A Sharing Pre-regulator for Low Dropout Linear Regulator

A pre-regulator for Low-dropout regulator is presented.The sharing pre-regulator incorporates a subtraction circuit of power supply rejection(PSR) to increase the PSR of its bandgap reference,and uses a current negative feedback to decrease the sensitivity of its temperature coefficient(TC) and PSR with threshold variation for the bandgap reference and decreases the output noise for the LDO regulator.Simulated results show the variation of TC and that of PSR are 0.11×10-6/℃ and 7 dB respectively when the variation of threshold is ±20%.The RMS noise of the LDO regulator in 10 Hz～100 kHz is 13 μV.Measurement shows that the PSR of the bandgap reference is-68 dB in the low frequency,the line regulation and load regulation of the LDO regulator are 4 mV/V and 0.04 mV/mA respectively.The LDO regulator with sharing pre-regulator is fabricated in CSMC 0.6 μm mixed-signal CMOS process with chip area of 600 μm×400 μm and power of 1.5 mW.