Fast Load Current Sensing Apparatus with Tracking ADC
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Solution Overview
Problem
Existing load current sensing technologies face challenges in accurately and rapidly tracking current transients due to low bandwidth filters, leading to delayed detection of current excursions and incorrect telemetry, which can result in inefficient power management and thermal throttling in System-on-Chip (SoC) devices.
Innovation Solution
A fast load current sensing apparatus using a tracking ADC with adaptive step size and a finite state machine to rapidly detect and respond to current excursions by sending a maximum current limit code, allowing for timely throttling and reducing guard banding, while maintaining low silicon area and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low pass filter is used to filter voltage across inductor, then noise is reduced, but bandwidth is reduced leading to delayed current detection
Solution Approach 1:
The patent introduces an intermediary mechanism - a tracking ADC with adaptive step size that acts as a mediator between the filtered voltage signal and the current measurement. This tracking ADC dynamically adjusts its conversion steps to follow the inductor current waveform, effectively bridging the gap between the filtered signal and the need for fast current transient detection without requiring a high-bandwidth filter
Solution Approach 2:
The patent changes the parameter of the ADC conversion process by implementing adaptive step size that varies dynamically. The step size is adjusted based on the slope of the inductor current, allowing larger steps during rapid transients and smaller steps during steady state, thereby achieving fast response without sacrificing measurement precision
2Speed
If tracking ADC with adaptive step size is used, then current tracking speed is improved, but device complexity increases
Solution Approach 1:
The tracking ADC system is self-regulating through its adaptive step size mechanism. The finite state machine automatically adjusts the conversion step size based on the detected current slope, eliminating the need for external complex control circuitry. The system serves itself by using the current waveform characteristics to drive its own conversion process, reducing overall device complexity despite the enhanced tracking capability
3Productivity
If guard banding is reduced to allow higher maximum current, then power efficiency is improved, but risk of exceeding current limits increases
Solution Approach 1:
The patent implements a feedback mechanism where the tracking ADC continuously monitors the inductor current and provides real-time information about current excursions. This feedback enables the system to detect when current approaches or exceeds limits, allowing for dynamic adjustment of operating parameters while maintaining reliability even with reduced guard banding
Data Source
AI summary
A fast load current sensing apparatus and scheme provides instantaneous detection of peak current excursions using low silicon area and power efficient techniques. The response time for detecting signal excursions and measuring a signal (e.g., load current) is independent of resolution or precision and can be applied to high resolution telemetry. The apparatus sends out maximum current limit (FHC_limit) code at any instant the load current is detected to be more than a digital-to-analog converter (DAC) code. If the load current is less than the FHC_limit the scheme restores to a next DAC code as per a counter's next value. In case load current is more than FHC_limit, the scheme updates the DAC code to FHC_limit code and starts the counter from the FHC_limit.