DAC-Trimmed Current Mirror for Precise Multi-Channel Matching
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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 digital-to-analog converter (DAC) trimmed outputs in current mirror circuits allows for precise adjustment of each output current, providing a linear trim transfer function within a small circuit area, using transistors and resistors configured to enable selective sourcing or sinking of current for accurate matching of output currents across multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual trimming and degeneration resistors are used in current mirror circuits, then output current matching can be achieved, but circuit area and complexity increase
Solution Approach 1:
The patent combines multiple trimming functions into a single DAC (digital-to-analog converter) unit that can simultaneously trim multiple output currents. Instead of using separate trimming circuits for each current output, the invention uses one shared DAC to generate trim currents that are distributed to multiple transistor branches, thereby reducing circuit complexity while maintaining matching precision.
Solution Approach 2:
The DAC unit serves multiple functions: it generates trim currents for multiple output channels, provides linear trim transfer function, and eliminates the need for additional logic-level translators. This multi-functional approach replaces what would otherwise require multiple separate trimming circuits and associated control logic.
2Manufacturing precision
If individual trimming circuits are used for each output current, then current matching precision improves, but circuit area increases
Solution Approach 1:
Multiple trimming functions are merged into a single DAC unit that shares common circuitry for generating and distributing trim currents. This consolidation eliminates redundant components that would otherwise be required in separate trimming circuits, significantly reducing the total circuit area while maintaining the ability to precisely match multiple output currents.
3Manufacturing precision
If degeneration resistors are used for current matching, then output current accuracy improves, but non-linear trim transfer function and additional logic-level translators are required
Solution Approach 1:
The invention replaces the mechanical/resistive approach of degeneration resistors with a digital control approach using a DAC. Instead of adjusting current through resistor values (which creates non-linear transfer functions), the DAC provides digital-controlled current trimming that yields a linear transfer function, simplifying the control logic and eliminating the need for additional logic-level translators.
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.