The RT9718 is an integrated circuit optimized to protect low voltage system from abnormal high input voltage (up to 30V). The IC monitors the input voltage, battery voltage and the charging current to make sure all three parameters are operated in normal range. When the input voltage exceeds a certain OVP threshold voltage level, the IC will turn off the power MOSFET within 1ms to remove the power before any damage occurs. The RT9718 also can provide a voltage output without the existence of battery.
The current in the power 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 also has a 4-bit binary counter that accumulates during an OCP event. When the total count reaches consecutive 16 times, the power MOSFET is turned off permanently unless the input power is recycled.
The IC also monitors the battery voltage, Once the battery voltage exceeds 4.35V and last for more then 180us blinking time, the RT9718 will turn off the MOSFET. The internal logic control will turn off the power MOSFET permanently when the battery over-voltage event occurs for consecutive 16 times.