Hybrid SAR-ADC Using Voltage-to-Time Conversion for Low-Power Resolution
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Solution Overview
Problem
Traditional successive-approximation-register (SAR) analog-to-digital converters (ADCs) face challenges in power efficiency and scalability as they use high gain amplifiers that consume large amounts of power, making them unsuitable for emerging technology nodes with smaller feature sizes.
Innovation Solution
A hybrid SAR-ADC that combines voltage-based signal processing to determine most significant bits and time-based signal processing to determine least significant bits, utilizing a voltage-to-time conversion element to achieve low power consumption and compact area, while improving resolution with deep submicron scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional SAR-ADC uses high gain amplifiers to achieve high resolution, then measurement precision is improved, but use of energy increases significantly
Solution Approach 1:
The patent divides the conversion process into two independent stages: a voltage-based SAR-ADC for MSB conversion and a time-based SAR-ADC for LSB conversion. This segmentation allows each stage to operate optimally for its specific function, with the voltage-based stage handling coarse conversion and the time-based stage handling fine conversion, thereby achieving high overall resolution without requiring high gain amplifiers throughout the entire system.
Solution Approach 2:
The patent replaces the traditional voltage-based signal processing with a time-based signal processing approach for the LSB conversion stage. By converting the residue voltage to a time domain representation and using time-based comparison, the system achieves high resolution measurement without the power-consuming high gain amplifiers required by conventional voltage-based approaches.
2Reliability
If traditional SAR-ADC uses high gain amplifiers to maintain signal integrity, then reliability is improved, but use of energy increases
Solution Approach 1:
The patent substitutes time-based signal processing for voltage-based signal processing in the LSB conversion stage. This replacement eliminates the need for high gain amplifiers while maintaining signal integrity through time domain representation and comparison, thereby improving reliability without the associated power consumption penalty.
Solution Approach 2:
The patent introduces a voltage-to-time conversion element as an intermediary between the voltage-based MSB conversion and the time-based LSB conversion. This intermediary transforms the residue voltage into a time domain representation, enabling the subsequent time-based processing to maintain signal integrity without requiring power-consuming high gain amplifiers.
3Measurement precision
If traditional SAR-ADC is designed for high resolution in deep submicron nodes, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the ADC into two distinct conversion paths: voltage-based SAR-ADC for MSB and time-based SAR-ADC for LSB. This segmentation allows each subsystem to be optimized independently for its specific resolution requirements, reducing the overall device complexity compared to a single high-resolution voltage-based SAR-ADC that would require complex high gain amplifiers and calibration circuits.
Solution Approach 2:
The patent replaces the complex voltage-based signal processing chain with a time-based approach for the LSB conversion. This substitution simplifies the circuit implementation in deep submicron nodes by avoiding the need for complex high gain amplifiers and associated calibration circuits, thereby achieving high resolution with reduced device complexity.
Data Source
AI summary
A circuit includes a voltage-to-time conversion element configured to receive an input voltage at an input and to generate a time domain representation of the input voltage. The voltage-to-time conversion element includes an amplifier having an amplifier input coupled to the input, a zero crossing detector coupled to an output of the amplifier, and a current source selectively coupled to the amplifier input by way of a switching element.