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Questions tagged [common-mode-choke]

A type of choke in which two coils are wound on a single core in order to pass differential currents while blocking common mode currents.

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Common-mode choke in ECG circuit

I'm designing a PCB for single lead ECG measurement and I ran across this TI reference design that contains a common-mode choke (P/N Murata DLW31SN900SQ2L). What's strange is that I can't find any ...
Adam Jones's user avatar
2 votes
1 answer
112 views

What is this SMD common mode choke?

A pair of components was accidentally destroyed on my Korg Volca Modular synth: Through the magic of getting another identical synth, I was able to see how it is supposed to be on a working unit: ...
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Common mode choke rated current

I have ordered a common mode choke (https://product.tdk.com/system/files/dam/doc/product/emc/emc/cmf_cmc/data_sheet/30/db/ind_2008/b82721s0.pdf) to reduce the common mode noise available on the 5V DC ...
Alex Mixich's user avatar
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Are common mode chokes really needed for Conducted Emission standards when there are only two terminals?

Common mode chokes make sense for power inputs when there are three terminals: power line, power return line and an "earth ground". You measure the noise of power line with reference to ...
aaroniero's user avatar
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How to create schematic of common mode choke that reflect on Common mode, differential mode and mixed mode? [closed]

I aim to create a schematic that can replicate the results exactly as seen in the measured S4P file. I have conducted the measurement using a VNA and am attempting the schematic simulation in CST. ...
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Can a common mode choke be used to filter a SMPS dual power supply?

I have a switched mode dual power supply with +12V, GND and -12V outputs. I'm seeing a lot of high frequency noise on the output of this power supply that I'd like to attempt to filter out. The noise ...
Jordan Melo's user avatar
2 votes
3 answers
366 views

Current Rating in Common Mode Choke

What is the meaning of this current rating which says "unbalanced" current? I know in common mode chokes the common mode current rating is given. Why here it is written as Iunbal.?
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How can I select a common mode choke for DC/DC power conversion stages

I want to attenuate 15 MHz noise signal using a common mode choke at 5 V power lines stage of a circuit that generate digital signals with less than 100Mhz. When you use a common mode choke for a ...
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How are SPICE files created compared to S4P files generated from a VNA?

When measuring impedance versus frequency using the same data in both SPICE and S4P formats, why do I obtain different results? COMMON MODE IMPEDANCE Common mode impedance 10514 Ohm at 79.1 MHz S4P ...
Alaska's user avatar
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LTspice parameters

I want to know how the .mod/.lib files in Ltspice are created by manufacturers. Let's say we have a Common Mode Choke (CMC). It will have some parameters as per its equivalent model at different freq ...
Andr7's user avatar
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Challenges in Bandwidth in Common mode Choke Modeling

I'm currently working on characterizing a common mode choke (CMC). However, I'm encountering difficulties aligning the bandwidth of my model with the measured results. Specifically, when I attempt to ...
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Why is a bandwidth discrepancy occurring despite consistent Q factors in the given Graph?

I was trying to do curve fitting the common-mode choke in CST Studio according to the selected S4P file from TDK (ACT1210G-800-2P-TL05). However, the common-mode impedance measured from the file does ...
Alaska's user avatar
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Why my Common mode choke with 2 turns showing multiple Peaks in the graph?

I analyzed the CMC choke by Wurth Electronics (part no: 744830039080) using VNA and obtained the insertion loss for both common mode and differential mode. The graphs match with the datasheet: While ...
Alaska's user avatar
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Why is the core resistance modeled as 2*Rp and capacitance as Cp/2 in a common-mode choke?

I directed my attention to a paper regarding the modeling of common-mode chokes. Within this paper, the authors structured the circuit in such a manner that they designated the core resistance (...
Alaska's user avatar
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Choke Placement for POE top or bottom?

a colleague designed the pcb and I wanted to remove the bottom components and place them on top so that we may attach a flex pcb to the back side. Attached is an image of the L3 choke, is there a ...
Wes Ellgass's user avatar
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Is Noise filter needed for CAN passthrough?

The structure is simply diagrammed as follow. My Board provides only routing connecting each connector for other ECUs using CAN channel. My queistion is if i need additional CMCs on the routing. Are ...
min_c's user avatar
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Multiple resonance frequencies of common-mode choke

In the datasheet of the CMC (common-mode choke) below (Würth Elektronik 744830017132), the impendence vs frequency graph has multiple peaks (resonances) which I marked. The first one is the Self ...
Andr7's user avatar
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Common mode choke placement for good EMC performance

I am interfacing a deserializer with Quectels smart module. The CSI lines of the deserializer are connected to the CSI lines of smart module. A common mode choke is placed in between them. The ...
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Common-Mode or Differential-Mode Choke Circuit

This circuit, located at the entrance of our power circuits in the products produced in the company I work for, caught my attention. The design of the circuit was completed a long time ago, and now ...
Nafi Can Ereli's user avatar
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Sizing a Common Mode Choke - Inrush or Normal Current

I am looking to use an LS05-13B05R3 in a design, and am looking at a choke such as the RN114-0.3-02-47M. Is this suitable given the lower current requirement of the LS05, or should I size it for the ...
Jeff's user avatar
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Equivalent circuit of CM and DM EMI filter

This is the diagram of an EMI filter consisting of both CM and DM filters: This is the equivalent circuit of the CM filter: Could someone explain why in the equivalent circuit, it's Lcm and not 2Lcm?...
ORion's user avatar
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Common mode choke on internal cable to pass EMC testing

I am undecided whether or not to add a common mode choke in my product that needs to undergo EMC testing for CE marking. Let me describe my case... My device is split into 2 parts, connected with each ...
mdir's user avatar
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Is this component correctly used?

So, There is this schematic that a previous collegue made for a project that I took over that have some EMC problems (Burst/EFT). The problem is that 12V on the secondary side of the transformer(not ...
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inductance for choke inductor EMI filter

How do you select the choke inductance for an EMI filter? I'm trying to design an EMI filter for a primary side of a transformed which takes 230VAC and steps it down to 24VAC at maximum of 600VA (~3A ...
KMN's user avatar
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Common mode choke impedance selection USB 2.0 Data line [duplicate]

Below schematic shows a USB connection diagram.IN this you can see a common mode choke (DLW21HN900SQ2L) The common mode choke impedance is given as 90 Ohms @ 100 MHz .The USB is working at 480Mbps. I ...
Confused's user avatar
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Saturation current of Common Mode Choke

I am currently designing a driver for a brushed DC-Motor. The motor is driven by a full bridge (PWM) that switches at about 20kHz. For our application, it is required to increase the inductance of the ...
Mau5's user avatar
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Surge suppresor design - DM, CM chokes and resistor is series with varistor

While designing a surge suppressor, I came up with an online schematic where they use a differential mode choke and a common mode choke. I put one toroid choke coil as the differential mode choke. ...
15 Volts's user avatar
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2 votes
1 answer
176 views

How to choose a common-mode choke for DisplayPort 1.4?

I'm trying to pick a CMC for a DisplayPort 1.4 interface which I'm going to impalement in my design. I came across this LCFE121002A900TG CMC which I found at Mouser (let's say I'm interested in the ...
Firas Abd El Gani's user avatar
7 votes
1 answer
744 views

How to check the polarity of a common-mode choke?

I purchased some common-mode chokes and the documentation provided states: As this pinout does not correspond to other chokes of the same format, I have doubts about the position of the dots (pins 1 ...
Nikita's user avatar
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Why are there two common-mode chokes on AC input?

This is a part of an AC/DC converter schematic from TI. There are two common-mode chokes on the AC input side. I have no idea why two CMCs (L100, L101) are used. Could anyone explain this?
sangrae lee's user avatar
0 votes
2 answers
394 views

Common mode choke - short?

I am experiencing weird behavior with a common mode choke and had a few questions. The circuit in question is this: I am using a desktop power supply at 28V and 200mA current. This is the first time ...
jgauthier's user avatar
3 votes
1 answer
111 views

Measuring / estimating unknown common mode choke and transformer

Out of curiosity and to improve my reverse-engineering skills, I'm currently reverse engineering a rather simple 12V switch-mode power supply adapter. Most of the markings and the topologies are fine, ...
polemon's user avatar
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What is the exact type of this common mode choke?

I have this(on the picture) element missing from my PCB but I cannot find the exact model and specification. The text on it says G8276D3. Can somebody recognize it?
InTERpLAY's user avatar
4 votes
1 answer
812 views

ESD protection only with a common mode choke

In general, for a successful CAN/CAN FD communication one needs protection against ESD pulses and common mode noise. Most of the time the protections are made by TVS diodes and common mode choke (see ...
THz_Tim's user avatar
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3 votes
1 answer
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USB-C pulldown resistors before or after common-mode choke?

I'm designing a board with a USB-C upstream-facing port (UFP) for power only (no data). I've included a common-mode choke, as well as a ferrite bead filter in pi configuration. Since I'm presenting as ...
TypeIA's user avatar
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Isolation voltage of common mode choke, if used as coupled inductor?

I have a project where I need a small coupled inductor for isolated low baudrate communication. The line is short and I don't really care if only half of signal goes through. I need it really cheap, ...
elektrinis's user avatar
2 votes
1 answer
377 views

Signal reference with common-mode filter on the power lines

What is the recommended way to handle the following situation regarding the control signals? Since the ground is separated with a common-mode choke between the source and the destination I'm thinking ...
perla's user avatar
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2 votes
1 answer
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10 dBuV EMI noise suppression from 0.8 to 1.8 MHz

The 30 V 500 mA power supply I'm working on needs to pass the EMC (EN55015) test. I am attaching the necessary circuit diagram (common mode and differential mode filters) to pass the test according to ...
Mehmet ABUS's user avatar
1 vote
1 answer
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Paralleling common mode chokes

Regular chokes can certainly be used in parallel so that multiple smaller chokes with a lower current rating can be used. But does this also work for common mode chokes? I would assume that ...
Lars Hankeln's user avatar
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Common Mode Choke Usage

I am using a ACM70V-701-2PL-TL00 Datasheet to attempt to filter out A/C ripple in an in-vehicle audio device. I've run the input 12v through one channel of the ...
t3ddftw's user avatar
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2 votes
1 answer
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Common mode choke - Why only impedance?

Why are most common mode chokes only given with a impedance curve, inductance at a specific frequency and current rating (this is clear😅). Wouldn't be S-parameter better? I know it's more work, but ...
R098's user avatar
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Common mode choke - alternative part

I have sent out a PCB for manufacture and the manufacturer has suggested an alternative part. The application is a mains powered (220V AC 50Hz) device. The common mode choke is being used to filter ...
jhorwood28's user avatar
3 votes
1 answer
389 views

Can CM choke windings be used for LC filter at the output of SMPS or DC-DC Converter?

I need to filter out switching noise at the output of SMPS/DC-DC converter with an LC filter. I have a bunch of CM chokes lying around. Can I use a common-mode choke: with both CM windings connected ...
Platypus's user avatar
2 votes
1 answer
1k views

How to choose a common mode choke for ethernet?

I'm currently working on a design which contains gigabit ethernet. Due to some weird size constraints, I can't use a magjack or one of those transformer ICs, so I'm using discrete magnetics. I've ...
Harry Brooke's user avatar
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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 ...
Felipe Schneider's user avatar
0 votes
3 answers
139 views

DC-DC fixed voltage output converter and EMI Design, where to begin and roadmap?

I'm in a group of people tasked to design and implement a DC-DC converter with an output voltage of 24 volts, with an input voltage from 9 to 36V, with an EMI filter, which must comply with the ...
Burak Can Koca's user avatar
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1 answer
995 views

Common-mode choke on LTSpice

Can someone suggest to me how to select a three-phase common-mode choke with self and mutual inductance in LTSpice?
Ady's user avatar
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Isolated BNC connector in metal chassis, EMC considerations

I consider using an isolated BNC connector for a precision application, in which the BNC Shell will be either grounded via an internal switch or used as a Guard electrode. The motivation behind this ...
tobalt's user avatar
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4 votes
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Why are common mode chokes with 90 ohm @ 100 MHz recommended for USB 2.0 Hi-Speed data lines?

When one looks at common mode chokes for USB 2.0 applications choke manufacturers always recommend CMC with a common mode impedance of 90 ohms @ 100 MHz. Example How does this relate to USB 2.0 ...
CatastrophicFailure's user avatar
1 vote
2 answers
543 views

How to choose DC resistance parameter of a USB 2.0 common mode choke?

How do i know whether i have to choose a bigger sized common mode choke with lower DC resistance for USB 2.0 D+/D- lines or using a smaller one with higher DC resistance is also just ok? In fact there ...
CatastrophicFailure's user avatar