A high speed transceiver with a transmitter eliminating crosstalk induced jitter and a receiver with adaptively controllable reference voltage

Abstract

In the ultra high speed interface of the semiconductor memory such as PC main memory, graphic memory uses many channels, which are bus lines between CPU and memory. A memory interface that has 1-GHz data rate needs 4~16 Channels, moreover, a 5-Gbps graphic memory interface has 32~64 Channels. In this mass channel environment, crosstalk occurs between one line and other lines, which is the coupling of the energy from one line to other lines. There is no crosstalk in a single channel, but multi channels are affected by each other. The effect of crosstalk occurs differently according to the phase difference of the signals. The even mode of the signal is the same phase and the odd mode of the signal is the opposite phase. Crosstalk in the even mode makes late delay compare to the odd mode. Thus, Jitter is made by crosstalk due to the phase difference between the adjacent signals. The valid window of the data output decreases by means of these jitters. Another speed issue of the transmitter is that the charge error by the parasitic capacitance of the current mode output driver lowers the swing of the output driver. Capacitance coupling affects the negative effect in the high speed operation. The stable reference voltage is required for an input receiver. It distinguishes low or high level of the data of the transmitter whose source is from a transmission line or from a self generation. In a high bandwidth, the signal distorted by ISI (Inter symbol interference) reduces the noise margin. Thus reference voltage should be treated to get a better receiver performance. This thesis presents a voltage mode output driver to eliminate the crosstalk in the multi-channel as well as to improve signal integrity. This proposed output driver consists of the sub-drivers to provide crossly controllable driver strength, a short pulse generator, a selector, a splitter, additional pull-up/pull-down drivers, and driver control circuits. It is used for an arbitration technolog...