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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336 views

Common Mode Noise filtering for Diff Mode Circuit

I have a circuit that has only two pins and there is no earth ground. However, I have to test it for BCI and design a common mode filter with diff mode. Designing diff mode filter is simple but common ...
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59 views

Near field probing technique

I am reading about the near field probing using Electric field probes and Magnetic field probes. I understand that E field probes would pickup voltage changes and the H field probes would pick up ...
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1answer
160 views

Sequencing modes for FCC “Intentional Radiator” test

I'm FCC certifying as an "intentional radiator" a product that uses a custom antenna and off the shelf Broadcom WiFi module. The module has an antenna port, so single-modular and limited single-...
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36 views

How to decide input filter specifications for linear power supply design

I am newbie trying to design a precision linear power supply and I have already chose a transformer which will meet my output requirements. Now, I am not sure how to figure out what parts should I use ...
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1answer
93 views

Could have EMI destroyed a module?

I have a device, that consists of logic controller, with some inputs, outputs, switching power supplies, relays, communication (all the usuall stuff) and an RFID module, rated for some higher powers (...
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2answers
50 views

EMC regulations versus electronics in the market

I am wondering about starting low quantity sale of some of my products, that I've developed by myself. And there is a question - what are the regulations that I have to meet? Do I need to realize ...
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2answers
657 views

Chassis grounding for multiple daisy-chained units

I'm designing a system that provides power/ethernet/serial for up to 5 daisychained units. All of the boxes will be metal and my initial plan is to run power and signal ground through the 14 pin ...
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3answers
101 views

Near field and far field EMI

I was reading this article on EMI near field vs far field. I am confused on how the Electric field and Magnetic field are separate within the near field and suddenly after a certain distance, these ...
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1answer
507 views

Emi Filter Design with Tracopower isolated power supply in railway application

I'm designing, for a railways application, the power supply circuit on a pcb board that supply 5Vdc starting from a 24Vdc(coming from a not clearly defined source, sure a 24Vdc line). I'm using the ...
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1answer
31 views

Is it allowed to place a capacitor between the LISN and the DUT using CISPR25 spec?

I am very new to the EMC world (co worker quit Friday and now its my problem) I was asked by my supervisor to check the CISPR25 spec to see if it is allowed to put a 1000 uf cap between HV+ and HV- ...
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1answer
664 views

Overloading of ESD protection diode on CAN lines through current during Bulk current injection - test

I have a design checklist question for a typical CAN circuit for an automotive application as below : The question is related to the ESD suppressor : "Was a capacitor parallel to the diode considered, ...
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2answers
216 views

What's the current leak path of the electrostatic discharge during an EMC test?

When we develop a new product we need to pass the EMC test,I really wonder what's the current path during a electrostatic discharge test. Here is the test situation: Q1: If the EUT(equipment under ...
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19 views

What is 16A TLP in ESD diode and how it determines the clamping voltage of an ESD diode?

Please explain the meaning of 16A TLP in ESD diodes? Is the clamping voltage determined at 16A transient current flowing through diode? Please see the table in the below picture:
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38 views

Y capacitors in surge suppressor in a TN-C-S system

"Surge Protectors", "power strip", etc. I noticed many of them have Y caps (line-earth/neutral-earth) usually 102 or 222M Y safety caps to filter line and earth neutral and earth ...
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40 views

Use of common choke with more than 2 wires

I've been looking around and I couldn't really get a good answer to this question, not even in Henry Ott's book (so far), so here it goes: What is the best approach when there is the need to place a ...
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1answer
34 views

Data sheet clarification for JTD1524S12

I am trying to design a PCB for JTD1524S12 DC-DC converter. I was going through the datasheet and on page 3 the following tables are provided: I got the idea that these tables are related to EMC. On ...
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41 views

Antenna connector near a shielded inductor

Is it a bad idea to put a U.FL connector near a shielded inductor? The connector is for 2.4GHz Wifi signal, the inductor is connected to the output of a buck converter with 700 kHz switching frequency....
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1answer
686 views

Use of internal PCB ground plane as ESD baseplate/EMC reference plane of product in plastic enclosure

I am designing an electronic product which will be housed in a plastic (non-conductive) enclosure. There are a number of, mostly shielded, I/O cables (Copper 10/100/1000Mb/s Ethernet, USB 2.0, RS232, ...
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48 views

Picking up EMI when measuring NTC near laser causing board reset

I tried searching for this to no avail. I hope I'm not all too wrong asking it here. I have set up my 60W CO2 Laser with a SKR 1.4 Turbo board and connected a 10k NTC thermistor to measure the ...
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1answer
38 views

EMI input filter for low frequency heater controller [duplicate]

A meanwell 24V, 280W AC-DC power adapter is used to supply a PWM-driven heater control circuit. The power adapter is fully enclosed and protected (model GST280A24). The load is a pure resistive ...
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4answers
160 views

What could be generating this waveform in an EMC Compliance test?

We are having trouble with a CISPR-11 (EN55011) Radiated Emissions Class B compliance test in one of our solutions. The troubling part of it is basically an industrial motherboard (with a commercial ...
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1answer
478 views

EMI/Y-capacitor in inverter phase outputs?

Is it good or even used practice to filter out common-mode EMI in 3-phase industrial inverter (IGBT) phase outputs using phase-to-earth Y-capacitors? High du/dt might limit the lifetime of such ...
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1answer
422 views

Basics of board level shielding and grounding

I have been designing MCU based PCB that must be withstand hard EMI tests. This PCB includes ethernet transceivers, can transceivers, rs485 transceivers, II2 chips, 25MHZ oscillators, optoisolators ...
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45 views

Gigabit Ethernet: capacitor isolation (1st device) - transformer isoaltion (2nd device) will it work?

I am designing an adapter board for a camera which is an original device with Gigabit Ethernet interface. The previous version of the adapter board was using LAN7500 and transformer as a USB dongle ...
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1answer
52 views

EMI and reliability considerations for low-frequency, low-voltage DC load drive

In my application I need to drive a 240W pure-resistive load with a nominal voltage of 24V. The input is a standard 280W AC-DC external power adapter, the Meanwell GST280A24. The load switch is ...
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1answer
36 views

EMI voltage ripple issue for low side NFET

Under some user suggestion, I decided to drive my 10-ohm load heater using a low side NFET. I put a 1k resistor (R1) at the NFET gate to reduce ringing. I got, before placing the resistor, a very bad ...
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2k views

Spikes induced on PCB. EMC problem?

I designed the following PCB, where after testing a faced a severe (EMC related?) problem. This board houses an STM32F103 developing board. On the right of the PCB, there are 6 thermistors connected ...
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24 views

Industry Standard Horn/buzzer/bell EMC/EMI Problem

I'm recently having the pleasure of integrating a horn to my product. The industry standard for most products seem to be horns like this, functioning exactly like an electric Bell, but with a ...
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37 views

What is the impact of using high X caps values on EMI filters in a DC DC converter?

I am working with traditional single stage EMI filter. I see CE EMI test passing with a high X cap values of 6.8 uF. This is used in DC DC converter with 8 kW power out at 400 V DC. I see no issue ...
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1answer
340 views

Impedance mismatch in LISN for EMI/EMC test

I am currently designing LISN for CE-102 test.The schematic of the circuit is provided below. When I connect the circuit to the network analyzer the impedance is coming as shown below expected graph ...
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2answers
343 views

ESD/EMI Design for CE, Recommendation seems wrong from test lab

I have designed a product for a customer, that now needs to pass UL/FCC/CE Testing, It passed UL & FCC but failed CE for both 8kv ESD and EMI. The Chinese test lab my client went through sent me ...
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227 views

Placement of RC filter used for slew rate limiting (for EMC)

I've seen RC combinations used on many circuits now which i believe have been included for slew rate limiting. They usually feed off to a connector. Do the placement of these matter in the circuit? ...
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2answers
60 views

Power path around 4 layer PCB

I'm designing a 4 layer PCB (Signal-GND-PWR-Signal) that has power input and motor connectors placed as seen in the picture. In order to avoid thick traces I traced a power path around the PCB ...
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1answer
266 views

MicroSD with STM32 and SPI mode - pull-ups and EMI filters

In the context of using the STM32F103C8T6 microcontroller I wonder I am thinking about the most practical and relevant method of the microsd application in the device from the point of device security....
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28 views

Differential Mode EMI Filter Position

In the AC input power supplies; input EMI filters(common + differential) are connected between mains and the rectifier. In some low power power supplies; only differential mode filter is used and this ...
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1answer
52 views

Understanding RF spectrum of SMPS power supply

I have a (third-party) device that has failed EMI testing, and have been asked to investigate the cause and fix the issues. The device is an automobile accessory, and has 12 V DC power input. ...
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1answer
73 views

Should I put fuse before safety capacitor or after, when designing an unregulated power supply?

I am designing an unregulated power supply to power a few linear voltage regulators, as shown in the image. The power supply will use a 230vac to 9vac 2 coil step down transformer. Since the power ...
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32 views

Does active power factor correction help with internal radiated/conducted noise?

I am choosing parts for the supply of a device. The case will be a metal chassis and there will be an AC-DC (12 V) converter module inside mounted on the chassis. The total AC power draw will be less ...
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2answers
91 views

EMI concern about the length of return traces

I have many IR leds to drive, with MOSFETs and a single constant 60 mA low side current regulator. The leds are PWM at 1 MHz (50% duty cycle), and the farthest leds are 60 cm away from the regulator. ...
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878 views

The Pin 1 Problem in Audio, Star and Mesh Ground, and Contradictory Grouding Practices in Audio and Digital Systems

I recently came across the concept of "Pin 1 Problem" known in the pro-audio electronics. It seems straightforward at first, but becomes confusing when it comes to grounding. Let me describe ...
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210 views

Placement of damping resistors, closer to driver or load?

I'm connecting an FPGA and MCU and currently optimizing the placement. Does it matter if it's randomly placed? Should I place it like a series terminating resistor and strictly place it close to the ...
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3answers
62 views

EMI consideration for Microwave Sensor Module

I'm using Microwave Solutions MDU1720 datasheet with recommendation that The length of leads connecting the MDU to the signal processing circuitry must be minimised, to reduce pick up of ...
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2answers
227 views

EMC CISPR 14 conducted emissions terminals

I'm trying to improve my understanding of the CISPR 14.1 EMC test procedures and requirements, with a view to performing precompliance testing. In particular, I'm looking at conducted emissions ...
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124 views

ESD protection for ESP32 GPIOs

I want some of the ESP32's GPIOs to be accessible via 3.5mm headphone jacks or RJ11 jacks and therefore need suitable ESD protection. I wonder how much is needed for optimal protection. Conditions/...
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82 views

Placement of components on PCB

I have a four layered PCB with two major high frequency component placed on the top layer. One is JN5169 and other is SE2431l (front end module), both operate in GHz. While evaluating the circuit (...
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67 views

Layout of multichannel 20-bit DACs

I've been reading various app notes as well as Ott trying to figure out how to lay out multiple converters on a board. Most explain how to route the data lines but not much about routing the power ...
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46 views

Electromagnetic Interference

I am designing an SMPS with flyback topology. The PWM IC is viper. I have a doubt that should I place the IC at the bottom side of PCB or both the transformer and the IC on the same side(top side) in ...
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55 views

How to determine which type of coupling is this?

A new model sports car had a disconcerting problem: occasionally the dashboard lights would all illuminate simultaneously. Two services call later, replacement of a wire harness for the spark plugs ...
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2answers
333 views

2 vs 4 PCB layers

I have a 2 PCB layer. Bottom and Top layer are used for signals and power and the remaining area is copper ground. I read about EMI etc and I decided to go to 4 layers for reduced EMI. I realized now ...
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104 views

Why does crosstalk occur in high speed design only?

I am studying to get a job in EMC and my exams are coming soon. I am currently studying "high speed design" techniques, and I stumbled upon this thing called "crosstalk." I know ...

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