Low-Power Single-Slope Analog-to-Digital Converter with Intermittently Working Time-to-Digital Converter

Abstract

We propose a single-slope analog-to-digital converter (ADC) with an intermittently working time-to-digital converter (TDC). Applying an n-bit TDC reduces the conversion time by a factor of 2ⁿ, and using multiphase clock signals achieves timing consistency and realizes robust metastability. We focus on the operation time of the TDC. Since a TDC must operate continuously, it requires a large dissipation power. We propose generating the pulse-width modulation (PWM) signal of a single-slope ADC and apply a scheme for limiting the TDC operation period in order to reduce the TDC power dissipation. We designed and fabricated a 12-bit ADC, which consists of a 6-bit TDC and a 6-bit single-slope ADC, by using a 0.18 μm CMOS process. The ADC operated at 100 kS/s consumed 5.5 μW from a 1 V supply. Its INL and DNL were +1.9/-1.9 LSB and +0.5/-0.8 LSB, respectively.