A 6th order Butterworth SC low pass filter for cryogenic applications from −180°c to 120°c

This paper presents a sixth order Butterworth switched capacitor (SC) low pass filter with radiation-hardened-by-design (RHBD) for cryogenic applications. Implemented in a 0.5 mum SiGe BiCMOS technology, this cryogenic SC filter is capable of operating over an ultra-wide temperature (UWT) range from -180degC to 120degC and under high-energy particle radiation environment on the lunar surface. This is the first SC filter, operating over 300degC temperature range with RHBD, reported so far. The measured results show that the filter approximates a sixth order Butterworth filter response in range of -180degC to 120degC. The clock-to-cutoff frequency ratio is 100:1. The clock feedthrough is less than 10 uV_RMS with single 3.3 V supply. It consumes only 640 uA at 200 kHz clock frequency current and occupies only 0.4times1.4 mm².