For electronic circuit using switching devices, generally the drain voltage of the switching device is sensed to execute the line under voltage lockout (UVLO) or over voltage protection (OVP). Traditional technology uses a metal run to cross over the drift region to connect the drain pad and the resistor divider together to get the required sensed voltage. But for high voltage switching device applications, the high voltage drop across the metal run will greatly decrease the breakdown voltage of the switching device, and even break the switching device.
Prior art have tried various ways to eliminate the above effect. One approach is to isolate metal's effect on the silicon surface's electrical field distribution by making two poly plate layers, which complicates the process and leads to switching device's low reliability. Another approach uses an extra drain pad outside of the switching device to connect to the resistor divider, and uses bonding wire to connect two drain pads to the lead frame. Such approach needs an extra pad, which increases cost.