Digital Current Sensor for On-Die Voltage Regulator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing analog current sensing techniques for inductor-based switching voltage regulators are inefficient in terms of power, area, and design complexity, and do not scale well with process nodes, leading to increased costs and complexity in dynamic current sensing for portable devices.
Innovation Solution
A synthesizable digital current sensing scheme that utilizes a bridge with high-side and low-side switches, Slope Logic to generate a pulse signal proportional to the load current, and Conversion Logic to convert this signal into a digital code, allowing for efficient dynamic current sensing and mode switching without the need for additional analog components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog current sensing schemes (series sense-resistor, replica sense-FET, or inductor DCR) are used, then current sensing functionality is achieved, but power loss, area, design complexity, and cost increase
Solution Approach 1:
The patent replaces the mechanical/analog sensing system with a digital sensing system. Specifically, it substitutes analog current sensing circuits (sense resistors, sense FETs, Gm-C filters) with a digital voltage detection approach that measures the voltage at the switching node during dead-time periods and converts it to a digital current value through calculation and lookup tables, thereby eliminating complex analog components
Solution Approach 2:
The patent extracts the essential sensing function from the complex analog circuitry and isolates it into a simplified digital measurement process. By taking out only the necessary voltage measurement during dead-time and performing digital processing, it removes unnecessary analog components like sense resistors, sense FETs, operational amplifiers, and Gm-C filters while retaining current sensing capability
Solution Approach 3:
The patent changes the sensing parameter from direct current measurement to voltage measurement during dead-time periods. By measuring the voltage at the switching node when switches are off and using the known relationship between voltage, dead-time duration, and current, it transforms the sensing approach from analog current detection to digital voltage-based current calculation
2Measurement precision
If series sense-resistor scheme is used, then current sensing is achieved, but conduction power loss and component cost increase
Solution Approach 1:
The patent removes the series sense-resistor component entirely from the circuit. Instead of forcing current through a dedicated sensing resistor, it extracts current information by measuring the voltage at the switching node during dead-time periods when no current flows through the switches, thereby eliminating the conduction loss associated with sense resistors
Solution Approach 2:
The patent introduces dead-time periods as an intermediary mechanism to enable current sensing without continuous current flow through sensing elements. During these dead-time intervals, the switching node voltage reflects the inductor current state, allowing indirect current measurement without the need for power-dissipating sense resistors
3Measurement precision
If inductor DCR based sensing is used, then current sensing is achieved, but additional filtering circuits and calibration circuits are required increasing area and power
Solution Approach 1:
The patent replaces the analog filtering system (Gm-C filter) with a digital processing system. Instead of using continuous analog filtering to process the inductor DCR voltage, it samples the voltage during dead-time periods and performs digital filtering and current calculation, eliminating the need for large-area analog filter circuits
Solution Approach 2:
The patent removes the Gm-C filter and calibration circuits from the design. By extracting current information directly from switching node voltage during dead-time and using digital processing with lookup tables, it eliminates the need for analog filtering components and complex calibration circuitry that would occupy additional chip area
4Reliability
If analog current sensing schemes are used, then current sensing works at present process nodes, but they do not scale well to newer process nodes
Solution Approach 1:
The patent replaces the process-sensitive analog sensing system with a digital sensing system that is insensitive to process variations. By using digital voltage measurement and calculation methods that rely on timing and digital processing rather than analog component matching, the design achieves scalability across different process nodes without requiring re-design
Solution Approach 2:
The patent creates a universal current sensing approach that can be applied across multiple process nodes and technology generations. The digital measurement and calculation methodology is not tied to specific process characteristics, allowing the same design to function reliably in both mature and advanced process nodes without modification
Data Source
AI summary
Described is an apparatus which comprises: an output node; a capacitor; an inductor having a first terminal coupled to the output node, and a second terminal coupled to the capacitor; a bridge to receive an input power supply and to generate a switching voltage signal at the output node; and a current sensor to determine slope of the switching voltage signal on the output node.