Questions tagged [emc]
Electromagnetic compatibility (EMC) is a branch of electronics related to identifying and solving problems caused by electromagnetic interference (EMI) between devices. It encompasses both attempting to prevent unwanted emissions from a device and also ensuring that emissions from another device will not cause spurious operation. EMC depends upon many system-level details; when asking questions, please provide as much information as possible.
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Should I remove the ground plane under AC traces in my PCB?
Attached below are images of a 2-layer PCB layout I am currently designing. I have always had the habit of removing the ground plane underneath AC signals, but a more experienced PCB designer advised ...
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Is there issue to connect metal chassis to Earth ground with resistor in between
I would like to know if it is safe to connect metal chassis to earth ground with 1Mohm resistor in between or this was causing issue for ESD. The reason I am doing this is to reduce coupling noise by ...
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How concerned should I be about the level of EMI generated by simple isolated DC-DC converters?
I'm in the early prototyping stage for a system that integrates with DMX512. One of my design goals is to make the DMX interface extremely robust. To that end I'm going to be using THVD2410, which is ...
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Does it make sense to separate an analog and digital ground plane in the Eurorack modules?
Eurorack synthesizer is quite a specific standard.
centralized power supply unit,
modules are connected to the backplane using IDC ribbons - that means parasitics,
they are patched with external ...
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When cascading a ferrite bead and inductor in the form C-L-C-L-C, which is best to put first, particularly for a buck converter?
I am asking this question specifically for buck converter inputs, but am happy to consider answers that are more general -- not specific to buck converter ICs, or focused on the output filter.
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EMI filter design for a DC-DC converter
I am doing an EMI filter for a step down flyback DC - DC converter 20 V to (20 V and 10 V) multiple outputs. The controller used here is UC3842. I have the following questions for making this EMI ...
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Which one is correct ( better ) for ESD Protection? Chassis or Signal Ground
I should to place a PCB in a metallic enclosure having an Ethernet and and USB port. The connectors are placed on dedicated small PCBs mounted on enclosure and connecting to the main PCB by cables.
I ...
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EMC problem at half PWM frequency
Save, I have a problem with an EMC qualification. My system has PWM controlled fans with a frequency of 25kHz. In fact, in the spectrum of the conducted emission I see lines at 25kHz, 50kHz, 75kHz and ...
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inductive sin cos position sensor EMC considerations
I am studying the use of an linear inductive sensor of approximately 250mm movement.
Available IC's include TI LDC5072, Renesas IPS2550 and others.
Reference https://www.celeramotion.com/inductive-...
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How can I reduce the parasitic inductance of a metal film resistance
One example of a common resistor is metal film resistor, which has a high ESL. What are the practical steps to reduce ESL, other than to increase the area of the conductor and reducing the length of ...
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Does the spacing of ferrite clamps affect their performance?
During an EMC seminar (by Würth, I believe) some years ago, I remember learning that if you are going to put multiple ferrite clamps after each other on a cable, they should be separated by some ...
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Understanding Conducted emission test setup
Why is the main conducted emission setup separated by 0.8 meters from any metal surface and also from ground plane?
(Image source: Electromagnetic Compatibility (EMC) course offered for Msc. ...
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EMC and System-ESD Design Guidelines for Board Layout Infineon XTAL Layout
I am going through this material from Infienon.Below is the XTAL layout given in the document.
The explanation for this arrangement is given below.
What I understood from this document is they are ...
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Paralleling EMC filter
I have the following architecture:
This is the first time I see an architecture like this. I am more familiar with this king of architecture:
I would like to have your opinion on this subject. The ...
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Varying sine frequency with varying amplitudes
I am simulating AFCS by injecting Sine wave with varying frequencies with varying amplitudes.
I have 128 different frequencies aith 128 different amplitudes. How do I simulate it ?
I have saved all ...
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Edge ground loop on a PCB
I recently added a ground edge on my PCB to reject EMI noise on. Adding this ground loop have a strong effect on rejecting EMI noise:
My PCB is a 12-layer board, currently I have this ground loop on ...
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How can copper function as a Faraday Cage and Antenna?
How can copper serve both purposes of capturing waves as an antenna and also block waves when used as a faraday cage for EMI shielding? How can the same material do both: capture and block?
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How to calculate the distance between two vias in a Via Fence
I am designing a 2 layer PCB for an IoT application. Its a 2 layer PCB with onboard antennas for GSM and GNSS. The board uses wired communication protocols like I2C, CAN, UART and SPI. I have stitched ...
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Connecting Power pins on BGA packages
For BGA packages, I never see people tying power/GND pins together on BGA package (e.g. tying +1.1V_FPGA pins together as shown). Usually I see one ball to one via like how the GND is layout as shown. ...
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Even harmonics from oscillator
I am using a 24MHz microchip oscillator to drive an Lattice FPGA clock input. The design failed radiated emission at 720MHz by 17dB which is even harmonics (24MHz x 30). When I used a near-field ...
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For a PFC Boost converter, how significant is front end EMI filter damping?
Power converters are said to have a negative dynamic input resistance as long as the control loop is active( ie, within the gain crossover frequnecy).
Since the voltage control loop of PFC converters ...
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USB breakout board for turning off device - SHIELD help needed
Currently I design a breakout board which I plan to introduce between USB device (e.g. keyboard) and USB host (e.g. computer). For reference take a look at picture below.
On breakout board there is ...
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What is the right way to model power converter noise? Should it be considered as voltage or current?
This reference models the converter noise as voltage and the filter is an LC filter (from right to left).
Another source mentions the converter noise should be considered as current source. Again ...
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External spread spectrum phase-shifted clocks versus unsynchronised spread spectrum in multiple buck converters
I'm working on a design where I have a need to generate about 10A at 5V across a long bar-shaped board. This is generated from an incoming 12V DC rail. For a number of reasons (physical constraints, ...
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How does DC converter switching cause broadband noise in this case?
As per Source1:
"a broadband disturbance is defined as an electromagnetic disturbance which has a bandwidth greater than that of a particular measuring apparatus, receiver or susceptible device.”
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Higher capacitance for EMI return cap in isolated DC-DC-SMPS?
A typical SMPS converter usually includes a small capacitor of ~1 nF in tight proximity to the isolation transformer to return the common-mode switch noise to the primary side switch for EMC reasons.
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Is this explanation of chassis grounding correct?
In Henry Ott's Electromagnetic Compatibility Engineering, Section 3.2.5: Chassis Grounds explains that circuit ground should be connected to the chassis where the I/O cables come in, as shown:
This ...
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How does current in the cable shield affect the signal in the wires within
The common anecdotal explanation for why the screen of signal cables should only be grounded at one end is to avoid ground loops. Magnetic fields through ground loops generate current in the loop. ...
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Passing EN-55032 (Class B) Conducted Emission Test with POE+ Mode (Design based on AG5724-LPB Silvertel)
I'm trying to pass Conducted Emission test for a product that I worked on that has Silvertel's AG5724-LPB.
Here is how the setup looks inside the lab:
Note 1: the red wire is a connection to CHASSIS ...
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Adding guard GND to a battery based system
I read the a post about adding a guard ring around a PCB to reduce EMI noise:
In my case I have a transimpedance amplifier system working @ 4MHz bandwidth and it is battery based. My question is do I ...
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Why is the common mode current said to be equal in magnitude for both line and neutral when clearly the path impedances are different?
When I look at the current flow for common mode noise current, I don't see equal impedance between the two paths. I think the equality should be valid only if there are symmetrical paths.
Case 1:
In ...
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Why doesn't common mode current on an isolated PCB cause EMI problems?
I was reading "Signal and power integrity simplified third edition" by Eric Bogatin and on chapter 11.16 the author states that connecting an external cable to a PCB that contains an ...
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Why is the Y-capacitor named so?
I guess X-caps are named so since they are connected across the Line and return. Similarly is there any reason for naming Y-caps, which are connected between L/N and GND ?
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Noise Voltage from Sinusoidal Flux Density Derivation
From page 52 of Electromagnetic Compatibility Engineering by Henry Ott; How was the imaginary and omega component in eq. 2-12 derived from eq. 2-11? And how did the negative sign disappear?
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Help reading schematics for design reviews [closed]
I'm reaching out to those with more experience in reading electronic schematics. As the Compliance engineer on the team, I primarily handle testing, pre-testing, and certifications. Recently, I've ...
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Seeking product reference for an EM Noise reduction PCB Filter of DC motor [closed]
I have this DC motor (comming from an unknown bigger appliance), shown in the following photo.
There is an EMI/EMC noise reduction filter soldered on it.
The PCB of this filter can be seen in the ...
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Best PCB design techniques regarding signals in micro/nano amps?
I have a design where I am measuring square waves of currents in the order of microamps, specifically 100nA to 200uA (trace 1). I also have a triangle wave on the same board running at 1kHz, 10Vp-p (...
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Why is it bad to have unconnected metal areas around PCBs/enclosures for EMI?
I've heard that it is generally bad to have unconnected metal around PCBs due to both safety reasons of charge buildup, but also EMI in the sense that these metal pieces can act as antennas and re ...
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Visualizing 2 Layer PCB Return Currents
Hobbyist moving a manhattan-style prototype of an analog FM radio to a PCB for ease of assembly and access to SMT parts. I have attempted a 2 layer FR4 board with a 1.6mm thickness, as I feel that ...
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Recertify against EMC (automotive E-Mark) due to software changes
There is a digital output control module with a CAN interface that I will be working on. Its already certified against EMC, e-mark (UNECE 10).
As the previous contractor will no longer support the ...
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Telecom Lines Conducted emissions noise travel
I am seeking an explanation of how conducted emissions on telecom lines are measured.
The frequencies of interest are at 150kHz to roughly 850kHz.
The size of the unit is 30cm by 30cm by 15cm. The ...
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Does LISN eliminate differential mode noise?
Do I understand correctly that this LISN circuit doesn't eliminate differential mode noise? And when I get a spectrum, there are two parts of noise: differential mode (DM) and common mode (CM)?
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LDO vs voltage reference when input signal is noisy
I am designing an active EMI-filter (AEF) with an op amp (LTC6227). The AEF suppresses noise from a DC/DC converter. Ther op amp requires a supply voltage of 9V and a reference voltage of 4.5V at the ...
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GND plane between tracks or tracks closer enough to remove the GND tracks
I am working in a design with many signals, no high speed signals, just some switches signals and encoders tracks. However I had problems with the ground uniformity sometime ago, therefore I would ...
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Telecom Lines Conducted emissions [closed]
We have rented a Telecom line ISN to conduct some in-house pre-compliance testing. The test setup closely follows the CISPR32 standard. We encountered issues with conducted emissions in the lab, which ...
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Ground plane for SMPS EMI-Filter?
I am designing a board including various switch mode power supplies, e.g. Buck, boost, and so on. The application notes recommend using split ground planes for power and analog parts, however after ...
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Why is my encoder showing abnormal spikes on the oscilloscope readings? Any suggestions on what might be causing it?
So to summarize, I have these winch drives that I've put together. One of them went berserk during testing and now I'm diagnosing the problem. I have attached an oscilloscope to where the KEB servo ...
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EMI/EMC: Connecting PCB mounting holes to chassis in multi-board system
I am working on a system which has a metal chassis connected to the earth. The system gets power from a dedicated PSU. The power lines of the PSU (VCC_PSU / GND_PSU) are fed into a master PCB and ...
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Is there any issue when mixing low frequency power with high frequency digital in a single board? [closed]
Summary
In a board is it okay to just join low frequency power(>10 Hz, 1-15 A, 24 V) with “high” frequencies(~100-480 MHz), being supplied by “different” power supplies but referenced with the same ...
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What differences in terms of fields does a grounded metal and an unconnected metal object have
I previously asked a question regarding absorption and reflections of waves to metal. But id like to know the differences that say a PCB metal pour that is connected to a signals return path, and a ...
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