Design of Sixth-Order Lowpass Elliptic Switched-Capacitor Filter

In this paper the design and implementation of sixth-order lowpass elliptic switched-capacitor filter (SCF) for interface circuit of Micro-Electro-Mechanical System (MEMS) sensor are presented. This work aims to lower total harmonic distortion (THD) without deteriorating other performances. After system design in Simulink, the filter is realized in transistor level and finally fabricated in Central Semiconductor Manufacturing Corporation (CSMC) 0.5 μm metal-oxide-semiconductor (CMOS) technology. Typical measured results are: it operates with 25:1 clock-to-corner frequency ratio and a 10 kHz maximum corner frequency. The maximum passband ripple is about 0.49 dB and the minimum stopband rejection is 40 dB for the temperature from -20 ℃ to 80 ℃. For the 250 kHz clock frequency setting, given the 1 kHz, -8 dBVrms input signal, the measured worst case THD is -64 dB. The active area of the chip is 2.8 mm 2 with 8 pads. The analog power dissipation is 10 mW from a 5 V power supply.