adc: is there a way to get the VBG out of the nrf?

[Richard]

Hi,

is there a way to get the VBG reference voltage out of the nrf51822? we want to drive a very low current with it.

Thank you. Richard

[Asbjørn]

There's no way of driving anything from the VBG, but you could drive some small circuits directly from the GPIO/VDD. Would this be an option for you or do you have any voltage requirements that would make this difficult?

[Richard]

Thanks for your reply. I know the version with the GPIO/VDD (this is my current design), but in case of adc measurement this brings also a lot of trouble. So i try to use the internal VBG reference to drive a voltage divider (around 7kOhm), but it looks like there is no way to get the VBG out of the device.

I have a 1,85V power supply for my chip. So i cant't use the VDD directly for aref. But i can prescaling it internal with 1/2. Do you know how exact the prescaling is? Thanks again,..:)