Powering MangOH Red on 3.3V

mangOH Red
1

Hello MangOH forum,

I’m working on a PoC with the MangOH Red and have a 3.3V power supply. I see the MangOH Red can be powered thru two 5V USB interfaces or thru the Li-battery charging interface. However, the battery charging interface only seems to power on the module (RC7611) between 3.3 and 3.7V, but doesn’t actually allow for network registration to occur unless the voltage is above 3.68V (at least from my bench testing). The module appears to be in a reboot cycle if the battery voltage is not sufficient.

So, is there a way to power the MangOH Red off of a 3.3V (3A) power supply?

Please let me know.

Thanks,

Max

2

Hi Max,

Welcome to the forum.
For the behavior you observed, guess maybe related to the voltage threshold setting, can you check response of below?

AT!PCINFO?
AT!PCVOLT?
AT!PCVOLTLIMITS?

Thx

3

Hello Lotam,

Thanks for your response.

Here are the results from the requested AT commands -

at!pcinfo?
State: Online
LPM voters - Temp:0, Volt:0, User:0, W_DISABLE:0, IMSWITCH:0, BIOS:0, LWM2M:0, OMADM:0, FOTA:0
LPM persistence - None

OK
at!pcvolt?
Volt state: Normal
Power supply voltage: 3660 mV (ADC: 37146)

OK
at!pcvoltlimits?
ERROR

For this PoC we have found a way to get more current from the 5V power supply and that should be sufficient in powering the MangOH RED. At the moment we don’t need the 3.3V option but I still appreciate you looking into this.

Thanks again,

Max

4

Thanks Max!
Just to explain, RC76 does monitor the input voltage to decide the working state.

Per info you shared, the detected voltage input is 3.6V which is normal level, so I guess it is able to register to network?
And during this test, are you using the USB as power supply?
If so, would you please check again below using the battery interface?

AT!ENTERCND="A710"
AT!PCINFO?
AT!PCVOLT?
AT!PCVOLTLIMITS?
AT!GSTATUS?

So you can see any differ between voltage input and detected value, and whether it fall into normal range reported by !PCVOLTLIMITS.

Also please check PTS for power supply design requirement, i.e. section 3.2:
https://source.sierrawireless.com/resources/airprime/hardware_specs_user_guides/airprime---rc76xx---product-technical-specification/

Thx