An 8-bit 20-MS/s ZCBC Time-Domain Analog-to-Digital Data Converter

Abstract

An 8-bit 20-MS/s time-domain analog-to-digital data converter (ADC) using the zero-crossing-based circuit technique is presented. Compared with the conventional ADCs, signal processing is executed in both the voltage and time domains. Since no high-gain operational amplifier is needed, this time-domain ADC works well in a low supply voltage. The proposed ADC has been fabricated in a 0.18-μm CMOS process. Its power dissipation is 4.64 mW from a supply voltage of 1.8 V. This active area occupies 1.2 × 0.7 mm 2 . The measured signal-to-noise-distortion ratio achieves 44.2 dB at an input frequency of 10 MHz. The integral nonlinearity is less than ±1.07 LSB, and the differential nonlinearity is less than ±0.72 LSB. This time-domain ADC achieves the effective bits of 7.1 for a Nyquist input frequency at 20 MS/s. Index Terms-Analog-to-digital converter (ADC), delay-locked loop (DLL), time domain, zero-crossing-based circuit (ZCBC).