Common Voltage Ladder PWM DACs for Matched Output Voltages
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) experience mismatched output voltages due to process, voltage, and temperature variations when using separate voltage ladders, leading to inconsistent reference voltages across multiple DACs.
Innovation Solution
Implementing a common resistive voltage ladder shared among multiple pulse-width modulation (PWM) DACs, where a reference current source generates reference voltages used by each DAC, ensuring that the DACs receive consistent reference voltages and reducing the impact of variations by using a bandgap-based current reference and pulse-width modulation techniques to alternately gate selected reference voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate voltage ladders are used for each DAC, then each DAC can operate independently, but mismatched output voltages occur due to process, voltage, and temperature variations
Solution Approach 1:
The patent merges multiple separate voltage ladders into a single shared voltage ladder that serves all DACs. This common voltage ladder generates reference voltages that are distributed to multiple DACs, ensuring they all use the same reference voltages and thereby achieving matched output voltages despite process, voltage, and temperature variations.
Solution Approach 2:
The shared voltage ladder is designed to serve multiple DACs simultaneously, making it a universal reference source. The voltage ladder generates multiple reference voltages that are commonly used by all DACs in the system, ensuring consistency across all digital-to-analog conversion operations.
2Manufacturing precision
If a common voltage ladder is used for multiple DACs, then reference voltages remain consistent across DACs, but the system complexity increases
Solution Approach 1:
The common voltage ladder is designed as a universal reference source that serves multiple DACs simultaneously. By making the voltage ladder multi-functional, the patent reduces the total number of voltage ladders needed while maintaining reference voltage consistency across all DACs, thereby managing system complexity.
Solution Approach 2:
The voltage ladder is segmented to provide multiple reference voltages at different taps, which are then distributed to various DACs. This segmentation allows the single voltage ladder to serve multiple functions and multiple DACs without requiring complex additional circuitry for each individual DAC.
3Measurement precision
If pulse-width modulation is used to alternately gate reference voltages, then linear resolution is enhanced, but the circuit complexity increases
Solution Approach 1:
The patent employs pulse-width modulation where reference voltages are alternately gated using periodic clock signals. The PWM circuitry modulates the reference voltages at different duty cycles determined by digital input codes, achieving enhanced linear resolution through the periodic switching action without requiring complex additional components.
Data Source
AI summary
A voltage ladder is used to generate reference voltages. The voltage ladder is used by multiple digital-to-analog converters (DACs). In particular, the voltage ladder is used by multiple pulse-width modulation (PWM) DACs. Having multiple DACs utilize a common voltage ladder for their reference voltages reduces mismatched output voltages between DACs. Having multiple DACs utilize the common voltage ladder helps ensure that the reference voltages used by different DACs are not affected by process, voltage, and/or temperature variations in the reference voltages that would occur when using different voltage ladders for each DAC.