An NMOS Low Drop-out Voltage Regulator with -17dB Wide-Band Power Supply Rejection for SerDes in 22FDX

A fully on-chip Low Drop Out (LDO) regulator that uses an NMOS output transistor, designed in 22FDX technology, is presented. Proposed LDO capitalizes on technological advantages of back gate bias available in 22FDX to reduce the drop out voltage for regulator and achieve wide band power supply rejection. Charge-pump is used to apply forward back-bias on the NMOS pass device to reduce its threshold voltage down to 0V and enable low drop out regulation. The LDO generates 0.91V output from 1.35V input supply with load current capacity of 15mA. Proposed LDO provides wide band power supply rejection achieving worst case PSR of -17dB across 1Hz-10GHz frequency spectrum essential for SerDes applications. Unity gain bandwidth of >15MHz is achieved along with fast transient response of 63mV peak-to -peak for a current step of 14mA in 100ns.