Dual DAC Gain Control for Precise Reference Signal Slope
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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 digital control of the gain adjustment, utilizing a current-output type DA conversion circuit with upper and lower current-source cells for precise control of the reference signal slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional DA conversion circuit is used for generating reference signals in single-slope integration type AD conversion, then the circuit structure is simple, but the gain adjustment precision is insufficient
Solution Approach 1:
The DA conversion circuit is divided into two separate sections: a first DA conversion section for generating the basic 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 circuit design.
Solution Approach 2:
The second DA conversion section serves multiple purposes: it generates the gain control output signal for precision adjustment, works in conjunction with the first DA conversion section to produce the final reference signal, and enables digital control of the gain. This multi-functionality achieves high-precision gain adjustment without requiring entirely separate dedicated circuits.
2Measurement precision
If the slope of the reference signal is adjusted for gain control, then the AD conversion accuracy is improved, but the control precision becomes difficult to achieve
Solution Approach 1:
The second DA conversion section acts as an intermediary between the digital gain control input signal and the reference signal slope adjustment. It converts the digital gain control signal into an analog gain control output signal that precisely adjusts the slope of the reference signal, making the control process easier and more precise than direct adjustment methods.
Solution Approach 2:
The invention changes the parameter control approach by using a digital gain control input signal value to control the second DA conversion section, which then adjusts the slope parameter of the reference signal. This parameter transformation from digital domain to analog domain enables precise control that is easier to implement than direct analog adjustment.
3Measurement precision
If a single DA conversion section is used, then the circuit is simpler, but high-precision gain control cannot be achieved
Solution Approach 1:
The DA conversion functionality is segmented into two specialized sections: the first DA conversion section handles the primary reference signal generation, while the second DA conversion section handles the gain control function. This segmentation achieves high-precision gain control by dedicating specific circuitry to each function, with the second section providing fine-adjustment capability that would be difficult to achieve in a single unified circuit.
Solution Approach 2:
The second DA conversion section is essentially a copy of the first DA conversion section's architecture but optimized for gain control purposes. By replicating the core DA conversion structure and adapting it for gain control, the invention achieves precision without requiring entirely novel circuit designs, thereby limiting the increase in overall complexity.
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.