Crystal Oscillator Amplifier BIST for Transconductance Testing
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Solution Overview
Problem
Conventional methods for testing the transconductance of crystal oscillator amplifiers are costly and time-consuming, hindering the production efficiency and time-to-market of final products.
Innovation Solution
A built-in self-test (BIST) system that includes a current mirror circuit, ADC, DAC, and test control circuitry to estimate the transconductance of crystal oscillator amplifiers without external hardware, using a single-pole, double-throw switch and single-pole, single-throw switch to transition between normal and test modes, and calculate transconductance based on test voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional testing methods using voltmeter, ammeter and source meter are used to measure transconductance, then measurement accuracy is achieved, but testing time and cost increase significantly
Solution Approach 1:
The system uses the crystal oscillator amplifier's own internal circuitry (current mirror circuit, existing transistors, and internal nodes) to perform the transconductance measurement. The amplifier tests itself by utilizing its internal current mirror to generate test currents and measuring the resulting voltages at internal nodes, eliminating the need for external measurement equipment and reducing testing time while maintaining accuracy
Solution Approach 2:
The invention extracts only the essential measurement function from the conventional testing setup. Instead of using full external measurement equipment (voltmeter, ammeter, source meter), the system extracts the core measurement capability by using the internal current mirror circuit to generate test signals and measure responses, thereby reducing complexity and testing time while preserving measurement accuracy
2Reliability
If conventional testing methods using multiple hardware instruments are used, then comprehensive testing is achieved, but device complexity and cost increase
Solution Approach 1:
The internal current mirror circuit serves multiple functions: it acts as the test signal generator, the current source for measurement, and part of the measurement system itself. The same amplifier circuit that performs oscillation also performs self-testing, eliminating the need for separate external testing equipment and reducing overall system complexity while maintaining comprehensive testing capability
Solution Approach 2:
The invention merges the testing function with the amplifier's internal circuitry. The current mirror circuit, which is already part of the amplifier structure, is utilized for both normal operation and test mode. The switching mechanism integrates the test function into the existing amplifier architecture, combining multiple functions into a unified system that reduces external component requirements
3Measurement precision
If conventional production testing methods are used, then accurate fault identification is achieved, but production efficiency decreases
Solution Approach 1:
The system performs preliminary self-testing during the amplifier's operation or initialization phase. By using the internal current mirror and switching mechanisms already present in the amplifier, the test function is integrated into the production flow without requiring separate testing steps, thereby maintaining fault identification accuracy while improving production efficiency
Solution Approach 2:
The amplifier performs its own fault identification using internal circuitry. The current mirror circuit generates test currents, the switching mechanism routes these currents through appropriate paths, and the system measures the responses to determine if the transconductance is within specification. This self-testing capability eliminates the need for time-consuming external testing equipment while maintaining accurate fault identification
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 efficient and cost-effective testing of transconductance, reducing testing time and costs while ensuring accurate identification of faulty amplifiers.
Implementation Method 1
a current mirror circuit that mirrors current flowing through the base transistor into a test resistor to develop a test voltage at a test node
Implementation Method 2
an analog to digital converter (ADC) that converts a self-bias voltage developed on the input node to a digital bias code
Implementation Method 3
the transistor has a control terminal coupled to an input node. The feedback resistor is coupled between the input and output nodes. The crystal oscillator amplifier generates negative resistance to an externally-coupled crystal
Data Source
AI summary
A BIST system and method for a crystal oscillator amplifier including current mirror circuitry, an ADC, a DAC, and test control circuitry. The amplifier includes a current source, a base transistor and a feedback resistor. The ADC converts a self-bias voltage on an input node into a digital bias code during a normal mode when the current source is coupled to the base transistor. During phases of a test mode, the base transistor is coupled instead to the mirror circuitry, which mirrors current through the base transistor into a test resistor. The digital bias code is converted into upper and lower digital bias codes using a delta value, which are converted by the DAC into corresponding bias voltages driven onto the input node during respective phases of the test mode. The ADC converts corresponding test voltages on the test resistor into test codes used to estimate the amplifier transconductance.