SAR ADC Reference Voltage Switching for Noise and Power Control
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Solution Overview
Problem
High-resolution successive-approximation-register analog-to-digital converters face performance limitations due to noise from comparators and digital-to-analog converters, which affect their accuracy and efficiency.
Innovation Solution
An analog-to-digital converter design that includes a sample/hold circuit, a reference voltage driver, a digital-to-analog converter, a comparator, and a logic circuit, where the reference voltage driver switches between an external supply voltage and a sampled reference voltage during different conversion phases, optimizing the reference voltage supply to reduce noise and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a successive-approximation-register analog-to-digital converter is used to achieve high-resolution conversion, then conversion precision is improved, but noise from comparator and digital-to-analog converter degrades performance
Solution Approach 1:
The reference voltage supply is segmented into multiple phases: a first conversion phase using an external supply voltage and a second conversion phase using a sampled reference voltage. This segmentation allows the system to optimize performance by switching between different voltage sources based on conversion progress, thereby reducing noise impact while maintaining high conversion precision.
Solution Approach 2:
The sampled reference voltage is obtained in advance during a sampling phase before the conversion phases begin. This preliminary action stores a clean reference voltage that can be used during the second conversion phase to minimize noise interference, thus improving the signal-to-noise ratio without compromising conversion accuracy.
2Speed
If reference voltage is continuously supplied during conversion phases, then conversion speed is maintained, but static power consumption increases
Solution Approach 1:
The reference voltage supply operates periodically with distinct phases: the first conversion phase uses the external supply voltage, then switches to the sampled reference voltage for the second conversion phase. This periodic switching reduces static power consumption by utilizing pre-sampled voltage values during the second phase while maintaining conversion speed through proper timing and control.
3Use of energy by stationary object
If external supply voltage is used throughout conversion phases, then power consumption is reduced, but noise performance deteriorates
Solution Approach 1:
The conversion process is divided into two phases with different power consumption and noise characteristics. The first conversion phase uses the external supply voltage (lower noise), while the second conversion phase uses the pre-sampled reference voltage (higher noise immunity). This segmentation allows the system to achieve both low power consumption and good noise performance by appropriately selecting voltage sources for each phase.
Solution Approach 2:
The sampled reference voltage is captured in advance during the sampling phase when noise levels are lower. This pre-captured voltage is then used during the second conversion phase to avoid real-time noise interference, thus improving noise performance without requiring continuous high-power supply throughout the entire conversion process.
Data Source
AI summary
An analog-to-digital converter, including a sample/hold circuit; a reference voltage driver; a digital-to-analog converter; a comparator; and a logic circuit, wherein the reference voltage driver includes: a first voltage supplier circuit configured to output an external supply voltage provided from outside of the analog-to-digital converter; a second voltage supplier circuit configured to output a sampled reference voltage that is obtained during a sampling phase based on control signals received from the logic circuit; and a switching driver configured to electrically connect the first voltage supplier circuit to the digital-to-analog converter during a first conversion phase after the sampling phase based on the control signals received from the logic circuit, and to electrically connect the second voltage supplier circuit to the digital-to-analog converter during a second conversion phase based on the control signals received from the logic circuit.