Current Sense Resistor Calibration for Drift and Common-Mode Error
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Solution Overview
Problem
Polysilicon high-sheet resistance (HSR) resistors used in sense circuits experience significant resistance changes due to aging and temperature variations, leading to accuracy issues in current-sensing applications, which existing technologies fail to adequately address.
Innovation Solution
A system comprising a drift sense circuit and a driver calibration controller that dynamically adjusts the resistance values of trimmable resistors to account for drift over time, using a calibration process involving both VTEST and VDD voltages to minimize common-mode errors and maintain current sense accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polysilicon HSR resistors are used in sense circuits, then the circuit can be manufactured with standard processes, but the resistance value drifts significantly over time due to aging and temperature
Solution Approach 1:
The patent applies preliminary action by performing calibration before the resistor drift becomes critical. A calibration circuit measures the actual resistance value of the sense resistor at manufacturing or initialization, and stores this calibrated value in memory. This pre-measurement allows the system to compensate for future drift by comparing against the known initial value, thereby maintaining sensing accuracy despite the inherent instability of polysilicon HSR resistors.
Solution Approach 2:
The patent implements feedback through a calibration system that periodically or continuously monitors the resistance value and adjusts the sensing circuit accordingly. The calibration controller compares the actual resistance against the stored calibrated value and generates correction signals to compensate for drift. This closed-loop feedback mechanism ensures that the sense circuit maintains accuracy over time and across temperature variations, resolving the reliability issue while keeping the manufacturable polysilicon HSR resistor.
2Measurement precision
If resistor calibration is performed to maintain accuracy, then sensing precision is improved, but the device complexity increases due to additional calibration circuits and control logic
Solution Approach 1:
The patent merges the calibration function with the existing sense circuit by integrating the calibration controller and calibration resistor into the same circuit block. The calibration controller shares control signals and power supply with the main sensing operation, and the calibration resistor is placed in parallel with the sense resistor, allowing both sensing and calibration to occur through the same physical infrastructure. This merging reduces the overall device complexity while maintaining measurement precision.
Solution Approach 2:
The calibration controller is designed to perform multiple functions: it controls the calibration switch, measures the calibration voltage, stores the calibrated resistance value, and generates correction signals for drift compensation. This multi-functional design eliminates the need for separate dedicated circuits for each function, thereby improving measurement precision without proportionally increasing device complexity. The universal calibration controller handles both initial calibration and ongoing drift compensation.
Data Source
AI summary
A system includes: a drift sense circuit; and a driver calibration controller. The drift sense circuit has an input terminal, an output terminal, and a ground terminal. The drift sense circuit includes: a resistor having a first terminal and a second terminal, the first terminal of the resistor coupled to the input terminal; and a reference component having a first terminal and a second terminal, the second terminal of the reference component coupled to the ground terminal. The drift calibration controller is coupled to the output terminal of the drift sense circuit. The drift calibration controller is configured to: obtain a sense signal responsive to an input voltage applied to the input terminal; determine a drift result of the resistor responsive to the sense signal; and update a control operation responsive to the drift result.