A high PSR LDO with adaptive loop switching control and feedforward ripple cancellation techniques

Abstract

This paper proposed a low-dropout regulator (LDO) with adaptive loop switching control (ALSC) and high-pass filter-based feedforward ripple cancellation (HPFRC) techniques. The ALSC circuit can be utilized for wide-input-range LDO and provide a clean power supply for the bandgap reference (BGR) without a pre-regulator circuit. The power supply rejection (PSR) at low frequencies of the proposed LDO is insensitive to the limited PSR of BGR. In addition, the HPFRC circuit can enhance the mid-range PSR of the LDO. This circuit has been designed and verified in 0.25-μm BCD technology. The simulation results demonstrate that the output voltage of 5 V is stable with a 2.2 μF output capacitor when an input voltage from 5.25 V to 24 V is applied. The LDO consumes only 36.4 μA at full load, and the line and load regulation are simulated as 0.02 mV/V and 9.2 μV/mA, respectively. It achieves a PSR of –72 dB at 1 MHz for heavy loads.