Static Comparator Hysteresis Compensation Without Reset Phase
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Solution Overview
Problem
Static comparators exhibit significant hysteresis, which degrades performance and introduces ripple effects in signal chains, increasing bit error rates and degrading linearity in ADCs, whereas adding a reset phase to compensate for hysteresis would reduce the effective comparison time.
Innovation Solution
A comparator circuit with a hysteresis compensation circuit that applies a predetermined signal level shift at the output of the master amplifier circuit based on the signal level of the slave latch, minimizing the difference between high-to-low and low-to-high thresholds without requiring a reset phase, thus compensating for hysteresis without adding significant circuitry or capacitive loading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hysteresis compensation is implemented by adding a reset phase in static comparators, then hysteresis is compensated, but the effective comparison time is reduced
Solution Approach 1:
The hysteresis compensation is achieved by preliminarily adjusting the threshold voltage through the hysteresis compensation circuit (current source 35, switches 31, 32) before the comparison occurs, rather than adding a reset phase after comparison. The circuit proactively sets the appropriate threshold level based on the desired hysteresis compensation, allowing the comparison to proceed immediately without time loss.
Solution Approach 2:
The invention changes the threshold voltage parameter dynamically through the hysteresis compensation circuit. By controlling the current source 35 to connect to different nodes (103 or 104) via switches 31 and 32, the circuit adjusts the threshold voltage to compensate for hysteresis effects, achieving reliable hysteresis compensation without affecting the comparison time.
2Reliability
If hysteresis compensation circuitry is added to static comparators, then hysteresis is reduced, but device complexity increases
Solution Approach 1:
The hysteresis compensation circuit is merged with the existing comparator structure. The current source 35 and switches 31, 32 are integrated into the comparator circuit, sharing common nodes and signals with the master and slave latches. This merging approach adds hysteresis compensation functionality while minimizing the increase in overall device complexity.
Solution Approach 2:
The hysteresis compensation circuit components serve multiple functions within the comparator. The current source 35 not only provides hysteresis compensation but also works in conjunction with the latch circuits for signal level adjustment. The switches 31 and 32 are controlled by the same clock signals already present in the comparator, making them multi-functional elements that reduce the need for additional control logic.
Data Source
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AI summary
According to an aspect of the present inventive concept there is provided a comparator circuit comprising: a master latch comprising a first amplifier circuit and a first latch circuit coupled to an output of the first amplifier circuit; a slave latch comprising a second amplifier circuit having an input coupled to the output of the first amplifier circuit, and a second latch circuit coupled to an output of the second amplifier circuit; and a hysteresis compensation circuit coupled to the output of the second amplifier circuit and configured to cause a first predetermined signal level shift of an output signal of the first amplifier circuit in response to a high signal level at the output of the second amplifier circuit, and configured to cause a second predetermined signal level shift of an output signal of the first amplifier circuit in response to a low signal level at the output of the second amplifier circuit.