SAR ADC Programmable Delay for Sampling Noise Cancellation
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Solution Overview
Problem
Existing SAR ADCs use a fixed delay to reduce sampling noise, which is ineffective for input signals with frequencies different from the expected frequency or those driven by circuits with higher impedance than expected, and can lead to preamplifier saturation or increased power consumption.
Innovation Solution
Implementing a programmable delay across the preamplifier in SAR ADCs allows for adjustable delay based on current operating parameters such as input signal frequency, source impedance, and power mode, thereby reducing sampling noise across a range of use-cases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed delay is used across the preamplifier, then sampling noise is reduced for narrow use cases with predetermined input signal frequency, but the solution becomes ineffective for input signals with different frequencies or higher impedance sources
Solution Approach 1:
The patent implements a programmable delay unit that can dynamically adjust the delay time based on the input signal frequency and source impedance. Instead of using a fixed delay, the system allows the delay parameter to be changed programmatically, enabling optimal noise reduction across different operating conditions while maintaining adaptability to various signal sources and frequencies.
Solution Approach 2:
The patent changes the delay parameter from a fixed value to a programmable variable. By allowing the delay time to be adjusted based on input signal characteristics, the system optimizes sampling noise reduction for different frequencies and impedance levels without requiring multiple hardware configurations.
2Use of energy by stationary object
If a long delay time is used, then the bandwidth requirement and power of the preamplifier are reduced, but the preamplifier may saturate
Solution Approach 1:
The patent implements dynamic adjustment of the delay time based on real-time operating conditions. The programmable delay unit allows the system to select optimal delay values that balance power consumption and saturation risk, adapting to different signal amplitudes and frequencies to maintain reliable operation across varying conditions.
Solution Approach 2:
The patent varies the delay parameter to optimize the trade-off between power consumption and saturation prevention. By programmatically adjusting the delay time, the system can use longer delays to reduce power when conditions permit, while switching to shorter delays when saturation risk increases, thus maintaining reliability.
3Reliability
If a short delay time is used, then the likelihood of preamplifier saturation is reduced, but the bandwidth requirement and power used by the preamplifier increase
Solution Approach 1:
The patent uses dynamic delay adjustment to balance saturation prevention with power efficiency. The programmable delay unit enables the system to select shorter delay times when saturation risk is high, while accepting increased power consumption, and switch to longer delays when power efficiency is more critical and saturation risk is low.
Data Source
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AI summary
An analog-to-digital converter (ADC) includes a digital-to-analog converter (DAC), a comparator coupled to an output of the DAC, a successive approximation register (SAR) logic unit coupled to an output of the comparator, and a programmable delay unit. The comparator includes a preamplifier having an input coupled to the output of the DAC and a latch having an input coupled to the output of the preamplifier and an output coupled to the input of the SAR logic unit. SAR logic unit generates a control signal, and programmable delay unit adjusts a delay between the control signal and a delayed control signal based on at least one parameter, such that comparator receives control signal and delayed control signal. In some implementations, the parameter is at least one of a frequency of a signal input to the DAC, a source impedance of a circuit driving the input signal, and a preamplifier power mode.