Measure current consumption by the ST25R3911B on the X-NUCLEO-NFC05A1

[Joseph Chan]

Posted on February 28, 2018 at 22:28

I would like to measure the current consumption during the 'Wake-up' mode with capacitive or inductive sense, and also during  the active rf-reads. Currently, the chip is powered by 5V and 3.3V. I am thinking to remove the 5V source and connect the Vdd to 3.3V as well. I can monitor the current coming from the 3.3V source. I should also remove the power LED to eliminate the current draw.

Anything else I am missing?

[Travis Palmer · Accepted solution]

Posted on March 06, 2018 at 08:54

Hi Joseph,

This sounds like a good plan. 

Please be aware that pin 2 and 4 of CN6 are both connected to 3.3V plane and that the power consumption in inductive wake-up and HF-field-on (

active rf-reads)

will be different/lower if the chip is supplied via 3.3V instead of 5V.

BR Travis

[Joseph Chan]

Posted on March 19, 2018 at 17:38

Hi Travis,

I made the changes as described and disconnect pin 2 on CN6. I then programmed the wake-up Timer Control Register (31h) with a value of 0 in order to observe the wake-up current. When I measure the current through the 3V3 line, I got 5.5µA, but the datasheet says 3.6µA. How can I get closer to that value?

Thanks.

P.S. I am using the demo firmware from 

http://www.st.com/content/st_com/en/products/embedded-software/st25-nfc-rfid-software/x-cube-nfc5.html

[Travis Palmer]

Posted on March 22, 2018 at 10:18

Dear Joseph

Can you please confirm that the oscilator and mcu_clk is not turned on?

And the following conditions are fullfilled?

Which kind of amp-meter have you used?

The values for this mode would be 1.6µA min, 3.6µA typical and 8µA max.

BR Travis