The ET9931 is an advanced 5A unidirectional power switch for USB PD. It includes under voltage lockout, over voltage lockout, reverse current protection and over-temperature protection circuits. It is designed to automatically isolate the power switch terminals when a fault condition occurs. Both VBUS and VINT pins have 29V tolerance in shutdown mode. Two ET9931 chips can be used in parallel to support dual power inputs connecting to the same charging circuit. The device has a default 22V over voltage protection threshold, and the OVP threshold can be adjusted by using an external resistor divider on OVLO pin. A 20ms De-bounce time is deployed every time before the device is switched ON, followed by a soft start to limit the inrush current. Designed for operation from 2.9V to 29V, it is used in USB PD power control applications to offer essential protection and enhance system reliability. ET9931 is offered in a small WLCSP15 (2.530mm ×1.510mm ×0.555mm ) package.