Split-Source LF Driver Current Sensing With Low Die Area
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Solution Overview
Problem
Existing switching amplifier designs face challenges in accurately measuring output current due to the switched nature of the signal and the complexity, cost, and size issues associated with existing current sensing approaches, such as external sense resistors and current copy circuitry.
Innovation Solution
A switching amplifier circuit with an embedded split gate-source transistor switch and a current sense resistor placed only on the source of the small sense transistor, allowing for efficient and accurate measurement of driver current through a low-cost, area-efficient implementation, using separate power and sense transistors to minimize die area and additional costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sense resistors are used for current measurement, then current measurement capability is achieved, but device complexity and cost increase
Solution Approach 1:
The current sense transistor is merged with the output driver transistors to form a split gate-source configuration. The sense transistor shares the same gate control signal and is integrated into the existing driver circuitry, eliminating the need for separate external sense resistors while maintaining accurate current measurement capability through the intrinsic resistance of the sense transistor.
2Measurement precision
If current copy circuitry is used for current measurement, then current measurement accuracy is improved, but die area and cost increase
Solution Approach 1:
The output driver transistors themselves serve as the current sensing elements. The sense transistor's channel resistance provides the sensing mechanism, and the same transistor structure that drives the output current also measures it through voltage sampling at the source terminal, eliminating the need for separate current copy circuitry and reducing die area.
3Measurement precision
If high precision current sensing is implemented, then measurement accuracy is improved, but additional cost and power consumption increase
Solution Approach 1:
The current sensing function is performed by the output driver transistors themselves using their intrinsic channel resistance. The sense transistor operates in the same current path as the driver, requiring no additional power for separate sensing circuitry. The voltage developed across the sense transistor's source terminal during normal operation is directly sampled to obtain accurate current information without additional power expenditure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides a low-cost, area-efficient method for accurately measuring antenna driver current, maintaining sufficient current measurement accuracy while minimizing the effective switch resistance and die area, suitable for low-frequency driver applications.
Implementation Method 1
an output current sensing circuit for measuring a current through the output load with an integrated circuit current sensing transistor connected between a supply voltage line
Data Source
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AI summary
A switching amplifier circuit (200) connected to drive an impedance-based output load (230) includes high side and low side switches (201-204) configured and connected to connect first and second supply voltage lines to first and second output nodes (ANTP, ANTN) in response to gating control signals, and also includes an output current sensing circuit for measuring a current through the output load with a current sensing resistor (Rs) connected between the second supply voltage line and a source of one or more split gate-source switching transistors (203C) in the low side gate-source switching transistor, where a voltage sense circuit connected across the current sensing resistor is configured to sample a voltage across the current sensing resistor for measuring a sense current at the current sensing resistor.