The “Supply regulator” is a fully integrated NMOS-based linear regulator designed for ultra-low input voltage operation. The core of the LDO comprises an NMOS pass transistor, an error amplifier (EA), and a charge pump-based gate voltage booster known as the invert-phase synchronized self-oscillating charge pump (I-SOCP). This architecture enables the system to regulate output voltage with a dropout voltage well below the threshold voltage of the pass transistor, even under supply voltages below 1V.
The NMOS pass transistor is driven by a gate voltage (VG) generated by the I-SOCP, which operates without an external clock and maintains VG above the input voltage. This elevated VG allows the NMOS transistor to enter the triode region and minimize the dropout voltage. Simultaneously, the I-SOCP output is used as the supply for the EA, thereby ensuring adequate headroom and linear regulation even under sub-1V input conditions.
Unlike conventional LDOs with step-up charge pumps, the proposed architecture does not require large flying or output capacitors. Instead, the gate capacitance of the pass transistor is used directly, reducing area and power overhead. The I-SOCP operates in a self-oscillating and phase-synchronized manner, which improves the voltage boosting capability by enabling both rising and falling edge operations of internal nodes.
This NMOS LDO is ideal for low-power SoC platforms where minimal dropout and high efficiency under low voltage supplies are critical. Its fully analog regulation, self-oscillating clock generation, and compact capacitor-less boosting structure make it suitable for integration in advanced battery-powered systems.