A current limiter for LDO regulators with internal compensation for process and temperature variations

A current limiter that securely clamps the LDO output current upon load over-current is presented. Although the approach relies on absolute values of parameters such as resistance and MOSFET threshold voltage on subsequent I/V and V/I conversions of the LDO sensed current, a reference current to the arbitration circuit is derived in such a manner that the dependence of the clamping value ICLP on process and temperature variations is canceled out at good extent. Furthermore, the sense circuit uses a p-MOSFET depletion device to comply with very low dropouts. For a nominal value of 750mA, minimum and maximum simulated values of ICLP are 570mA and 930mA, respectively, for a broad biases, process spread and temperatures ranging from −40°C to 150°C. An LDO with 400mA-current capability and 250mV-dropout embedding the proposed limiter was integrated on a high-voltage process. Experimental data attest the clamping functionality and accuracy of the proposed circuit for low and large dropouts.