This reference design describes a Li-ion battery charger for one 3.6V Li-ion battery cell by using the low cost 8-pin MC68HC908QT2 MCU. This flash MCU has all the critical features that a single cell Li-ion battery charger controller needed, for example, four ADC channels for measuring the charging battery’s status, powerful timer which can be config as PWM output, internal clock generator which save cost by eliminated external oscillation circuitry. In this Li-ion battery charger reference design, the design concept is to make the cost as low as possible but at the same time maintain all the necessary Li-ion battery charger functions and performance. This reference demo provides reader a reference on how to implement constant current, constant voltage charging method for Li-ion battery and how to in-circuit-programming M68HC908QT/QY MCU in system.

RD68HC908LBC Features
Capable to rapid charge a 3.6V Li-ion battery cell
Auto-detect of battery insertion.
Applied constant current and constant voltage charge method
Implemented trickle charge mode when battery voltageare too low
Charge cut off and signify battery full when charging current fall below 75mA
Over current, over voltage, over temperature protection.
In-circuit programming for firmware upgrade