Hybrid Capacitor-less LDO with Switched-Mode Dead-Zone Control

Abstract:
A hybrid capacitor-less low-dropout regulator that includes switched-mode dead-zone control is proposed. Differently from the prior art, the combination of one digital and two analog low-dropout regulators effectively mitigates the oscillations of the output voltage within the dead-zone and reduces the overall power consumption. The digital part consists of an 1-bit comparator, shift-registers and the PMOS array, and the analog part is constructed by an error amplifier and a pass transistor. In addition, a single-stage high gain amplifier without extra circuitry or an output capacitor is included ensuring that the hybrid LDO operates for load currents between 10 muA - 10 mA, offering significant savings in area. The digital part is modeled using Verilog-A/AMS and the analog part and the output PMOS array of the digital part are designed using 180 nm X-fab CMOS technology.