Asking for technical help

[alireza]

Dear Friends,
I have used AT73C501(ATMEL chipset solution for metering) for a power metering system.unfortunately I have faced a problem in mass production that I hope somebody here can help me to solve it.
as a matter of fact,everything was ok with the prototype and system worked without any problem.but in mass production of 50 systems,most of them doesn't work properly.

AT73C501 needs a Crystal of 3.2768MHz to operate and I noticed that the source of problem is with the Crystal. it doesn't oscilate normally but when I put probe of a osciloscope on it ,it starts oscilation and system works correctly...

Is there anybody here to direct me how to remove this problem?

I appreciate your help in advance.

 

[ted]

I had a brief look at the data sheet (doc1035.pdf).

I am not impressed about the way Atmel specifies the crystal oscillator / crystal at all. I didn't see if the crystal should be serial or parallel resonant (usually it is parallel). In case of parallel resonant crystal one needs to have defined load capacitance, which means also two small capacitors from each end of the crystal to the ground. because the internal capacitance of the chip is usually less than needed.

You should talk with Atmel and ask specifically about the crystal oscillator specification and how it looks internally. Also what kind of crystals you use have a lot to do with the thing.

Good luck

Ted