Ultrasonic Probe Switch Circuit for Safe Loopback Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The ultrasonic-wave diagnosis apparatus faces challenges in performing internal-signal loopback tests on transmission/reception circuits without damaging the low-voltage reception circuit due to high-voltage signals from the transmission circuit, especially with the increasing complexity of two-dimensional array probes, where thousands of pads make electrical testing difficult and prone to destruction.
Innovation Solution
A transmission/reception separation switch with two high-withstand-voltage MOS transistors connected in series, where the gate-source voltage is lowered during loopback tests to prevent voltage violations, using voltage division by the on-resistance of the switch and a low-voltage MOS to attenuate the signal, allowing for safe loopback testing without additional attenuators and maintaining low noise and loss during reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transmission circuit supplies high-voltage drive signals to the oscillator, then the ultrasonic wave transmission capability is improved, but the reception circuit may be electrically destroyed due to high voltage
Solution Approach 1:
The transmission/reception separation switch is divided into two series-connected high-withstand-voltage MOS transistors (first and second transistors), creating distinct transmission and reception pathways that prevent high-voltage damage to the reception circuit while maintaining transmission capability
Solution Approach 2:
The transmission/reception separation switch acts as an intermediary component between the transmission circuit and reception circuit, using high-withstand-voltage transistors to isolate the low-voltage reception circuit from high-voltage signals while allowing controlled signal passage
2Reliability
If the transmission/reception separation switch uses high-withstand-voltage device, then the electrical characteristics for withstanding high-voltage signals are improved, but the circuit area increases
Solution Approach 1:
The high-withstand-voltage MOS transistors in the transmission/reception separation switch serve multiple functions: they provide high-voltage withstanding capability, enable signal switching between transmission and reception modes, and facilitate loopback testing, thereby reducing the need for separate dedicated components and optimizing circuit area
3Reliability
If the gate-source voltage is lowered during loopback test, then the reception circuit is protected from voltage violation, but the signal amplitude must be attenuated
Solution Approach 1:
The gate-source voltage of the transmission/reception separation switch is dynamically adjusted based on operational mode: lowered during loopback testing to prevent voltage violations and protect the reception circuit, and optimized for low loss during normal reception operations
4Reliability
If additional attenuators are added to the reception signal path, then the signal amplitude can be reduced safely, but the circuit complexity and noise increase
Solution Approach 1:
The transmission/reception separation switch serves as a multi-functional component that provides both signal switching and signal attenuation capabilities, eliminating the need for separate dedicated attenuators in the reception signal path and thereby reducing overall circuit complexity
Solution Approach 2:
The transmission/reception separation switch performs self-adjustment of signal amplitude through gate-source voltage control, automatically providing appropriate attenuation during loopback testing without requiring external attenuator components
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
Enables reliable internal-signal loopback testing of transmission/reception circuits without destroying the low-voltage reception circuit, reducing circuit area and noise, and allowing for the testing of actual transmission/reception operations, while ensuring high reception performance and testability.
Implementation Method 1
using voltage division by the on-resistance of the switch and a low-voltage MOS to attenuate the signal
Data Source
AI summary
A test for screening defects of a transmission/reception circuit in an IC is enabled at low cost, without withstand voltage violation, and without carrying out electrical contacts with many terminals connected to oscillators. In a transmission/reception separation switch circuit using transistors as switch elements, a potential of a gate is lowered in a test more than the potential in a case of reception to avoid gate-source withstand-voltage violation when a large-amplitude signal is input, and an internal-signal loopback test is carried out without destroying a reception circuit.