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Problem with ADuM6401

Question asked by Zloun on Nov 11, 2011
Latest reply on Nov 21, 2011 by MSCantrell

Hello!

 

I have a problem with ADuM6401. I use this part for isolation AD7793. I have it on SPI bus with other parts (LCD, EEPROM, another AD7793 (non-isolated), DAC).


And now about my problem. When ADuM6401 is connected to bus, there is a problem with MISO wire. Sometimes data goes, sometimes not, and it is for all parts, which use MISO wire (EEPROM, non-isolated AD7793), other parts (LCD,...) which don't use MISO wire are OK. I looked at this by osciloscope and sometimes there is indeterminate state (not zero, not 3.3V).

 

I tried slow down communication speed, but the problem is still there. Than I tried connect two AD7793 on breadboard, one was isolated and the another wasn't. The problem was still there, but when i set right input filter for DC/DC converter, the problem was gone.
But when I get it back on the PCB with other parts, the problem is still there, and I have input filter, which is described in datasheet. I tried change its parametrs, but no change on result.
I use AVR MCU.

 

Do you have any ideas?

 

Thanks for your answers. 
And sorry for my english.

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