Multi-Mode DAC Output Range and Slew Rate Control
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Solution Overview
Problem
Conventional digital-to-analog converters (DACs) have fixed granularity, output range, and offset, requiring multiple DACs for complex systems, and suffer from noise and uncontrolled slew rates, leading to increased component count and cost due to external capacitors and pins.
Innovation Solution
A multi-mode DAC with selectable output range, granularity, and offset, and controlled slew rate, utilizing a counter, clock, control word processor, mode detector, and slew rate bias generator to minimize response time and adjust slew rate through clock frequency, allowing for flexible operation with reduced pin count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional DACs with fixed granularity and output range are used, then each subsystem requires a dedicated DAC, but the component count and cost increase
Solution Approach 1:
The patent implements a single DAC that can operate in multiple modes (fine mode and coarse mode) by reconfiguring its internal R-2R ladder structure. In fine mode, the DAC provides high-resolution output for precision requirements, while in coarse mode, it provides larger output steps for rapid adjustments. This multi-functionality eliminates the need for multiple separate DACs for different subsystems, reducing component count while maintaining adaptability to various operational requirements
Solution Approach 2:
The patent employs dynamic reconfiguration of the DAC's R-2R ladder structure through switching mechanisms that can alter the resistance network configuration in real-time. This allows the DAC to dynamically change its granularity and output range based on the operational mode selected, enabling a single device to adapt to different precision and speed requirements without requiring multiple fixed-configuration DACs
2Speed
If rapid changes are made to the digital control word, then the analog output responds quickly, but noise and slew rate problems occur
Solution Approach 1:
The patent implements a controlled transition mechanism that updates the DAC output in periodic steps rather than allowing instantaneous changes. The counter increments or decrements the digital control value at a controlled rate, and the R-2R ladder reconfigures in discrete steps, creating a periodic action that limits the slew rate. This prevents noise and instability while maintaining acceptable response time for the power supply control application
3Object-generated harmful factors
If external capacitors are used to control slew rate, then noise is reduced, but pin count and component count increase
Solution Approach 1:
The patent extracts the slew rate control function from the external capacitor approach and implements it internally through the reconfigurable R-2R ladder structure and controlled transition mechanism. By taking out the dependency on external capacitors and their associated pins, the invention achieves slew rate control and noise reduction while maintaining a lower pin count and simpler external circuit requirements
Data Source
AI summary
Various apparatuses, methods and systems for a multi-mode DAC with selectable output range, granularity and offset and controlled slew rate are disclosed herein. For example, some embodiments of the present invention provide an apparatus for supplying a reference signal, including a digital-to-analog converter, a counter and a clock. The digital-to-analog converter has a digital input and an analog output that supplies a reference signal based on the digital input. The counter has a digital control word input, a clock input, a clock enable output and a count output connected to the digital input of the digital-to-analog converter. The counter is adapted to assert the clock enable output when the digital control word input requests an output count that is different from an actual count at the count output of the counter. The clock has an enable input connected to the clock enable output of the counter and a clock output connected to the clock input of the counter. The clock is adapted to produce clock pulses on the clock output while the enable input is asserted.