How Much Power Can Be Harvested via STM NFC Dynamic Tags (e.g. ST25DV) Using ST25R3916B?

[MERSI]

Hi everyone,

I’m currently working on a low-power embedded system that uses an STM NFC Dynamic Tag (such as the ST25DV series) in a passive NFC setup. The goal is to harvest energy from the RF field generated by an ST25R3916B NFC reader (13.56 MHz, ISO 15693 / NFC Forum compatible).

I’m trying to find concrete information about the amount of power (in mW or mA at a given voltage) that can realistically be harvested by the tag under optimal or typical conditions (e.g. at a short distance of a few cm). However, I haven’t found precise figures in the datasheets or application notes — most just say “energy harvesting supported” or give vague hints.

Specifically, I’d like to understand:

1. What are the typical and maximum output currents/voltages that can be harvested from the energy harvesting (EH) pin on STM dynamic tags (e.g. ST25DV04K or ST25DV64K)?

2. Are there any absolute limits or practical guidelines for how much power can be supplied to external circuits through the EH pin?

3. Are there differences depending on which reader is used (in my case: ST25R3916B)? Can this reader deliver more field strength or current than standard phones?

Any real-world measurements, app notes, or insights into how to design a circuit that makes the most of harvested power would be greatly appreciated!

Thanks in advance!

[JL. Lebon · Accepted solution]

Hello, 

You can have a look at the application note AN4913 https://www.st.com/resource/en/application_note/an4913-energy-harvesting-delivery-impact-on-st25dvi2c-series-behaviour-during-rf-communication-stmicroelectronics.pdf

There are some figures in this application note for the ST25DV as well as some information on communication vs energy harvested.

Basically, the max power you can get is about 20mW in best conditions.

Best regards.