disappointing DCDC current improvement

[mistert69]

I am trying to get the DCDC running on my custom NRF51822 board.

It is running but the results are a bit disappointing.

If I do a test and enable the TX with and without the  DCDC enable  I only see a difference of a little bit more then 1mA.

From 18.5mA to 17.3mA, if I read through some posts here, on the development board it goes from 17.62 to 14.83mA almost 3mA difference !

I am running on a coin cell of 3.3V and when I enable the DCDC I see 1.86V on AVDD if not enabled I see the Vbat.

We didn't use the  CBMF1608T100K  10UH coil because it was not on stock but a replacement : GLFR1608T100M-LR powerline inductor.

Could this be the problem and can I expect a 3mA drop in current consumtion or is 1mA the best I can expect ?

 

[Stian Røed Hafskjold]

Are you able to test with a lab power supply? If the battery is not able to deliver the current needed for the peak currents the voltage will drop, and the DCDC efficiency is proportional to the input voltage.

[mistert69]

Indeed that was the problem..

I was testing with a coin cell that was not new :( Stupid mistake.

A new one falls back to 2.9V with 20mA load this one falled back to 2.4V.

Now I see an improvement of almost 3mA.

Tried it with a powersupply and  I see an improvement of 4mA!

Thanks for the reply Stian !