Design of a High-performance LDO with Reverse-voltage Protection
A large reverse current can damage an LDO when the input voltage of the LDO is reversed.The conventional structure uses diodes for reverse protection,which significantly increases the dropout voltage of the LDO.In this study,the diode is replaced with an MOS transistor for reverse voltage protection.Through optimizing the error amplifier and adjusting the size of the power transistor,the dropout voltage of the LDO is as low as 251 mV(500 mA at full load).However,the introduced anti-reverse MOS transistor increases the capacitance load of the gate driver of the power transistor,which affects the stability of the loop.A zero-pole cancellation technique is proposed to solve the problem of LDO loop stability.This design is implemented using a TSMC 0.18 μm BCD process.The measured results show that the output voltage of the circuit is 1.2 V with an accuracy within±1％when the input voltage is 2.5-20 V and the load current is 0-500 mA.The load and line regulations are 0.85 μV/mA and 11.65 μV/V,respectively.The PSRR is 93.4 dB@100 Hz.
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