SWITCH CIRCUIT AND SEMICONDUCTOR SWITCH, FOR BATTERY-POWERED EQUIPMENT

摘要

A switch circuit for battery-powered equipment, for example a mobile telephone or a portable computer, comprises a 4-terminal bi-directional semiconductor switch (M1) and a protection diode (Dbg). The switch (M1) has a control-gate terminal (g) for applying a control signal (Vg) to form a conduction channel (12) in a body region (11) of the switch, for turning the switch (M1) on and off between a battery (B) and a power line (2) of the equipment. The switch (M1) also has a back-gate terminal (b; bg) in a bias path that serves for applying a bias potential (Vmin) to the body region (11). The protection diode (Dbg) has a diode path in series with the back-gate terminal (b; bg) so as to provide in the bias path a rectifying barrier (25; 25') that blocks current flow between the body region (11) and the gate-bias terminal (b, bg) in the event of a reverse voltage polarity across the switch (M1), for example when recharging the battery (B). Preferably the protection diode (Dbg) is integrated with a semiconductor device body (10) of the switch (M1), with a p-n junction (25') or Schottky barrier (25) forming its rectifying barrier in the bias path between the body region (11) and the gate-bias terminal (bg).