YT4057 is a linear lithium-ion battery linear charger with a complete trickle/constant current/constant voltage three-stage charging mode. Its input/output port has a voltage tolerance of up to 10.5V, making the YT4057 suitable for a variety of USB power supply and adapter power supply operating environments. Due to the internal PMOSFET architecture and anti-reverse charging circuit, external detection resistors and isolation diodes are not required. The thermal feedback adjusts the charging current to limit the chip temperature during high-power operation or high ambient temperatures.

    The charging voltage is limited to 4.2V and the charging current is regulated by an external resistor. After reaching the target charging voltage, when the charging current is reduced to 1/10 of the set value, the YT4057 will automatically end the charging process. When the input voltage (AC adapter or USB power supply) is removed, the YT4057 automatically enters a low current state, reducing the battery leakage current to less than 2uA. The YT4057 can also be set to stop operation, so that the power supply current is reduced to 35μA.

    YT4057 built-in anti-reverse connection function, in the lithium battery reverse connection to ensure that the IC will not be broken down resulting in battery self-discharge accidents.

    Other features include: charge current monitoring, undervoltage latching, automatic recharging and full and start charging signs.