Comparator-Based Power-On-Reset With Noise-Filtered Trip Detection
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Solution Overview
Problem
Conventional power-on-reset circuitry in integrated circuits faces challenges in accurately monitoring multiple power supply voltages, especially as core power supply voltages decrease and transistor sizes shrink, leading to increased susceptibility to process and temperature variations, which degrades accuracy and makes it difficult to generate reliable power-on-reset signals.
Innovation Solution
The implementation of comparator-based voltage trip point detectors with a voltage reference source, voltage divider, and voltage multiplier circuitry to generate desired voltage trip points, along with power-on-reset controller logic and feedback circuitry to produce a power-on-reset output signal, while being responsive to the power-up sequence and capable of suppressing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional power-on-reset circuitry is used with shrinking transistor sizes, then device scaling is achieved, but accuracy of power supply voltage monitoring deteriorates due to increased susceptibility to process and temperature variations
Solution Approach 1:
The patent changes the monitoring approach from direct transistor threshold voltage comparison to a ratio-based measurement system. By measuring the ratio of two currents (one through a reference transistor and one through a sensing transistor), the circuit becomes insensitive to absolute threshold voltage variations caused by process and temperature changes. This parameter transformation converts an absolute voltage measurement problem into a relative ratio measurement problem, resolving the accuracy degradation issue.
Solution Approach 2:
The patent introduces an intermediary current measurement mechanism that indirectly monitors power supply voltage. Instead of directly comparing voltages using transistors whose thresholds vary with process and temperature, the circuit uses current mirrors and sensing transistors to create intermediate current signals that can be compared ratio-wise. This intermediary approach isolates the monitoring function from the variations in transistor characteristics.
2Reliability
If multiple power supply voltages are monitored, then comprehensive power-on-reset control is achieved, but circuit complexity increases
Solution Approach 1:
The patent designs a universal monitoring circuit block that can monitor any power supply voltage. The same circuit topology (sensing transistor, current mirror, comparator) is used for each power supply voltage, making the circuit multi-functional. This universal block can be replicated for multiple voltages without increasing the fundamental circuit complexity, as each block performs the same function independently.
Solution Approach 2:
The patent divides the multi-voltage monitoring task into separate independent monitoring blocks, each dedicated to a specific power supply voltage. Each block contains its own sensing transistor, current mirror, and comparator. This segmentation allows each block to be optimized independently and simplifies the overall design by breaking down the complex multi-voltage monitoring problem into manageable identical units.
3Use of energy by moving object
If core power supply voltage decreases, then power consumption is reduced, but monitoring accuracy deteriorates due to smaller voltage headroom
Solution Approach 1:
The patent changes from absolute voltage monitoring to ratio-based current monitoring. By measuring the ratio of currents through sensing transistors rather than absolute voltages, the circuit maintains accuracy even when the core power supply voltage is low. The ratio measurement is independent of the absolute voltage level, allowing accurate monitoring at reduced voltages.
Solution Approach 2:
The patent replaces direct voltage comparison (electrical field measurement) with current ratio measurement through transistor sensing. This substitution allows the use of transistor current characteristics, which remain relatively stable even at low voltages, to infer power supply voltage status. The current mirror and sensing mechanism provide a more robust measurement approach at reduced voltage levels.
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
This solution enhances the accuracy and reliability of power-on-reset signals by effectively monitoring multiple power supply voltages, reducing the impact of process and temperature variations, and ensuring that integrated circuits operate within valid power supply ranges, preventing errors and data corruption.
Implementation Method 1
A voltage reference source such as a bandgap voltage reference may supply a reference voltage to the trip point detectors
Implementation Method 2
A comparator in each trip point detector may be used to compare a power supply voltage that has been received by that detector to the voltage trip point for that detector
Data Source
AI summary
Power-on-reset circuitry is provided for integrated circuits such as programmable logic device integrated circuits. The power-on-reset circuitry may use comparator-based trip point voltage detectors to monitor power supply voltages. The trip point detectors may use circuitry to produce trip point voltages from a bandgap reference voltage. Controller logic may process signals from the trip point detectors to produce a corresponding power-on-reset signal. The power-on-reset circuitry may contain a noise filter that suppresses noise from power supply voltage spikes. Normal operation of the power-on-reset circuitry may be blocked during testing. The power-on-reset circuitry may be disabled when the bandgap reference voltage has not reached a desired level. The power-on-reset circuitry may be sensitive or insensitive to the power-up sequence used by the power supply signals. Brownout detection blocking circuitry may be provided to prevent the output from one of the trip point detectors from influencing the power-on-reset circuitry.