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AD7192 Update Rate with Multiple Channels and Filter Notches

Question asked by mroush on Feb 27, 2014
Latest reply on Mar 11, 2014 by JohnnyG

I am using the AD7192 with two bipolar differential channels from load cells.

 

With only channel 0 or 1 selected my update rate seems correct but with both channels enabled it seems too slow.

 

Mode Reg = 0x18003C (Sinc4=1, REJ60=0, FS[9:0]=0x03C (60)

That would give an update rate of 4.92Mhz / 1024 / 60 = 80 hz.

 

Config Reg = 0x000113  or 0x000213  (chan 0 or chan 1)

 

WIth only channel 0 or 1 enabled I get a rate of 80 hz which is what I expect.

 

If I set the Config Reg = 0x000313 (chan 0 and 1 both enabled) the update rate (RDY low) drops to 20 hz but at every update only one channel is available so the effective rate per channel is actually 10 hz.

 

I think the settling time of Fadc / 4 for the Sinc4 filter is why I get only a 20 hz update rate but I don't understand 10 hz per channel.

 

Can anyone tell me if my 10 hz update rate per channel is correct?

 

Also, if 10 hz per channel is correct, will that give me filter notches at 10, 20, 30, ... hz or at 20, 40, 60, ... hz?

 

Thanks.

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