Ramp Wave Feedback Circuit for PVT-Stable Fingerprint ADCs
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Solution Overview
Problem
The performance of fingerprint identification systems deteriorates due to the influence of process/voltage/temperature (PVT) variations on ramp wave generation circuits and clock generators in existing analog-to-digital conversion circuits.
Innovation Solution
A ramp wave generation circuit with a feedback control loop and transconductance amplifier, where bilateral switches are controlled by phase-reversed and non-overlapped periodic signals, and a signal regulation circuit monitors the ramp wave signal to output a regulation control signal for error correction, ensuring the amplitude of the output ramp wave signal remains stable despite PVT changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional ramp wave generation circuit and clock generator are used in the analog-to-digital conversion circuit, then the circuit structure is simple, but the performance of the fingerprint identification system deteriorates due to PVT variations
Solution Approach 1:
The patent introduces a feedback control mechanism where the ramp wave generation circuit and clock generator are regulated through feedback loops. The feedback continuously monitors the output and adjusts the circuit parameters to compensate for PVT variations, thereby maintaining stable performance without requiring a complete redesign of the entire system.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the operating parameters of the ramp wave generation circuit and clock generator in response to PVT conditions. This includes modifying bias voltages, current levels, and timing parameters to optimize performance under varying process, voltage, and temperature conditions.
2Measurement precision
If the amplitude of the ramp wave signal is allowed to vary with PVT changes, then the circuit operation is simple, but the performance indicators such as gain error, resolution, and non-linearity deteriorate
Solution Approach 1:
The patent implements a feedback control mechanism where the amplitude of the ramp wave signal is continuously monitored and regulated. The feedback loop detects deviations in amplitude caused by PVT variations and automatically adjusts the signal generation parameters to maintain constant amplitude, thereby preserving ADC performance indicators such as gain error, resolution, and non-linearity.
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for PVT effects on the ramp wave signal amplitude. The circuit is designed to anticipate and counteract the expected amplitude variations before they degrade ADC performance, using pre-calibrated correction factors and proactive signal regulation.
3Manufacturing precision
If bilateral switches are controlled without phase-reversed and non-overlapped periodic signals, then the control circuit is simple, but the ramp wave generation accuracy is affected by PVT variations
Solution Approach 1:
The patent employs periodic action by using phase-reversed and non-overlapped periodic signals to control the bilateral switches. This periodic control scheme ensures that the switches operate in a synchronized and predictable manner, reducing the impact of PVT variations on ramp wave generation accuracy while maintaining a manageable control circuit complexity.
Solution Approach 2:
The patent applies asymmetry by using phase-reversed signals with specific non-overlapped timing characteristics to control the bilateral switches. This asymmetric control approach optimizes the switch operation to minimize PVT sensitivity, creating a more robust ramp wave generation mechanism that maintains accuracy under varying conditions.
Data Source
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AI summary
The present invention, related to the technical field of fingerprint identification, discloses a ramp wave generation circuit, a digital-to-analog conversion circuit, and a fingerprint identification system. The ramp wave generation circuit comprises: an integrating circuit, configured to output a ramp wave signal; a signal regulation circuit, comprising a feedback control loop and a transconductance amplifier connected in series, wherein the feedback control loop monitors the ramp wave signal output by the integrating circuit, and outputs a regulation control signal to the transconductance amplifier, the transconductance amplifier corrects, according to the regulation control signal, a ramp wave signal output by the integrating circuit within a next period; and a voltage generation circuit, configured to respectively output a reference voltage signal to the integrating circuit and the signal regulation circuit. With the fingerprint identification system, the problem that a ramp wave generation circuit and a clock generator cause deterioration of the performance of a fingerprint system due to impacts of PVT in the related art may be solved.