Maximizing the Data Rate of an Inductively Coupled Chip-to-Chip Link by Resetting the Channel State Variables

Abstract

A technique is proposed for increasing the data rate transmitted through an inductively coupled chip-to-chip link by resetting the channel state variables. This allows the data rate to be increased well beyond what is implied by the channel bandwidth. In the proposed scheme, the two sides of the link are resonated at the highest possible quality factor, maximizing link gain, and minimizing interference. The transmit signal is a binary matched pulse which maximizes the received signal for a given transmitter voltage limit. High-efficiency switching transmitters can be used for this type of signal. The proposed technique can be applied to communication links in which channel state variables are accessible for reset. For increasing the data rate, it is shown that the proposed state-variable reset technique results in a higher signal-to-noise ratio of the received signal and a higher energy efficiency compared to reducing the quality factor to widen the bandwidth, using equalization, or using multi-level signaling. The technique is demonstrated on a chip-to-chip link with coupled 1.5 mm $\times1.5$ mm planar inductors separated by 0.5 mm in a 0.18 $\mathrm {\mu m}$ CMOS process. 500 Mb/s data rate is achieved over a link which has a band-pass bandwidth of 185 MHz.