A single-ended 10-bit 200 kS/s 607 μW SAR ADC with an auto-zeroing offset cancellation technique**Project supported by the National Science and Technology Support Program of China (No. 2012BAI13B07) and the National Science and Technology Major Project of China (No.2012ZX03001020-003).

Abstract

This paper presents a single-ended 8-channel 10-bit 200 kS/s 607 μW synchronous successive approximation register (SAR) analog-to-digital converter (ADC) using HLMC 55 nm low leakage (LL) CMOS technology with a 3.3 V/1.2 V supply voltage. In conventional binary-encoded SAR ADCs the total capacitance grows exponentially with resolution. In this paper a CR hybrid DAC is adopted to reduce both capacitance and core area. The capacitor array resolves 4 bits and the other 6 bits are resolved by the resistor array. The 10-bit data is acquired by thermometer encoding to reduce the probability of DNL errors which are typically present in binary weighted architectures. This paper uses an auto-zeroing offset cancellation technique that can reduce the offset to 0.286 mV. The prototype chip realized the 10-bit SAR ADC fabricated in HLMC 55 nm CMOS technology with a core area of 167 × 87 μm2. It shows a sampling rate of 200 kS/s and low power dissipation of 607 μW operates at a 3.3 V analog supply voltage and a 1.2 V digital supply voltage. At the input frequency of 10 kHz the signal-to-noise-and-distortion ratio (SNDR) is 60.1 dB and the spurious-free dynamic range (SFDR) is 68.1 dB. The measured DNL is +0.37/−0.06 LSB and INL is +0.58/−0.22 LSB.