TRF7970A: TRF7970 working

Hello Abhyuday,

what exactly is your concern? The solder connections of the IC? You could contact the IC pins at the side wall of the IC package and measure the connection to the board.

Or are you concerned about the board schematics and layout? If you followed the considerations in chapter 7 of the data sheet (https://www.ti.com/lit/gpn/trf7970a), the reference design in chapter 3 of the FAQ document (https://www.ti.com/lit/pdf/sloa246) and the layout design guide (http://www.ti.com/lit/pdf/sloa139) then the probability for a working application is maximized.

Or do you want a schematics and layout review of another person in order to minimize the probability of mistakes or hardware bugs?

Best regards,

Andreas.

Hello Andreas,

The schematics and the layouts were reviewed by one of your colleagues and they are are all perfect, my query is working of the TRF7970 board using the TI launchpad. We have made the necessary connections yet we are not able to detect the data through the antenna. Is there any way we can debug this or is there a procedure to follow?

Regards,

Abhyuday

Hello Abhyuday,

what about firmware for the TI launchpad? Ideally you could start with an existing demo firmware, which is known to work and where you can interact with a GUI (for example https://www.ti.com/lit/zip/sloa227 on MSP-EXP430F5529LP).

Do you also have a known working RF opposite (tag, transponder, P2P)?

There is no special procedure to follow. I would recommend to first focus on SPI communication to the TRF7970A in order read the status and to control the setup. Once the LP firmware is working, then you could focus on RF performance relevant aspects if necessary.

From you last post I assume you might already have SPI control, but no RF communication. Can you share more details?

Best regards,

Andreas.

Hello Andeas,

I've resolved the issue. The crystal was the problem all along. By any chance can I get the part no. of the crystal used in the TRF7970A booster pack. It would be really helpful.

Regards,

Abhyuday

Hello Abhyuday,

I'm glad to read that you solved the board function issues.

The DLP-7970ABP booster pack is a third party board design of the company DLP, so I don't have details, such as part numbers. Here is an old E2E post, linking to some comparable reference design: https://e2e.ti.com/f/1/t/602149. Also the FAQ document (https://www.ti.com/lit/pdf/sloa246) is listing some reference design resources in chapter 3.1 and 3.4. I don't know the exact part number of the booster pack, but the BOM in the reference design is listing a 13.56 MHz ITTI Company I30 series crystal. Anyway, I think it would be possible to use a comparable replacement part, as long as the load capacitance value of your board is matching to the crystal datasheet.

Best regards,

Andreas.

Hello Andreas,

I wanted to know if there any way we enable the internal antenna on the booster pack, as our requirement demands usage of four antennas implementing the RF switch will optimize our design. We want test it on the booster pack before we implement it in our design.

Regards,

Abhyuday

Hello Andreas,

Sorry for not replying about the crystal, I'll test various crystals and get back to you.

Regards,

Abhyuday

Hello Abhyuday,

I'm afraid that I did not fully get the point of your question regarding the booster pack antenna. If you want to switch to another antenna then the best would be to remove R5 in the reference design (https://www.ti.com/lit/pdf/tidrcm2) and connect your alternative antenna at the TP8 side. That node is 50 Ohm matched and thus compatible with many standard antennas. I guess DLP followed that reference design and you might be able to find the same 50 Ohm node on the booster pack.

In case I misunderstood your question, then please help to clarify.

Best regards,

Andreas.

Hello Andreas,

The link you have provided for the reference design of the booster pack is not working. If you can share the images it would be helpful.

Regards,

Abhyuday

Abhyuday,

here is a screenshot of the schematic:

And here again the link to the PDF:

https://www.ti.com/lit/pdf/tidrcm2

Best regards,

Andreas.

Hello Andreas,

Thanks for the schematic. I have an another doubt related to the crystal used, is the ESR value of the crystal a constraint? If it is, then what value of ESR should I be looking for?

Regards,

Abhyuday

Hello Abhyuday,

I think the ESR of the crystal is not so critical.

The shunt capacitors are more critical, but also here the oscillator might tolerate some mismatch.

See here older E2E threads, discussing these aspects

https://e2e.ti.com/support/wireless-connectivity/other-wireless-group/other-wireless/f/other-wireless-technologies-forum/699141/trf7970a-crystal-esr-requirements

https://e2e.ti.com/support/wireless-connectivity/other-wireless-group/other-wireless/f/other-wireless-technologies-forum/249061/trf7970a-crystal-selection

Best regards,

Andreas.

Hello Andreas,

The below are the shunt capacitance of the crystals I'm trying out. Please tell me if these values are alright and also please give me a range I can stick to.

Regards,

Abhyuday

Abhyuday,

maybe my wording was misleading. The external shunt capacitors need to match the calculated value, based on the required load capacitance in the crystal datasheet. The formula and an example can be found in chapter 6.6 of the TRF7970A datasheet (https://www.ti.com/lit/gpn/trf7970a).

Best regards,

Andreas.

Hello Andres,

Understood, I've calculated the the shunt capacitance according to the document. The problem is the crystal I order initially based on the external shunt capacitance did not work for me so I used the crystal from TFR booster pack and it worked. I've placed order for some various crystals to test out, depending on the results I'll update you.

Regards,

Abhyuday