Crosstalk, EMI AND EMC

Homework?

martin

Intelligent Design.

Keep what thin? The copper? Tell your PCB manufacturer.

That depends on the customer's specification.

Practice, practice, practice.

Tell the pointy-haired boss he's an idiot, that's impossible; you have to start from scratch.

Observe the 10% amplitude point, and the 90% amplitude point, and measure the time between them.

Good design practices.

He needs to know exactly what you want done.

Good Luck! Rich

Hi, I have follwing questions

1. What are the best ways to minimize crosstalk, EMI and EMC in digital and analog circuits from printed circuit board's view point?

I read that the trace height above the ground planes paly very important role in minimizing crosstalk. The formula, crosstalk = k / (1+ (d/h)^2 ), where d is the distance between the conductors and h is the height above the ground plane. K is coefficient of coupling . What can I do to keep it thin? Any comments!

1. What is the allowable or okay value of cross talk, EMI and EMC in circuits?

1. How can I measure crosstalk , EMI and EMC ?

2. I have a diffeerential amplifier with a CMRR of 90db, I need to increase the CMRR upto 120db. What would be the better solution?

1. What is the method to calculate the rise time of the signal before designing the printed circuit board?

2. How can I keep the inductance and impedance of solid plane ( power or ground) as minimum as possible? what specifications or data the manufacturer needs, if I want to design the planes with control impedance and inductance?

Please advice!

Thanks John

Hi,

Its not a home work. I am trying to develope some steps that I can always use to design the printed circuit board.

John

martin

Hi,

If you do not like the questions or do not want to answer them then do not bother to post anything. Let somebody else answer it. your childish behaviour is discouraging other people to answer these questions. These questions might help me or somebody else who do not about these things in details. you never know. please be ethical and patient.

John

Specify the dielectric thickness to the PCB manufacturer. Won't help much if it's a 2-layer board though. There are a lot of formulae around, but beware of taking them too literally; sometimes they are conveniences for 'works most of the time'.

Depends on the circuit.

With appropriate test equipment. Each here has different test requirements.

Get a different amp.

The rise time of a signal is usually 10%-90% (but beware - in certain signalling specs it's 20% to 80%). Fall time measured from 90[80] to

If you're asking 'Can I know the rise and fall times on a PCB before I commit to fabrication'? then the answer is 'To a close appoximation, yes, with the right tools after layout'. if it's '...before I do the layout' then the answer is 'to a not so close approximation'.

The first part of the question seems rather basic and affects most electronic circuitry.

For controlled impedances, tell the manufacturer what you need; they'll tell you what track thicknesses to use with the stack they define to achieve the controlled layers. There are tools available to calculate such things, should you desire to do so.

You seem to be asking for the knowledge of decades, and the answer to that is you'll spend decades getting that knowledge, providing you are working with these issues all that time. Indeed, most here have been active for 3, 4 or even 5 decades in this field (perhaps more) and are still learning ;)

I also suggest reading some texts on these subjects and perhaps transmission lines. Google is your friend.

Cheers

PeteS

Very large scope of question...lots for you to study. I suggest authors like Howard Johnson, Jim Williams, Mark Montrose, Bob Pease. Re the desired CMRR: very difficult to achieve, although can be done with properly designed transformers. Paul Mathews