Input Pad Sensor Circuit With Feedback Overvoltage Protection
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Solution Overview
Problem
Integrated circuits (ICs) face reliability issues due to varying input signal voltages exceeding safe operating thresholds, particularly in lower technology nodes, leading to potential damage of transistors and performance degradation.
Innovation Solution
A fail-tolerant input pad sensor circuit is implemented, comprising a sensor input transistor, voltage clamps, level shifters, and a Vt booster circuit, which dynamically adjusts input signal voltages to stay within safe thresholds, preventing overvoltage conditions and ensuring reliable IC operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the input pad receives signals with varying voltages from peripheral circuits, then the IC can interface with different voltage domains, but the voltage may exceed the safe operating threshold of thick gate oxide devices
Solution Approach 1:
A sensor circuit is introduced as an intermediary component between the input pad and the thick gate oxide device. The sensor circuit includes a sensor input transistor with its gate connected to the input pad, and a level shifter that adjusts the voltage level before applying it to the gate of the receive transistor, preventing overvoltage damage while maintaining voltage domain compatibility
Solution Approach 2:
The sensor circuit uses feedback mechanisms where the voltage at the input pad is sensed and used to control the gate voltage of the sensor input transistor. This feedback loop ensures that the voltage applied to the thick gate oxide device remains within safe operating limits even when the input voltage varies
2Reliability
If voltage clamping and level shifting circuits are added to protect against overvoltage, then device reliability is improved, but circuit complexity increases
Solution Approach 1:
The sensor circuit combines multiple protection functions into a single integrated structure. The sensor input transistor, level shifter, and voltage control mechanisms are merged into one compact circuit that simultaneously provides overvoltage protection, voltage level adaptation, and gate voltage control without requiring separate protection circuits
3Adaptability or versatility
If the gate voltage of the sensor input transistor is increased to handle higher input voltages, then voltage tolerance is improved, but the threshold voltage drop causes signal degradation
Solution Approach 1:
The gate voltage of the sensor input transistor is made dynamic rather than fixed. The level shifter continuously adjusts the gate voltage based on the input voltage level, allowing the circuit to adapt to different voltage conditions while maintaining optimal signal transmission and minimizing threshold voltage drop effects
Data Source
AI summary
A fail tolerant sensor circuit for adjusting an input signal received at an input pad to be provided to an integrated circuit (IC). The circuit includes a sensor input transistor including a first terminal coupled to the input pad, a second terminal coupled to a receiver circuit, and a gate. The circuit further includes a feedback loop that includes a first voltage clamp circuit having an input coupled to the second terminal of the senor input transistor and providing an output, and a first level shifter including an input coupled to the output of the first voltage clamp circuit and providing the feedback output coupled to the gate of the sensor input transistor.