Voltage-Mode Transmitter Equalizer With Constant Current Back-Match

Solution Overview

Problem

Conventional voltage-mode transmitter equalizers experience inefficiencies due to varying supply current with data patterns, leading to signal and system performance degradation, as they draw a supply current that varies significantly with the output signal level, causing signal-switching noise and supply voltage fluctuations.

Innovation Solution

A voltage mode transmitter equalizer that maintains a substantially constant supply current from the power supply and provides constant back-match impedance, with output voltage controlled based on input data, using dynamically varying resistance values in pull-up and pull-down circuits to achieve fine-granularity equalization settings, ensuring the return impedance matches the transmission lines.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If voltage-mode transmitter equalizer uses varying supply current with data patterns, then output signal level can be controlled, but signal-switching noise and supply voltage fluctuations increase

Engineering Contradiction:

Improveoutput signal level controlVSAvoidsignal-switching noise

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The transmitter equalizer is divided into two independent functional blocks: a constant current source that provides stable supply current, and a separate voltage divider network (using resistors R1-R4) that controls the output signal level. This segmentation allows the current source to remain constant while the voltage division ratio varies with data patterns, eliminating signal-switching noise caused by current variations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines the constant current source with a voltage divider network in a unified circuit architecture. The current source feeds into the voltage divider, which then connects to the transmission line. This merging allows the system to maintain constant current while achieving variable output voltage through the voltage division ratio, solving both the noise problem and the signal control requirement simultaneously.

Inventive Principle:

Principle #5Merging (Combining)

2Ease of operation

If voltage-mode transmitter equalizer draws varying supply current, then power efficiency is reduced, but output signal control is achieved

Engineering Contradiction:

Improveoutput signal controlVSAvoidpower efficiency

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The transmitter equalizer is divided into two independent functional blocks: a constant current source that provides stable supply current, and a separate voltage divider network (using resistors R1-R4) that controls the output signal level. This segmentation allows the current source to remain constant while the voltage division ratio varies with data patterns, eliminating signal-switching noise caused by current variations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines the constant current source with a voltage divider network in a unified circuit architecture. The current source feeds into the voltage divider, which then connects to the transmission line. This merging allows the system to maintain constant current while achieving variable output voltage through the voltage division ratio, solving both the noise problem and the signal control requirement simultaneously.

Inventive Principle:

Principle #5Merging (Combining)

3Object-generated harmful factors

If voltage-mode transmitter equalizer uses constant supply current, then signal-switching noise is reduced, but output signal level control becomes more difficult

Engineering Contradiction:

Improvesignal-switching noise reductionVSAvoidoutput signal level control

Core Design Contradiction:

Object-generated harmful factorsVSEase of operation

Solution Approach 1:

The patent introduces a voltage divider network (using resistors R1-R4) as an intermediary between the constant current source and the transmission line. This voltage divider acts as a mediator that converts the constant current into a variable output voltage by adjusting the division ratio according to data patterns, thereby maintaining constant current while achieving signal level control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the resistance values in the voltage divider network (R1-R4) dynamically based on data patterns. By varying the resistance parameters in the voltage division ratio, the output signal level is controlled while the supply current remains constant, enabling signal control without current variations.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8633733B2Voltage mode transmitter equalizer

Publication Date: 2014.01.21 RAMBUS INC

AI summary

A voltage mode transmitter equalizer has high efficiencies, yet consumes substantially constant supply current from the power supply and provides constant back-match impedance. The voltage mode transmitter equalizer is configured such that the output voltage of the signal to be output on a pair of transmission lines can be controlled according to the input data, but its return impedance is substantially matched to the differential impedance of the transmission lines and it draws substantially constant supply current from the power supply regardless of the output voltage of the signal. Further, an equalizer for a voltage-mode transmitter provides fine-granularity equalization settings by employing a variable pull-up conductance and a variable pull-down conductance. Conductance is varied by selectively enabling a plurality of conductance channels, at least some of which have resistance values that are distinct from one another.