A Low Drop-Out Regulator With Feed-Forward Ripple Cancellation Technique

This paper presents a low drop-out (LDO) regulator with feed-forward ripple cancellation (FFRC) technique, utilizing a capacitively coupled method. Power supply rejection (PSR) is identified as one of the most critical specifications, alongside performance over a wide frequency range and at maximum load current. The paper presents a technique to enhance the PSR of the LDO and demonstrates the feasibility and relevance of these methods through equation derivation. The proposed LDO is designed using a 0.18 µm process, with input voltage specifications ranging from 1.3 V to 1.8 V, an output voltage of 1.2 V, and a static current consumption of 38.6 µA, utilizing an external regulator capacitor of 1 µF. This design achieves a PSR of -60 dB at load currents ranging from 1 mA to 40 mA. It also extends the bandwidth when the LDO is supplied with larger load currents, achieving a PSR of -73 dB at a frequency of 500 kHz and maintaining a PSR of -61 dB or more at 1 MHz.