When using the AD9705 with the 1.25V internal reference what should be the voltage on the FS ADJ pin?
FS ADJ is the same voltage as REFIO. So if you use internal reference (1.025V not 1.25V) then FS ADJ is also about 1.025V. If you use external reference, it can go up to 1.25V.
We have been unable to see this behavior on our chip. We have tried three different chips. Two on our board, and one on a breakout. We are using the example circuit with the AD5620 shown in this circuit note. https://www.analog.com/media/en/reference-design-documentation/reference-designs/CN0156.pdf
Here is our circuit
We have been running the AD9705 in pin mode.
And R85, R86 R91-94, R96? Where do you measure Iout?
R 91-94 open
R96 is now open
We have been measuring at pin 3 of transformer usually.
Try short out R92 and put populate R91 with 100ohm.
That did it. Thanks so much!
My pleasure. Glad to help!