An area-efficient automotive LDO with scalable maximum load current exhibits excellent response to line and load transients

Abstract

A compact LDO with scalable maximum load current is presented. A transconductor with multiple current outputs implements the error amplifier, as well as two feed-forward paths. A push-pull output stage is employed to drive the gate of the pass transistor. Zeros are created by the feed-forward paths, as well as by an RC network to realize an area- and power-effective frequency compensation, that ensures the LDO stability over a wide range of load currents and capacitances. The proposed LDO was implemented in a 0.13 µm CMOS process. The sizing strategy is presented in the paper, along with simulation and measurement results that validate the design. The LDO provides a stable 1 V output voltage when the input voltage varies between 1.2 V and 1.5 V, the load current varies between zero and 100 mA, and the load capacitance takes values between 100 nF and 10 µF. Its nominal quiescent current is just 9.6 µA while the die area is exceptionally small, only 0.0065 mm2. The integrated LDO exhibits excellent responses to load and line transients: when the load current jumps between 100 µA and 100 mA in 0.3 µs the measured output voltage overshoot and undershoot are below 3.6% of nominal value for CLOAD = 470 nF; the measured overshoot and undershoot caused by the line voltage jumping between 1.3 V and 1.5 V in 3 µs are smaller than 1.2% for the same CLOAD.