topic Re: qn9080 in Wireless MCU

qn9080

kennethtait — Tue, 04 Dec 2018 20:51:01 GMT

Using QN9080 part.

PA06 labeled ADC_EXT_CAP..implies I need to place a cap on this to use internal ADC, yet there is no explanantion in data sheet or user's manual for this..so DO I need a cap or Can I use this as a GPIO and still use ADC?

Re: qn9080

stephanie_m — Wed, 05 Dec 2018 18:46:33 GMT

Hello,

Could you please share with me where are you seeing this label? I was not able to locate any reference to it

Regards,

Estephania

Re: qn9080

kennethtait — Wed, 05 Dec 2018 18:56:52 GMT

QN908X data sheet rev 1.2

page 11. pin description

PA06 in Alternate function col. ADC_EX_CAP

also look at Dev kit schematics and you will see a cap on this pin.

Re: qn9080

stephanie_m — Fri, 14 Dec 2018 21:30:15 GMT

Hello,

You can use the pin as a GPIO and still use the ADC. As stated in the User manual of the QN9080 page 426, that capacitor if added will only act as a filter for the bandgap.

Regards,
Estephania

Re: qn9080

kennethtait — Fri, 14 Dec 2018 22:18:20 GMT

Thanks for the answer!

Does this mean that if I use the bandgap reference with ADC and no cap

it will lose some lsb bits in reading without the cap. What's the

benefit of filtering the reference?

Ken

Re: qn9080

stephanie_m — Fri, 14 Dec 2018 23:05:59 GMT

The capacitor it's only intended if you will be using the bandgap voltage, the ADC can work with a reference that it's not the bandgap one, so it does not have to do with the effective number of bits.

The capacitor should be added if you are planning to use the bandgap and if you want the bandgap to be really accurate, the capacitor will only filter the noise.

Regards ,

Estephania