EMI Rejection in Temperature Sensing Diode Circuits
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Solution Overview
Problem
Existing temperature measurement circuits in digital systems are prone to errors due to electromagnetic interference (EMI) when using twisted pair wires, which induces current errors and requires the use of shunting capacitors that slow down sampling rates and increase power consumption.
Innovation Solution
A circuit using common mode rejection to deliver ratioed currents to a remotely located semiconductor device, eliminating the need for shunting capacitors by maintaining identical impedances at the anode and cathode, thereby rejecting EMI signals and maintaining fast sampling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shunting capacitors are used to block EMI-induced currents from flowing through the remote diode, then measurement precision is improved, but sampling rate decreases and power consumption increases
Solution Approach 1:
The patent extracts the harmful EMI-induced current from the measurement path by providing it with a separate return path through the cathode wire to ground, rather than allowing it to flow through the diode. This separates the harmful current path from the measurement current path, eliminating the need for shunting capacitors while maintaining measurement accuracy and fast sampling rates
Solution Approach 2:
The patent introduces ground as an intermediary node that provides a low-impedance return path for EMI-induced currents. By connecting the cathode wire to ground, the patent creates an intermediate path that safely directs harmful currents away from the measurement circuit without affecting the measurement signal
2Measurement precision
If shunting capacitors are used to reject EMI signals, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent extracts the harmful EMI-induced current from the measurement path by providing it with a separate return path through the cathode wire to ground, rather than allowing it to flow through the diode. This separates the harmful current path from the measurement current path, eliminating the need for shunting capacitors while maintaining measurement accuracy and fast sampling rates
Solution Approach 2:
The patent introduces ground as an intermediary node that provides a low-impedance return path for EMI-induced currents. By connecting the cathode wire to ground, the patent creates an intermediate path that safely directs harmful currents away from the measurement circuit without affecting the measurement signal
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
This approach effectively reduces EMI-induced errors in temperature measurements, allowing for faster and more accurate temperature readings without the need for shunting capacitors, thus improving the precision and efficiency of temperature measurement systems.
Implementation Method 1
The circuit may be configured to use common mode rejection to reject EMI signals when performing temperature measurements using the remotely located semiconductor device
Implementation Method 2
VBE may be defined as a function of absolute temperature by the equation where η is the ideality factor of the PN junction, k is Boltzman's constant, q is the charge of a single electron, T represents absolute temperature
Data Source
AI summary
In one set of embodiments, a circuit may be implemented to deliver accurately ratioed currents to a remotely located semiconductor device that has a substantially non-linear input-output characteristic that varies with temperature and is subject to effects of electromagnetic interference (EMI). The circuit may be configured to use common mode rejection by establishing an identical impedance at each of the two terminals of the remotely located semiconductor device, in lieu of coupling shunting capacitor(s) across the terminals, in order to reject EMI signals while performing temperature measurements using the remotely located semiconductor device. This may facilitate maintaining fast sampling times when performing temperature measurements, while providing a more effective method for handling EMI induced currents that may lead to temperature measurement errors, thereby eliminating those errors.