Application of a CMOS current mode approach to on-chip current sensing in smart power circuits

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 it is based on a CMOS current mode building block presenting a wide frequency bandwidth as well as temperature insensitivity. Two current sensing cells are necessary to detect open load, 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). The performance of these functions is analysed by electrical PSPICE simulations and experimental results obtained from a silicon test chip.