SerDes Driver Common-Gate Buffer for High-Swing Level Shifting

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Solution Overview

Problem

High-speed serializer/deserializer (SerDes) systems face challenges in maintaining signal integrity due to limited output voltage swing in low power supply domains, which can lead to reliability issues when core devices are used in high power supply environments.

Innovation Solution

A driver circuit for SerDes transmitters is introduced, featuring a common-gate buffer circuit that level-shifts high-speed signals from a low power supply domain to a high power supply domain, increasing the output voltage swing and using a voltage generation circuit to ensure PMOS transistors operate within their working range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If core devices are used in high power supply domain, then device performance is improved, but reliability deteriorates due to limited output voltage swing

Engineering Contradiction:

Improvedevice performanceVSAvoidreliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

A level-shifting circuit is introduced as an intermediary component between the high power supply domain and the core devices. This circuit translates voltage levels, allowing core devices to operate safely in the low voltage domain while still interfacing with high power supply domain components, thus resolving the contradiction between performance and reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the voltage domain parameter by introducing a level-shifting mechanism. Core devices operate in a low voltage domain (e.g., 1.0V) while interfacing with high power supply domain (e.g., 1.2V) through controlled parameter transformation, enabling both high performance and reliability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If output voltage swing is increased, then signal integrity is improved, but device operating range is exceeded

Engineering Contradiction:

Improvesignal integrityVSAvoiddevice operating range

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The circuit is segmented into distinct voltage domains: a high power supply domain for signal integrity and a low voltage domain for core device operation. The level-shifting circuit acts as a boundary between these segments, allowing each to operate optimally without interfering with the other's safety margins

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The level-shifting circuit serves as a protective intermediary that prevents high voltage swing signals from directly affecting core devices. It translates the signal while maintaining electrical isolation, ensuring signal integrity is improved without exceeding device operating ranges

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11139843B1SerDes driver with common-gate-based buffer to use core devices in relatively high power supply domain

Publication Date: 2021.10.05 QUALCOMM INC

AI summary

Certain aspects of the present disclosure generally relate to a driver circuit for a serializer/deserializer (SerDes) transmitter and techniques for operating such a driver circuit. One example driver circuit generally includes a pre-driver circuit, an output stage circuit, and a common-gate buffer circuit coupled between an output of the pre-driver circuit and a first input of the output stage circuit.