Supply Voltage Detector Gating for Reliable Reset Flags
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Solution Overview
Problem
Conventional supply voltage level detectors produce unreliable flag signals when the voltage source is reset, as the bandgap reference voltage generator does not generate a stable voltage until the supply voltage returns to a specific level, leading to improper functioning.
Innovation Solution
A supply voltage level detector is designed with a control circuit that disables the comparing device until the bandgap reference voltage is available, and a forcing circuit that sets the output terminal to a specific value to prevent erroneous flag signals, ensuring reliable operation once the voltage source is ready.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the comparing device operates continuously to detect voltage levels, then the detection responsiveness is improved, but unreliable flag signals are generated when the bandgap reference voltage is not ready
Solution Approach 1:
The control circuit performs preliminary action by disabling the comparing device before the bandgap reference voltage is ready, and enabling it only when the voltage stabilizes. This preliminary control prevents unreliable comparisons while maintaining detection capability, resolving the contradiction between continuous detection and signal reliability.
Solution Approach 2:
The control circuit acts as an intermediary between the bandgap reference voltage generator and the comparing device. It monitors the readiness of the bandgap voltage and mediates the enabling/disabling of the comparing device, ensuring that comparisons only occur when reliable reference voltage is available, thus preventing erroneous flag signals.
2Reliability
If the comparing device is disabled when bandgap reference voltage is unavailable, then flag signal reliability is improved, but detection capability is lost during voltage source reset
Solution Approach 1:
The system dynamically adjusts the operating state of the comparing device based on the readiness of the bandgap reference voltage. The control circuit continuously monitors voltage stability and dynamically enables or disables the comparing device, optimizing both reliability and detection capability according to real-time conditions.
Solution Approach 2:
The comparing device operates periodically rather than continuously - it is enabled when the bandgap reference voltage is ready and disabled when unavailable. This periodic operation pattern, controlled by the control circuit, maintains flag signal reliability while preserving detection capability during voltage source reset conditions.
3Reliability
If the forcing circuit is used to set output terminal voltage, then erroneous flag signals are prevented, but additional circuit complexity is introduced
Solution Approach 1:
The forcing circuit acts as an intermediary element that sets the output terminal voltage to a specific level when the comparing device is disabled. This simple voltage forcing mechanism prevents erroneous flag signals without requiring complex control logic, resolving the contradiction between reliability and circuit complexity.
Data Source
AI summary
Supply voltage level detectors are disclosed. The supply voltage level detector comprises a voltage source divider dividing a voltage source to generate a detection voltage, a bandgap reference voltage generator, a comparator comparing the detection voltage with a bandgap reference voltage generated by the bandgap reference voltage generator to determine if the voltage source is ready, a control circuit, and a forcing circuit. To ensure reliability of the comparison result, the control circuit disables the comparing device until the bandgap reference voltage is available. The forcing circuit is coupled to the output terminal of the comparing device and is controlled by the control circuit. When the comparing device is disabled, the forcing circuit forces the voltage level of the output terminal of the comparing device to a specific value indicating the voltage source is unready.