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AD7609 unused parallel outputs in serial mode

Question asked by marekm on Mar 4, 2016
Latest reply on Apr 3, 2016 by KarenNE

The AD7609 datasheet says: "When the serial interface is selected, the DB[15:9] and DB[6:0] pins should be tied to AGND."

But, I'm a bit nervous about shorting so many outputs, in case the part accidentally starts in parallel mode (say, bad solder joint on the PAR/SER pin could be read as random logic state - incorrect operation is bad too, but not as bad as damage from shorted outputs).

In an earlier prototype board design with the AD7608, I accidentally left these DB pins unconnected, and it seems to work.

Only DB[15:14] are documented as type DO/DI but not specified what they do as inputs.  The other pins are specified as type DO only.

So, I'm considering to use two pull-down resistors for DB[15:14] and leave DB[13:9] and DB[6:0] floating.  Or is this wrong?

 

Thanks,

Marek

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