On-chip overcurrent and openload detection for a power MOS high-side switch: a CMOS current mode approach

A novel accurate CMOS current sensing circuit for the protection of smart power MOS switches, using the current mode approach, is proposed. It has the advantage of not requiring any passive components and is based on a CMOS current mode building block named current mode operational amplifier (CMOA), presenting a wide frequency bandwidth as well as temperature insensitivity. Two current sensing cells are necessary to detect openload, short-circuit and overcurrent situations. Detection is achieved by monitoring a small portion of the power switch current provided by a single-cell transistor (SENSEFET). Performance analysis of these functions is made through electrical PSPICE simulations and experimental results obtained from a silicon test chip