11.1 An oversampled 12/14b SAR ADC with noise reduction and linearity enhancements achieving up to 79.1dB SNDR

Abstract

Autonomous wireless sensor nodes for cloud networks require ultra-low-power electronics. In particular, sensor readout interfaces need low-speed high-precision ADCs for capturing, e.g., bio-potential signals, environmental information, or interactive multimedia. For these applications, state-of-the-art SAR ADCs can provide highly power-efficient solutions (<;10fJ/conversion-step) but with limited accuracy (SNDR <;63dB) [1,2]. Alternatively, ΔΣ ADCs offer higher precision at the cost of lower efficiency (e.g. 84dB SNDR with 54fJ/conversion-step [3]). This work bridges the existing performance gap by extending the accuracy of low-power SAR ADCs to SNDRs in the order of 70-to-80dB. Feedback-controlled data-driven noise reduction [1], oversampling, chopping [4] and dithering [5] techniques are combined to increase both SNR and linearity in a power-efficient way. Various ADC modes are supported by making these techniques individually programmable, thereby extending the application range.