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TMS3705: Temperature Issues

Rob DeVries
Prodigy 85 points

Part Number: TMS3705
Other Parts Discussed in Thread: TMS37157

Hello,

We are using the TMS3705A in a automotive environment and are having some issues.

One issue we are having is a limited range when it gets cold.  We  can get about 5inches in 20C but less than 1inch in -20C and about 0.5inches in -40C.  Also the Noise I see gets much worse cold than warm.

What could be making this happen and how would I go about fixing it?

Another issue is I am getting some different wave forms than what the data sheet says, and I am getting data out when no RFID tag is near?

In the document Notes on using the "TMS3705A1DRG4 for TI Low Frequency Read Only & Read\Write Transponders" I am not able to get wave forms like that how was the test setup done?  I can see the charge but no discharge.

Any help would be great.

Thank you

  • 0
    TI__Guru*** 135355 points
    Hello Rob,

    I've submitted an inquiry to the product team about the expected behaviors at low temperature.

    What document are you referring to? Can you provide a TI literature number?
  • 0 in reply to Ralph Jacobi
    TI__Guru*** 135355 points

    Hello Rob,

    Further questions from the product team:

    • Is this is a new design or a running application? If it's a new design, we would recommend to use the latest version of the product: TMS3705D
    • Is the reported issue seen with a single device, or is it repeatable with multiple devices?
    • Can you provide us the screenshots of the waveforms you are referring to?
    • Can you provide a circuit schematic? If needed, we can exchange the schematic privately via the E2E friend mechanism.

    We have not seen issues with this device at low temperatures and we will try to help you debug the issue to uncover whats wrong.

  • 0 in reply to Ralph Jacobi
    Prodigy 85 points

    Hi Ralph,

    This is a new design which replaces the RI45538.  We are not able to work with the D version, the only chips available are A and B.

    This issue is across all assembled units and all act the same way when cold.  Even the manufacturer data shows issues.

    I can provide any information required but I would like to send it privately due to the nature of application, if you could let me know how to do it.

    I will be putting together a demo board to isolate the TMS3705 from any other circuits to see how it operates, is there some code I could use?

    The code which is not mine (I have been hired independently by the purchasing company to investigate and correct this issue) and I do not have access to any other code.  

    Thank you,

    Rob

  • 0 in reply to Rob DeVries
    TI__Guru*** 135355 points
    Hello Rob,

    The TMS3705 is not a drop-in placement for the RI45538, and it doesn't sound like this application is using the RI-STU-MRD1 correct?

    When migrating from the RI45538 to the TMS3705, it is required to change the antenna, the firmware and schematic completely. Do you know how much of this has been done so far?

    I've sent you an E2E friend request so we can receive and review the schematic through private channels.

    Firmware wise, you can look at the base station projects provided in this guide which may have other useful collateral for you as well: www.ti.com/.../swra309a.pdf - like for example the base station board schematics include the TMS3705.
  • 0 in reply to Ralph Jacobi
    Prodigy 85 points
    Correct the TMS3705 is not a drop-in replacement for the RI45538. The manufacture did keep some items from the old design an reuse it.
    They kept the antenna design since they kept the transmitter (charging) side. The processor is new with new firmware. The design does work for the most part, but not enough range which is about 5inches at 20C. When the design gets cold (-20C -40C) the range decreases to less than 0.5inches. I have gone through a lot of the app notes and I based my demo board on one of them. What i did find was that the TMS37157 has demo boards, software and seems like a better chip.
    I will get my info together and send it to you.
    Thanks,
    Rob