Switched Capacitor and Infinite Impulse Response Summation for a Quarter-Rate DFE with 4Gb/s Data Rate

Abstract

This paper presents a novel area effective 2-tap speculative Decision Feedback Equalizer (DFE) with one switched-cap and one IIR summation for data recovery in standard CMOS 180nm technology node. The conventional first-tap speculative quarter rate DFE is composed of eight different paths, which have exactly same hardware. By using the switched-cap method, it is possible to get rid of the duplicated paths. Instead of having a large number of feedback taps in conventional DFE, one single Infinite Impulse Response (IIR) tap in the DFE can compensate the effects of the multiple post-cursors. An input of the second tap is fed back from Infinite Impulse Response (IIR) filter with self-adjusted time constants (τ1). Less number of taps is used in the proposed scheme. The eight summers with two taps in conventional scheme are changed to four current integrating summers and one speculative tap and one general tap by using switched capacitor and IIR filter, respectively. The proposed DFE consumes 12.76mW with 1.8V supply when equalizing 4Gb/s data passed over a channel with 28 dB loss at 2GHz.