
Circuit Diagram USB Battery Charger With LM3622
Feature USB Battery Charger With LM3622
- Versions for charging of 1 cell (4.1V or 4.2V) or 2 cells (8.2V or 8.4V)
- Versions for coke or graphite anode
- Precision (±30mV/cell) end-of-charge control
- Wide input range: 4.5V-24V
- Low battery drain leakage: 200nA
- 15 mA available to drive low cost PNP