A Deterministic Digital Background Calibration Technique for VCO-Based ADCs

作者：Rao Sachin^*; Reddy Karthikeyan; Young Brian; Hanumolu Pavan Kumar

来源：IEEE Journal of Solid-State Circuits, 2014, 49(4): 950-960.

DOI：10.1109/JSSC.2013.2293753

• Background calibration
• calibration
• deterministic calibration
• open-loop delta sigma
• time based ADC
• VCO based ADC.

This paper presents a digital background calibration technique to realize a linear voltage-controlled-oscillator ( VCO) based ADC. The distortion caused due to the VCO's nonlinear tuning characteristics is eliminated by introducing an inverse voltage-to-frequency transfer function in the signal path. The proposed calibration unit runs in the background and detects the inverse transfer function using a highly digital frequency locked loop. Like many other VCO-based ADCs, the proposed technique does not require analog building blocks such as operational amplifiers, multi-bit feed-back DACs etc., and retains the scaling friendly properties. Implemented in a 90 nm CMOS process, the on-chip calibration improves SNDR of an open-loop VCO-based ADC from 46 dB to more than 73 dB in 5 MHz signal bandwidth while consuming 4.1 mW power. The ADC achieves a figure-of-merit of 91-112 fJ/conv-step for different input frequencies.

• 出版日期2014-4