Current Mirror Circuit With Per-Output DAC Trimming
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Solution Overview
Problem
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 of current sources or degeneration resistors lead to non-linear trim transfer functions and require additional logic-level translators.
Innovation Solution
The implementation of a digital-to-analog converter (DAC) for each current output in current mirror circuits allows for precise trimming of output currents, providing a linear trim transfer function within a smaller circuit area, thereby enabling accurate matching of multiple output currents without the need for additional logic-level translators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual trimming of current sources or degeneration resistors is used, then current matching accuracy can be improved, but circuit area and complexity increase
Solution Approach 1:
The patent changes the trimming parameter from physical resistor values or current source characteristics to digital control codes. Each current output is controlled by a DAC that accepts digital trim codes, allowing precise current adjustment through digital parameter changes rather than physical component modifications. This reduces circuit complexity while maintaining trimming accuracy.
Solution Approach 2:
The patent replaces mechanical/physical trimming mechanisms (such as physical resistor adjustment or current source trimming) with a digital control system. DACs controlled by digital trim codes substitute for traditional physical trimming components, eliminating the need for additional logic-level translators and reducing overall circuit complexity while preserving current matching accuracy.
2Measurement precision
If traditional trimming methods are used, then current matching can be achieved, but non-linear trim transfer functions and additional logic-level translators are required
Solution Approach 1:
The patent implements a universal digital trimming interface where all current outputs are controlled through DACs with consistent digital input interfaces. This universal approach eliminates the need for different trimming mechanisms and associated logic-level translators for different current channels. The same digital control methodology applies across all current mirrors, simplifying the overall system architecture.
Solution Approach 2:
The patent substitutes digital control signals for analog trimming mechanisms. Instead of using physical trimming components that require logic-level translators, the system uses DACs controlled by digital trim codes. This digital substitution provides a linear trim transfer function and eliminates the need for additional logic-level translators, reducing circuit complexity while maintaining precise current matching.
3Measurement precision
If multiple DAC trimmed outputs are implemented, then current matching accuracy improves, but circuit area increases
Solution Approach 1:
The patent uses digital parameter changes through DAC trim codes to achieve precise current matching. By controlling current outputs through digital codes rather than physical component variations, the patent achieves high current matching accuracy (0.05%) without requiring large physical trimming components. The digital control approach compactifies the trimming functionality.
Solution Approach 2:
The patent replaces physical trimming components with compact digital control circuits. DACs controlled by digital trim codes substitute for traditional physical trimming mechanisms, achieving the same or better current matching accuracy in a smaller area. This substitution eliminates bulky physical trimming components and their associated logic-level translators, reducing overall circuit area.
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.