nRF52811 Antenna Design

[Kaveh.M]

Hi, 

I am using nRF52811-CAAA bare chip on a standard 2 layer FR4 board and want to design a PCB trace antenna for it to achieve overall x100-200m range.

Is there an example or a PCB reference design for this BGA package I can use for this purpose?

Please advise. 

[mathiaso]

Hi, Kaveh.

We have this white paper describing how to design a λ/4 PCB monopole antenna for 2.45 GHz. Beware that there are other factors as well, in addition to the antenna, that impact the wireless performance.

Best regards,
Mathias

[Kaveh.M]

Thanks. Is there a PCB layout example or recommendation of footprint for nRF52811 CAAA WLCSP package. 

I can see in the datasheet there is just an example for QFN48 package.

[mathiaso]

Yes, please have a look at the nRF52811-CAAA's reference layout which can be downloaded from here.

[Kaveh.M]

Thanks. Also in the datasheet for nRF52811, there is recommendations for using GPIOs close to RF antenna port in section "7.1.4 GPIO pins located near the radio". In this section there are recommendations only for QFN package and nothing mentioned for CAAA WLCSP package.

Are there recommendations for using GPIOs near RF antenna port of nRF52811 CAAA WLCSP package?

[mathiaso]

If you have a look at the GPIO pins mentioned under GPIO pins located near the radio, you'll see that those GPIOs aren't present in the WLCSP ball assignments. That's why there is no mention of the WLCSP package.

[Kaveh.M]

Thanks. For programming this chip, I see on the pins there are only VDD, GND, RESET, SWDIO, SWDCLK are available. Are these pins sufficient (SWO seems missing) and can they be directly interface with a Segger J-Link Debugger for programming the chip? 

[mathiaso]

Yes, that would be sufficient. The bare minimum would actually be VDD, GND, SWDIO, and SWDCLK.

Through SWDCLK and SWDIO you can interface directly with a debugger, as shown in the debug section of the PS.

[Kaveh.M]

Thanks. For clock, the 32.768kHz option is sufficient or I have to use 32MHz crystal as external clock source? 

[mathiaso]

Could you please elaborate? You'll need the 32 MHz crystal to, e.g., operate the radio, as explained in the clock control section of the PS.