Shared Impedance String DAC for Multi-Resolution Low-Power Outputs
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) face challenges in achieving medium-high resolution while maintaining low power consumption, particularly in battery-powered sensors, where increased resolution leads to higher power consumption due to leakage currents, especially at higher temperatures.
Innovation Solution
A multiple output DAC circuit utilizing a shared impedance string, such as a resistor string, to generate multiple outputs with different resolutions, reducing circuit complexity, power consumption, and leakage current, by coupling different numbers of impedance strings to output nodes for varying resolutions like 12-bit and 6-bit outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAC resolution is increased to reduce quantization noise and improve accuracy, then measurement precision is improved, but power consumption increases due to more switches and leakage currents
Solution Approach 1:
The patent merges multiple DAC outputs into a single shared impedance string structure. The first DAC (higher resolution) and second DAC (lower resolution) share the same impedance string and switching network infrastructure, allowing multiple analog outputs to be generated simultaneously without proportionally increasing the number of impedance elements. This consolidation reduces the overall switch count and leakage current while maintaining the required resolution for each output channel.
2Measurement precision
If DAC resolution is increased to reduce quantization noise, then measurement precision is improved, but device complexity increases due to more switches
Solution Approach 1:
The shared impedance string serves multiple functions simultaneously: it provides the reference ladder for the first DAC, the reference ladder for the second DAC, and enables both high-resolution and low-resolution output channels. The switching network is designed to selectively connect different portions of the shared impedance string to different output nodes based on the digital input codes, allowing a single structure to fulfill what would traditionally require separate DAC circuits.
3Measurement precision
If more impedance strings are used to increase DAC resolution, then measurement precision is improved, but area occupied increases
Solution Approach 1:
The patent combines multiple DAC reference ladders into a single shared impedance string. Instead of implementing separate impedance strings for the first DAC and second DAC, the invention uses one common impedance string that both DACs share. This sharing approach maintains the resolution requirements for both output channels while significantly reducing the total area occupied by the DAC circuitry compared to using separate impedance strings for each DAC.
Data Source
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AI summary
A multiple output, multiple impedance string digital-to-analog converter (DAC) circuit can provide a first output having a first resolution in response to a first digital input signal and a second output having a second resolution in response to a second digital input signal. A main impedance string and a secondary impedance string can be coupled using switching networks to provide a first DAC output. By coupling additional switches to the main impedance string and by sharing the main impedance string, a second DAC output can be realized.