P1 operating at less than 3.3V?

Hardware
1

Hi,

Does the P1 require 3.3V at all times? I ask because the processor minimum voltage is 1.8V - other products like the Electric Imp allow for lower voltage until Wifi is enabled and requires a 3.3V. Is similar functionality available on the P1? Ideally I would like to disable my switching regulator unless it is absolutely necessary.

1 Like
2

@scottmc, how will you be providing power to the P1 if the switching regulator is turned off?

3

A switching regulator with a pass-through mode. Something similar to this:
https://electricimp.com/docs/attachments/hardware/reference/nora/impee-nora-sch.pdf

4

Cool! Sorry i’m not so familiar with the other product so i had to ask :wink:

It’s not built into the Photon itself and the SMPS IC used (RT8008-33GB) does not have this feature built in.

What’s your concern with regards to turning off 3V3?

@mohit and @BDub will be able to give some advice here!

5

I know this is not possible with the Photon - I thought maybe with the P1? If I am able to operate the processor directly from battery, I can minimize losses in the regulator by decreasing the time I enable it.

Theoretically, the different power pins on the P1 may not all require 3.3V - some may operate the processor down to 1.8V

1 Like
6

@scottmc great question! At this time the only pin that is spec’d at handling a lower input voltage is VBAT_MICRO. May I ask how are you intending on using the MCU at 1.8V with Wi-Fi off? It’s possible you may be able to save even more power by just putting the MCU in STANDBY mode (aka System.sleep(SLEEP_MODE_DEEP, 1800);

7

My thought was using the MCU for sensor readings and then enabling the boost conversion right before enabling WiFi. I thought this may be possible since the MCU itself is capable of operating at 1.8V (according to http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00237391.pdf)

Theoretically,VDD3V3 (which in the P1 datasheet block diagram leads to the MCU) is 1.8V capable. Is this actually true?

8

The block diagram comes from USI’s datasheet which recommends a minimum of 3.0V. However, it could be just a conservative number and not the true minimum. I’ll add a task to figure this out, but I can’t promise it will be done super soon. If you are looking to buy a lot of P1’s based on this working please send me a PM and I’ll get you in touch with sales.

9

I’m really like the idea of operating the P1 from batteries and only enabling a boost regulator when Wifi needs it.

Anybody made any further progress or investigation on this?