Dual-Section DA Converter for Precise Reference Slope Control
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Solution Overview
Problem
Existing DA conversion methods face challenges in achieving high-precision gain adjustment, particularly in adjusting the slope of the reference signal for single-slope integration type AD conversion, which is crucial for accurate analog signal processing in semiconductor devices like CMOS imaging devices.
Innovation Solution
A DA converter configuration with a first DA conversion section for generating an analog output signal and a second DA conversion section for generating a gain control output signal, allowing for digital control of the gain of the analog output signal, enabling precise adjustment of the reference signal slope. This configuration employs a current-output type DA conversion circuit with upper and lower current-source cells controlled by digital bits, facilitating coordinated operations to achieve high-precision gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single DA conversion section is used to generate the reference signal, then the device complexity is reduced, but the gain adjustment precision deteriorates
Solution Approach 1:
The DA converter is segmented into two independent sections: a first DA conversion section for generating the base reference signal and a second DA conversion section for generating the gain control signal. This segmentation allows each section to be optimized for its specific function, with the second section providing precise digital-controlled gain adjustment without complicating the overall structure.
Solution Approach 2:
The second DA conversion section serves multiple purposes: it generates the gain control signal for adjusting the reference signal slope, and its output is used by the control circuit to regulate the first DA conversion section. This multi-functionality achieves high-precision gain control without requiring separate dedicated circuits.
2Device complexity
If analog amplification is used to adjust the reference signal slope, then the device complexity is reduced, but the adjustment precision deteriorates
Solution Approach 1:
The patent replaces analog amplification mechanisms with a digital-based DA conversion system. The second DA conversion section uses digital input signals to generate precise gain control voltages, substituting imprecise analog amplification with digitally-controlled voltage generation that offers superior precision while maintaining circuit simplicity.
Solution Approach 2:
The system changes the control parameter from analog amplification factors to digital voltage levels generated by the second DA conversion section. By controlling the slope through digitally-generated voltage steps rather than analog gain factors, the system achieves higher precision in slope adjustment while keeping the circuit structure simple.
3Measurement precision
If high-precision gain control is implemented through complex circuitry, then the gain control precision is improved, but the device complexity increases
Solution Approach 1:
The patent merges the gain control function with the reference signal generation function by using the second DA conversion section to generate both the gain control signal and by extending its output to control the first DA conversion section. This merging achieves high-precision gain control without adding separate complex control circuits.
Solution Approach 2:
The second DA conversion section acts as an intermediary between the digital control input and the analog reference signal generation. It converts digital gain control codes into precise analog voltage levels that regulate the first DA conversion section, providing high-precision control through this intermediate digital-to-analog conversion stage rather than direct complex analog control.
Data Source
AI summary
A DA converter includes a first DA conversion section for obtaining an analog output signal in accordance with a digital input signal value, and a second DA conversion section for obtaining an analog gain control output signal in accordance with a digital gain control input signal value. In the DA converter, the gain control of the analog output signal generated by the first DA conversion section is performed on the basis of the gain control output signal generated by the second DA conversion section.