A Low-Noise Fast-Startup Low-Dropout Regulator with Off-Chip Filter Capacitor

In this paper, a low-noise fast-startup low-dropout regulator with off-chip filter capacitor is presented, which is fabricated in a 180nm CMOS process. For achieving excellent output noise performance, two technique methods are adopted: reducing reference internal noise and applying off-chip filtering. In order to reduce the noise of the reference, a novel optimization method is proposed. At the same time, a fast-startup circuit is carefully designed to avoid off-chip filtering capacitor slowing down the startup time of the system. The integrated output noise of the LDO with an off-chip 47nF capacitor is 13.03$\mu V_{RMS}$, and the startup time is less than 41$\mu$s. The static current consumption is 45$\mu$ A@ 5V, and the chip occupies the area of 0.44mm$^{2}$.