MOSFET Gate Control Circuit for Post-Bonding Leak Current Measurement
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Solution Overview
Problem
It is challenging to accurately measure the leak current of a MOSFET after it is connected to a control IC due to the impact force applied during bonding, which can lead to decreased quality of the motor drive IC, as the pull-up resistor allows a smaller electric current to flow, making it difficult to measure the leak current effectively.
Innovation Solution
A control device with a test operation mode that electrically separates the control terminal of the load drive semiconductor element from the power source or ground by turning off another semiconductor element, allowing for easy measurement of the leak current even after connection, by using a test control circuit to manage the gate voltage of the MOSFET and prevent current flow during measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pull-up resistor is used to keep the gate voltage at high level when MOSFETs are turned off, then the control circuit can maintain proper voltage levels, but the pull-up resistor allows a smaller electric current to flow making it difficult to measure the leak current of the MOSFET
Solution Approach 1:
The patent divides the control circuit into separate functional blocks: a normal operation mode circuit with the pull-up resistor for maintaining gate voltage, and a test operation mode circuit with a separate measurement path. This segmentation allows the measurement function to operate independently without being affected by the pull-up resistor's current limitations.
Solution Approach 2:
The patent introduces a test control circuit as an intermediary component that provides a separate current path for leak current measurement. This test control circuit acts as a mediator between the MOSFET and the measurement instrument, enabling accurate leak current measurement without interfering with the normal pull-up resistor operation.
2Ease of manufacture
If the MOSFET is connected to the control IC through bonding wire, then the motor drive IC can be manufactured, but impact force during bonding may break the MOSFET decreasing the quality of the motor drive IC
Solution Approach 1:
The patent implements a test operation mode that can be performed after bonding but before final assembly. This preliminary testing allows detection of MOSFET damage caused by bonding impact forces, enabling defective units to be identified and removed before they reach the customer.
Solution Approach 2:
The patent establishes a feedback mechanism where leak current measurement results provide information about MOSFET integrity. This feedback loop allows the manufacturing process to adjust and re-test MOSFETs after bonding, ensuring only high-quality devices are assembled into the final product.
3Measurement precision
If leak current measurement is performed before connecting the MOSFET to the control IC, then the measurement can be done, but the MOSFET cannot be tested after bonding to check for impact damage
Solution Approach 1:
The patent designs the control IC with a universal test operation mode that can measure leak current both before and after MOSFET bonding. The test control circuit is integrated into the IC itself, providing multi-functional capability that adapts to different testing stages in the manufacturing process.
Data Source
AI summary
A control device for controlling a load drive semiconductor element for driving a load has a test operation mode for measuring a leak current of the load drive semiconductor element. In the test operation mode, a control terminal of the load drive semiconductor element is electrically separated from a power source or a ground by turning off another semiconductor element. Therefore, no electric current flows from the power source to the control terminal or from the control terminal to the ground. Therefore, the leak current of the load drive semiconductor element can be easily measured, even after the load drive semiconductor element is electrically connected to the control device for fabricating one-packaged IC.