Differential Voltage-Based Current Sensing With PVT Offset Calibration
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Solution Overview
Problem
Current current sensing technologies in microelectronics face inaccuracies due to current mirror mismatches and resistive losses in mirror-based current sensors, particularly in Globally Distributed Head Switches (GDHS) and Block Head Switches (BHS), which are exacerbated by voltage offsets and variations in Process, Voltage, and Temperature (PVT) conditions.
Innovation Solution
A voltage-based current sensing apparatus is introduced, utilizing a voltage-based current sensor with input amplifiers, voltage-to-current converters, oscillators, and a calibration module to generate ADC codes, which includes a differential architecture to mitigate inaccuracies by calibrating coarse and fine offsets and tracking PVT variations, ensuring accurate current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mirror-based current sensing is used, then current monitoring capability is provided, but measurement precision deteriorates due to current mirror mismatches and resistive losses
Solution Approach 1:
The patent replaces the traditional mirror-based current sensing mechanism with a voltage-based sensing approach. Instead of using current mirrors that are sensitive to mismatches and resistive losses, the invention measures voltage drops across sense resistors and converts these voltage signals to current measurements through calculation, thereby eliminating the fundamental sources of error in mirror-based systems
Solution Approach 2:
The patent changes the measurement parameter from direct current comparison to voltage measurement. By measuring voltage drops across known resistance values and computing current from these voltage measurements, the system achieves higher precision and stability without the mismatches inherent in current mirror configurations
2Measurement precision
If voltage offsets are present in the sense amplifier, then circuit operation is maintained, but measurement precision deteriorates due to low drain to source voltages
Solution Approach 1:
The patent extracts and separately compensates for voltage offset errors in the sense amplifier. By measuring and characterizing the offset voltages and then subtracting them from the measurements, the system removes this source of error while maintaining the ability to operate with low drain-to-source voltages in the switch tiles
Solution Approach 2:
The patent implements offset calibration procedures that measure the amplifier offsets under known conditions and use this information to correct subsequent measurements. This feedback mechanism allows the system to maintain high measurement precision despite the presence of inherent amplifier offsets
3Area of stationary object
If large circuit area is used for switch tiles, then current gating capability is provided, but measurement precision deteriorates due to current mirror mismatches
Solution Approach 1:
The patent eliminates the need for current mirrors in large switch tile configurations by replacing them with voltage-based sensing. This substitution allows the use of large circuit areas for switch tiles without introducing the mirror mismatch errors that would otherwise occur
Solution Approach 2:
The patent introduces voltage measurements as an intermediary between the current flowing through large switch tiles and the final current measurement. By measuring voltage drops rather than directly comparing currents, the system can handle large circuit areas without the precision losses associated with current mirror mismatches
4Measurement precision
If resistive losses vary among circuit traces, then signal transmission is provided, but measurement precision deteriorates due to additional current sensing errors
Solution Approach 1:
The patent replaces current-based sensing that is vulnerable to trace resistive losses with voltage-based sensing. By measuring voltage drops directly at the sensing points and using these measurements to calculate current, the system becomes immune to variations in trace resistance along the signal paths
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances current sensing accuracy by effectively removing voltage offsets and compensating for PVT variations, thereby improving the reliability of current measurements in microelectronic applications.
Implementation Method 1
a voltage-to-current converter coupled to the input amplifier, a first oscillator and a second oscillator, wherein the first oscillator and the second oscillator are coupled to the voltage-to-current converter
Implementation Method 2
the first oscillator generates a first oscillator waveform and the second oscillator generates a second oscillator waveform. In one example, the first oscillator waveform has a first oscillator waveform frequency which is proportional to a first current measurement of the first current output, and the second oscillator waveform has a second oscillator waveform frequency which is proportional to a second current measurement of the second current output
Data Source
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Figure 3~4
AI summary
Aspects of the disclosure are directed to voltage-based current sensing. In accordance with one aspect, voltage-based current sensing may include performing a coarse calibration of a voltage based current sensor to determine a coarse offset; performing a fine calibration of the voltage based current sensor to determine a fine offset; performing a frequency calibration of the voltage based current sensor to determine a frequency offset; and performing a transfer function calibration of the voltage based current sensor to determine a sensor transfer function using one or more of the coarse offset, the fine offset and the frequency offset; and measuring a load current using the sensor transfer function.