Data Output Circuit Using Impedance Codes for Pre-Emphasis
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Solution Overview
Problem
Conventional data output circuits require additional pre-emphasis drivers, which increase circuit area and capacitance, reducing slew rate.
Innovation Solution
A data output circuit that performs pre-emphasis or de-emphasis operations without additional drivers by controlling existing pull-up and pull-down resistors based on impedance codes, selectively turning on/off resistors during emphasis periods to adjust impedance and enhance drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional pre-emphasis drivers are added to improve data output characteristics, then drivability is enhanced, but circuit area and capacitance increase, reducing slew rate
Solution Approach 1:
The patent makes existing pull-up and pull-down drivers perform dual functions: normal data output and pre-emphasis operations. By controlling these drivers to operate in different modes (normal mode and pre-emphasis mode) based on control signals, the circuit achieves pre-emphasis functionality without adding dedicated pre-emphasis drivers, thus avoiding the increase in circuit area and capacitance that would otherwise reduce slew rate
2Reliability
If additional pre-emphasis drivers are added to enhance drivability, then data output characteristics improve, but device complexity increases
Solution Approach 1:
The patent assigns multiple functions to existing drivers - they serve both as normal output drivers and as pre-emphasis drivers when activated by control signals. This eliminates the need for separate pre-emphasis driver circuits, thereby maintaining simple circuit architecture while achieving improved drivability through dynamic impedance adjustment during pre-emphasis periods
3Reliability
If additional pre-emphasis drivers are added to improve data output characteristics, then drivability is enhanced, but capacitance increases, reducing slew rate
Solution Approach 1:
The patent makes existing output drivers perform both normal data output and pre-emphasis functions by dynamically adjusting their operating state. During pre-emphasis periods, the drivers are controlled to provide enhanced drive strength; during normal periods, they operate in standard mode. This approach achieves improved drivability without adding extra drivers that would increase output capacitance and degrade slew rate
Data Source
AI summary
A data output circuit includes a plurality of drivers configured to be turned on/off according to impedance codes to output data to an output node. The impedance codes are divided into a first group having a value to turn on the drivers, and a second group having a value to turn off the drivers, and at least some of the drivers controlled by the second group are turned on during a pre-emphasis period.