Ramp Signal Slope Correction for Constant ADC Analog Gain Linearity
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Solution Overview
Problem
Existing electronic devices with analog-to-digital converters (ADCs) face challenges in maintaining constant linearity of analog gain due to parasitic resistances affecting the slope of ramp signals, leading to undesirable adjustments in analog gain.
Innovation Solution
Incorporating a slope correction circuit that adjusts the slope of the ramp signal based on a correction code signal, reflecting resistance values to correct for parasitic resistances formed between the ramp signal generator and voltage terminals, thereby maintaining constant linearity of analog gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the slope of the ramp signal is adjusted according to analog gain, then the analog gain can be changed to adapt to different ambient illuminance conditions, but parasitic resistance causes the slope to deviate from the desired value, leading to non-constant linearity of analog gain
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for parasitic resistance effects in a lookup table before operation. During runtime, the system simply retrieves the appropriate correction value based on the selected analog gain setting, rather than performing complex real-time calculations. This preliminary preparation enables both analog gain adaptability and maintains linearity precision without requiring complex real-time compensation circuits.
Solution Approach 2:
The patent implements feedback by using the analog gain control signal itself to index into a correction lookup table, which returns a compensation value that is applied to adjust the ramp signal slope. This feedback mechanism automatically compensates for parasitic resistance effects based on the current gain setting, ensuring that linearity is maintained across all analog gain values without requiring external calibration.
2Manufacturing precision
If a slope correction circuit is added to correct parasitic resistance effects, then the linearity of analog gain can be maintained constant, but the device complexity increases
Solution Approach 1:
The patent uses copying by creating a digital lookup table that stores pre-calculated correction values, which is then accessed during operation. Instead of implementing complex analog correction circuits, the system copies the correction data from the lookup table into a register and applies it through digital-to-analog conversion. This approach maintains manufacturing precision while significantly reducing circuit complexity compared to pure analog correction methods.
Solution Approach 2:
The patent replaces what would traditionally be a complex analog correction circuit (mechanical/electrical system) with a digital lookup table and microcontroller-based correction mechanism. By substituting the analog correction approach with a digital processing approach, the system achieves the same linearity correction function with simpler, more flexible, and more easily manufacturable components.
Data Source
AI summary
An electronic device may include a ramp signal generator suitable for generating a ramp signal having a slope corresponding to an analog gain, and a slope correction circuit suitable for correcting the slope based on a correction code signal.