Bandgap Reference Failure Detection for Medium-Rate Voltage Drops
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Solution Overview
Problem
Existing systems fail to detect failures in bandgap reference voltage circuits in a timely manner, particularly during medium rate drops in supply voltage, which can lead to data loss in ferroelectric random access memory (FRAM) due to insufficient detection by slow comparators and fast failure detectors.
Innovation Solution
A bandgap reference failure detection circuit that compares a present bandgap reference voltage to a stored model value or uses an RC filter to create a delayed representation, asserting a failure signal to initiate a reset operation before charge on buffer capacitors is dissipated, ensuring reliable operation of critical circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slow comparators and fast failure detectors are used to monitor bandgap reference voltage, then power consumption is reduced and circuit simplicity is maintained, but detection speed is insufficient during medium rate voltage drops leading to data loss
Solution Approach 1:
The monitoring system is segmented into three distinct components: slow comparators for power efficiency, fast failure detectors for rapid response, and a new failure detection circuit with RC filtering for medium-rate detection. Each component operates in specific scenarios, collectively covering the full spectrum of voltage drop rates without requiring a single high-speed monitor that would consume excessive power.
Solution Approach 2:
An RC filter circuit is introduced as an intermediary between the bandgap reference voltage source and the comparison logic. This RC filter creates a delayed representation of the voltage that enables detection of medium-rate drops that are too fast for slow comparators but too slow for ultra-fast detectors, filling the detection gap with appropriate response timing.
2Productivity
If fast failure detectors are used to improve detection speed, then detection timeliness is improved, but power consumption increases and circuit complexity increases
Solution Approach 1:
The detection system divides monitoring tasks across multiple components with different speed and power characteristics. Fast failure detectors handle only ultra-rapid voltage drops, while the new RC-filtered circuit handles medium-rate drops, and slow comparators handle gradual changes. This segmentation allows each component to operate at optimal power levels for its specific function rather than all components running at high speed.
Solution Approach 2:
Instead of implementing a fully fast detection system for all scenarios (which would consume excessive power), the patent applies partial fast detection only where absolutely necessary (ultra-rapid drops) and uses the RC-filtered intermediate detection for the broader range of medium-rate events, achieving sufficient detection speed without the full power cost of exclusively fast detectors.
3Measurement precision
If RC filter is used to create delayed representation of bandgap reference voltage, then detection accuracy for medium rate drops is improved, but circuit complexity increases
Solution Approach 1:
A simple RC filter circuit serves as an intermediary that transforms the raw bandgap reference voltage into a delayed representation suitable for detection. This passive filter network (resistor and capacitor) adds minimal complexity compared to active detection circuits while providing the necessary time-delay characteristic to catch medium-rate voltage drops that occur between the response times of slow and fast detectors.
Solution Approach 2:
The RC filter circuit serves multiple functions: it acts as a low-pass filter to smooth high-frequency noise, creates the necessary time delay for medium-rate detection, and provides a stable voltage representation for the comparator. This multi-functionality reduces the need for additional separate circuits, thereby limiting the increase in overall system 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
Enables early detection of bandgap reference circuit failures, allowing FRAM to complete memory operations before charge is drained, thereby preventing data loss and ensuring system reliability.
Implementation Method 1
uses an RC filter to create a delayed representation
Data Source
AI summary
An integrated circuit is provided with a bandgap voltage reference circuit having a bandgap reference voltage output. A bandgap failure detection circuit is coupled to the bandgap reference voltage output. The bandgap failure detection forms a model value of the reference voltage from a first time, compares a present value of the reference voltage at a second time to the model value; and asserts a bandgap fail signal to indicate when the present value is less than the model value by a threshold value. The integrated circuit is reset by the bandgap fail signal. The detection circuit may be operated from a failsafe voltage domain that also allows a critical circuit to complete a pending operation during a reset.