Comparator Offset Compensation via Propagation Delay Measurement
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Solution Overview
Problem
Comparators in high-performance applications face challenges in minimizing input offset voltage and propagation delay, especially when detecting small signal differences, as manufacturing variations can cause incorrect decision polarity and dramatic changes in propagation time due to logarithmic relationships between signal magnitude and delay.
Innovation Solution
A comparator apparatus with an offset compensator that includes a measurement circuit, a time-to-digital converter, and a controller to measure and adjust propagation delays across multiple output terminals, allowing for real-time compensation of input voltage offsets without altering the signal path or increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the comparator is used to detect small differences in input signal, then the input voltage sensitivity is improved, but the propagation delay increases dramatically
Solution Approach 1:
The patent applies preliminary action by measuring the propagation delay of the comparator before it is used for its intended function. The measurement circuit measures the delay between the differential input signals and the output signals, and the controller uses this measured delay to adjust the sampling clock phase in advance, thereby compensating for the delay effect before the actual signal processing occurs.
Solution Approach 2:
The patent implements feedback by using the measured propagation delay to adjust the sampling clock phase. The controller receives the propagation delay measurement and automatically adjusts the clock phase to compensate for the delay, creating a closed-loop system that continuously optimizes the timing based on actual comparator performance.
2Reliability
If manufacturing variations cause input offsets similar in magnitude to the signals being compared, then the device complexity increases, but the reliability of decision polarity decreases
Solution Approach 1:
The patent uses feedback by measuring the propagation delay caused by input offsets and using this information to adjust the sampling clock phase. This automatic adjustment compensates for the offset effects without requiring complex additional compensation circuits, thereby improving decision reliability while maintaining relatively simple device architecture.
Solution Approach 2:
The patent introduces an intermediary approach by using the propagation delay measurement as an indirect indicator of input offset effects. Instead of directly measuring and compensating for the offset voltage, the system measures the resulting propagation delay and uses this as a proxy to adjust the timing, thereby compensating for offset effects without requiring direct offset measurement circuits.
3Measurement precision
If the propagation delay is measured and adjusted in real-time, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the measurement circuit to serve multiple purposes. The same measurement circuit that determines propagation delay is also used to control the sampling operation, and the sampling clock distribution network serves both as a clock source and as a delay compensation mechanism. This multi-functionality reduces the need for separate dedicated compensation circuits.
Solution Approach 2:
The patent implements feedback by creating a closed-loop system where the measured propagation delay directly controls the sampling clock phase adjustment. The controller automatically adjusts the clock phase based on the measured delay, eliminating the need for complex manual calibration circuits or additional compensation hardware while maintaining high measurement precision.
Data Source
AI summary
A method for compensator for comparator offset is provided. A first propagation delay for a first signal traversing a comparator to a first output terminal of the comparator and a second propagation delay for a second signal traversing the comparator to a second output terminal of the comparator are measured. The first and second propagation delays are then compared to generate a comparison result, and the comparator is adjusted to compensate for an input voltage offset based at least in part on the comparison result.