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Connecting Vref on AD5338R

Question asked by ollie1400 on Sep 8, 2016
Latest reply on Sep 16, 2016 by ollie1400

If I want to use an external reference with the AD5338R, how should I connect this to Vref?  If I tie Vref to the desired reference voltage (5V for example), will I kill the chip?

 

My fear is that by connecting, a 5V rail straight to the Vref pin, this could cause problems since at startup the internal voltage reference generator is on, and driving Vref at 2.5V.

 

I could put some resistance between the rail (5V) and Vref (2.5V) but from experience, when the internal reference is off, the voltage at Vref is slightly less than 5V (presumably due to some leakage current? or even just current through the resistor string?).

 

What is the best way here?

 

(by the way, i understand that for 5V, I could just leave Vref disconnected and set the GAIN to x2, but I want to know another option)

 

Thanks!

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