What should VDD level be on unprogrammed device?

[ScottBBBB]

We are supplying the nRF52840 from 5 V into the VDDH pin.  We are not using the USB interface, so VBUS is grounded.

When we apply power to unprogrammed devices and measure the voltage on VDD, which is the output of internal regulators, we see a variety of values.  I've seen a few at 2.4 V, but also some at 2.1, 2.2 V or 2.3 V.  This doesn't make sense to me -- I would think they should be consistent unit to unit.  I've not used this particular Nordic IC before.  What should we expect to see?

Thanks,

Scott

[Kazi Afroza Sultana]

Hello Scott,

For normal operating voltage, VDD should be in the range of 1.7 to 3.6 V https://infocenter.nordicsemi.com/topic/ps_nrf52840/power.html?cp=4_0_0_4_2_7#unique_706563143 .  For high voltage mode, it should be 1.8 V if you have not changed the value of REGOUT0 (default value is 1.8V). 

https://infocenter.nordicsemi.com/topic/ps_nrf52840/uicr.html?cp=4_0_0_3_4_0_7#register.REGOUT0 

You can check the above mentioned links to know about electrical specification and registers used for high voltage mode.

Thanks.

Best Regards,

Kazi Afroza Sultana

[ScottBBBB]

Hello Kazi,

I'm afraid that this doesn't fully address our question, though -- the parts are not yet programmed, so we have not set any registers, and we are so far not able to program the parts. We can read registers, but have not been able to write to flash nor run code.  We are thus trying to figure out what's wrong, and one of the questions is whether or not we are doing something wrong with how power is supplied.  I saw the 1.8 V default setting in the datasheet, but as I noted we are not seeing 1.8 V, but rather a range of higher voltages. 

Regards,

Scott