A CMOS adaptive continuous-time forward equalizer, LPF, and RAM-DFE for magnetic recording

A continuous-time forward equalizer with one adaptive zero and a seventh-order linear-phase low-pass filter are described. The forward equalizer cancels precursor intersymbol interference (ISI), A mixed-signal four-tap RAM decision-feedback equalizer (DFE) is also included on the prototype to cancel the postcursor ISI, Both precursor and postcursor ISI are canceled in the analog domain. The adaption is done digitally. The low-pass filter and forward equalizer together occupy 6.7 mm(2) in a 1-mu m CMOS process. They dissipate 280 mW from a 5-V supply when operating at 80 Mb/s. Including the RAM-DFE, the entire chip occupies 11.2 mm(2) and dissipates 630 mW.