PHOTODIODE FRONT END WITH IMPROVED POWER SUPPLY REJECTION RATIO (PSRR)

摘要

An area effective system and method for improving power supply rejection ratio (PSRR) in an optical sensor front end, is provided. Moreover, low pass filter (LPF) that enables the reference voltage in the front end of the optical sensor, to be referred to the same substrate as that employed by the sensor. In one example, the LPF includes a capacitor, implemented using a Deep-N-Well (DNW) depletion capacitor, which is utilized to connect the reference voltage to the same substrate. Additionally, the DNW allows an area efficient realization of the LPF. The system and method disclosed herein improves the PSRR by a factor of around 40dB for 5 MHz modulation.