nRF52 Reference Layout (pin 37,38 & 6-pin JTAG)

[FA]

Hi,

I want to confirm two points in the PCB layout of nRF52:

• In the data sheet and in the reference circuits section, there are no caps on pins 37 and 38 (QFN package). However, in the Altium files there are two 12pF caps on these nodes. My assumption is that these two caps have been added to these nodes as they are very close to RF pins. So, if I don't use these IOs, can I avoid adding these two?

• For 6-pin JTAG, similar to nRF51 beacon board, do we need to connect pins 3 and 6 to two IOs? and these can be any IO?

Thanks, FA

[bjorn-spockeli]

The capacitors on pins 37 and 38(P0.25 and P0.26) are due to Errata 138: RADIO: Spurious emission on GPIO exceeds limits in radiated tests.

If you do not use these pins then you can simply connect them to ground.

If you want to add a programming header to your design then you should take a look at the nRF52 DK layout, found here, specifically the Debug In connector.

Best regards

Bjørn

[FA]

I'm still a little bit confused about the JTAG pins. I checked the nRF52-DK, that one has 10-pin connector and pin 6 and 10 of that is P0.18 AND P0.21. I want to use the TC2030-CTX Plug-of-Nails Cable, which will convert pin6->pin6 and pin10->pin3. My question is that do I HAVE to use P0.18 and P0.21 on my board OR any other IO will also work for these 2 pins. Reason is saving space by using closer IOs to the connector.

[bjorn-spockeli]

Yes, P0.21 is the reset pin and the reset functionality cannot be re-directed to another pin. P0.18 is the SWO/Tracedata pin, which is not necessary for programming the device, only debugging.