Choosing a microcontroller with good immunity to emi or noise

It is not the micro it is the design and implementation. Both micros can do well in high noise.

All suppliers claim to be good in this aspect :)

Smaller packages will be better than larger ones, and the less you need to attach, the better.

We have found the SiLabs C8051F series to be good, because they are small, and the on chip osc removes the Xtal Pickup nodes.

but it all depends on what you mean by "high emi noise environments", and what freqencies/energies this thing has to tolerate, as well as what happens if it fails to tolerate them ....

-jg

Thank you for your quick input.

My application is a switching power supply 230vac/48vdc,1.5kw the controller would be monitoring the voltages,currents etc. and mounted on the same pcb i.e smps pcb.

if the processor gets affected due to noise it may say some thing out of limit and may switch things off. or show false alarms or fail to show the right alarms.

this processor may in future participate in controlling the pwm .

I hope now my application segement is clear.

on the package part yes I like to use smaller package now. but beyond the circuit desing and system design aspects if anybody wants to throw some light on the inherent immunity of the cpu itself that is welcome. I will study the 8051F as per ur suggestion Thank you Narender

Jim Granville wrote:

Look for chips that say they have good electromagnetic noise immunity, and also consider looking for chips that target motor control, or automotive applications because they tend to be a nasty noise environments similar to that of a switching power supply.

I'd also avoid chips that use less than 5 volts because the lower Vcc takes away from noise immunity.

A lot of companies have app notes similar to this one:

This app note discusses tips for using a cheap 8 bit hc08 MCU in this kind of application:

Eric

I second this comment, especially with regards to the importance of proper implementation. Your power and ground system desgin will go a very long ways towards determining if you have noise (EMI) troubles or not. You can use the best micro in the world with regards to being the least noise sensitive and it will still be worthless if not applied correctly.

Another thing to consider regarding the design in its entirety, is that factors that make your design radiate less also tend to make it less susceptible to interference. This is especially important for swithing power supplies.

Take a look at the Renesas M16C / M8C familly of controllers. These are designed for automotive control, can do PWM, are easy to work with, and very good with regard to EMI.

HTH

Markus

Schematic and PCB design is much more important than the particular MCU type.

Interesting claim - I've never shipped a schematic inside the box with the PCB :)

Bad layout can make any good uC fail, but it is much harder to compensate for a poor uC, with 'good' PCB design.

The best solution is a good uC and good layout.

-jg

You should try it once in a while. Your customer might be happy to find it. :-P

On the other side good layout can not compensate for the bad circuit design.

WBR, Yuriy.

Not impossible, but it would be much easier to separate the micro and smps pcbs. You can control the spacings and shieldings better. By the way, we just did a 12V to 18V smps together with a 1.8V to 5V micro.

The danger is that if the micro crash, it could burn everything up.

A good chip in a bad package can also be a problem, think about a

40/64 bin DIL package with power supply pins in the corners :-). There is no way of doing a proper layout, since you have no control over the last few centimeters of each track inside the package, thus, getting a decent power supply decoupling is very hard and at higher frequencies, these tracks are a significant part of a wavelength, implemented as badly matched radiating lines.

Paul

Years ago, before the lawyers got involved. schematics were provided with electronic devices. I have old radios with the schematics pasted inside. Same with tape recorders and audio amps. It made it possible for a technician to repair a failure. Jeesh, nowadays, you just throw it out and buy a new one. I don't!

Al

It is very well understood that weakness of each stage has to be dealt with within that stage instead of trying to compensate in an another stage

like microcontroller as component should be inherently more immun compared to the general purpose controller ,this care I think we shoul take right at the begining of a system design which is prone to thi problem.

the schematic/system design should take into account like isolatio casing filter caps etc

the layout should be immune like, should not radiate or should not picku , multi layer with gnd plane ,location of filer caps the routing o sensitive signals etc

But Here the question is very specific to the component selection onl please.

I would like to hear from any component manufacturer if they can quote the figures or comparison results of their component vs other genera purpose components in terms of field strength under which their controlle works well and the spikes it can tolerate on the pins etc.

designers are also welcome but please restrict the discussion to the component selection only.