ST25R3916B one antenna detailed schematics

Shay · ‎2024-07-31

Hello,

I inherited a ST25R3916B design with two antennas.

I need to change the design to one antenna interface.

Is there any detailed schematic with ST25R3916B and one antenna?

Thanks

Shay

Travis Palmer · ‎2024-08-07

Hello Shay,

Below my comments due to your schematic from ‎2024-08-04 02:07 AM.

Decoupling caps:

You have both decoupling pairs on VDD_DR and VDD_RF. You could put C30 and C31 to d.n.p. only one pair of decoupling caps is required here. To have a spare footprint for C30 and C31 is a good idea. C17 and C18 should be as close as possible to the pins 14, 12, 16.

C32 is 10nF. The recommendation is 100nF, but this value is dependent on your supply.

If you want to use the new wave shaping feature of the 3916B you do no need C22 assembled => d.n.p. (further details: AN5965).

C42 and C43 seems a bit high - without knowing the xtal parameters. please have a look at AN6134.

R33 and R77 are terminating via 50Ohm the TAD's to GND. this is not required. => d.n.p.

Matching network:

The topology seems fine. You should check/measure the RFI voltage once you receive the HW. Maybe C11 needs to be adjusted.

I cannot state about the other component values.

BR Travis

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Peter BENSCH · ‎2024-07-31

For example, you can orientate yourself on the design of the X-NUCLEO-NFC08A1, which works with one antenna.

Hope that helps?

Good luck!
/Peter

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Shay · ‎2024-07-31

Hi Peter,

The above design uses the device two channels (RFO1/2 and RFI 1/2), I thought there is an implementation with one channel as in the DS (see below).

Is it better to use the two channels with one antenna?

Thanks

Shay

Peter BENSCH · ‎2024-07-31

You can drive the antenna either differential or single. As you mentioned, the X-NUCLEO-NFC08A1 works differentially, which is why RFO1/2 and RFI1/2 are used. If you want to use single driving, you only use either RFO1/RFI1 or RFO2/RFI2 and set the corresponding bits (IO configuration register 1, bits 7 and 6).

Hope that helps?

Regards
/Peter

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Shay · ‎2024-08-04

Hi Peter,

I hope the following request is not an excessive request.

We designed the ST25R3916Bwith one antenna based on the X-NUCLEO-NFC08A1 schematics. Please find it attached.

We don't have much RF experience.

Can you please review our schematic and comment (basically if we forgot something)?

Thanks

Shay

Travis Palmer · ‎2024-08-07

Hello Shay,

Below my comments due to your schematic from ‎2024-08-04 02:07 AM.

Decoupling caps:

You have both decoupling pairs on VDD_DR and VDD_RF. You could put C30 and C31 to d.n.p. only one pair of decoupling caps is required here. To have a spare footprint for C30 and C31 is a good idea. C17 and C18 should be as close as possible to the pins 14, 12, 16.

C32 is 10nF. The recommendation is 100nF, but this value is dependent on your supply.

If you want to use the new wave shaping feature of the 3916B you do no need C22 assembled => d.n.p. (further details: AN5965).

C42 and C43 seems a bit high - without knowing the xtal parameters. please have a look at AN6134.

R33 and R77 are terminating via 50Ohm the TAD's to GND. this is not required. => d.n.p.

Matching network:

The topology seems fine. You should check/measure the RFI voltage once you receive the HW. Maybe C11 needs to be adjusted.

I cannot state about the other component values.

BR Travis