Analog-assisted digital low dropout regulator with fast transient response and low output ripple

An analog-assisted digital low dropout regulator (AAD-LDO) is proposed to solve the problems of a slow transient response and a large output ripple in a conventional digital LDO. In the AAD-LDO, a fast-response auxiliary analog LDO is added to the digital LDO in parallel. Compared with the digital LDO, the measured AAD-LDO in 180 nm CMOS reduces the transient response time and the output ripple by 59 and 28%, respectively, at the same current efficiency of 97.1%. The line regulation is 15 mV/V and the load regulation is 0.63 mV/mA.