A High Dynamic Range Pulse Frequency Modulation ADC for Ambient Light Sensor

In this paper, we propose a high dynamic range pulse frequency modulation (PFM) analog-to-digital converter (ADC) with adjustable range for ambient light detection, which employs a buffered direct injection(BDI) input stage circuit to improve the low injection efficiency of the traditional input stage PFM ADC under weak illumination, and a digital range control circuit and current divider to improve the dynamic range loss and non-linearity caused by the residual charge of the integrating capacitor and the reset loop delay. The ADC circuit was designed in a 0.35-$\mu \mathrm{m}$ CMOS process. The simulation results show that the dynamic range of the ADC is more than 132dB, the maximum operating current is $8.7\mu \mathrm{A}$, and the maximum non-linearity is only 0.113% under 3. 3V supply.