ADC128D818: Internal Reference on Pin 1?

Peter Muthesius

Part Number: ADC128D818

I'm surprised that I can't measure the internal reference voltage on Pin 1. As it is recommended to put a bypass capacitor there, I expected to read the reference voltage when put a DMM on Pin 1 (VREF). But i read 0 mV. Is this normal?

Regards, Peter

over 6 years ago

0 Joseph Wu over 6 years ago

TI__Guru* 97585 points

Peter,

I believe that the VREF pin is only used as the input external reference. The pin table in the datasheet lists it only as an analog input.

If the internal reference is used, the pin is unused and should be left unconnected. In that case, the bypass capacitors are unnecessary. I did find one E2E post where we recommended that the bypass capacitors be left unpopulated so that an external reference could be wired in. This would be an option if the internal reference did not give the desired performance.

e2e.ti.com/.../629952

Joseph Wu

0 Peter Muthesius over 6 years ago in reply to Joseph Wu

Prodigy 210 points

It was the answer under e2e.ti.com/.../268075 , that made me think the internal reference will be output at VREF.

Data converters

Data converters forum

ADC128D818: Internal Reference on Pin 1?