Voltage Mode Transmitter De-emphasis Control via Resistive Network
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Solution Overview
Problem
Conventional voltage mode transmitters require a large number of source series termination units to achieve desired de-emphasis values, leading to increased circuit complexity and unmatched impedance issues due to the need for additional impedance calibration circuits.
Innovation Solution
A voltage mode transmitter with a de-emphasis value controller and a resistive network that generates output signals by weighting input voltages, allowing for adjustable de-emphasis values without changing the number of enabled units, thus maintaining a fixed output impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of source series termination units are used to achieve desired de-emphasis values, then de-emphasis performance is improved, but circuit complexity increases and impedance matching becomes difficult
Solution Approach 1:
The patent changes the control parameter from the number of enabled SST units to the resistance value selected from a set of predetermined resistance values. By adjusting which resistance value is connected to the output node, the de-emphasis value can be precisely controlled without changing the number of active units, thus maintaining fixed output impedance while achieving accurate de-emphasis adjustment.
Solution Approach 2:
The resistive network with multiple predetermined resistance values serves multiple functions: it provides precise de-emphasis control, maintains fixed output impedance, and eliminates the need for impedance calibration circuits. This universal solution replaces the complex combination of multiple SST units and calibration circuits with a single multi-functional resistive network.
2Adaptability or versatility
If the number of enabled source series termination units is changed to adjust de-emphasis values, then de-emphasis adjustment is achieved, but output impedance becomes unmatched
Solution Approach 1:
Instead of changing the number of enabled units to adjust de-emphasis, the patent changes the resistance value parameter selected from predetermined options. The output node is connected to different resistance values (R1, R2, R3, etc.) based on the desired de-emphasis level, while the number of enabled SST units remains constant, thereby maintaining fixed output impedance across all de-emphasis settings.
3Reliability
If additional impedance calibration circuits are added to maintain impedance matching, then impedance matching is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for separate impedance calibration circuits by designing the resistive network to inherently maintain fixed output impedance. The calibration circuit functionality is taken out of the system entirely, as the resistive network configuration automatically ensures impedance matching without requiring additional calibration components or control logic.
Data Source
AI summary
A voltage mode transmitter includes a resistive network and a de-emphasis value controller. The resistive network receives plural input voltages and provides plural weighting values corresponding to respective input voltages. A sum of the products of the plural input voltages and the corresponding weighting values is equal to an output voltage. The de-emphasis value controller receives a first signal. After the first signal is inverted as an inverted first signal and the inverted first signal is delayed for a time period, the de-emphasis value controller generates a second signal. The de-emphasis value controller further receives a value control signal. At least one of the plural input signals is provided by the first signal and at least one of the plural input signals is provided by the second signal according to the value control signal.