A Charge-Sharing IIR Filter With Linear Interpolation and High Stopband Rejection

This article introduces a new discrete-time (DT) charge-sharing (CS) low-pass filter (LPF) that achieves high-order filtering and improves its stopband rejection while maintaining reasonable duty cycle of the main clock at 20%. It proposes two key innovations: 1) linear interpolation sampling capacitor 2) charge re-circulation history capacitors for deep rejection. Fabricated in 28-nm CMOS, proposed IIR LPF demonstrates 1–9.9-MHz bandwidth (BW) programmability record-high 120-dB 100 MHz consuming merely 0.92 mW. The in/out-of-band IIP3 is +17.7 dBm/+26.6 dBm, input-referred noise 3.5 nV/ $\sqrt {\mathrm{ Hz}}$ .