Switched-Capacitor Filters Are 8th-Order Elliptic

The MAX7400/MAX7403/MAX7404/MAX7407 series of 8th-order elliptic, low-pass switched-capacitor filters provide corner frequencies from 1 Hz to 10 kHz while drawing 2 mA quiescent and 0.2 µA in shutdown. The filters are well-suited for low-power anti-aliasing and post-DAC filtering applications. MAX7400/MAX7404 devices provide a sharp roll-off with a 1.5 transition ratio and 80 dB of stop-band rejection, while the MAX7403/MAX7407 devices provide a sharper roll-off of 1.2 transition ratio and 58 dB of stop-band rejection. For all four filters, the low output offset of ±4 mV can be adjusted via an offset adjustment pin. The filters' switching can be self-clocked with an external capacitor or clocked externally for tighter control of the corner frequency. Their fixed output response simplifies the design task compared to that of selecting a corner frequency by setting the clock frequency.