A Comparison of Single-Ended, NRZ Unidirectional Signaling and Single-Ended, NRZ Simultaneous-Bidirectional Signaling for Die-to-Die Links

This article compares single-ended, NRZ unidirectional (UD) signaling to single-ended, NRZ simultaneous bidirectional signaling for ultrashort-reach (USR) die-to-die (D2D) links in terms of power and bit error rate (BER). We show that for the same transceiver architecture, aggregate bandwidth, and BER, a simultaneous bidirectional link is able to achieve better power efficiency and a wider eye opening than a UD link. Furthermore, the signal-integrity constraints for each signaling approach is examined in terms of the insertion-loss-to-crosstalk ratio and main-cursor-to-crosstalk ratio for three different arrangements of USR D2D links in organic substrates.