When 52840 is powered by VDDH is VDD/VEXT switched when in low power mode?

[GJSea]

When I power the 52840 from a LiPo connected to VDDH and using VDD/VEXT to power 3V3 components, when the chip is put to sleep is the output on VEXT switched off? Or do I need to add a FET switch controlled by a GPIO to turn off the 3V3 rail?

Thanks!

[Andreas]

Hi,

 

See the product specification: Supplying external circuitry is allowed in both System OFF and System ON mode.

 

Best regards,

Andreas

[GJSea]

Thanks for your response. Might there be a way in future versions of the SoftDevice to turn off the regulator by adding an additional REGOUT0 registry value, eg: Value 8 = 0V Output voltage?

[Andreas]

Hi,

 

Unfortunately not with the current design. The REG0 also supplies REG1 (the nRF52840 1.3V regulators) directly, setting REGOUT0 to 0V would basically cut the power of the entire device.

From what I understand you would like being able to cut the line between the VDD pin and the REG0 output when needed. Currently that is not possible, I believe because it needs the decoupling caps on the VDD pins. So for the time being, if you need to cut the supply to any external circuitry being supplied by REGOUT0, you need to switch it using a GPIO unfortunately.

 

Also I forgot to mention: For the time being, you should be aware of errata 197 and errata 202.

 

Best regards,

Andreas

[GJSea]

Thanks, the only device on the rail is an SPI Flash chip which has a power-down current of 1uA so I can accept the current draw being that low.

For Errata 202 given the standby current draw from the Flash Chip is only 10uA I don't believe it should cause the errata issue, do you think?

[Andreas]

Hi,

 

I would expect 10µA to be low enough for this to be fine, but I can not find a threshold current between what is ok and not. You should expect a revision where both of these erratas have been fixed shortly though.

 

Best regards,
Andreas

[GJSea]

Is the fix for the errata in an updated softdevice version?

Thanks!

[Andreas]

Hi,

 

The update will be in a new HW revision where this is fixed, and should not require a softdevice update. For details and schedules I have to refer you to our RSM responsible for your region, let me know if you do not know who this is.

 

Best regards,

Andreas