NRF52840 maximum peak vs continuous current from VEXT/VDD supply

[jtrovato]

Hello,

I am designing my second revision of custom hardware and am debating replacing my external regulator with the nrf52840's internal REG0 stage. I have read the product spec and noticed that maximum current supplied by the REG0 (IEXT) stage to VEXT is 25mA when radio is <=4dbm but only 5mA when the radio is >4dbm. I would like to run the radio at +8dbm, and I have components that should nominally consume <5mA, but when taking into account the maximum possible power consumption with VDD voltage at 1.9V it is possible that my devices connected to VEXT would consume up to 8mA for very brief periods of time (1ms). Not too mention it would be very unlikely that ALL of my devices are in high-power modes at the same time. 

So my question is about the condition of maximum current draw (IEXT) from VEXT. Are these value maximum continuous draw or maximum peak draw? What are the risks in in exceeding this value for brief periods of time? Will I burn up my chip operating under these conditions? does the REG0 stage have any o ver-current protection or will it shutdown if that current is exceeded?

Should I replace my regulator with the nrf52840's?

Thank you!

[Kaja]

Hi, 

I have forwarded this internally, I will get back to you soon with an answer. 

 Best regards,
Kaja

[Kaja]

Hi, 

here is the answer: 

the total output current from REG0 counts and is specified to max 50mA. The limit accounts for continuos current, and peak current, when peak current duration is more than few us.

Slight exceeding should not burn the device nor collapse the supplies and overall risk of malfunction should be moderate. However, as the device has not been characterized over 50mA, it is on users responsibility.  

Best regards,
Kaja