NRF52833 VDD External Power

[chethans]

Hi,

Is it possible to power external devices through VDD ports of NRF52833 provided we follow the VDDH supply configuration?

We are looking to power sensors from the controller. The total current will be less than 10mA.

Thank you,

Chethan  

[ketiljo]

External power from the VDD pin is not supported on the nRF52833.

[chethans]

Hi,

Needed one more clarification for the power supply.

Does NRF52833 operate at 3.7V connected to VDD?

We have 3.6V batteries and initially their voltage will be a little high. Can NRF still operate with this slight extra voltage?

[ketiljo]

No, max voltage on the VDD pin is 3.6 V. If you have higher supply voltage than that, you need to use it in high voltage mode, with the power supply connected to VDDH.

If you're using LiPo batteries, max voltage is well above 4 V from those. This is what REG0 (VDDH) is designed for.

[chethans]

Hi Ketiljo,

In VDDH mode, what kind of quiescent current are we looking at for the additional LDO?

Thank you,

Chethan

[ketiljo]

That depends on the mode the regulator is in. It changes mode depending on the load. In sleep mode, when REG0 is in refresh mode, it will have a quiescent current of ~0.2 µA. 

[chethans]

Thanks ketiljo.

Can we get the different modes and currents for it?

We are designing a low power product and every uA is crucial.

With the ldo turned on, does it burn complete power across vddh - regout0? Or is there some smart mechanism which avoids this?

[ketiljo]

You will be better off using the nRF52840 as this have a DCDC mode for REG0 (VDDH). This is a lot better for low current applications. The nRF52833 doesn't have DCDC mode at REG0 so this will just burn off the current as any other LDO.

The nRF52840 can power external circuitry as well.  

[chethans]

Only if 52840 could support 105 deg

[ketiljo]

Ok. The best will be to use an external DCDC converter to take the battery voltage down to 3 V or so as this will be much more efficient than the LDO in the nRF52833.

I didn't expect hat you needed 105 degrees since you where talking about batteries, that won't work too unless the battery is somewhere else?

[chethans]

We are using a variant of lithium thionyl chloride batteries which can support up to 125 deg. Its an industrial iot application with very stringent requirements

[ketiljo]

The advice will be to use an external DCDC converter with the nRF52833 then. Or maybe the nRF52820 can fit the bill: https://www.nordicsemi.com/News/2020/03/Nordic-nRF52820-SoC-the-sixth-addition-to-the-nRF52-Series?utm_campaign=SoMe%20promotion&utm_source=facebook&utm_medium=social&utm_content=News%20release:%20nRF52820