Flexible ADC Reference-Level Control for Low-Voltage CMRR
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Solution Overview
Problem
Analog-to-digital converters (ADCs) face challenges in achieving flexibility in input range due to the requirement for high common-mode rejection ratio (CMRR), which is difficult to obtain, especially with decreasing supply voltages in newer fabrication processes, limiting their ability to handle varying common-mode voltages and currents effectively.
Innovation Solution
The ADC incorporates a first and second range-control unit to generate control values for the input range size and midpoint, respectively, along with a reference-level unit to produce reference levels, allowing for adjustable input ranges and reducing common-mode variations, thereby relaxing the CMRR requirements on internal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ADC uses known circuit topologies with good CMRR, then the common-mode rejection ratio is improved, but the supply voltage requirement increases beyond what is allowed by newer fabrication processes
Solution Approach 1:
The patent implements dynamic range control by making the reference levels adjustable through digital control interfaces. The first range-control unit adjusts the spread of reference levels to match the input signal range, while the second range-control unit adjusts the midpoint of the reference levels to match the common-mode voltage of the input signal. This dynamic adaptability allows the ADC to maintain good CMRR performance across varying common-mode voltages without requiring high supply voltage.
Solution Approach 2:
The patent changes the parameters of the reference levels (their spread and midpoint) based on the input signal characteristics. By digitally controlling the reference level positions to match the input signal range and common-mode voltage, the system adapts to different operating conditions, achieving good CMRR performance with lower supply voltage requirements compatible with newer fabrication processes.
2Adaptability or versatility
If the ADC is designed with adjustable input range for flexibility, then the adaptability is improved, but the common-mode rejection ratio becomes difficult to maintain
Solution Approach 1:
The patent uses digital control interfaces that allow the reference levels to be adjusted based on the desired input range and common-mode voltage. The range-control units digitally program the reference level positions, creating a feedback mechanism where the reference levels adapt to match the input signal characteristics, thereby maintaining good CMRR even with adjustable input range.
Solution Approach 2:
The reference levels are made dynamically adjustable through digital control, allowing the ADC to adapt its reference level spread and midpoint to match the input signal range and common-mode voltage. This dynamic adjustment maintains optimal CMRR performance across different operating conditions while providing flexible input range adjustment.
3Ease of manufacture
If the supply voltage is decreased to match newer fabrication processes, then the manufacturing compatibility is improved, but the ability to achieve high CMRR becomes difficult
Solution Approach 1:
The patent changes the reference level parameters (spread and midpoint) to adapt to lower supply voltage conditions. By digitally controlling the reference levels to match the input signal characteristics, the system achieves good CMRR performance with reduced supply voltage, making it compatible with newer fabrication processes that have lower voltage requirements.
Solution Approach 2:
The ADC implements dynamic reference level adjustment that allows it to maintain good CMRR performance across varying supply voltage conditions. This adaptability enables the converter to work effectively with lower supply voltages required by newer fabrication processes while still achieving the necessary common-mode rejection ratio.
Data Source
AI summary
An analog-to-digital converter (1). The analog to digital converter (1) comprises a first range-control unit (100) adapted to generate a first range-control value for controlling a size of an input range of the analog-to-digital converter (1). The analog to digital converter further comprises a second range-control unit (200) adapted to generate a second range-control value for controlling a midpoint of the input range. Further, the analog-to-digital converter (1) comprises a reference-level unit (300) operatively connected to the first range-control unit (100) and the second range-control unit (200). The reference-level unit (300) is arranged to generate a plurality of reference levels at least based on the first and the second range-control value. The analog-to-digital converter further comprises a comparison unit (400) operatively connected to the second range-control unit (200) and the reference-level unit (300). The comparison unit (400) is arranged to perform at least one comparison between a difference between an analog input value of the analog-to-digital converter (1) and the second range-control value and individual reference levels of the plurality of reference levels. The comparison unit (400) is further arranged to generate a digital output value of the analog-to-digital converter (1) based on the at least one comparison.