DAC Test Circuit Using Differential Charge Comparison
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Solution Overview
Problem
Existing semiconductor devices with digital-analog converters face challenges in conducting accurate tests due to noise components in the fixed voltage within the chip, even when using a highly accurate external power supply as a reference voltage.
Innovation Solution
A semiconductor device with a digital-analog converter equipped with a test circuit that includes current cells, a charge information holding circuit, a reference voltage generation circuit, and a comparison circuit, allowing for the determination of differential charge information and comparison with a reference voltage to output a comparison result, thereby enabling highly accurate testing of the D/A converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a highly accurate external power supply is used as a reference voltage for test, then the reference voltage accuracy is improved, but the test accuracy deteriorates due to noise component in the fixed voltage inside the chip
Solution Approach 1:
The patent converts the harmful noise component into a beneficial differential measurement approach. By measuring the voltage difference between two points (Vout and Vref) rather than absolute voltages, the common-mode noise present in both signals is rejected, transforming the noisy environment into an advantage where only the differential signal matters.
Solution Approach 2:
The patent introduces a differential voltage measurement mechanism as an intermediary between the power supply and the test circuit. This intermediary subtracts the reference voltage from the output voltage, creating a noise-rejected differential signal that accurately represents the D/A converter performance without being affected by the noisy fixed voltage.
2Manufacturing precision
If traditional test methods are used, then the device complexity is reduced, but the manufacturing precision deteriorates due to inability to cancel noise
Solution Approach 1:
The patent merges the reference voltage generation and the test measurement into a single integrated test circuit block. The reference voltage generation circuit and the differential measurement circuit are combined, allowing the test function to be performed without adding separate external reference voltage sources or complex external measurement equipment.
3Measurement precision
If the output voltage of the D/A converter is tested using conventional methods, then the ease of operation is maintained, but the measurement precision deteriorates due to noise influence
Solution Approach 1:
The test circuit performs self-service by generating its own reference voltage internally and using that reference to measure the D/A converter output. The circuit automatically subtracts the reference voltage from the output voltage, eliminating the need for external operators to provide separate reference voltages or perform complex measurement procedures.
Data Source
AI summary
A semiconductor device includes a digital-analog converter provided with a plurality of current cells, and a test circuit electrically connected to the digital-analog converter to test the digital-analog converter. The test circuit includes: a charge information holding circuit that holds, as differential charge information, a difference value between a first charge according to a first current and a second charge according to a second current by at least one or more current cells among the plurality of current cells; a reference voltage generation circuit that generates a reference voltage to be comparative object; and a comparison circuit that compares a determination voltage according to the differential charge information and the reference voltage to output a comparison result.