Current Sense Amplifier Trimming for Input-Referred Offset Accuracy
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Solution Overview
Problem
Conventional current sensing amplifier circuits face inaccuracies due to offset RTI voltage generated during manufacturing, which varies with input voltages and reference voltage, leading to errors in current sensing results, and require complex trimming processes that are laborious and only applicable to specific conditions.
Innovation Solution
A current sensing amplifier circuit with a simplified trimming method that generates a trimming current proportional to input and reference voltages, using a current source circuit to adjust resistances and compensate for error resistances, ensuring accurate current sensing across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional trimming method using built-in programmable feedback resistor chain is used, then offset RTI voltage can be trimmed, but the trimming process becomes complex and laborious
Solution Approach 1:
The patent changes the trimming parameter from resistance adjustment (conventional method) to current adjustment. By using a current source circuit to generate adjustable trimming current, the method simplifies the trimming process while maintaining accuracy. The trimming current is adjusted to compensate for offset RTI voltage without requiring complex resistor chain programming.
Solution Approach 2:
The patent extracts the trimming function from the feedback resistor chain and implements it separately through a current source circuit. This separation allows the trimming operation to be performed independently using current adjustment rather than resistance programming, reducing the complexity of the overall trimming process.
2Measurement precision
If conventional trimming method is used, then offset RTI voltage can be compensated, but the trimming is only applicable to specific conditions and not adaptable to varying input voltages
Solution Approach 1:
The patent implements a dynamic trimming current that can be adjusted based on varying input conditions. The current source circuit generates a trimming current that adapts to different input voltages and reference voltage conditions, making the offset compensation effective across a wide range of operating conditions rather than being fixed for specific conditions only.
Solution Approach 2:
The current source circuit serves multiple functions: it generates the trimming current for offset compensation, adapts to varying input voltages, and works with different reference voltage conditions. This universal approach allows the same circuit to handle various operating conditions without requiring condition-specific trimming configurations.
3Ease of manufacture
If resistor R31 is coupled to reference voltage Vref to reduce common mode voltage, then amplifier cost can be reduced, but offset RTI voltage errors remain due to resistor manufacturing deviations
Solution Approach 1:
The patent introduces a current source circuit as an intermediary element that generates a trimming current to compensate for the offset RTI voltage caused by resistor manufacturing deviations. This intermediary component corrects the accuracy issue without requiring changes to the resistor network or amplifier selection, maintaining the cost benefits of using standard components.
Solution Approach 2:
The patent implements a feedback mechanism where the trimming current is adjusted based on the actual offset RTI voltage present in the circuit. This feedback approach ensures that the current sensing accuracy is maintained despite variations in resistor values, allowing the use of standard, lower-cost resistors and amplifiers while achieving the required precision.
Data Source
AI summary
A current sensing amplifier circuit includes: an amplifier configured to generate an output voltage correlated with a current to-be-sensed according to a first input voltage at a first input end and a second input voltage at a second input end in a normal operation mode; and a current source circuit configured to generate a trimming current according to the first input voltage and a reference voltage in a trimming mode and to provide the trimming current to trim an offset referred to input (RTI) voltage generated by the current sensing amplifier circuit in the normal operation mode. The current source circuit is coupled between: a first resistor and a non-inverting input end, a second resistor and the output voltage, a third resistor and the non-inverting input end, or a fourth resistor and an inverting input end.