Dynamic Current Sense Calibration Circuit
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Solution Overview
Problem
Sense circuits in electronic devices face accuracy issues due to aging and stress-induced errors, leading to degraded common-mode rejection ratio (CMRR) after being soldered onto printed-circuit boards, which affects the precision of current-sensing applications.
Innovation Solution
A circuit system comprising a driver circuit, test circuit, sense resistor, current sense circuit, calibration controller, and switch controller is implemented to self-calibrate and maintain the CMRR by obtaining sense signals from both test and supply voltages, allowing for dynamic adjustment of trimmable resistors to compensate for resistor drift and stress-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If initial CMRR tuning is performed during manufacturing, then manufacturing precision is improved, but reliability deteriorates due to aging and stress-induced errors after soldering
Solution Approach 1:
The patent performs initial CMRR tuning during manufacturing as a preliminary action, but then adds a calibration routine that executes after soldering to correct for stress-induced changes. This combines preliminary manufacturing tuning with post-assembly calibration to maintain both manufacturing efficiency and long-term reliability.
Solution Approach 2:
The calibration routine dynamically adjusts trimmable resistors to change the CMRR parameter in response to measured errors. This allows the system to adapt the electrical parameters of the sense circuit after manufacturing, compensating for aging and stress effects that occur during soldering and operation.
2Reliability
If dynamic calibration is implemented to maintain CMRR accuracy, then reliability is improved, but device complexity increases
Solution Approach 1:
The calibration routine is self-executing and uses the existing sense circuitry to measure its own performance. The system automatically applies test voltages, measures CMRR degradation, and adjusts trimmable resistors without external intervention, making the complex calibration process transparent to the user while maintaining simplicity in operation.
Solution Approach 2:
The calibration routine reuses existing circuit components (sense amplifier, trimmable resistors, test voltage sources) for multiple purposes: normal operation and calibration. This multi-functionality reduces the need for dedicated calibration hardware, thereby limiting the increase in device complexity while still achieving reliable CMRR maintenance.
3Adaptability or versatility
If trimmable resistors are used for CMRR adjustment, then adaptability is improved, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The system performs preliminary CMRR tuning during manufacturing using the trimmable resistors, establishing an initial accurate state. The resistors are set to specific values during assembly to achieve target CMRR performance, and this preliminary adjustment is later refined by the automated calibration routine that compensates for stress-induced changes.
Solution Approach 2:
The calibration routine measures the actual CMRR performance and uses this feedback to adjust the trimmable resistors to their optimal values. This closed-loop feedback mechanism compensates for manufacturing variations and stress-induced changes, maintaining manufacturing precision through automated adjustment rather than relying solely on tight initial tolerance matching.
Data Source
AI summary
A circuit includes: a driver circuit; a sense resistor; a test circuit; a current sense circuit; a calibration controller; and a switch controller. The current sense circuit is configured to: obtain first sense signals responsive to a test voltage applied to the sense resistor by the test circuit, the test voltage being a direct-circuit voltage; and obtain second sense signals responsive a supply voltage applied to the sense resistor by the driver circuit, the supply voltage including a common-mode voltage. The calibration controller is configured to calibrate the current sense circuit responsive to the first sense signals and the second sense signals. The switch controller is configured to update switch control signals provided to the driver circuit responsive to current sense signals obtained by the calibrated current sense circuit.