Why is there a current from 1,5mA bellow 1,8V?

[Richard]

Hi,

I use a step-down converter(not the integrated one) to generate 1,85V for the nRF51822 in my application.

When the applications starts the output voltage from the converter grows "slow" to 1,85V. I recognized, that the nRF draws some current bellow the 1,75V minimum voltage. So i started to measure: In the screenshot bellow you can see the input voltage in the upper window and the current in mA(not mV!!!) in the under window. You can see that from 0,8-1,6V the nRF draws around 0,5mA and from 1,6-1,75V 1,5mA. Then the uC starts up and go to idle. Is there a way to reduce this current without using external components like FETs?

Thank you for your help.

[Nikita]

There is required operating conditions for nRF51822 described in Product Specification.

You can see in "7 Operating conditions" there is maximum tR_VDD (Supply rise time (0 V to 1.8 V)) = 60 ms and note:

The on-chip power-on reset circuitry may not function properly for rise times outside the specified interval.

So I don't think it's possible to do anything with this problem without additional external components.

[Richard]

thank you, perfect,.. and my rise time is faster than 60ms,..:)