ISSCC 2011 / SESSION 25 / CDRs & EQUALIZATION TECHNIQUES / 25 . 7 25 . 7 A 10 Gb / s Half - UI IIR - Tap Transmitter in 40 nm CMOS

Two commercially important standards for 10Gb/s serial data transfer include the SFI specification, associated with SFP+ optical modules and copper twinaxial cable [1], and the 10GBASE-KR specification for backplane channels in computer servers and networking equipment [2]. The SFI specification requires the transmitter to operate with both low data-dependent jitter (DDJ) and low transmitter waveform dispersion penalty (TWDPc where the “c” denotes direct-attach copper cable). The SFI TWDPc specification is associated with the copper twinaxial cable channel in [1] and is defined as the ratio (in dB) between the signal-to-noise ratio (SNR) of a matched-filter receiver and the SNR at the slicer input of an ideal, adapted, FFE+DFE receiver [3]. In data center applications it is necessary to use the same serial transmitter IC (with no change in transmitter programming) with both hot-pluggable twinaxial cable and optical modules as shown in Fig. 25.7.1. Because of the use of limiting laser drivers in optical modules, DDJ produced by the transmitter cannot be equalized by the receiver at the far-end of an optical fiber link. Therefore it is necessary for the transmitter to satisfy both the SFI TWDPc and DDJ specifications at the same time.