Capacitor-free low dropout regulators using nested Miller compensation with active resistor and 1-bit programmable capacitor array

A capacitor-free CMOS low dropout regulator (LDR) using the nested Miller compensation with an active resistor (NMCAR) is presented. It can efficiently control the damping factor and reduce the required Miller compensation capacitance. It can also resolve the trade-off between dc loop gain and damping factor, which existed in the LDR using the nested Miller compensation. To reduce the total Miller compensation capacitances further, a capacitor-free CMOS LDR using both the NMCAR and a 1-bit programmable capacitor array is presented. For this LDR, the total on-chip compensation capacitance is reduced 40% without influencing its stability. Furthermore, it also enhances the recovery time, compared with the LDR using the NMCAR technique. Two proposed LDRs with bandgap voltage references have been fabricated in a 0.35mum CMOS process. They can operate with and without output capacitors.