Differential Serial Driver Charge Injection for Low-Power Pre-Emphasis
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Solution Overview
Problem
Traditional differential serial I/O circuits require separate pre-emphasis paths, increasing area and power consumption, and consuming 3-6 pJ/bit, whereas existing transmitter circuits need to maintain high-speed operation with reduced power requirements.
Innovation Solution
A transmitter circuit design incorporating a pre-emphasis circuit with an output stage and termination circuit, which reduces area and power consumption by using a single data path and clocking path, achieving 0.5-0.7 pJ/bit power consumption, and employing 100 Ohm differential termination to minimize termination current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional separate pre-emphasis paths are used in differential serial I/O circuits, then signal transition assistance is achieved, but area and power consumption increase
Solution Approach 1:
The patent combines the pre-emphasis function with the output driver circuit by integrating charge injection capability directly into the output stage transistors. This merging eliminates the need for separate pre-emphasis paths, reducing both area and power consumption while maintaining signal transition quality through shared circuit resources.
Solution Approach 2:
The output driver circuit is designed to perform multiple functions: standard signal buffering and differential output generation, plus selective charge injection for pre-emphasis. This multi-functionality allows the same circuit to assist signal transitions without requiring dedicated pre-emphasis hardware, thereby reducing overall power consumption to 0.5-0.7 pJ/bit.
2Speed
If standard SerDes transmitter implementations are used, then high-speed operation is maintained, but power consumption increases to 3-6 pJ/bit
Solution Approach 1:
The charge injection is applied periodically and selectively only during signal transitions rather than continuously. The circuit detects transition events and activates charge injection only when needed, reducing average power consumption while maintaining high-speed operation capability when transitions occur.
Solution Approach 2:
The invention dynamically adjusts charge injection parameters (amount and timing) based on signal transition requirements. By changing operational parameters rather than maintaining fixed high-power operation, the circuit achieves high-speed performance only when necessary, reducing overall power consumption to 0.5-0.7 pJ/bit while preserving speed capability.
3Loss of energy
If 100 Ohm differential termination is used, then termination current is minimized, but circuit design complexity increases
Solution Approach 1:
The termination function is merged with the output driver circuitry, using the same transistors and nodes for both signal driving and termination. This integration achieves 100 Ohm differential termination with minimal additional complexity, as the same circuit elements serve dual purposes rather than requiring separate termination components.
Data Source
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AI summary
Apparatuses and methods are disclosed, including an apparatus that includes a differential driver with charge injection pre-emphasis. One such apparatus includes a pre-emphasis circuit and an output stage circuit. The pre-emphasis circuit is configured to receive differential serial signals, and buffer the differential serial signals to provide buffered differential serial signals. The output stage circuit is configured to receive the buffered differential serial signals and drive the buffered differential serial signals onto differential communication paths. The pre-emphasis circuit is configured to selectively inject charge onto the differential communication paths to assist with a signal transition on at least one of the differential communication paths. Additional embodiments are disclosed.