Power management of nRF7000 using nPM1300

[andychess]

Hi,

We're working on a cellular design using the nRF9151 with an nRF7000 for location finding.  We have a working prototype on the Thingy91x and are currently focusing on the power management aspects.  This is not so easy to model, given the separate PMIC for the nRF7002. 

My question is: How can we best regulate the power to the nRF7000 directly from one of the nPM1300 Bucks? Your AI suggests that this should be possible but couldn't give any specific advice.  What do we need to consider in terms of hardware design and software considerations, e.g. timings, confirmation of device ready etc?

Our use-case envisages powering the nRF7000 continuously for 10 or 30 minutes up to 3 times per week in order to obtain the device location via WiFi.

If you can give some code snippets, this would be helpful.  We're already aware of the Zephyr npm13xx library from the fuel gauging sample.

As always, any help would be greatly appreciated.

Best regards,

Andy  

[Ressa]

Hi Andrew,

 Please expect some delay as it is holiday season. I will try to get back to you by end of this week.

Best regards,
Ressa

[FARLY7]

I'm also interested in knowing if it is possible to use the nRF7002 with nPM1300 :)

I have a design with nPM1300, nRF54, nRF7002, and nRF9151.

However, only the nRF9151 or the nRF7002 will be active at one time.

[Ressa]

Hi Sean,

Please note that max current consumption of nRF7002 is 262 mA which is higher than supply current of nPM1300 bucks. If you check thingy 91x , the WiFi chip supply coming from nPM6001. 
But if you are only going to use passive scan mode (no TX transmission) then I suppose it is possible with nPM1300 bucks. You just need to make sure never exceed 200 mA current (even for short period of time) otherwise there will be unknown behaviors.

Best regards,
Ressa

[FARLY7]

Hi Ressa,

Thanks for your response.

Indeed, I see that "Table 16: Transmit current consumption (QFN package)" of the nRF7002 datasheet shows:

So, while some 2.4GHz schemes would allow the nRF7002 to be powered by the nPM1300's buck regulator, others do not.

However, after further reviewing the nRF7002 datasheet for a better understanding, it appears that the nPM1300 is not required to power the nRF7002? My understanding is now that:

The nRF7002 has its own Buck regulator that can be used instead of the nPM1300's buck, and it is intended to be supplied directly from the battery via the VBAT pin.

This would allow me to only use the nPM1300 to power my nRF54, nRF9151, and sensors, and connect the nRF7002 directly to the battery via VBAT. The nRF54 would then turn the nRF7002 and its buck regulator on or off via the BUCK_EN pin.

Is my understanding correct here? Am I missing any issues? Does powering the nRF7002 "outside" of the nPM1300 cause any issues with fuel gauging, for example?

EDIT: Or should I connect the nRF7002's VBAT pin to the nPM1300's "pass through" VSYS pin, just like the nRF9151 is meant to be used with the nPM1300, which also has its own internal buck regulator?

Thanks,

Sean

[andychess]

I don't like to be rude, but my original question seems to have been hijacked!

[FARLY7]

Completely fair, apologies .. but I thought we were essentially asking the same question and I was ticking it along!

[andychess]

No problem;-). 
I would really like a clear answer to the specific question, whether the nRF7000 can be powered directly from the nPM1300.  There is, afaik, no specific datasheet or EK for the nRF7000, so we are reliant on information from Nordic.  We're planning to move from the Thingy91X to our own custom design in March and don't want to waste time and money either on a design that is not reliable or on additional BOM components 'just in case'. 
As contructive feedback on the Thingy91X (of which we have three), the inclusion of the nRF7002 and the associated nPM6001 seem fairly pointless, given that the nRF9151 can't run the full WiFi stack.  I would prefer to see a tailored device for location finding which would fit better with the capabilities of the nRF9151. 

[Ressa]

Hi Sean, 

Thanks for the clarification. Using unregulated VSYS for nRF7002 (and other circuits) is possible of course as long as it does not exceed the current limit which is more than 1 A. Supplying nRF7002 directly from battery is also possible but the fuel gauging will not be accurate enough, for accurate fuel gauging all current must pass though PMIC. Using VSYS for powering up nRF7002 with pass through VSYS is better option. 

[Ressa]

Hi Andrew,

Similarly I don't see any issue using unregulated VSYS as supply for nRF7000 and then using VOUT for IOVDD. Just you need to make sure about unregulated voltage range not to exceed the limits for nRF7000. Using nPM6001 has been for this purpose(to ensure the voltage range).