topic Re: PN7160 filter choke current and value in NFC

PN7160 filter choke current and value

michael_d_1983 — Wed, 20 Sep 2023 08:47:00 GMT

Hello,

according to AN13219 antenna design guide (PN7160), a type with at least 400mA is recommended for the EMC filter choke.

At the same time it says that for asynchronous matching the current is 160mA - 180mA and I_txldo must not exceed 250mA.

With careful design of the matching circuit, could a choke with 240mA also be used or is this strictly not recommended?

I would like to use a 180nH choke with 240mA as these are far more available (second source) than 160nH types with 1A (LQW18CNR), this is pretty much single source from the parameters.

Thanks,
Mike

Re: PN7160 filter choke current and value

Tomas_Parizek — Mon, 02 Oct 2023 06:02:55 GMT

Hello Michael,

I answered your questions via the "ticketing system" but I did not get any feedback. So not sure if you could see it.

Can you share the part number of the inductor you would like to use, please? Is it wire wound one ferrite one? The current of 240 mA should be fine for your application but we need to check some other parameters.

The inductors we described in the app note are very well-tested in NFC. Especially for ferrite inductors, you have to be very careful, they can easily go to saturation.

Tomas

Re: PN7160 filter choke current and value

michael_d_1983 — Tue, 03 Oct 2023 07:49:34 GMT

Hello Tomas,

sorry for my late reply.
Your ticket mail must have been lost in our system.

In retrospect, I don't know if it's good to use types with such low current, since temperature derating would also have to be taken into account here.

I think that the type suggested by NXP is well suited, but due to the technical parameters there are very few alternative types (second source).

From the 180nH inductor I have not yet considered a specific type.
Possible candidates with similar parameters:

Manufacturer	Type	L	Tol	Current	RDC	SRF	Q
Johanson	L-14WR15JV4E	180nH	5,00 %	240mA	0,92	1GHz	35
Bourns	CW160808	180nH	5,00 %	240mA	0,92	1GHz	100
Ferrocore	CW0603	180nH	5,00 %	240mA	1,25	1GHz	30
Murata	LQW18ASR18J00	180nH	5,00 %	240mA	1,25	990MHz	25
Pulse	AWCS00161008R16	180nH	5,00 %	240mA	1,25	990MHz	25

Thanks & Best Regards,
Michael

Re: PN7160 filter choke current and value

Tomas_Parizek — Tue, 03 Oct 2023 08:59:40 GMT

Hello Michael,

The inductors you listed look OK. As they are wire-wounded, there is no risk of saturation effect. This is very critical for SMT ferrite inductors.

From the list you shared, I would go for some inductors with very low RDC resistance. e.g., L-14WR15JV4E or CW160808. You can also consider lower inductance e.g. 120nH which has even lower resitance -> less losses.

Tomas