Mangoh red with external power regulator


#1

Hello,

We are trying to power source the mangoh red through an external regulator via the battery connector.
Yes, we know it is going beyond “regulations” but this is our requirement.

The regulator provides 5V ±4% with a maximum continuous current of 2.5A (more than a USB port) connected to the battery connector. The input goes up to 25V (this is our application requirement). Charging is obviously disabled. Power on the sierra module is reported to be 4.9V by the processor itself.

The board boots and software can be executed properly.

However, the radio module won’t come online. We have tried various combinations with the cm radio command, but no error is reported. It simply does not come up. If we go back to usb power then the radio works again.

In the design, BQ24296RGER is in charge of generating a single 3V7 signal that it is later separated to power the VBATT_BB and VBATT_RF signals, and we cannot identify any other dependency.
Note that BQ24296RGER is rated to support a VBAT input of 6.2V.

Thanks a lot.


#2

If you are powering through the battery connector, then that has a max rating of < 4.6V.
Why dont you set your input to 4.0v?


#3

Why not just feed the 5V to one of the USB sockets?


#4

Hi,

It is complicated… we have a batch of 20 regulators with fixed output at 5v to power 20 mangoh. We selected a fixed one due to vibration considerations from those that use variable resistors.
For the very same reason we need to connect to the battery port… the USB is unreliable.

Changing them to 4-4.5v will depend on the willingness of the manufacturer.

The weird thing is that the output from the bq24296 is good enough for the digital part in the processor, but not for the RF part. The data sheet recommends around 4.5 but the absolute max is set to 6.2.

Tomorrow we will check voltages through the test points and inject 4.5v to see if by reducing those 0.5v we sort out the problem.

We will report our finding in case someone else has the same requirement.


#5

Hi,
It is a drone application. Vibration and connectors are key, so we have a front face interface to rugged connectors. Moreover the input power comes from 4 cell lipos, so we need specific regulators that are generally available in the market set up to 5/12v.

The external USB are not used for that reason, We use the rasp port for communications.


#6

if you do a mod on the board, you can feed the power through the Rpi pins.
You cannot input 5V through battery connector though.


#7

It was cleaner through the battery connector. We will try to downgrade the voltage.
Yes, the Rpi is one alternative, however it is already crowded in our design as we connect a uart and a usb (a mod already implemented). The other one is the middle pin in the jumper structure that controls which usb powers the board.
Funny how you can trick the schematics.


#8

Confirmed, 4 to 4.5 V on the battery port works just fine.
We will update our regulator to that figure.
Thanks


#9

Best would be to use 3.9 or 4V .
4.5V is above the CF3 module spec. (3.4 to 4.3V is CF3 spec)