Chain-Chopping Current Mirror for Output Current Stability
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Solution Overview
Problem
Conventional current mirrors, including cross-chopping current mirrors, experience output current variations and differences between adjacent current channels due to imperfections in the IC process, leading to unequal current distribution across output nodes.
Innovation Solution
A chain-chopping current mirror circuit is introduced, featuring multiple output nodes, a bias source unit, current mirroring units, and switch components controlled by clock signals, where each switch component connects the output terminal of a current mirroring unit to either the current or next output node, ensuring series switching operations to enhance current equality and reduce differences between adjacent channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cross-chopping current mirror is used to average currents between adjacent channels, then current equality between paired channels is improved, but current difference between adjacent channels remains significant
Solution Approach 1:
The patent segments the current mirroring function into multiple independent current mirroring units (MP1-MP5), each generating current for a specific output node. This segmentation allows independent control and averaging of currents across multiple nodes through the chain-chopping mechanism, rather than relying on a single mirrored current source.
Solution Approach 2:
The patent implements periodic switching action through clock signals CK and CKB that alternately control the transmission gates. During different clock phases, adjacent current mirroring units are selectively connected to different output nodes, creating a periodic exchange of current sources that averages out process variations over time.
2Manufacturing precision
If transmission gates are added between transistors to enable current averaging, then device complexity increases, but current distribution equality improves
Solution Approach 1:
The transmission gates SW1-SW8 serve multiple functions: they act as switches for chain-chopping current exchange, function as current mirrors themselves, and provide routing between different current sources and output nodes. This multi-functionality reduces the need for separate dedicated components for each function.
Solution Approach 2:
The patent merges the current mirroring function with the switching function by making the transmission gates themselves function as current mirrors. Each transmission gate both switches currents and mirrors them between nodes, combining what could be separate functions into unified components.
3Quantity of substance
If more current mirroring units are added to increase output nodes, then current coverage is improved, but current variation across nodes increases
Solution Approach 1:
The chain-chopping mechanism creates a feedback-like effect where current from one node is periodically exchanged with adjacent nodes. This continuous exchange during switching cycles compensates for process variations, as each node receives averaged current from multiple sources over time, improving matching accuracy across all nodes.
Solution Approach 2:
The patent changes the temporal parameter of current delivery by implementing time-division multiplexing through the chain-chopping mechanism. Instead of static current assignment, each output node receives current from different sources at different time intervals, and the averaging effect over time improves current matching accuracy.
Data Source
AI summary
A chain-chopping current mirror and a method for stabilizing output currents are disclosed. The current mirror includes multiple output nodes, a bias source unit, multiple current mirroring units and multiple switch components. The bias source unit provides a reference bias according to the received current. Each of the current mirroring units outputs an output current according to the reference bias. The control terminal of each the switch component receives a clock signal and determines whether the first terminal thereof is coupled with the second terminal or the third terminal thereof according to the clock signal, wherein the first terminal of the ith switch component is coupled with the output terminal of the ith current mirroring unit, the second terminal thereof is coupled with the ith output node and the third terminal thereof is coupled with the (i+1)th output node, where i is a natural number.