How to route VDD and AVDD: nRF51822

[IP]

Hi all,

I am new to the EE/hardware world. Coming from the CS side, I am trying to grasp little bit of knowledge every day.

I looked at the reference designs and am using the qfaa reference file. Since I am planning to build a board for BLE application:

1. I should be referring to nrf51822_qfaa_pcb and not _1v8 or _dcdc. Right?
2. I want to attach a coin cell battery (3V) and because VDD and AVDD are all the same net, VCC_nRF, can I route it like this: (two images below)

Image 1:

Image 2:

3. What if I do this connect AVDD to battery and leave VDD connected to each other:

Image 3:

4. Also when should I use VDD vs AVDD

I know these are beginner questions. Thanks for taking the time :)

Thanks! -IP

[Asbjørn]

Q1: Yes, you should start looking at the nrf51822_qfaa_pcb as you have done.

Q2: Yes, you could do as you have done it the two images. I would consider/recommend you to add at least footprint for a slightly larger capacitor, (uF-range so a 0603 component) if not two of these footprints, between the battery and C2/via. You wouldn't necessarily use the footprints, but in the case you do need to filter out noise from other parts or use a different/noisier voltage source you are able to easily solder in an additional capacitor or two on the power supply.

Q3 and Q4: AVDD is used if you are using the onboard DCDC converter to separate between the supply to the DCDC and the supply from the DCDC. So VDD would supply the DCDC and AVDD would be connected to the output of the DCDC to power the analogue parts of chip. So unless you plan on using the DCDC, keep VDD and AVDD connected together.

[IP]

Thanks! Asbjørn.