Current-Mode DAC Offset Compensation With Adjustable Weighting Currents
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Solution Overview
Problem
Conventional digital-to-analog conversion circuits in current mode suffer from inefficiencies due to large circuit area waste and accuracy reduction caused by voltage/current offset, making on-chip trimming inconvenient and accuracy challenging.
Innovation Solution
A digital-to-analog converter design incorporating an amplifier, voltage relaxation circuit, base current source, and weighting current sources that adjust the base current and weighting currents to align the output voltage with target voltages, effectively compensating for offsets and maintaining conversion accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a current mode digital-to-analog conversion circuit is used, then the circuit structure is simpler and circuit area is saved, but on-chip trimming is inconvenient and voltage/current offset occurs reducing accuracy
Solution Approach 1:
The circuit is divided into separate functional modules: voltage relaxation circuit for offset correction, base current source for initial voltage adjustment, and weighting current sources for precision control. This segmentation allows each module to be optimized independently while maintaining overall simplicity.
Solution Approach 2:
A voltage relaxation circuit is introduced as an intermediary component between the amplifier and the output, specifically designed to relax voltage constraints and enable convenient on-chip trimming operations without complicating the overall current mode architecture.
2Reliability
If high-voltage circuit elements are used in a digital-to-analog conversion circuit requiring only a few microamperes, then the circuit can operate in the required range, but a charge pump circuit is needed resulting in large circuit area waste
Solution Approach 1:
The circuit employs dynamic parameter adjustment through adjustable base current and weighting currents, allowing the same circuit elements to operate effectively across different current ranges (microampere to higher currents) without requiring separate high-voltage generation circuits, thereby eliminating the need for charge pumps and reducing circuit area.
3Area of stationary object
If very small current is operated in a digital-to-analog conversion circuit, then the circuit elements can be small, but voltage/current offset problem occurs easily reducing conversion accuracy
Solution Approach 1:
The base current source provides preliminary adjustment of the initial voltage output before the weighting current sources perform precision adjustment. This preliminary action compensates for offset errors in advance, ensuring that even very small currents operate accurately without being susceptible to offset problems.
Solution Approach 2:
The circuit incorporates feedback mechanisms where the adjustable base current and weighting currents are controlled based on the actual output voltage, enabling real-time compensation for offset errors and maintaining high conversion accuracy even at very low current levels.
Data Source
AI summary
A digital-to-analog converter includes an amplifier, a voltage relaxation circuit, a base current source, a first weighting current source, and at least one second weighting current source. The amplifier receives a reference voltage and a feedback voltage, and generates an output voltage according to the reference voltage and the feedback voltage. The base current source is coupled to an output end of the amplifier through the voltage relaxation circuit, and is configured to generate an adjustable base current. The first weighting current source generates an adjustable first weighting current between a reference ground end and one of a current load and the voltage relaxation circuit according to a first bit of input data. The second weighting current source generates at least one second weighting current according to at least one second bit of the input data.