5 45 mA Fast Charge LiFePO4 Design

Figure 5-1 provides a solution that will charge at 45 mA and demonstrates the required resistors to modify the allowable battery temperature range.

• R-ISET will set fast charge current to 45 mA, 6.6 kΩ.
• Following the recommendation from Data Sheet section ISET Pin Detection, a RC circuit has been added in parallel with R-ISET to achieve a more stable current signal.
• R-CHM_TMR will set chemistry to Li+ with the safety timer disabled, 62 kΩ.
• R-VSET will set the output voltage to 3.7 V for a 1 cell LiFePO4 battery, 62 kΩ,
• R-TS is required, a 10 kΩ NTC in battery pack is connected to pin. Add Rs and Rp to adjust temperature range. RS 1.9 kΩ and RP 400 kΩ sets range to 0°C to 60°C.
• STAT1/STAT2 LEDs are used together to indicate charge status and faults, they are optional.
• /CE pin is left floating; IC operation is enabled by default.

This application supports smaller capacity batteries.