Symmetrical Digital Resistor Layout for Low-Leakage Linearity
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Solution Overview
Problem
Digitally-controlled resistors face challenges in achieving linearity and high resolution at low power due to leakage currents, particularly at mid-code changes, which degrades their performance in ultra-low power circuit designs.
Innovation Solution
The implementation of a digitally-controlled resistor with a central switch-resistor segment and symmetrically arranged switch-resistor segments, where each switch-resistor segment includes a resistor and a complement switch, and a parallel switch, allowing for controlled switching based on digital bits to maintain linearity and reduce leakage impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high resolution is achieved in digitally-controlled resistors, then measurement precision is improved, but switch leakage currents increase and degrade linearity
Solution Approach 1:
The resistor is divided into multiple segments with different resistance values, each controlled by individual switches. This segmentation allows selective activation of segments to achieve high resolution while managing leakage currents through controlled switching patterns that minimize the impact of leakage on linearity.
Solution Approach 2:
The patent employs multiple resistance values (R, 2R, 4R, etc.) and controls the switching states to achieve desired resistance changes. By carefully selecting which segments to activate and their resistance values, the system achieves high resolution while the complementary switching strategy minimizes leakage-induced non-linearity.
2Measurement precision
If more switches are used to achieve high resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple switch-resistor segments into a unified digitally-controlled resistor structure. By merging the functionality of multiple switches into a coordinated switching system controlled by digital bits, the design achieves high resolution while managing complexity through integrated control logic and shared circuit elements.
Solution Approach 2:
The switching network is designed to perform multiple functions: achieving high resolution, minimizing leakage impact, and providing linear resistance control. The same switch-resistor segments serve both as resolution elements and as leakage management components through their coordinated switching patterns.
3Reliability
If switch leakage is reduced to maintain linearity, then reliability is improved, but area increases due to larger switch sizes
Solution Approach 1:
The patent maintains continuous control over the resistance value through coordinated switching of multiple segments. By ensuring that switching transitions are managed continuously and smoothly, the system maintains linearity without requiring oversized switches, as the continuous control strategy compensates for leakage effects rather than relying on large switch sizes.
Solution Approach 2:
The system uses multiple resistance parameter values (R, 2R, 4R, etc.) to achieve the desired resistance range and resolution. By changing resistance parameters through segment selection rather than relying solely on switch size, the patent achieves both linearity and compact area utilization.
Data Source
AI summary
An electronic device having a digitally controlled resistor is provided. The digitally controlled resistor includes various switch-resistor segments between voltage nodes. In one embodiment, the switch-resistor segment may include a resistor and a switch coupled parallel to the resistor. In another embodiment, the switch-resistor segment may include a resistor, a complement switch coupled in series with the resistor, and a switch coupled parallel to the resistor and the complement switch. Each switch included in the switch-resistor segment operates based on digital bits. Based on the logic value (either ‘0’ or ‘1’) assigned, the switches turn ON (when logic value is ‘1’) and OFF (when logic value is ‘0’). In some embodiments, the switches and the resistor included in the switch-transistor segment are arranged in a symmetrical manner between voltage nodes.