Patent for Sale

Low Power Differential Line Driver

Self terminating low voltage differential signaling (LVDS) line driver employs Class-B Differential Signaling, low voltage headroom, and doubles signal-to-noise ratio (SNR).

Overview

Class-B Differential Signaling or CBDS channels full amplitudes of matched positive and negative currents into differential interconnect, providing maximum signal swing for a given supply current. Capable of being designed as self-terminating, the CBDS line driver eliminates external termination and associated signal attenuation, maximizing SNR. Also capable of very low voltage headroom operation, CBDS additionally reduces power consumption for a given signal swing requirement. CBDS is an LVDS enhancement that improves SNR, reduces power and provides true differential low EMI signaling.

Problem Solved by the Technology

Technology scaling for integrated circuits requires higher performance at lower power and energy consumption. Chips and circuits must operate at low voltages for low energy operation, while inter-chip communication needs to maintain high signal to noise ratio. LVDS filled this need to this point, but suffers from high voltage headroom requirement, signal loss due to termination, and SNR degradation due to line drive on one wire of an interconnect pair with termination connection to the other wire. CBDS or Class-B Differential Signaling designed to be self terminating and providing true differential, low EMI signaling addresses these LVDS issues as well as low energy, low voltage operation. Because CBDS channels full positive and negative currents into differential interconnect without a need for external termination, it provides twice the signal as an LVDS driver of the same supply current and extends reach for long cable applications such as HDMI.

How the Technology Solves the Problem

Most differential signaling drivers such as LVDS require external or integrated (with driver) termination that reduces load impedance to one-half the interconnect characteristic impedance. This reduces signal swing by the same factor. CBDS can be self-terminating and does not have this signal swing penalty. LVDS as specified by the TIA/EIA must operate with voltage headroom greater than 2.5V in order to meet the specification. For a given signal swing and corresponding supply current Icc, power is at least 2.5V*Icc. CBDS line drivers can operate from 1V, and typical differential receivers use capacitive coupling at the input and are compatible with LVDS or CBDS. CBDS power is hence only about 40% that of LVDS (1/2.5). CBDS provides matched positive and negative currents into the interconnect signal pair. The currents are actively matched, and may also be calibrated as needed. This ensures true differential signaling as opposed to LVDS that provides a current into one wire and connects a termination impedance to the other wire of a differential interconnect pair.

Primary Application of the Technology

All high-speed differential signaling applications served by LVDS. PCI-Express and other low latency binary data transmission applications. DisplayPort and other multimedia data communication applications. Serial-ATA, USB etc. forming microprocessor system to peripheral device high-speed serial communication links.

Other Potential Applications