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AD7988 digital output status when VREF/VDD powered down

Question asked by swenner on Sep 27, 2017
Latest reply on Dec 1, 2017 by Gnib

Good morning!  I am using two AD7988-5 parts in a chain mode as seen in datasheet figure 38.  VREF and VDD (pins 1 and 2) are connected to a 2.5V source that is turned on when data collections are required otherwise it is 0V (low duty cycle every minute).  VDDIO (pin 10) is connected 3.3V source that is always powered.  I have a 100 kohm pullup on the Conversion pin 6 to VDDIO and a 100 kohm pulldown on the Sck pin 8.

 

My question is this....I am trying to have NO power consumed at all until I turn the 2.5V (VREF/VDD) power on.  Since VDDIO is always powered are SDO and SCK driven as totem pole outputs such that they never float?

 

Thanks

Steve

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