PMODDA4 limited to 2.5 V

[jocker84]

Hi 

I have a PMODDA4 which works fine. However the maximum output voltage seems to be only 2.5 V instead of 5 V. It seems as if it does not have an internal reference of 2.5 V instead but rather 1.25 V. I checked also with the reference manual of the AD5628-1 which is soldered on the PMOD and this seems to be consistent. Is this correct?

Thanks

Johannes

[jpeyron]

Hi Johannes,

In the reference manual under section 2. Interfacing with the Pmod it says that users should note that the PmodDA4 by default attempts to use an external reference voltage. However, as there is no external reference voltage provided on the Pmod, users must write to the register to program the chip to use its internal reference voltage of 2.5V. The diagram is in the reference manual here. Hope this helps.

cheers,

Jon

[jocker84]

Hi Jon,

thanks for your answer. If I don't switch on the internal reference voltage, there is no output at all. However, my problem is that the output is limited to 2.5 V because the internal reference voltage seems to be only 1.25 V instead of 2.5 V. The reference manual of the DAC family describes two different DACs i.e. AD5628-1 with internal reference voltage of 1.25 and AD5628-2 with reference voltage 2.5 V.

If you look at the picture of the PmodDA4 the description says  AD5628-1 with an internal reference voltage of 1.25 V and gain 2. Hence the maximum output voltage is limited to 2.5 V. This is what I see electrically.

 

Thanks

Johannes

[Bianca]

@jocker84

Hi Johannes,

I'm really sorry for this trouble. Indeed you are right. The module is equipped with AD5628-1 and has an internal reference voltage of 1.25 with gain 2. You won't be able to get out 5V. The reference manual is wrong and we're really sorry. I will modify the web version later today and ask someone to edit the PDF version.

Best regards,

Bianca