Integrated circuit, method for controlling differential signal and communication system

Abstract

Described are communication systems that convey differential and common-mode signals over the same differential channel. Noise-tolerant communication schemes use low-amplitude common-mode signals thatare easily rejected by differential receivers, thus allowing for very high differential data rates. Some embodiments employ the common-mode signals to transmit backchannel signals for adjusting the characteristics of the differential transmitter. Backchannel control signals are effectively conveyed even if the forward channel transmitter is so maladjusted that the received differential data is unrecognizable. Systems in accordance with the above-described embodiments obtain these advantages without additional pins or communications channels, and are compatible with both AC-coupled and DC-coupled communications channels. Data coding schemes and corresponding data recovery circuits eliminate the need for complex, high-speed CDR circuits.

Description

technical field [0001] User demands for digital video, high-speed communications, and ever-increasing processing speeds are driving manufacturers to adopt faster data transfer solutions. Although the data transmitted is usually digital, designers are keen on analog communication schemes that use low-voltage differential signaling, especially for moving data within a system. The transmission medium or "channel" can be a pair of copper wires, but is more commonly a pair of circuit board traces running between integrated circuits. The use of differential signals allows common mode noise to be suppressed and thus enables data transmission to be particularly fast and immune to common mode noise. Background technique [0002] The Telecommunications Industry Association (TIA) publishes standards that specify the electrical characteristics of Low Voltage Differential Signaling (LVDS) interface circuits that can be used to interchange binary signals. LVDS uses low-voltage different...

AI Technical Summary

Problems solved by technology

Adding leads and signal paths is expensive and undesirable

As an alternative, bi-directional communication can support reverse channel signaling, but this option may reduce the bandwidth of forward communication

[0006] In a paper titled "Phantom Mode Signaling in VLSI Systems," Thaddeus Gabara describes how the common-mode signals to achieve reverse-channel communication in high-speed differential channels. These circuits take advantage of the ability of modern differential receivers to reject common-mode signals; Inserting a common-mode signal is no different than inserting common-mode noise. Therefore, a reverse-channel communication scheme that relies on common-mode signaling techniques will undesirably limit the transmission speed of the forward channel. Therefore, there is a need for a reverse channel that can be achieved through a high-speed differential channel Protocols and circuits for channel communication without unduly limiting differential signal bandwidth.

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