For AC/DC charger applications, the Charger ASSP Flash MCU HT45F5Q-2 includes a battery charger management module, which can be used for the constant voltage and constant current closed loop charging control. The device therefore reduces the need for the usually required external TL431 component, operational amplifier and resistance analogic D/A Converter in traditional battery charging circuits. Therefore the peripheral circuit is more reduced, resulting in a smaller PCB area.
The charger management module is composed of two parts. The first part contains two groups of OPAs and D/A Converters, which are used to control the charging voltage and current. The upper limit value of the charger constant voltage and constant current can be obtained by configuring the D/A Converters in the software. The 12-bit D/A Converter is used for constant voltage control while the 8-bit D/A Converter is used for constant current control. The second part of the charger management contains a fixed gain operational amplifier which is used for current amplification. This improves the current resolution and allows the use of smaller current detection resistors thus reducing the resistor power consumption.
The D/A Converter in the charger management module is not only used for setting charging voltage and current, but also can be used together with the specific charger production fixtures for improving the traditional manual calibration techniques. By using the external production fixtures, the charger current voltage/current conditions can be confirmed. If the margin of errors is exceeded, the MCU will correct the error by fine tuning the D/A Converter, and store the corrected parameters to EEPROM. When the charger is recharged, the D/A Converter will be given a new correction value to implement correction purpose. Refer to the Holtek application notes for more details.