Dual-String DAC Voltage Divider Without Impedance Isolation

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Solution Overview

Problem

Dual-string digital-to-analog converters (DACs) face challenges in maintaining ideal voltage across secondary voltage dividers without impedance isolation, leading to increased area usage, power consumption, and slower performance due to the need for operational amplifiers for isolation.

Innovation Solution

Incorporating an adjusting circuit with fractional resistance in the primary voltage divider to maintain ideal voltage across the secondary voltage divider, eliminating the requirement for impedance isolation between the primary and secondary voltage dividers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If impedance isolation circuits (operational amplifiers) are added between primary and secondary voltage dividers, then ideal voltage is maintained across secondary voltage divider, but area usage increases, power consumption increases, and performance decreases due to settling time requirements

Engineering Contradiction:

Improvevoltage accuracyVSAvoidcircuit area

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent removes the impedance isolation circuits (operational amplifiers) from the DAC architecture by applying polarity compensation techniques. This extraction eliminates the harmful isolation requirement while maintaining voltage accuracy through alternative compensation methods that do not require additional isolation components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes the primary and secondary voltage dividers directly interconnected without isolation, allowing the same circuit structure to serve multiple functions. The voltage dividers simultaneously perform voltage division and direct signal transmission, eliminating the need for separate isolation circuits while maintaining system accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

Engineering Contradiction:

Improvevoltage accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by stationary object

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

Engineering Contradiction:

Improvevoltage accuracyVSAvoidsettling time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

4Area of stationary object

If direct connection between primary and secondary voltage dividers is made without impedance isolation, then area usage decreases, power consumption decreases, and performance increases by eliminating settling time, but ideal voltage cannot be maintained across secondary voltage divider

Engineering Contradiction:

Improvecircuit areaVSAvoidvoltage accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent converts the harmful direct connection effect (which would normally cause voltage inaccuracy due to loading) into a beneficial configuration. By deliberately designing the voltage divider ratios and applying polarity compensation, the direct connection's loading effect is transformed into a predictable and correctable parameter, ultimately improving area and performance while maintaining accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements polarity compensation that effectively creates a feedback mechanism to correct voltage inaccuracies. The compensation circuit monitors and adjusts for the loading effects of the direct connection, ensuring that the secondary voltage divider maintains ideal voltage accuracy despite the absence of impedance isolation.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8884799B2Dual-string digital-to-analog converters (DACs), and related circuits, systems, and methods

Publication Date: 2014.11.11 QUALCOMM INC

AI summary

Dual-string digital-to-analog converters (DACs), and related circuits, systems, and methods are disclosed. In embodiments disclosed herein, a primary voltage divider of the dual string-DAC is comprised of at least one adjusting circuit. The adjusting circuit is configured to maintain the ideal voltage of a selected resistor node pair across a secondary voltage divider circuit in response to a primary switch unit selecting a selected resistor node pair. In this manner, impedance isolation is not required between a primary voltage divider and the secondary voltage divider circuit of the dual-string DAC. As a result, as non-limiting examples, the area on an integrated circuit (IC) for a dual-string DAC may be decreased, power consumption of the DAC may be decreased, and/or the dual-string DAC may have increased performance by not requiring a settling time.