Peak Junction Temperature Sensing for Semiconductor SOA Protection
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Solution Overview
Problem
Conventional methods for protecting semiconductor devices from safe operating area (SOA) violations, such as temperature sensing and overcurrent protection, are inadequate as they fail to accurately detect peak junction temperatures, leading to potential device destruction due to excessive heat.
Innovation Solution
A system comprising a peak power dissipation sensor, a temperature sensor, and a peak junction temperature computation circuit that calculates the peak junction temperature based on sensed peak power dissipation and average temperature, allowing for accurate detection of thermal SOA violations by comparing the computed peak junction temperature with a maximum allowable threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional temperature sensor is used near the output driver device, then the sensor can sense the average temperature in the vicinity, but it fails to accurately detect peak junction temperature excursions, leading to undetected SOA violations
Solution Approach 1:
The patent introduces a computational intermediary that processes multiple temperature readings from different locations and time points to derive the peak junction temperature. Instead of relying on a single sensor near the driver, the system uses temperature readings from various points (including embedded sensors and external sensors) combined with thermal modeling to calculate the peak temperature that occurs during transient conditions, thereby achieving accurate SOA violation detection without requiring a sensor directly at the junction point.
2Measurement precision
If an embedded temperature sensor is used within the device, then the sensor is positioned close to the heat source, but it suffers from false trip and latch up issues caused by parasitic junctions and layout-dependent inaccuracies
Solution Approach 1:
The patent uses computational thermal modeling as an intermediary to bridge the gap between embedded sensor readings and actual peak junction temperature. The system combines readings from embedded sensors with thermal resistance networks and transient thermal models to calculate the true peak junction temperature, thereby avoiding the false trips caused by direct embedded sensor readings while maintaining measurement accuracy.
Solution Approach 2:
The patent extracts the temperature sensing function from being solely dependent on embedded sensors within the high-power device. Instead, it separates the sensing function (using external or less intrusive sensors) from the measurement function (using computational models to derive peak junction temperature), thereby eliminating the parasitic effects and latch-up issues associated with embedded sensors while maintaining accurate temperature monitoring.
3Device complexity
If overcurrent protection is used to protect against SOA violations, then the protection mechanism is simple to implement, but it is inadequate because SOA violations can occur at lower current levels when voltage across the device is higher
Solution Approach 1:
The patent replaces the simple overcurrent protection mechanism with a thermal-based protection system that monitors actual junction temperature and power dissipation. Instead of relying on current thresholds, the system uses temperature sensors combined with thermal models to detect when the device approaches dangerous temperature levels, providing accurate SOA violation protection that accounts for the relationship between voltage, current, and temperature rather than simply limiting current.
Data Source
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AI summary
A peak junction temperature monitoring system for a semiconductor device includes a peak power dissipation sensor for sensing the peak power dissipation in the device. A temperature sensor senses an average temperature of the device, and a peak junction temperature computation circuit generates a signal representative of a peak junction temperature based on input from the peak power dissipation sensor and the temperature sensor.