Design of a Low-Noise Low Dropout Regulator for CMOS Pixel Sensors

A low-noise Low Dropout Regulator (LDO) is designed in a Semiconductor Manufacturing International Corporation (SMIC) $0.18~\mu $ m process, aiming at supply of a clean and constant clamping voltage in the operation of Correlated Double Sampling (CDS) for elimination of switching and reset noise in CMOS Pixel Sensors (CPS) applied to high energy physics experiments. In order to decrease noise of the LDO, a noise model of the LDO consisting of blocks, such as a pass transistor, a resistor network, and an error amplifier, is constructed and noise contributions made by these blocks are analyzed in detail. According to results of the noise analysis, the error amplifier is identified as the major noise source. For the purpose of reduction in noise, especially 1/f noise, an error amplifier exploiting a chopper stabilization technique is proposed. Simulation results demonstrate the effectiveness of the proposed method. The Power Spectral Density (PSD) of the LDO’s output noise is only 60 nV/ $\surd $ Hz at 10 Hz and total integrated noise within the bandwidth is $40~\mu $ V.