A new parallel link interface with current-mode incremental signaling and per-pin skew compensation

Abstract

This paper proposes a new current-mode incremental signaling parallel link interface with per-pin skew compensation. Per-pin skew compensation is carried out in a calibration phase where clock-like training data are sent to all channels along with a reference clock of the same frequency. Training data are deskewed with respect to the common reference clock using DLLs such that all channels are skew-compensated simultaneously. New encoding and decoding scheme have been proposed to reduce the signal critical path at the transmitter. Transimpedance amplifiers with replica biasing are used to perform current-to-voltage conversion at the receiving end with a minimum sensitivity to supply voltage fluctuation. To evaluate the performance of the proposed skew compensating technique, a 1 Gbytes/s parallel link interface consisting of two data channels and one reference clock channel has been implemented with UMC 0.13 μm 1.2 V CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BIM3V3 device models. The channels are modeled as 50 ? microstrip lines on a FR-4 substrate. Simulation results of the parallel link at all process corners have demonstrated that the proposed parallel link interface provides a minimum deskew range of 1.2 ns (±0.6 ns in each direction).