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 ...

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How much electromagnetic interference/pollution is produced by home power-line network adapters?

How much electromagnetic interference/pollution is produced by home power-line network adapters? How do they compare for example to WiFi routers? They operate on high frequencies to achieve high ...
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41 views

Current-Mode Logic Explanation

I was reading about the HDMI standard and therefore the CML logic, and some alegations are not clear for me about the advantages of the CML. One of its advantages is the low output voltage swing, so ...
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41 views

LT1084 as Current control Regulator

I am using LT1084 as a current control Regulator. Circuit shown below Since the transistor Q2 is controlled by a PWM pulse so output voltage of LT1084 is varying as shown below Since it is used as ...
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80 views

EMI due diligence

I had an idea to use the World Semi WS 2801IC used for addressable led strips with a power mosfet driver so that each address can be tied to a high current (~1-1.5A) load. The chip indicates the PWM ...
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177 views

How is EMI avoided inside of an IC?

I was re-watching this video about how CPUs are made and at the time of the video the link points to, I thought "Isn't there some EMI problems with all those transistor signals flying all over the ...
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45 views

Why a ground loop a problem, not a ground plane(patch attena)?

The question is as the title says: I see various material saying using a solid ground plane. Why would not that be a problem, since a solid ground plane could be a patch antenna?
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loop area and EMI

I always hear something like "reduce the loop area" when reading materials on EMI reduction. Why we need to minimize the loop area? I have two guesses: Smaller loop area will influence less signal ...
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87 views

EMI in charge pump switching regulator

I want to use a charge pump to convert 5V to regulated 3.3V output. The charge pump I want to use has the switching frequency of 1200 kHz max. Do I need to be concerned about this switching frequency ...
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106 views

EMI suppression low frequency

I'm dealing with a PWM generator which drives a load at 12V with pretty high currents (5-10A) The PWM frequency is in the band of 100-200 Hz. Which is the best choice and right configuration of ...
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52 views

Terminating SDRAM on opposite side of board

I have a 4-layer board with the micro and sdram on opposite sides, the ram signals are short, but I still want to terminate them (I can test the board later and determine if I really need ...
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68 views

Shielding effectiveness calculation

From The Basic Principles of Shielding: Apertures, or holes, have SE. The SE of an aperture and ultimately the entire electronic enclosure is determined by the size, shape and number of the ...
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79 views

Connection between metal enclosure and 0V in industrial system?

I have been testing an industrial system. I have developed a test device to properly test this industrial system. I am currently finalizing the test device and have put it in an enclosure to EMC proof ...
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71 views

EMC Design of Aluminium Enclosures

When designing Aluminium enclosures (rack mounted units), I've previously used an Iridite NCP finish to ensure electrical conductivity between panels (i.e. no oxide). Does anyone have any papers or ...
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61 views

Should the ground plane of a noisy mezzanine card be connected to the ground plane of the main card by metal mounting hardware?

I have a mezzanine card, 60 by 40 mm, mounted near one end of a main PCB, about 160 by 40 mm. This card is a known source of EMI problems and, in fact, has a metal shield over it. But, I suspect ...
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166 views

Can smd ferrite beads be avoided [closed]

I am redesigning an input interface circuit for digital input. Its a basic signal conditioning circuit for reverse polarity protection, EMI ESD protection, and filtering voltage surges. For EMI EMC, ...
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161 views

3.3V UART over 20cm ribbon cable inside an enclosure - EMC considerations

I am currently designing a device which internally consists of two circuit boards inside a fairly large, grounded metal enclosure. I'm designing one of the boards myself, the other is a bought part ...
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1answer
163 views

Long wire PWMed LED lights

so I plan to build a house (at some point in future) and I'd like to implement some sort of home automation. Now one of the things I'd like to have is PWMed lighting. Most of the lights would be 12V ...
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201 views

PCB layout for 8-16MHz crystal very near WiFi module AND small DC motor

I'm designing an "Internet of Things" appliance where space and layout are constrained by mechanical and cost requirements. The main processor is a PIC18 and its crystal (probably 8MHz, maybe 16) is ...
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99 views

Optimal PWM Frequency for EMI & EMC

I am planning to design a 65W power supply which will use a PWM frequency of around 100kHz. I am specifically concerned about conducted EMI (not as much about radiated for now). I am currently ...
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185 views

Tying ground planes together with a non-zero Resistor

I was reviewing the schematic of a motor driver board and noticed that the digital and analog grounds are tied together with a 3.9 ohm 1/4 watt resistor. I am still trying to find the gerber files to ...
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149 views

EMC testing of unenclosed PCB assembly

What is the most common practice in performing EMC tests for PCB assemblies that will be sold without a housing? In my case it is an FPGA development board. Is it possible to design excessive ...
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1answer
200 views

eeprom data corruption during power failure

I recently found a problem with eeprom of a PIC16F877A which is used to control the speed of a dc motor. The drive is supposed to work on the last set speed even if the power fails. But the problem is ...
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44 views

How to shield from electro surgical generator in close proximity?

Looking for help EMI hardening a SERDES interface in close proximity to electro surgical instruments. I believe there may be tips or reference designs from existing pacemaker applications that may ...
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46 views

LED selection for EMI/EMC considerations

For my system, I need to select panel-mount LED indicators which needs to withstand through EMI/EMC tests. Can I use normal panel mount LEDs coming in aluminium threaded sockets for my application? Is ...
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82 views

How does spread spectrum VCXO (voltage controlled oscillator improve EMI on your board?

I have seen people adding spread spectrum voltage controlled oscillator to EMI on the board, How is EMI affected by single spectrum crystal and with spread spectrum crystal.
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70 views

Cable shield as ground conductor

I have two circuits connected by a shielded cabled. The cable brings 3.3V DC and LVDS communication between the circuits. The shield is being used as the sole conductor for the reference ground to the ...
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94 views

Signal distribution, buffers, rise times and EMC

I am designing a DSP based audio mixer. There are 4 AD/DA converters (AD1939 and AD1974) and a DSP (OMAP L138), which is on a carrier module. I am distributing the frame clock (48kHz) and the bit ...
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182 views

What's the purpose of this ground connection circuit?

I inherited a power supply circuit design from another engineer, and he used a ground connection method I am not familiar with: The input comes from an external isolated 48 V AC/DC power brick. The ...
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131 views

Return Paths of Signals on Flat Flex Cable

I have a 4 layer PCB with a typical stackup (signal-gnd-vcc-signal) and on the top layer there's a CMOS sensor connected with a flat flex cable... I was wondering, since there's no reference plane ...
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106 views

TVS Diode Array with EMI Filters on ADC Input

Is there any problem with using this SP6002 TVS Diode Array/EMI filter to protect ADC inputs on a micro-controller? The ADCs will only measure DC voltages. I am a little worried that the filters will ...
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289 views

GND plane close to LVDS differential pair?

I have two LVDS differential pairs on my PCB, running from a connector. On the connector, I have the following sequence of nets: GND LVDS+ LVDS- GND LVDS+ LVDS- GND This is as I have seen ...
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313 views

Where to connect shield and ferrites in PCB with isolated planes

I have a device which has two sections of the PCB completely isolated form each other, but connected by an isolator IC (PN: ????). I think I need to shield the whole device for reducing EMI because ...
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2answers
104 views

Understanding source of EMI

I have a device which contains a USB chip which uses 19.2MHz external oscillator. When I measured the EMI generated from the device, I got series of peaks ranging from 100MHz to 1GHz+. The peaks ...
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617 views

EMI Filtering on LVDS lines

This question is slightly related to: What's radiating on my PCB? These are Beckhoff's EtherCAT industrial IO modules. Each module is connected to its neighbours by 100mbps LVDS. Each module contains ...
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147 views

Smoothing current drawn by PWM load

I have a PWM load which draws its current from a regulated DC supply. The supply and load will be separated by some distance, and I'm worried that the rapid changes in current through the current ...
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237 views

Square Wave pulses generating EMI

Following on my unanswered question about bluetooth noise, I have now believe that I have learned a bit more about my problem. I have built a Arduino controlled circuit to replace the pots and ...
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321 views

On referencing power planes and return current paths

I recently worked on a 16-layer board design that contained only 2 ground planes, at the outer layers of the board, and several power planes (+1V1, +1V8, +3V0, +5V0) in the middle: Since there are ...
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3answers
1k views

What's radiating on my PCB?

I recently did a proper EMC test on a PCB of mine. It failed the test, and seems to be radiating in the 300MHz - 1GHz region, with peaks every 50MHz, and little peaks on the 25MHz. Looking at the ...
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173 views

Crystal Harmonics EMC Failed

I have a failed on EMC Test 300MHz and 500MHz due to crystal harmonics. There is a lot of spike with a 25MHz harmonics. The first picture is the Top of the Board and the 2nd is the 2nd layer ...
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233 views

How to debug emc problem?

First time during my entire engineering career I have been to an emc lab last week. My design has failed to satisfy FCC requirements. The board uses a 25mhz clock and we have failed at 500mhz but I ...
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2answers
3k views

How does a ferrite core wire terminator work to reduce EMC?

The following question was asked on superuser: What is that cylinder on cables? How does that cylinder work? As far as I can tell, even if you put one on either end of the cable, any HF signal should ...
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2answers
1k views

What is the best way to layout a PCB with crystal oscillators and MCU?

I have heard that the clock circuit is a noise source and that the clock circuit is also sensitive to noise. I believe that keeping the clock circuit close to the MCU and keeping other routes or ...
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1answer
717 views

How can electromagnetic interference from a USB charger cause a capacitive touchscreen to malfunction?

Electromagnetic interference from a USB charger can cause a touchscreen on a mobile device to malfunction, with symptoms such as reduced sensitivity or spurious touches. As an example, see ...
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1answer
359 views

How to create EMI?

I want to subject my product to large amounts of EMI to see what happens. I figure I need the EMI to be broad-spectrum to be sure it will have the best chance of wreaking havoc. However, I don't ...
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1answer
259 views

How to identify and remove unintentional PCB antenna?

It has been pointed out to me, more than once, that I might be making a few too many antennas unintentionally on the PCB with the copper pour, an obvious example is this L shaped pour at the edge of ...
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373 views

common mode choke inductance question

In a common mode choke, my understanding is that common mode currents will produce fluxes that add together, which increases the effective inductance between them and so attenuating these currents. ...
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1answer
501 views

Placement/routing of decoupling cap straddling oscillator guard ring on dsPIC

Changes in my design are forcing me to replace my 44-pin dsPIC33FFJ16MC304 with a 64-pin (same package size, finer pin pitch) dsPIC33FJ64MC506. In the datasheets for both chips, Microchip recommends a ...
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3answers
1k views

Is it better to have a poor top layer copper pour or no copper at all?

For a few small 2 layers boards I'm doing, I'm using the top layer for parts and signals and a ground pour on the bottom layer with no or very short traces, based on comments and answers to my ...
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134 views

Effect of radiation detectors on electronic components

After the Fukushima nuclear disaster that took place in Japan in 2011, any imports from there are checked for nuclear radiations using radiation detectors. I recently ordered components from Digikey ...
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261 views

Digital RGB interface EMI filtering

Consider the following system: where: The motherboard contains a LCD controller (SSD1963 from Solomon Systech) and other components (application processor, solenoid drivers, power supplies, etc.) ...