Maximal Harvested NFC power with NHS3152

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Maximal Harvested NFC power with NHS3152

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Contributor I

Hello,

I am using the NHS3152 chip and want to operate it via NFC only.
For a measurement with a relatively energy hungry sensor I need a slightly higher power for a short time (~5mW for 500ms).
In the application note I could not find any concrete information about how much power I theoretically get via NFC. Only get that the IC has IOs that can drive up to 20mA and I can expect a voltage of about 1.8V in NFC operation. That should be enough so far.
With the Developent Kit and different resistors I made a few attempts what current I can drive. Here I could see that already with 0.9mA (~2kOhm) the µcontroller breaks down. Of course this is a lot less than what I need.
I read that you can improve the performance a bit by improving the quality of the antenna (Q-Factor).
Now to my question:
What is the Q-Factor of the antenna of the Deveopment Kit?
Or how much energy can I typically get harvested with the DK (of course it depends on the transmitter and the environment)?
What is the maximum Power that I can get if I use an antenna with a higher Q-Factor?

Thanks a lot and best regards
David

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1 Reply

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NXP Employee
NXP Employee

Hi,

The 20ma indicates the maximum the IOs can handle and still behave according to specification. To reach this level in a design, the IC must be powered through a battery. This amount can not be obtained when using NFC harvesting. In a passive mode, the energy harvested is clamped. It will not be possible to deliver 5mW (or any value in that order of magnitude) in passive mode. Improving the Q factor will not help at all.

I'm sorry, the sensor you have in mind cannot be used with a passive NHS31xx IC.

Best regards,
Dries.

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