An on-chip 250 mA 40 nm CMOS digital LDO using dynamic sampling clock frequency scaling with offset-free TDC-based voltage sensor

We have developed a fully logic-MOS-transistor designed on-chip digitally controlled LDO in 40 nm CMOS. The proposed TDC-based voltage sensor used as an ADC can reduce the offset error almost to zero. The area of this LDO with no analog circuits is only 0.057 mm². To suppress the AC voltage drop due to large load transient (LLT), we developed a LLT control method using dynamic sampling clock frequency scaling scheme. The measurement results show that the AC voltage drop can be suppressed to 50%. The peak efficiency is 99% at 250 mA.