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AD9984A abnorminal operation

Question asked by masaki on Sep 25, 2013
Latest reply on Oct 7, 2013 by raymondcarter

Hello we made 80 sets of trial PCB  for video suitcher.The PCB has 4ch analog video inputs using a couple of AD9984A.  However some of the PCB shows abnorminal operation on I2C operation. A micro-controller read/write data from/to AD9984A through same I2C line. To make different I2C address for the AD9984As,  we put external 10k ohm pull-up resistor ( to Vdd ) on VSOUT/A0 line of one AD9984A. And we don't put any pull-up nor pull-down resistor on  VSOUT/A0 line of another AD9984A. Now we try to put external pull-down resistor ( to GND ) on the VSOUT/A0 line of another AD9984A. So I need advise as followings;

 

(1)  Is it appropriate measure to put pull-down resistor on VSOUT/A0 line of another AD9984A to make " A0 = 0" address ?

(2)  If (1) is appropriate, how much resistor should we put ?  1k ohm, 10k ohm  or other ohm ?

(3)  When does AD9984A read data on  VSOUT/A0 for setting I2C address ?  After Vdd power-up or later ? We want to know precise timing !

 

Regards

Masaki 

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