ST (BAL-NRF01D3) and Johanson (2450BM14A0002) Balun Performance for nRF24LE1 QFN-24

[farzad.panahi]

Hi,

I am considering using baluns instead of discrete components next to my nRF24LE1 QFN-24 chip since board space is at premium. 

In application note AN4111 regarding ST's BAL-NRF01D3 balun it reads:

The BAL-NRF01D3 from STMicroelectronics is an ultraminiature balun for which the matching impedance has been customized for the nRF24LE1 QFN-32, nRF24AP2-1CH, nRF24AP2-8CH, nRF51422, and nRF51822 QFN Nordic Semiconductor circuits.

Also in application note nAN24-17 regarding Johanson's 2450BM14A0002 balun it reads:

This application note does not apply to nRF24LE1 QFN24 or nRF24LE1 QFN48. The 2450BM14A0002 balun is not suitable for these devices because of the different packet sizes.

As you can see both ST and Johanson have customized their baluns for QFN-32. I am using QFN-24 and wondering if there would be any significant performance difference or not.

- Anyone has any experience using any of these two baluns or any other balun with nRF24LE1 QFN-24?

- If I use any of these baluns, will the RF performance be as good as using discrete components?

I really appreciate any help or comment.

Thanks

[bjorn-spockeli]

Hi Farzad,

I have not seen any nRF24LE1 QFN24  designs that have used a balun customized for the QFN32 package. 

We expect that you will see lower RF performance when using NRF01D3 or 2450BM14A0002 as they are not designed for the QFN-24 package compared to using discrete components. 

Best regards

Bjørn

[farzad.panahi]

Thanks Bjørn, 

I am considering switching to QFN-32 if I know for sure the performance I get is as good as the discrete components. I can see that Nordic is using ST's BAL-NRF01D3 balun in nRF2723 nRFgo modules. Just wondering whether this balun is providing better RF performance compared to discrete components and that's why Nordic went with this choice? I think it would be really helpful and educational to know about the decision factors for this choice. I appreciate if you can share any insight. 

Cheers

Farzad

[bjorn-spockeli]

In general you will not get better RF performance with a balun compared to a well tuned PI network. At best the two alternatives will be on par with each other. 

As you have pointed out, using a balun reduces the BOM and saves space on your PCB, but this requires that you copy the reference design. Small changes in the layout might result in lower RF performance. One of the cons of using a balun is that you're not able to adjust the matching like you can with a discrete Pi network and you need to do another PCB iteration.