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LMX9838 no response / not discoverable

morph
Prodigy 30 points


Hi,

after several (perfectly working) LMX9838 designs, I encountered a serious problem.

We assembled a few new prototypes: some are working, most are not.

Tomorrow I will check if they are from the same batch, but anyway has somebody encountered a similar issue?

The external clock is working, but the TX line will stay low and the module is not discoverable over bluetooth. Also the start-up message is missing.

All use the same wiring. Since the systems have got dual supply (3.3V and 1.8V) we implemented this according to the datasheet.

Thanks in advance for any hints!

  • 0
    TI__Prodigy 725 points

    Hi Michael,

    Can you explain more on the previous prefectly working ones vs. the current not working ones? Were there any implementation differences between these 2?

    Also, what patch is on your LMX9838?

    Thanks.

     

    Ryan Lin

    ryanlin@ti.com

     

  • 0 in reply to Ryan Lin
    Prodigy 30 points

    Hi Ryan,

    they are exactly the same.

    The working ones have patch 212 as far as I know. Since the others are not responding in any way I can't determine the patch.

    This driving me crazy.... I have modules that were manufactured by NS and they are working fine. I was happy to see TI manufacturing them again, because I need tiny BT-SPP. But my latest order from Mouser seems to be a little tricky.

  • 0 in reply to morph
    TI__Prodigy 725 points

    Hi Michael,

    Please contact me directly at ryanlin@ti.com

    Let me know of your applications setup and I can help you further debug.

    Thanks.

    Ryan Lin

  • 0 in reply to morph
    Prodigy 20 points
    I am having EXACTLY the same problem. I did a design with the LMX9838 about 2 years ago. It worked perfectly. I designed a new board exactly the same way and none of them came up. I've spend the better part of two weeks and purchased more of the devices from digikey until I began to suspect the device. At that point, I soldered down a couple of parts on the old boards (which previously worked) and the new devices aren't working. They are not discoverable. They don't do anything. I verified the reset line is being cycled and I verified proper voltage at the 3.3 pins and verified that the 1.8 core voltage was up. In fact, it is about 1.75V. Frustrated!
  • 0 in reply to morph
    TI__Prodigy 725 points
    Hi Mike,
    As discussed, the parts can be optimized with the right manufacturing process as suggested. Please let me know if any further support is needed.
    Thanks!Ryan Lin
  • 0 in reply to Sam Michael
    TI__Prodigy 725 points
    Hi Sam,
    Thanks for bringing this to our attention. As communicated, we delivered more parts for your evaluation, and will help taking the parts you are having issues with and evaluate to suggest for further solutions. Please let us know of any other support we can assist with.
    Thanks!Ryan
  • 0
    Prodigy 130 points

    I got the same problem? It is almost as if the chip doesn't start-up correctly.. Please let me know of possible solutions. I have done a first prototype that worked great. So this is really not making sense..

  • 0 in reply to Bartho Horn51
    Prodigy 20 points

    Make certain the pull-ups on OP3, OP4 and OP5 are 1K.

    I had increased those values to reduce power consumption and as a result, the part comes up at the wrong baud rate.

    Verify core voltages.

    Although easy to work with, this part is a bit dated - especially for power consumption.

    It used to be my go-to part, but for battery powered operation, it leaves much to be desired.

    Sam Michael

  • 0 in reply to Bartho Horn51
    Prodigy 30 points

    Acutually I havent used the LMX since these issues came up.


    I have sent the remaining parts to TI for inspection, but they haven't returned a solution.

    So they still owe me 3 LMX modules and postage ;)