AD8235ACBZ-EVALZ No Vout despite apparent proper setup

Hi stuartsjg ,

Good day. Can you share an image of your setup? I want to check the state of the other switches and jumper connections. Thanks.

Regards,
Gilbeys

Hello,

Images below.   I believe from reading the IA data sheet, with zero V input i should get the offset voltage out.   I wonder if there's a fault with the board as if i press on the IA with an insulated tool, the output voltage rises to the +VS.   I could try reheating with hot air gun?

https://pasteboard.co/5IIPgcizGGm4.jpg

https://pasteboard.co/rMJ6oKFdgY4V.jpg

Thanks,Stuart

I posted a reply, but dont see it.  Ill try again, apologies for the duplicate if it does come through.

Test setup as below, i had expected to see the offset voltage at the output with zero V input.   I do notice if i press on the IA with an insulated tool then the output goes to +Vs so perhaps the board is faulty, i could reflow with hot air.

pasteboard<dot>co / 5IIPgcizGGm4.jpg

pasteboard<dot>co / rMJ6oKFdgY4V.jpg

(ill try without hyperlinks in the event the forum doesn't like links.

Thanks,

Stuart

Hi stuartsjg ,

Good day. From your images, the inputs seemed floating, making your amplifier operate outside the linear region. Can you evaluate by connecting the inputs to the ground? Also, can you measure the reference voltage? I agree with you, you can reflow with hot air. Thank you.

Regards,

Gilbeys

Hi,

I have tried with the input connected to Fluke mV calibrator voltage sources with both -IN grounded and un grounded.  Also both +IN and -IN to ground and the output is always 0V, i never see an output.

Vref = 1.585V

I have applied hot air and flux to try to reflow the device but this has not changed anything.

Ill return the development board to the vendor and seek a replacement as its so simple i can only assume there is a defect.

Thanks,

Stuart

Hi stuartsjg ,

Good day. Operating the part on a grounded input limits its operation outside the operating region of the diamond plot tool.

Hence an output of 0 is expected under normal operation. I would recommend adding an input within the operating region to check the functionality of the part. Hope this helps. Thanks.

Regards,
Gilbeys