nrf51822 AVDD pin issue

[hello_alberto_]

Hello,

I have a question regarding AVDD pin. I am using nRF51822 CEAA package. And the reference circuitry on the datasheet uses a 1.0nF capacitor between VDD and GND.

If I put a 2.2nF capacitor instead of 1.0nF capacitor, would it cause zero signal for advertising? I want to know how serious it would cause a problem for RF if used 2.2nF instead of 1.0nF capacitor in that place.

Other significant information: nRF51822 CEAA Package, VDD = 2.5V, internal LDO setup

Thank you!

[Hung Bui]

Hello Alberto,

That capacitor is simply a noise filter. It should be OK to use 2.2nF. And I don't think it would cause trouble to the RF part.

[hello_alberto_]

Thank you! I have one more question regarding RF. Let say, if we just have a balun whose SE pin is not connected to antenna(SE pin just left unconnected), should nrf51822 at least advertise weakly? or should it have no signal at all?

[Hung Bui]

You should connect the pin to something, a wire for example, with length of 2 cm should works. You should also check if the firmware working properly. You can use the radio test example in the SDK and monitor the VDDPA pin if it's high when the radio is supposed to transmit something.