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Three AD7997 on the same I2C bus

Question asked by giuseka on Jul 28, 2011
Latest reply on Aug 10, 2011 by JakubS

Dear forum,

 

I already used in the past two AD7997-1 on the same bus, connecting the AS pin to Vdd and GND.

 

Now I have to design a modular system composed by three identical boards (so I can't use AD7997-0 and AD7997-1). On each board I have to use one AD7997. The same flat cable will connect those boards together and to the controller board.

 

I know I can use up to three AD7997-1 on the same I2C bus, with AS to Vdd, Gnd and float. I think the best solution is to provide the board with an address selection jumper bank. On the bus, I have to set a different address on each board, moving the jumper.

 

What about leaving AD pin floating? Should I expect it will work without problems? I have read to avoid extra big capacitance on AS pin, but what about RF noise? Could it be better to place a network resistors (47k/47k) to set AS pin to a midpoint voltage?

 

Thank you for any help...

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