nRF52832QFAA TX power readings

RE: nRF52832QFAA TX power readings

Jared — Thu, 11 Jul 2024 09:11:50 GMT

Hi Julius,

You're absolutely correct, I see now that the datasheet for the LPF specifies the pin to be connected to the GND layer. As for pin 31, it has to be connected to the centerpad, and unfortunately the only advice I could give you is to do a redesign. If you decide to do a redesign then I would also suggest using our matching network by placing the single components instead of using the LPF, as we have seen that placing the single components usually result in a better RF design in terms of loss. This makes it possible for us to optimize the matching network if you send it in for tuning.

regards

Jared

RE: nRF52832QFAA TX power readings

JT898 — Tue, 09 Jul 2024 15:33:54 GMT

Hi Jared,

The nrf52 reference design used an LC circuit on the ANT pin, I am aware of grounding the "ground" pin on C3 (from the reference design) to the nrf52 ground pad only with a keepout from the rest, I had that design in the very early stage of my first design.

Now I am not using a LC circuit but a Johanson impedance matched LPF for the 50ohm transmission line on the ANT pin. See attached for their reference circuit implementing their LPF with the nrf52.

I do see that I need to short pin 31 back to the center pad of the nrf52. Now to figure out how do I verify/test that theory..

Thank you!

Julius

RE: nRF52832QFAA TX power readings

Jared — Tue, 09 Jul 2024 08:17:00 GMT

Hi,

Pin 31 should not be connected directly to the GND plane, but grounded through the centerpad as in the reference design, this is very important for harmonic filtering, which can affect the measured TX power:

regards

Jared

RE: nRF52832QFAA TX power readings

JT898 — Mon, 08 Jul 2024 14:47:36 GMT

Hi,

Here you go. I am suspecting it's the absence of the two ground vias at the LPF but I hope you can tell me better!

Thanks

Julius

RE: nRF52832QFAA TX power readings

Jared — Fri, 05 Jul 2024 11:59:35 GMT

Hi,

[quote user=""]

1) What will cause a drift in measured TX power to default set TX power? Will using the LDO or the internalDCDC affect this?

[/quote]

No, I don't think this is a result of DC/DC or LDO,do you see any difference whether LDO or DC/DC is enabled/disabled?

The nRF52832 has a Radio accuracy of +-4 dB. However most devices will be within +-2 dB.

The schematic look ok, a bit more decoupling on VDD than recommended but I don't think that's related to what you observe.

Can you share the layout as Gerber files?

regards

Jared