Resistor-String DAC Pass Transistor Grouping for Smaller Source Drivers
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) in source drivers for display devices face challenges in minimizing chip area due to the need for high voltage endurance, leading to increased device size and complexity, especially when handling gradation voltages with significant voltage differences.
Innovation Solution
The implementation of a DAC with a resistor string, pass transistors, and a decoder that groups pass transistors based on gradation voltage values, using different types or the same type of transistors within groups, and controlling them with signals that swing between upper and lower limit voltages to optimize voltage differences and reduce chip area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If devices with high voltage endurance are used to handle gradation voltages with several volts amplitude, then the device can reliably operate at high voltages, but the channel length and width must be increased, leading to increased chip area
Solution Approach 1:
The pass transistor array is divided into multiple groups, with each group handling a specific voltage range. This segmentation allows each transistor group to be optimized for its specific voltage range rather than requiring all transistors to handle the full voltage range, reducing the overall chip area while maintaining reliability.
Solution Approach 2:
Different types of pass transistors are used in different groups based on their voltage requirements. Transistors in groups handling lower voltage ranges can use smaller channel dimensions optimized for low voltage, while only transistors in high voltage groups require larger dimensions for voltage endurance. This local optimization reduces the total chip area.
2Adaptability or versatility
If the DAC is designed to handle the maximum operating voltage of several volts, then it can provide the required gradation voltages, but the device size increases due to larger channel dimensions
Solution Approach 1:
The voltage range is segmented into multiple groups, with each group of pass transistors handling a specific voltage portion. This allows the DAC to cover the full voltage range while using smaller transistors in each group, reducing the overall device area compared to using a single set of large transistors for the entire voltage range.
Solution Approach 2:
The decoder dynamically selects which group of pass transistors to activate based on the required voltage level. This dynamic switching between groups allows the DAC to adapt to different voltage requirements without requiring all transistors to be sized for maximum voltage, optimizing the device area.
Data Source
AI summary
A digital-to-analog converter including a resistor string configured to provide a plurality of gradation voltages formed by receiving a top voltage at one end thereof and a bottom voltage at the other end; a plurality of pass transistors including a pass transistor having one end which is electrically connected to the resistor string and outputting any one among the plurality of gradation voltages; and a decoder configured to control the plurality of pass transistors. The plurality of the pass transistors are included in any one among a plurality of groups according to values of the gradation voltages, and the pass transistors included in the any one group are divided into a first group and a second group according to output gradation voltages, and pass transistors included in the first group and pass transistors included in the second group are different types of pass transistors.