This application note explains how to use the VIPER20, ST62 µController, and TSM102A to implement a dual Li-Ion battery charger in an SMPS-type battery charger. It features constant current/constant voltage charging, battery type recognition, precision voltage control, temperature and failing battery protection, and end of charge detection.
This document details a dual Li-Ion battery charger design utilizing a Silicon Triplet consisting of the VIPER20 PWM controller, the ST62T25C microcontroller, and the TSM102A analog interface IC. The solution is intended for SMPS-type battery chargers featuring constant current/constant voltage charging, battery type recognition, and protection features.
The VIPER20 handles primary side control with an integrated MOSFET, while the ST62T25C manages battery recognition and charging logic. The TSM102A provides analog interfacing, including voltage and current regulation via comparators and a precision voltage reference, ensuring safe and precise charging of two Li-Ion cells in parallel.
| VIPER20 Output Power | up to 20W |
|---|---|
| VIPER20 MOSFET Voltage | 600V |
| VIPER20 MOSFET Current | 0.5A |
| ST62T25C I/O Pins | 20 I/O pins |
| TSM102A Supply Voltage | up to 36V |
| Voltage Reference Range | 2.5V to 36V |
| Voltage Reference Accuracy | 0.4% or 1% |
The Silicon Triplet consists of the VIPER20, the ST62T25C Controller, and the TSM102A.
The charger can detect batteries with a maximum cell voltage of 4.1V or 4.2V.
End of charge is detected when the charge current drops lower than a fixed threshold value, usually one fifth to one tenth of the constant current charge value.