IC Power-Up Circuit Using Threshold Detectors
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Solution Overview
Problem
Modern integrated circuits face challenges in providing a reliable and accurate reference voltage during power-up due to fluctuations in transistor threshold voltages, leading to improper enabling of circuit blocks.
Innovation Solution
A circuit and method that utilize multiple threshold voltage detector segments to generate enabling signals for a bandgap reference circuit, ensuring accurate and stable reference voltage by activating and disabling signals at specific voltage levels, with a second threshold voltage detector modulating the voltage reset signal to indicate stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single threshold voltage detector is used to enable the bandgap reference circuit, then the circuit can be activated at a specific voltage level, but the reference voltage becomes inaccurate due to transistor threshold voltage fluctuations
Solution Approach 1:
The power-up circuit is divided into multiple independent threshold voltage detector segments (first detector segment with first threshold, second detector segment with second threshold). Each segment independently monitors the power supply voltage and generates enabling signals at different voltage levels, allowing the system to achieve both accurate reference voltage generation and reliable circuit operation by distributing the detection function across multiple segments with different threshold characteristics
Solution Approach 2:
The patent introduces an intermediary voltage detection mechanism that mediates between the power supply voltage and the bandgap reference circuit activation. The threshold voltage detector segments act as intermediaries that translate raw power supply voltage into controlled enabling signals, filtering out the harmful effects of direct voltage fluctuations on the reference voltage accuracy
2Productivity
If the bandgap reference circuit is enabled early to provide reference voltage, then other circuits can be powered up, but the reference voltage becomes unstable due to insufficient power supply voltage
Solution Approach 1:
The first threshold voltage detector segment performs preliminary detection of the power supply voltage and generates an enabling signal for the bandgap reference circuit as soon as the first threshold is reached. This preliminary action allows the reference circuit to start generating voltage early in the power-up sequence, improving overall power-up speed while the second detector segment provides additional stability verification
Solution Approach 2:
The second threshold voltage detector segment provides feedback control by monitoring whether the power supply voltage has reached a sufficient second threshold level. This feedback mechanism ensures that the reference voltage becomes stable before full circuit operation commences, preventing instability while maintaining fast power-up through the preliminary enabling action
3Device complexity
If transistor threshold voltage is used for voltage division, then the circuit can be simplified, but the enabling voltage level deviates due to fabrication process variations and temperature changes
Solution Approach 1:
The patent changes the critical parameters (threshold voltages) of the detector segments during fabrication to create distinct first and second threshold levels. By deliberately designing different threshold parameters for each detector segment, the system achieves precise voltage level detection despite fabrication variations, as each segment's threshold is optimized for its specific detection purpose
Solution Approach 2:
Each threshold voltage detector segment is designed with local quality characteristics - the first detector segment has threshold characteristics optimized for early enabling, while the second detector segment has threshold characteristics optimized for stability verification. This local optimization allows each segment to perform its specific function accurately without being affected by the variations that would impact a single uniform detector
Data Source
AI summary
The present invention is a circuit and method for providing a reference voltage and/or one or more circuit/circuit-block enabling signals for an IC. As the voltage level on a power supply line ramps upward towards or above a nominal operating voltage, a first threshold voltage detector circuit segment may be activated and may begin to generate a bandgap reset signal once the voltage level of the power supply reaches a first threshold voltage level. The bandgap reset signal may trigger the power-up and operation of a bandgap reference circuit segment, and according to further embodiments of the present invention, a second threshold voltage detector circuit segment, which second threshold voltage detector circuit segment may be matched with the first voltage detector circuit, may generate a voltage reset signal indicating that the bandgap reference source is powering-up. Once the supply voltage reaches a third threshold reference voltage, the first detector may disable the bandgap reset.