A resistor-less overload detector for dc/dc linear regulators

A compact resistor-less current detector that protects linear regulators against overcurrent is proposed. The circuit suits converters with either p- or n-channel pass-device, for different dropout voltages. The ratio between detection threshold I_TH and a reference current I_REF depends only on transistor geometry scaling, making the detector robust to process and temperature (PT) spread. As part of a 50 mA-linear regulator, the detector was designed and simulated according to a high-voltage 0.35 μm CMOS process. For a nominal value of 75mA, I_TH data are [79.3mA@-40°C, 81.9mA@150°C] and [84.1mA@-40°C, 85.8mA @150°C] for p- and n-MOSFET regulators, respectively, already including the hysteresis effect in the arbitration-circuit input. The converter total quiescent consumption is below 220 μA. Overload condition is flagged within 32 ns, typically. Additionally, the detector shows low susceptibility to a noisy power input voltage.