A High-Voltage Low-Dropout Regulator With Wide Ranges of Output Capacitance and Au80Sn20 Alloy Solder for Packaging

This article presents the circuit design and the implementation of a low-dropout (LDO) regulator with high-voltage operation across a broad temperature range from -55 degrees C to 125 degrees C. The proposed LDO operates stably over wide ranges of output capacitance C-OUT (from 1 to 100 mu F) and effective series resistance (ESR; from tens of milliohms ceramic capacitor to several ohms aluminum electrolytic capacitor). This LDO consumes not more than 200- mu A quiescent current. This low quiescent current is obtained by replacing the traditional high-voltage p-n-p bipolar power transistor with a p-type laterally diffused MOS (LDMOS) counterpart, reducing the quiescent current from tens of milliamperes to hundreds of microamperes. At the same time, the degradation of the transient response caused by the large gate capacitor of the p-type LDMOS power transistor is mitigated by an operational amplifier with a specially designed feedback path, class-AB bipolar driver, and dynamic bias. The measurement results show that when the load current jumps from 5 to 750 mA within 3 mu s, the output voltage overshoot remains as low as 50 mV with a 1 mu F of output capacitance C-OUT .