DAC-Trimmed Current Mirror for Multi-Channel Current Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current current mirror circuits in analog circuits face challenges in achieving accurate matching of multiple output currents due to increased circuit area and complexity, particularly in multi-channel digital-to-analog converter (DAC) circuits, where existing techniques such as individual trimming and degeneration resistors result in non-linear trim transfer functions and require additional logic-level translators.
Innovation Solution
The implementation of a current mirror circuit with digital-to-analog converter (DAC) trimming for each output current allows for precise adjustment of output currents, providing a linear trim transfer function within a smaller circuit area, using transistors and resistors configured to enable selective sourcing or sinking of current to match output currents across multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual trimming and degeneration resistors are used for each output current, then current matching accuracy is improved, but circuit area and complexity increase
Solution Approach 1:
Multiple current trimming functions are merged into a single DAC circuit. The DAC receives a digital trim code and generates corresponding trim currents for multiple output channels simultaneously, eliminating the need for separate trimming circuits for each channel while maintaining current matching accuracy
Solution Approach 2:
The DAC circuit is designed to serve multiple functions: it provides trim currents to multiple output channels, enables current matching across all channels, and replaces multiple individual trimming mechanisms. This multi-functional approach reduces overall circuit complexity while achieving the same current matching precision
2Measurement precision
If individual trimming circuits are implemented for each output current, then current matching precision is improved, but circuit area increases
Solution Approach 1:
Multiple current trimming functions are merged into a single DAC circuit. The DAC receives a digital trim code and generates corresponding trim currents for multiple output channels simultaneously, eliminating the need for separate trimming circuits for each channel while maintaining current matching accuracy
Solution Approach 2:
The trimming approach transitions from the spatial dimension (separate physical trimming circuits for each channel) to the digital dimension (a single DAC controlled by digital trim codes). This dimensional shift allows one circuit to control multiple channels without requiring proportional increases in physical circuit area
3Measurement precision
If degeneration resistors are used for current matching, then current accuracy is improved, but non-linear trim transfer functions and additional logic-level translators are required
Solution Approach 1:
The analog degeneration resistor trimming mechanism is replaced with a digital control system using a DAC. The DAC converts digital trim codes into precise trim currents, eliminating the need for resistors and associated non-linear transfer functions. This substitution simplifies the trimming operation and removes the need for additional logic-level translators
Solution Approach 2:
The trimming mechanism changes from resistance-based (degeneration resistors) to current-based (DAC-generated trim currents). This parameter change enables linear trim transfer functions and simplifies the control architecture by directly generating the required trim currents without intermediate conversion stages
Data Source
AI summary
A current mirror circuit includes a current output terminal, a first transistor, a second transistor, and a digital-to-analog converter (DAC). The first transistor includes a first terminal coupled to a power rail, a second terminal coupled to a current source, and a third terminal coupled to the current source. The second transistor includes a first terminal coupled to the power rail, a second terminal coupled to the second terminal of the first transistor, and a third terminal coupled to the current output terminal. The DAC includes an output terminal coupled to the second transistor.