A 94.7-dB Dynamic Range Fully Passive Switched-Capacitor Low-pass Filter with Enhanced Selectivity and Passive Gain

This paper introduces a low-noise area efficient fully passive switched-capacitor (SC) filter. For the first time, passive gain is incorporated in a SC charge rotation (CRSC) filter. Additionally, a passive feedback network is introduced that offers a sharp transition between the passband and stopband. Fabricated in 1 P6M $0.18 \mu \mathrm{~m}$ CMOS technology, the proposed filter operates at 1.8 V with a measured power dissipation of 1.52 mW. Using a 250 MHz clock allows tuning the filter’s cutoff frequency, $f_{3 \mathrm{~dB}}$, from 428 kHz to 6.75 MHz while maintaining a fixed DC gain of 1.33 dB. At $f_{3 \mathrm{~dB}}=\mathbf{2. 3 5 M H z}$, the measured in-band IIP3/IIP2 are $25 / 56 \mathrm{dBm}$ while their out-of-band values are 22.4/71.4 dBm, respectively. Input-referred integrated noise over 110 kHz to 2.35 MHz is $8.58 \mu \mathrm{~V}_{\text {rms }}$, resulting in a $94.7 \mathrm{~dB} 1 \% \mathrm{HD} 3$ dynamic range.