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.

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What is meant by the statement "Local bypass capacitors are needed to control EMC coupling with heat sink"?

During a talk, not sure what the speaker meant by the statement " We need to add local bypass caps to control EMC coupling with heat sink" He was referring to the MOSFETs in synchronous ...
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Is my surge and burst protection enough?

The above schematic is for surge and burst proection. Is it enough? Thanks.
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3 answers
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What is the core material being used in CMC (Common mode choke) and DMC (Differential mode choke)?

The core symbol in below diagram indicates that it is an iron core material but Iam not sure whether it is correct. I see the same representation in many other circuit schematics as well. Below ref ...
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Why are differential mode chokes (inductors) not generally coupled?

I understand there are both coupled and un-coupled versions of differential mode chokes as shown below. Which one is better? I see most of the designs having un-coupled version. What is the reason? ...
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What is the purpose of this pad

What is the purpose of this pad, located between the PCB in the picture and a wifi card? It is completely enclosed in Kapton tape and there are no exposed grounds on the PCB below, on the bottom of ...
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A question about CE marking

If an electrical enclosure is interfaced with CE marked devices, does it still require assessments before using CE marking on it? So if one makes an enclosure using a CE marked PSU and other CE marked ...
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Finding DC saturation behavior of clamp ferrites

While some chip ferrite datasheets specify maximum current and DC saturation behavior, it seems like many clamp ferrites omit both maximum current specification (which arguably is less critical) but ...
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Simulate EMI conduction

Here is the website for reference to Simulating EMI Conduction I ran the simulation according to the example, but the output voltage could not reach 19.5V.I know it's an open loop, but the voltage ...
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Stove spark igniter make the touch switch off/on

I've made a capacitive touch/on (currently on bread board) with TTP223 touch IC on active low mode and used 74HC74D as output flip flop. When I use this board near stove and power up the stove spark ...
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1 answer
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Kelvin connections in PCB

in the following webinar from youtube, a recommendation is presented about the kelvin connection at the 41st minute of the video. but I couldn't get it. (second language) https://www.youtube.com/watch?...
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EMI analysis for low power low voltage AC/DC

I've designed an 80W 220V-IN 400V-OUT PFC Boost converter in order to analyze its conductive EMI and design the proper active EMI filter for it. but as this is my first implementation project, working ...
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When to employ RF shield cover on PCBA?

During reparations and teardowns I have frequently come across PCB-mounted RF shields and covers. While I don't typically work with GHz processors or design RF modules I wonder if such covers could be ...
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Can I use MKT capacitor instead of MKP in the following topology?

The following topology is a boost PFC designed by STMicroelectronics. The input capacitor (C1) is an MKP one. Can I use an MKT (fig2) or polyester (fig3) capacitor instead of that?
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Current in inductors of emi filter

I am currently working on an EMI filter for a led driver (constant current). Here you can find the according schematic: My question now is, which (if any) current is going through the inductors/have ...
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EMI Filter - current in inductors / part selection

I want to use a NLDD-1400H LED Driver as constant current source with 1.4A ouput. On the last page of the datasheet there are information about an EMI Filter, I want to use. Here is the schematic: ...
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Cispr/EU testing: Large Loop Antenna System vs 60cm Loop antenna

I want to be able to do some pre-testing to EU standards, and I am not able to find clear information regarding the proper test equipment. From what I've read in an older version of the Cispr15 ...
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2 answers
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noisy environment between buffer and in-amp

I have some basic questions regarding the circuit shown below: The image is from this question. The buffer is sending signals through a twisted pair cable to an in-amp. My questions are: Does the ...
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Is it ordinary that near-field probes do not detect EM noise?

Last week we did a pre-certification test with a device and it failed. Description of the device: It is powered from Li-ion battery. It integrates a BQ24090DGQT which is a Li-ion battery charger, the ...
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Regarding validity of the EMC/EMI & safety test reports containing withdrawn IEC Standards for CE & UKCA declaration

I do have a question regarding the validity of the EMI/EMC & Safety test reports of the products which do have the withdrawn IEC standards. Like for an Example: If we do have tested the products ...
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Do I need EMI shielding for a 5V signal PCB placed beside high powered DC cable 48V 50A?

I have PCBs located just below the high-powered DC cable at 50A 48V. My PCB has input-output from 5V signal cables from all over the place. The 5V signals are for: 12V and 5V Signal driving the EM ...
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2 votes
1 answer
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Emissions issue with H-Bridge driving piezo transducers

I have the following block in a PCB design: This drives a ~ 5W piezo transducer at 113KHz. The functionality of the system is great, nothing heats up at all. The issue is when I did a quick pre-...
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3 votes
2 answers
60 views

EMI filter and bypass capacitors for Mornsun DC-DC

The datasheet for Mornsun K7805MT-500R4 DC-DC module has the usual required capacitors in typical application circuit: And just as pretty much any other datasheet they provide additional schematics ...
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1 answer
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How to deal with local capacitors near MOSFET PWM driver backfeeding other capacitors?

I'm designing a multi-channel low-side PWM driver board with eight channels. Each channel has a maximum current of 6A, with a maximum total of 20A at any point across the whole board. The input ...
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1 vote
1 answer
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ADC susceptibility to EMI from cellphone source

I'm having trouble with EMI induced noise in my prototype ADC project. The ADC functions well in all tests but my (admittedly unscientific) test of placing my cellphone beside the PCB or the power ...
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3 answers
106 views

Signal Integrity in electronic systems

When I went through EMC testing of some electronic boards, I observed that the frequencies of the EM waves generated by the boards are at the fundamental frequency with multiples of some whole number. ...
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Inductor position in low side buck converter

I am designing a PCB to control an RGBW-LED. To provide a regualted current for each color I am using the LM3407 buck converter from TI. The buck converter is powered with 12V and is configured to ...
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6 votes
1 answer
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What are the drawbacks of connecting circuit GND and Chassis via multiple mounting screws (for EMC and Safety)?

Although there are various suggestions around for how to connect circuit GND to the earthed chassis (say, the chassis has a point-to-point resistance of around 1 mΩ) in devices, there seem to be two ...
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3 votes
1 answer
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Roughly how fast can a constant current LED circuit ramp to 1A without EMI issues?

I have a constant current circuit supplying a 1A LED for a carefully controlled strobing application; for my application the LED needs to turn ON (no dimming) for ~1ms and then OFF (fully off), at a ...
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1 vote
1 answer
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How to prepare my firmware for FCC Part 15 testing

I have a device for which I want to do FCC Part 15 testing - unintentional radiation. (It includes an ESP WROOM Wifi/Bluetooth module with modular approval). This device connects to wifi every 20 ...
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5 votes
3 answers
188 views

LTspice common mode choke differential noise

Edit, changed circuit diagram to make explicit the signal source is the load I'm designing a medical device and I'm in process of determining the line filter I'm going to need. I'm not especially ...
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How do you build a spurious emissions test rig?

Naively, it seems like you could test for spurious emissions by: Placing the device-under-test (DUT) in a grounded metal box with a broadband antenna inside. Hook the antenna's coax cable to the S21 ...
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Protection from high voltage in high frequency ignition in plasma cutting machines

I am currently in the process of designing a circuit for detection of a short circuit of a plasma cutter nozzle with material when there is no arc. The important requirement is that detection ...
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1 answer
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Do I need shielding on a long, power-only USB cable?

I want to use a long, 3m USB cable to power a board with an ESP32 WROOM module. Power draw is less than 100 mA. I am not using the data pins on the USB cable. If the cable is NOT shielded, should I ...
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1 vote
1 answer
183 views

When does a PCB require a chassis ground connection?

Do all PCBs require a chassis ground connection point? I am designing a circuit board which will be used in many different types of assemblies. It is a small mixed-signal, low-voltage (24 VDC power, ...
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2 votes
1 answer
59 views

How should non-shielded connectors be handled in a casing design?

Assume a design with a mix of shielded connectors (e.g. USB, HDMI) and non-shielded connectors (e.g. standard 0.1" headers) A metallic casing is designed to mesh with the shielded connector ...
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GaN Power transitor said to "reduce EMI"

I have no experience in GaN, I am currently discovering the subject and I was studying a design from Infineon and I found on a GaN power transistor the following benefits: Here is the datasheet: ...
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1 answer
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Can you tolerate routing traces underneath high speed signals?

I am working on a 2 layer board with ground and power layer on top and bottom and I have reached a single point where the 2 layers are limiting my design. It is regarding SPI signals that would be ...
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0 votes
1 answer
62 views

Unwanted motor influence (RC snubber?)

Trying to make motors control, but have very significant influence of the motors between each other. When first motor is stopped (by built in limiter) second one (stopped) start turning cca 1/4 of ...
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0 answers
52 views

EMC issues for BLE certifcation

We have two different products but identical when it comes to the BLE SoC layout and almost identical otherwise besides an extra MCU on one of the products, which is on the bottom layer of the board. ...
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0 votes
0 answers
80 views

How to lessen emission of an enclosure box from I/O ports?

I am designing an enclosure box which will contain motor controllers(TB6600), microcontroller(ESP32 and Arduino Mega) and a 12 V power supply. I have not decided which material will enclose this. My ...
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1 answer
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Common mode choke and grounding

How would you connect the cable shielding, metal enclosures and power ground on following system: Since I had problems with noise before I wanted to add filtering on power input for "my PCB"...
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2 votes
1 answer
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Shielding AC magnetic field using cable shield connected to two grounds

I am currently reading a book about electromagnetic compatibility but I am confused about a section that talks about reducing the coupling between an external magnetic field \$ B_{ext}\$ and a circuit ...
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EMC according to IEC60335 or to IEC55014

I'm a bit confused about the IEC60335 and the IEC55014, since both seem to regulate the EMC conformity for household appliances. What I see in the IEC60335 are extremely high test values (EFT level 4, ...
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1 vote
2 answers
50 views

Brushed Motor with Wires - Where to put BEMF diode (EMI)?

I'm designing a system that drives brushed motors with PWM, where the motor and the PCB with the drive circuitry is separated by wires. Thinking about the EMI situation, would it be better to put the ...
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2 votes
1 answer
162 views

I2C versus interference

I'm going to drive a bunch of 230VAC motorized ball valves from an ESP32. I'll have several boards, each with 8 triacs driven by MOC3052 opto-triacs. This will be connected to another board with an ...
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2 votes
1 answer
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NPIC6C596 resets itself

This is a board with an ESP32, 16 relays, and other IO. I'm using two power shift registers NPIC6C596 to drive the relays... ...and here's one relay. NPIC6C596 normally runs on 5V, I used 3V3 by ...
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0 votes
1 answer
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What is a real-life situation where injected currents can impact a home appliance?

I am refreshing my study on EMC testing guidelines and I am reading a reference guide that mentions, the typical use of BCI (bulk current injection) is to inject a common-mode current into a cable or ...
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3 answers
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How exactly does the inductor in an LC filter reduce motor noise?

I'm currently working to quiet down the emissions from a stepper motor drive circuit. The motor drive frequency is 22kHz, and there is significant 60MHz noise that comes ONLY from the 36V side as ...
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1 vote
1 answer
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Does the negative voltage regulator emit noise into ground

I am designing an inverting voltage regulator using a LT3758 controller to generate -15 V from a 12 V / 5 V input. This is a non-isolated regulator. My biggest concern implementing the design is if ...
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  • 137
-1 votes
1 answer
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Why is the peak efficiency higher in Buck-Boost Controller when running below the AM band and lower above AM band?

I have seen this part LT8253/LT8253A, and it says in the datasheet that "The LT8253 can deliver up to 100W output power with 98% peak efficiency when running below the AM band. The LT8253A can ...
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