Power from 3.3V V_IO pin?

1

Hi,

how much power can I draw from the V_IO pin on the notecarrier B?

Regards, Gaute

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2

Hi @gauteh,

Everything you need should be in the Notecarrier-B datasheet. If not, please let me know and I’ll get you the answer!

Thanks,
Rob

3

Hi,

I couldn’t find anywhere on the datasheet whether the V_IO pin can supply any significant current? mAmps?

– gaute

4

Hi,

I also cannot see the info but if you take a look at the schematic and the datasheet of the DC/DC converters:

TPS62748(1.8V, 300mA) → 540mW → MAX17225(3.3V) → 92% → 497mW → 150mA

So, about 150mA @ 3.3V LESS the notecard consumption.

However, there is a note on the schematic at the 1.8V pin saying “150mA”. With this info, the current at the 3.3V pin would be about 75mA (less the notecard consumption).

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5

Thanks. If that is the case I might be able to power my MCU and sensor from it. Is there any reason why that shouldn’t be possible?

6

VIO should be considered a signal, and not a power supply pin. It was not specifically designed to serve as a stable power supply for external peripherals and may have unexpected side-effects.

Conversely, VMAIN is connected to the primary power source of the Notecarrier, and it offers the highest voltage of either VUSB or VBAT along with a protection diode. As a result, peripherals can be safely powered from VMAIN given the appropriate regulation.

As seen in the schematic, VIO does provide stable power on this variant of the Notecarrier, but there is no guarantee this will be true on future versions of the Notecarrier.

As a final warning, if too much current is drawn through VIO, it WILL interfere with the Notecard’s functionality.

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7

Thanks. That answers the question. I probably won’t use more than 10mA from the pin, but better to rely on something else.