Buffer Capacitor Circuit for Automotive Sensor Transient Immunity
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Solution Overview
Problem
Integrated circuits (ICs) in automotive sensor applications face challenges in withstanding large negative voltage transient events, leading to potential damage and prolonged recovery times, particularly due to digital core resets, which hinder accurate signal output.
Innovation Solution
A power and control system is designed for pressure sensors, incorporating a regulated power supply with a buffer capacitor, diode, and parasitic inductor/resistor components to stabilize voltage during transient events, preventing charge flow and reducing recovery time by using NMOS or PMOS field effect transistors and switches to manage current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the IC uses standard power supply design without additional protective components, then the device complexity is low, but the reliability during transient events deteriorates due to digital core resets
Solution Approach 1:
The buffer capacitor is pre-charged during normal operation to store energy before a transient event occurs. This preliminary energy storage enables the capacitor to immediately supply current during a negative voltage transient, preventing digital core resets without requiring complex real-time response circuits
Solution Approach 2:
The buffer capacitor acts as a cushion against voltage transients by absorbing voltage fluctuations and providing immediate current supplementation during negative transients. This beforehand cushioning protects the digital core from reset conditions without adding complex protection circuits
2Reliability
If the buffer capacitor is sized to maintain voltage above reset threshold throughout the entire transient duration, then the reliability is improved, but the capacitor size and energy storage requirements increase
Solution Approach 1:
The circuit maintains continuous power delivery to the digital core by seamlessly transitioning from the external power supply to the buffer capacitor during transients. The regulated output voltage remains continuous without interruption, ensuring the digital core operates without reset throughout the transient event
Solution Approach 2:
The circuit dynamically changes the effective capacitance value based on operating conditions. During normal operation, the buffer capacitor is charged to a higher voltage than the regulated output. During a transient, the capacitor discharges to maintain the output voltage, effectively providing variable energy storage that adapts to the transient duration and magnitude
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
The solution effectively prevents IC resets and reduces recovery time during negative voltage transients, ensuring stable output and improved responsiveness of the sensor by maintaining voltage above reset thresholds during transient events.
Implementation Method 1
The buffer capacitor may be rated to maintain a voltage output that is greater than a reset voltage threshold of the circuit for at least as long as the duration of one transient event
Implementation Method 2
the diode positioned between the external power supply and the regulated power supply to ensure charge from the buffer capacitor does not enter the external power supply or the first electrical load
Implementation Method 3
a regulated power supply with a buffer capacitor, diode, and parasitic inductor/resistor components to stabilize voltage during transient events
Data Source
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AI summary
A circuit for protecting a voltage supply to a sensor from a transient event is provided. The circuit includes at least one buffer capacitor configured to provide output during the transient event, the output substantially equivalent to output of a regulated supply during normal operation of the sensor. A method of fabrication and a sensor are disclosed.