Segmented Reference DACs for Accurate High-Voltage ADC Conversion
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Solution Overview
Problem
Semiconductor devices face reduced conversion accuracy due to the slower response speed of high-withstand-voltage transistors, which are necessary for supplying high-voltage references to upper DACs, when compared to low-withstand-voltage transistors.
Innovation Solution
A semiconductor device configuration that includes an upper DAC, a lower DAC, and an injection DAC, where the upper DAC operates at a high voltage, the lower DAC and injection DAC operate at a constant lower voltage, and an error shaping mechanism is used to eliminate reference errors and capacity mismatches, improving conversion accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-withstand-voltage transistor is used to supply high-voltage reference to the upper DAC, then the high-voltage reference can be supplied, but the response speed decreases and conversion accuracy deteriorates
Solution Approach 1:
The reference voltage generation is segmented into two independent DACs: upper DAC for high-voltage region and lower DAC for low-voltage region. Each DAC operates at its optimal voltage level with appropriately matched transistors, allowing the upper DAC to use high-withstand-voltage transistors while the lower DAC uses fast low-withstand-voltage transistors, thus resolving the speed-accuracy tradeoff
Solution Approach 2:
An injection DAC is introduced as an intermediary component with the same configuration as the lower DAC. It generates a correction signal based on the difference between expected and actual reference voltages, which is then injected into the lower DAC output to compensate for voltage errors and capacity mismatches, thereby improving overall conversion accuracy
2Adaptability or versatility
If multiple DACs operating at different voltages are used to expand input range, then the input range is expanded, but reference errors and capacity mismatches increase
Solution Approach 1:
The injection DAC implements a feedback mechanism where the actual reference voltage output is measured and compared with the expected value. The difference (error signal) is fed back to the injection DAC, which generates a correction signal that is added to the lower DAC output, continuously compensating for reference errors and capacity mismatches between the upper and lower DACs
Solution Approach 2:
The injection DAC serves as a mediator that bridges the gap between the upper and lower DACs. It has the same configuration as the lower DAC and operates at the same voltage level, allowing it to generate accurate correction signals that compensate for the inherent mismatches introduced by operating multiple DACs at different voltages
Data Source
AI summary
A semiconductor device performs sequential comparison of an analog input signal and a reference voltage to digitally convert the analog input signal. The semiconductor device includes an upper DAC generating a high-voltage region of the reference voltage based on a predetermined code, a lower DAC generating a low-voltage region of the reference voltage based on the code, and an injection DAC having the same configuration as that of the lower DAC and adjusting the low-voltage region of the reference voltage.