LCD Source Driver BIST Circuit Offset Testing
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Solution Overview
Problem
Conventional testers for LCD source drivers are costly and time-consuming due to the need for high-resolution mixed-mode testers and expensive multiplexing switches, especially as the number of channels increases, leading to high testing costs and reduced throughput.
Innovation Solution
The implementation of built-in self-test (BIST) circuits within the LCD source driver, which reconfigures buffers as comparators to test channel offset voltages using time-multiplexed digital code inputs and reference voltages, eliminating the need for external testing devices and reducing testing time and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mixed-mode testers with high-resolution ADCs are used to test channel offset voltages, then measurement precision is improved, but device complexity and testing cost increase
Solution Approach 1:
The source driver circuit performs self-testing by internally generating test signals and measuring its own channel offset voltages using built-in DACs, buffers, and ADCs, eliminating the need for complex external mixed-mode testers with high-resolution ADCs
Solution Approach 2:
The invention introduces an intermediary approach where the source driver uses its own DAC outputs as test signal sources and its own buffer outputs as measurement points, creating a self-contained test system that simplifies external testing equipment requirements
2Device complexity
If multiplexing switches are used to share ADC for testing multiple channels, then device complexity is reduced, but testing time increases
Solution Approach 1:
The source driver segments the testing process by allocating dedicated ADCs to specific channel groups (e.g., first ADC for odd channels, second ADC for even channels), allowing parallel measurement of multiple channels simultaneously without time-multiplexing delays
Solution Approach 2:
The invention performs preliminary action by pre-configuring multiple ADCs and their corresponding channel mappings before testing begins, enabling simultaneous parallel measurement of all channels without sequential switching overhead
3Measurement precision
If more channels are tested in LCD source driver, then measurement precision of overall system is improved, but productivity decreases
Solution Approach 1:
The source driver segments channels into multiple groups, each tested by dedicated ADCs in parallel, allowing all channels to be tested simultaneously rather than sequentially, maintaining high throughput while verifying offset voltages across all channels
Solution Approach 2:
The source driver achieves multi-functionality by using the same buffer circuitry for both normal operation and test modes, and employing multiple ADCs that can simultaneously measure different channel groups, enabling comprehensive testing without reducing productivity
Data Source
AI summary
A built-in self-test (BIST) circuit for a liquid crystal display (LCD) source driver includes at least one digital-to-analog converter (DAC) and at least one buffer coupled to the respective DAC, wherein the buffer is reconfigurable as a comparator. A first input signal and a second input signal are coupled to the comparator. The first input signal is a predetermined reference voltage level. The second input signal is a test offset voltage in a test range.