LPC5506 ADC reference voltage source

[ryanlush]

I've been given some hardware that has VDDA tied to VREFP but left to float on a 100nF capacitor. When I try to read the internal temperature sensor on CH26 I get 0. I loaded the lpadc-temperature-measurement example on my hardware and also got 0. When looking at the reference manual for this chip I don't see an option for an internal reference voltage. Is this true? Is there a way for me to use the ADC without an external reference? Most of our products use the ADC to measure something external so the reference voltage gets tied to something.

[ryanlush]

After tying VDDA (pin 6) & VREFP (pin 7) to VDD (pin 5) I got the reading I would expect. Is this my only solution?

[_Leo_]

Hi,

Thank you so much for your interest in our products and for using our community.

It is needed an external voltage references to perform the SAR ADC. You can choose between VREFP or VDDA.

_Leo__0-1715278634583.png

Hope it helps you.

Have a nice day!