R-2R DAC Ladder With Compensation Resistors for Lower DNL

Solution Overview

Problem

High-precision R-2R ladder resistor network architectures in digital-to-analog converters face challenges with large switch sizes, high design costs, and increased matching difficulty, leading to decreased product yield due to maximum Differential Nonlinearity (DNL) errors.

Innovation Solution

A digital-to-analog conversion circuit with compensation resistors integrated into the R-2R ladder resistor network architecture, where branch switches and bridge resistors are connected in series, with compensation resistors strategically placed to attenuate DNL errors and reduce switch sizes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the number of branches in the R-2R ladder network is increased to achieve high-precision transmission, then the precision is improved, but the total size of the switch required increases exponentially

Engineering Contradiction:

ImproveprecisionVSAvoidswitch size

Core Design Contradiction:

Measurement precisionVSArea of moving object

Solution Approach 1:

The patent applies local quality by differentiating the treatment of switches in different branches. Switches in higher-weight branches (which have greater influence on precision) are designed with larger sizes to maintain matching accuracy, while switches in lower-weight branches are reduced in size since they have relatively smaller influences on overall precision. This non-uniform distribution of switch sizes optimizes the balance between precision and area occupation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements partial action by not uniformly increasing all switch sizes proportionally to maintain precision. Instead, it selectively maintains larger switch sizes only where necessary (in higher-weight branches) and reduces sizes in less critical branches, thereby achieving acceptable precision without exponential area growth.

Inventive Principle:

Principle #16Partial or excessive action

2Area of moving object

If the size of branch switches is reduced to lower design cost and layout complexity, then the area occupation is reduced, but the matching difficulty and DNL error increase

Engineering Contradiction:

Improveswitch sizeVSAvoidmatching difficulty

Core Design Contradiction:

Area of moving objectVSManufacturing precision

Solution Approach 1:

The patent applies local quality by differentiating the treatment of switches in different branches. Switches in higher-weight branches (which have greater influence on precision) are designed with larger sizes to maintain matching accuracy, while switches in lower-weight branches are reduced in size since they have relatively smaller influences on overall precision. This non-uniform distribution of switch sizes optimizes the balance between precision and area occupation.

Inventive Principle:

Principle #3Local quality

3Area of moving object

If compensation resistors are added to reduce switch sizes, then the area occupation is reduced, but the DNL error increases when resistance changes are in opposite trends

Engineering Contradiction:

Improveswitch sizeVSAvoidDNL error

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The patent applies parameter changes by carefully designing the resistance values of compensation resistors to have specific relationships with branch resistors (e.g., Rcomp1 = R/2, Rcomp2 = R, Rcomp3 = 2R). These parameter relationships ensure that when process variations cause resistance changes, the compensation resistors can counterbalance the effects and maintain the R-2R ratio, thereby reducing DNL errors despite using smaller switch sizes.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20260095191A1Digital-to-analog conversion circuit based on r-2r ladder resistor network architecture

Publication Date: 2026.04.02 SG MICRO CORP

AI summary

The provided is a digital-to-analog conversion circuit based on an R-2R ladder resistor network architecture. The digital-to-analog conversion circuit based on an R-2R ladder resistor network architecture includes: branch resistors, branch switches, bridge resistors, a first compensation resistor, a second compensation resistor and third compensation resistors; specifically, the compensation resistors (the first compensation resistor, the second compensation resistor and the third compensation resistor) are introduced into an R-2R network in a progressive way, a Differential Nonlinearity (DNL) introduced by mismatch between the compensation resistor and on-state impedance of the branch switch may effectively attenuate due to decrease of the resistance of the compensation resistor at a higher branch, even if it may increase with increase of the resistance of the compensation resistor at a lower branch, the lower DNL may attenuate per se, so the overall DNL will decrease.