Segmented Resistor Ladder DAC for IR Drop Immunity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital to analog converters (DACs) face challenges in achieving accuracy and speed while maintaining low current consumption, particularly due to issues with variable IR drop and total unadjusted error, which affect their linearity and overall performance.
Innovation Solution
The proposed DAC incorporates a resistor ladder arrangement with a third segment providing immunity to variable IR drop and improved total unadjusted error, featuring a buffer amplifier and a configuration where the first segment is a least-significant-bit segment, the second segment is a most-significant-bit segment, and the third segment is designed to manage resistance values based on the digital control word, with specific resistor configurations and switch controls to optimize output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional resistor ladder arrangement is used in the DAC, then the device structure is simple, but variable IR drop affects accuracy and linearity
Solution Approach 1:
The resistor ladder arrangement is divided into three distinct segments: a first segment with resistors connected to the non-inverting input terminal, a second segment with resistors connected to the inverting input terminal, and a third segment with resistors connected between the output terminal and the first reference voltage terminal. This segmentation isolates the variable IR drop effects to specific segments while maintaining overall DAC accuracy.
Solution Approach 2:
Different segments of the resistor ladder arrangement are assigned different functions and connectivity patterns. The first segment handles the primary voltage division, the second segment compensates for IR drop effects through its connection to the inverting input terminal, and the third segment provides additional immunity to variable IR drop. This local differentiation of properties allows each segment to address specific accuracy issues.
2Measurement precision
If the resistor ladder arrangement is optimized for accuracy by adding multiple segments, then total unadjusted error improves, but device complexity increases
Solution Approach 1:
The three-segment resistor ladder arrangement serves multiple functions simultaneously: voltage division, IR drop compensation, and linearity improvement. By integrating these functions into a unified structure where segments are interconnected, the design achieves improved total unadjusted error without proportionally increasing complexity.
Solution Approach 2:
The three segments are merged into a single integrated resistor ladder arrangement that operates as a unified system. The segments share common nodes and references, allowing them to work together to cancel out errors and improve accuracy while maintaining a compact overall structure.
3Manufacturing precision
If high precision resistor configurations are used to reduce total unadjusted error, then DAC accuracy improves, but current consumption increases
Solution Approach 1:
The resistor ladder arrangement dynamically adapts to different operating conditions by distributing current through multiple segments. The three-segment configuration allows current to flow through different paths depending on the digital control word, optimizing the balance between accuracy and current consumption for each conversion operation.
Data Source
AI summary
A digital to analog converter (DAC) includes an amplifier including a buffer of the DAC, and a resistor ladder arrangement coupled to a non-inverting input terminal of the amplifier to generate a voltage based on a digital control word. The arrangement includes a first, least-significant bit, segment arranged in one of an R-2R or unit-R configuration, a second, most-significant bit, segment including one or more units each including a second-segment-resistor having a resistor terminal coupled to a respective second switch and having a second resistance, RMSB, and a third segment including one or more third-segment-resistors coupled in parallel to the non-inverting input terminal and connected to a first reference voltage terminal. M2 designates a number of bits in the digital control word for controlling the second switches, and the third segment has a total resistance, Rsp, based on M2.