A voltage scaling 0.25-1.8 V delta-sigma modulator with inverter-opamp self-configuring amplifier

Kentaro Yoshioka, Yosuke Toyama, Teruo Jyo, Hiroki Ishikuro

Abstract: A 2nd order discrete time (DT) ΔΣ modulator with very wide supply voltage range of 0.25–1.8 V is presented. An inverter-opamp self-configuring amplifier (IOSA) is proposed with sufficient gain through sub-threshold to strong inversion region. The amplifier senses the supply voltage and automatically configures either to operate as an inverter or an opamp. The prototype ADC fabricated in 180nm CMOS achieved SNDR of 53dB at a supply voltage of 0.3V and a best FoM of 0.09 pJ/step. At 1.8 V supply the modulator achieves SNDR 61dB and operates down to 0.25V.