High-Impedance Differential Current Sensing Without Sense-Node Loading
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Solution Overview
Problem
Current-sensing circuits in computing devices face challenges such as high power consumption due to low input impedance, voltage degradation at sense nodes, and limited availability of solder bumps for sensing, which affect precision and efficiency.
Innovation Solution
High-impedance current-sensing circuits are developed, utilizing amplifiers and current mirrors to minimize current draw and circuit size, while enabling precise current measurement and supporting multiple voltage domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional current-sensing circuits are used, then current measurement function is provided, but power consumption is high due to low input impedance
Solution Approach 1:
The patent inverts the conventional approach by using high input impedance instead of low input impedance for the current-sensing circuit. This inversion allows the circuit to measure current through voltage division ratios rather than direct voltage drop measurement, thereby reducing power consumption while maintaining measurement precision.
Solution Approach 2:
The patent changes the input impedance parameter from low to high, and utilizes voltage division ratios as a new measurement parameter. By measuring voltage at the second sense node and calculating current based on the known voltage at the first sense node and the voltage division ratio, the circuit achieves accurate current measurement with minimal power consumption.
2Measurement precision
If conventional current-sensing circuits are used, then current measurement is achieved, but voltage degradation occurs at sense nodes
Solution Approach 1:
The patent introduces voltage division ratios as an intermediary measurement mechanism. Instead of directly measuring voltage at sense nodes which causes degradation, the circuit uses the voltage division ratio between nodes to calculate current, thereby eliminating direct measurement-induced voltage degradation while maintaining measurement capability.
3Measurement precision
If more sense nodes are added for precise measurement, then measurement precision improves, but device complexity increases due to limited solder bumps
Solution Approach 1:
The patent makes existing sense nodes multi-functional by using them for both voltage sensing and current measurement through voltage division ratios. This eliminates the need for additional dedicated sense nodes or solder bumps, reducing device complexity while maintaining or improving measurement precision through ratio-based calculation.
Data Source
AI summary
Embodiments herein relate to a high-impedance current-sensing circuit. In one approach, the circuit includes first and second amplifiers which are coupled to first and second sense nodes, respectively, of a load to be monitored, one or more current mirrors to mirror a current to a voltage output node, and first and second resistors coupled to an input and output, respectively, of the one or more current mirrors. A voltage at the voltage output node is based on a current between the first and second sense nodes, and can be used for various purposes such as limiting the current through the load.