Two pseudo-differential transmitting circuits producing a constant common-mode current

Abstract

This paper covers two possible designs for a new type of pseudo-differential transmitting circuit (TX circuit) such that signaling ideally produces no common-mode current variation. Here, the TX circuit terminals intended to be connected to the interconnection ideally behave as if the TX circuit was composed of a floating circuit and a two-terminal circuit element connected between the common terminal and ground. This is in contrast with conventional pseudo-differential TX circuits in which the generation of signals produces a variable return current flowing in the reference conductor. We provide simulation results based on the same CMOS technology for both designs. We then consider the implementation of one of these TX circuits in a pseudo-differential link. This link being capable of low reflections and an almost constant common-mode current, it offers a good protection against external crosstalk.

Pseudo-differential links using a wide return conductor and a floating termination circuit

“…Section IV uses an ideal TX circuit, but two device-level designs for TX circuits dedicated to the ZXnoise method are described in [11].…”

Twelve pseudo-differential transmission schemes

“…A TX circuit may comprise a balancing circuit such that a constant common-mode current (CCMC) flows in the interconnection [4]. Such a TX circuit has a "common terminal" connected to the return conductor.…”