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 l_CLP 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 750 mA, minimum and maximum simulated values of I_CLP are 570 mA and 930 mA, respectively, for a broad biases, process spread and temperatures ranging from -40degC to 150degC. An LDO with 400 mA-current capability and 250 mV-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.