Crystal Driver Gain Margin Testing With Internal Current Bias
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Solution Overview
Problem
Existing methods for measuring the gain margin of a crystal driver are inaccurate due to the limitations of voltage forcing instruments, which can shift measurement points outside the linear region, leading to significant errors and variability across different testers.
Innovation Solution
An internal crystal driver gain margin measurement test circuit using a programmable current mirror and internal current references to force current biases, allowing precise measurement of gain margin through a current mode, reducing reliance on external testers and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage forcing instruments are used to measure gain margin, then measurement can be performed, but measurement precision deteriorates due to instrument accuracy limitations and potential shift outside linear region
Solution Approach 1:
The patent replaces voltage forcing instruments with an internal current forcing mechanism. Instead of using external voltage mode testers that have accuracy limitations, the invention uses an internal current mode test circuit that forces precise current through the crystal driver and measures the resulting voltage. This substitution of measurement methodology (from voltage forcing to current forcing) eliminates the primary source of measurement error and variability across different testers.
Solution Approach 2:
The patent implements a self-contained internal test circuit within the crystal oscillator device that performs gain margin measurement without requiring external testing equipment. The internal current reference and measurement circuitry operate autonomously to characterize the crystal driver's gain margin, making the measurement process independent of external tester accuracy and eliminating the need for multiple external instruments.
2Ease of manufacture
If external testers with voltage forcing capability are used, then gain margin can be measured, but device complexity increases due to reliance on external instrumentation
Solution Approach 1:
The patent merges the test circuit functionality directly into the crystal oscillator device by integrating current reference circuits, current forcing mechanisms, and voltage measurement capabilities within the same device. This consolidation eliminates the need for separate external testing equipment and creates a unified self-testing system that simplifies the overall manufacturing and testing process.
Solution Approach 2:
The internal test circuit is designed to perform multiple functions: it can force current through the crystal driver, measure the resulting voltage, calculate gain margin, and potentially characterize other driver parameters. This multi-functional internal circuit replaces the need for multiple specialized external testing instruments, reducing system complexity while maintaining comprehensive testing capability.
Data Source
AI summary
A device having a crystal driver to operate according to a voltage transfer curve and a current reference to provide a current bias to the crystal driver to produce a voltage from the crystal driver within a linear region of the voltage transfer curve of the crystal driver, and to determining a gain margin of the crystal driver based on the measured first voltage on the driver output. A method to force a current bias from a current reference on a driver input, to measure the voltage on the driver output within a linear region of the voltage transfer curve of the crystal driver, and determine a gain margin of the crystal driver based on the measured voltage on the driver output.