RT9709
Description
The RT9709 is an integrated circuit (IC) optimized to protect low voltage system from abnormal high voltage input up to 28V. The IC monitors the input voltage, battery voltage and the charging current to make sure all three parameters are operated in normal range. It also monitors its own temperature and turns the MOSFET off when the chip temperature exceeds 140°C.
The RT9709 can support AC charger or USB charger. When the input voltage exceeds the OVP threshold, the IC turns off the MOSFET within 1us to remove the power before any damage occurs.
The current in the MOSFET is also limited to prevent charging the battery with an excessive current. The current limit can be programmed by an external resistor between ILIM and GND. The OCP function has a 4-bit binary counter that accumulates during an OCP event. When the total count reaches 16 times, the MOSFET will be turned off permanently unless the input power is recycled.
The IC also monitors the battery voltage VB. When the...
