nRF52840 LDO accuracy for Japanese RF regulations

[Rashid Talib]

Hi

We are currently doing RF certifications on a product using a nRF52840. Japanese radio law has the power stabilization requirement:

"When the input power of equipment is changed by+/-10%, variation for input power to RF module must be less than +/- 1%"

Do you have specifications or measurement results we could give them? if not, we need to test the variantions ourselves, right?

Thanks for your help & best regards

Rashid

[bjorn-spockeli]

Hi Rashid,

My understanding is that the power stabilization requirement will only apply to external regulators as the nRF52840 is the "RF module", e.g. if you used an external LDO between the power source and the nRF52840. How the internal regulators of the "RF module" behave should not matter as the RF parameters(which are within the required limits) stated in the  nRF52840 Product Specification are independent of the input voltage, i.e. we guarantee the RF parameters within the valid input voltage range 1.7V - 5.5V. 

Best regards

Bjørn

[Rashid Talib]

Hi Bjørn

Thanks for your reply. Can we say that the speficied 1% ony applies if the supply powers the RF frontend directly (i.e. without any LDO in between)? this would make sense since changes in input voltage then lead to changes in output power. But if the internal LDO is used changes in input voltage don't lead to relevant changes in output power, right?

Thanks & best regards
Rashid

[bjorn-spockeli]

Hi Rashid,

Yes, the output power of the nRF52840 is independent  of the  input voltage to the nRF52840, i.e. a change in the input voltage will not lead to any change in the output power. Hence, the power stabilization requirement should not apply to the nRF52840. 

Best regards

Bjørn

[Rashid Talib]

Hi Bjørn

Ok, that makes sense.

Thanks for your support & best regards
Rashid