Output Driver Overvoltage Protection via Fractional Supply
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Solution Overview
Problem
Current integrated circuit output drivers are susceptible to electrical overstress, particularly when the power supply voltage is turned off, at low voltage, open-circuited, or connected to ground, and existing protection methods do not adequately address overvoltage issues in these conditions.
Innovation Solution
The implementation of a power conditioner that generates a protected supply voltage and well voltage, using a voltage divider and multiplexer to provide a fractional pad voltage when the power supply is absent, ensuring that transistors in the driver circuit are not subjected to overvoltage stress, even when the output pad voltage exceeds the supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing protection circuits are used, then overvoltage protection is provided when power supply voltage is turned on, but the output driver remains vulnerable when power supply voltage is turned off, at low voltage, open-circuited or connected to ground
Solution Approach 1:
The protection circuit dynamically adapts its operation based on the power supply voltage status. When VDD is present, the circuit operates in one mode; when VDD is absent, low, open-circuited or grounded, the circuit automatically switches to an alternative protection mode, ensuring continuous protection across all power supply conditions
Solution Approach 2:
The protection circuit is designed to perform multiple protection functions across different operating conditions. It provides overvoltage protection both when the power supply is active and when it is inactive, low, open-circuited or grounded, making it universally applicable to all power supply states
2Use of energy by moving object
If the output driver is designed for low power supply voltages (3V or less), then power consumption is reduced, but susceptibility to electrical overstress from external pads increases
Solution Approach 1:
The protection circuit acts as an intermediary between the low-voltage output driver and the external pad. It interfaces the low-voltage driver with higher-voltage external conditions, blocking harmful overstress while allowing normal operation, thus enabling the driver to maintain low power consumption without sacrificing protection
3Reliability
If protection circuits are added to protect against overvoltage, then transistor damage is prevented, but device complexity increases
Solution Approach 1:
The protection functions are merged with the existing output driver structure. The protection circuit shares components and integration resources with the driver, combining protection functionality into the existing architecture rather than adding completely separate protection elements, thus limiting the increase in overall device complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively protects the output driver transistors from electrical overstress by applying a protected supply voltage and well voltage, preventing damage from overvoltage conditions, such as those encountered during USB port usage, regardless of the power supply status.
Implementation Method 1
a power conditioner which generates a protected supply voltage and a protected well voltage in response to a pad voltage
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
An output driver in an integrated circuit includes a driver circuit operable by a power supply voltage and coupled to an output pad, and a driver power conditioner configured to generate a fractional pad voltage in response to a voltage on the output pad and to provide the fractional pad voltage to at least one transistor of the driver circuit as a protected supply voltage in response to an absence of the power supply voltage.