Two-Stage Post Driver Circuit for Transistor Voltage Stress Control

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Solution Overview

Problem

Conventional two-stage post driver circuits face the risk of transistor damage due to excessive voltage differences between drain and source voltages during level transitions, leading to potential circuit failure.

Innovation Solution

The proposed two-stage post driver circuit incorporates a controlling circuit that generates transient and steady-state pull-up and pull-down signals, using a first P-type transistor and a second P-type transistor, and a first N-type transistor and a second N-type transistor, respectively, to manage voltage differences and minimize stress on transistors during transitions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a two-stage post driver circuit is used to generate higher output voltage (3.3V) from core voltage (1.8V), then the output pad can withstand the required voltage stress, but the transistors may experience excessive voltage difference between drain and source during level transitions, leading to potential damage

Engineering Contradiction:

Improvetransistor reliabilityVSAvoidvoltage stress on transistors

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The controlling circuit generates control signals in advance to manage the switching sequence of transistors. During level transitions, the control signals are prepared and applied beforehand to ensure that transistors switch at the optimal moment, preventing excessive voltage differences between drain and source terminals before they occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The circuit dynamically adjusts the operation of transistors during level transitions. The controlling circuit monitors the transition state and modulates the control signals to P-type and N-type transistors accordingly, creating a dynamic balancing effect that maintains voltage differences within safe limits throughout the transition process

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If conventional two-stage post driver circuit is used, then voltage level conversion from 1.8V to 3.3V is achieved, but transistors are at risk of damage due to uncontrolled voltage differences during transitions

Engineering Contradiction:

Improvevoltage level conversion capabilityVSAvoidcircuit stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The controlling circuit acts as an intermediary between the core circuit and the output pad. It generates intermediate control signals that mediate the voltage transition process, coordinating the switching of P-type and N-type transistors to ensure smooth voltage level conversion from 1.8V to 3.3V while preventing harmful voltage stress on transistors

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8981818B2Method of controlling two-stage post driver circuit

Publication Date: 2015.03.17 GLOBAL UNICHIP CORPORATION

AI summary

A two-stage post driver circuit includes a controlling circuit, a pull-up unit and a pull-down unit. A first N-type transistor of the pull-down unit and a first P-type transistor of the pull-up unit are both connected to an output pad. The controlling circuit is used for controlling the first N-type transistor and the first P-type transistor. Consequently, when the pull-up unit or the pull-down unit is turned on, the voltage difference between the drain terminal and the source terminal of the first N-type transistor or the first P-type transistor is lower than a voltage stress.