GNSS LNA Power Recommendations - LDO or Buck Converter

[N.Weller]

With reference to the Thingy:91x reference design, I see that the LNA (SKY65943-11) on the GPS signal path is powered by one of the switching converters from the nPM1300: 3V3 => VDD_RF_FE_3V3’ => VDD_RF_FE_3V3. 

I have a consultant that is saying that it is practically mandatory to use something like an LDO to power the RF Front End to keep the noise low enough and get good performance.    

What is your experience and are there any recommendations with that?  On the Thingy91 (Infineon BGA524N6) and the Thingy91x (SKY65943-11) the GNSS LNA appears to be powered by a PMIC switching power supply.  

Thanks!

[Mariano Goluboff]

I'm not sure that the description of practically mandatory would apply here. The Thingy91:X uses the switcher from the nPM1300 to power the GNSS LNA, and this board has very good GNSS performance. The switching frequency of the nPM1300 is 3.6MHz. That's higher than the GNSS frequencies, and high enough that filtering can be done very effectively with small components. Make sure that your PCB traces are wide to minimize inductance.

The nPM1300 does have two LDOs if you want to use those, and if you are ok with the additional power consumption.

Mariano