A Low-Dropout Regulator With Tail Current Control for DPWM Clock Correction

A low-dropout (LDO) regulator with tail current control (TCC) is presented. The TCC consists of a dual differential pair, a 5-bit current digital-to-analog converter, and a current summation circuit. The TCC adjusts the tail current ratio of the dual differential pair of the LDO regulator to achieve a programmable output voltage using 5-bit digital signals. A supply-ripple isolation mechanism is added to improve the power supply rejection over a wide frequency range. The proposed design is fabricated in the TSMC 0.18-μm 1-poly 6-metal complementary metal-oxide-semiconductor process. Experimental results show that the LDO regulator has a 32-level programmable output voltage ranging from 1 to 1.2 V, making the LDO regulator suitable for correcting the oscillator frequency of a digital pulsewidth modulator.