Sensor Integrated Circuit Calibration for Single-Pin Current Output
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Solution Overview
Problem
Existing sensors with analog current output require additional connections for biasing the burden resistor, which is not feasible in tight space constraints and increases cost, and are susceptible to noise, especially in high current switching applications.
Innovation Solution
A sensor integrated circuit that generates an analog current output with a single connection, independent of burden resistor resistance, by calibrating an offset current to a fixed percentage of the supply voltage, using a voltage divider and operational amplifier to determine and store the offset current for bi-directional sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an additional connection is provided to bias the burden resistor for analog current output, then bi-directional sensing accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the burden resistor biasing function with the existing single output connection by implementing an on-chip current source that generates an offset current. This offset current is added to the sensor output current at the same output pin, effectively merging the biasing function into the existing connection infrastructure and eliminating the need for a separate bias connection.
Solution Approach 2:
The patent introduces an on-chip current source as an intermediary element that generates an offset current proportional to the supply voltage. This offset current serves as a mediator that compensates for the burden resistor voltage drop without requiring direct access to the output connection for separate biasing, thereby maintaining single-connection operation while achieving accurate bi-directional sensing.
2Measurement precision
If an additional connection is provided for burden resistor biasing, then sensor output interpretation accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges the burden resistor biasing function with the existing output connection by using an on-chip current source to generate an offset current that is added to the sensor output at the same pin. This integration eliminates the need for additional package pins and reduces the overall device complexity, leading to lower manufacturing costs while maintaining accurate sensor output interpretation.
3Ease of operation
If voltage signal is used for sensor output, then ease of interpretation is improved, but noise susceptibility increases
Solution Approach 1:
The patent changes the output signal parameter from voltage to current by maintaining an analog current output format. The on-chip current source generates an offset current that is added to the sensor output current, and this current signal is then converted to voltage at the external controller. Current signals are inherently more immune to noise during transmission, especially over long distances and in high-current switching environments, while still providing ease of interpretation through the burden resistor conversion at the controller end.
Data Source
AI summary
A sensor integrated circuit configured to generate a sensor output current indicative of a sensed parameter includes a power connection to receive a supply voltage, a ground connection, a sensing circuit configured to generate a parameter current proportional to the sensed parameter, and an output connection at which the sensor output current is provided. An output current calibration circuit is configured to determine an offset current that corresponds to a bias voltage at the output connection equal to a fixed percentage of the supply voltage when the parameter current is substantially zero. The sensor output current is provided as a combination of the parameter current and the offset current.