CN3762 dual series lithium battery charging

Introduction

CN3762 is a PWM step-down mode two-cell lithium battery charge management integrated circuit that independently manages the charging of two lithium batteries. It has the advantages of small package size, few peripheral components and simple use.

CN3762 features trickle, constant current and constant voltage charging modes, making it ideal for lithium battery charge management.

Features

Charging process

Trickle charging

In the charging state, if the battery voltage is lower than 66.5% (typical value) of the constant voltage charging voltage, the charger enters the trickle charging mode, and the charging current is 17.5% of the constant current charging current.

Constant voltage charging

In constant voltage charging mode, CN3762 modulates the battery voltage at 8.4V, which can also be adjusted upward through an external resistor Rx.

If a resistor is connected between the FB pin and the BAT pin of CN3762, the constant voltage charging voltage can be increased to offset the voltage drop of the battery's internal resistance and connection resistance, making the battery charge more fully. This external resistor is on the schematic diagram R3.

Now Rx is 10k, which is Vreg=8.48996V

Constant current charging current setting

In constant current charging mode, the charging current is set by an external resistor.

That is the R1 resistance. The current R1 is 0.06 ohms, then Ich=2A

This is the current when it is almost fully charged. It slowly decreases from constant current 2A to constant voltage charging.

The picture above shows the heat sink recommendation. The inductor, two Schottky diodes and the mos tube generate a lot of heat during charging.

Basically the description is copied from the data sheet, please refer to the data sheet for details.