1764 ADC reference voltage

[lpcware]

Content originally posted in LPCWare by samc on Sat Jul 10 15:09:53 MST 2010
Hi,

Id like to do Li-charging with the LPC1764 (surely it iwll do other things mainly :D)

So I need a precise reference for the ADC; my 3.3V is not very accurate, is form a DCDC.

It would be cheapest to connect a TL431 (2.500V) to the VREFP pin, but I am not too sure it this is allowed or not. The manual mentions it _should_ be equal to VDDA...

Does anybody know more about this issue?

Thanks,
Simon

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Sun Jul 11 05:58:38 MST 2010
My manual (lpc1764.lpc1765.lpc1766.lpc1767.lpc1768.pdf) describes a VREFP voltage range from 2.7V to VDDA.
With max VDDA of 3.6V you should have a range from 2.7V to 3.6V.

So your TL431 is out of range :mad:,
but there are a lot of other nice (and expensive) voltage references :).

I would suggest something small and cheap around 3V like:

Texas Instruments LM4040D30IDBZTG4 (SOT23 ~1€) ;)