IO Driver Stress Reduction via Self-Service Voltage Clamping

Solution Overview

Problem

High-speed LVCMOS bidirectional IO circuits face reliability issues due to overshoot and undershoot voltages at the IO circuit interface caused by impedance mismatch, which overstress MOSFETs and increase failure rates, and existing voltage clamping mechanisms require additional power and complexity.

Innovation Solution

The integration of PMOS and NMOS protect circuits in the IO circuit, activated only during receive mode, to clamp overshoot and undershoot voltages respectively, without requiring additional reference voltages, thereby reducing stress on the driver circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If voltage clamping mechanisms are used to protect against overshoot and undershoot voltages, then reliability of the IO circuit is improved, but power consumption and design complexity increase due to requiring additional reference voltages

Engineering Contradiction:

Improvereliability of IO circuitVSAvoiddesign complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protect circuit uses the existing IO supply voltage (VDDS) directly to activate the clamp transistors during voltage excursions, eliminating the need for separate reference voltage generation circuits. The circuit serves itself by utilizing its own power supply rail as the reference, thereby reducing external dependencies and simplifying the overall design while maintaining protection functionality

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The IO supply voltage VDDS serves dual purposes: it powers the normal operation of the driver circuit and simultaneously acts as the reference voltage for the protect circuit's voltage clamping function. This multi-functionality eliminates the need for dedicated reference voltage circuits, reducing both power consumption and design complexity while improving reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If voltage clamping mechanisms are used to protect against overshoot and undershoot voltages, then reliability of the IO circuit is improved, but power consumption increases due to additional reference voltages

Engineering Contradiction:

Improvereliability of IO circuitVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The protect circuit uses the existing IO supply voltage (VDDS) directly to activate the clamp transistors during voltage excursions, eliminating the need for separate reference voltage generation circuits. The circuit serves itself by utilizing its own power supply rail as the reference, thereby reducing external dependencies and simplifying the overall design while maintaining protection functionality

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The IO supply voltage VDDS serves dual purposes: it powers the normal operation of the driver circuit and simultaneously acts as the reference voltage for the protect circuit's voltage clamping function. This multi-functionality eliminates the need for dedicated reference voltage circuits, reducing both power consumption and design complexity while improving reliability

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Area of stationary object

If MOSFETs are used to fabricate IO circuits at advanced technology nodes, then device density is increased, but reliability decreases due to severe overstress from voltage overshoot and undershoot

Engineering Contradiction:

Improvedevice densityVSAvoidreliability of MOSFETs

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The protect circuit is designed to activate before the voltage excursions can cause damage to the MOSFETs. By detecting overshoot and undershoot conditions and immediately clamping the voltages, the circuit provides protective cushioning that prevents severe overstress to the density-optimized MOSFETs, allowing them to operate reliably at advanced technology nodes

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The protect circuit applies counter-action in advance by detecting voltage excursions and activating clamp transistors to counteract the harmful overshoot and undershoot voltages before they can reach damaging levels. This preliminary protective action neutralizes the threat to the MOSFETs, enabling the use of high-density devices without compromising reliability

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS9240400B2Scheme to reduce stress of input/ output (IO) driver

Publication Date: 2016.01.19 TEXAS INSTRUMENTS INC

AI summary

An input/output (IO) circuit is provided that reduces stress on a driver without using an additional reference voltage. The IO circuit receives an overshoot voltage and an undershoot voltage in a receive mode. The IO circuit includes a driver circuit. The driver circuit includes an NMOS transistor coupled to a PMOS transistor. A pad is coupled to the driver circuit. A PMOS protect circuit is coupled to the driver circuit and the pad. An NMOS protect circuit is coupled to the driver circuit and the pad. The NMOS protect circuit is configured to be activated only for a duration of the overshoot voltage received at the pad during the receive mode and the PMOS protect circuit is configured to be activated only for a duration of the undershoot voltage received at the pad during the receive mode.