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WL1835MOD: temperature issue

Errol Leon6
Expert 5850 points
Part Number: WL1835MOD


Hello team,

My customer has a design that incorporates WL1835MOD.  They are doing thermal testing on the product noticed an anomaly.  Before looking deeper into the issue, they wanted to get a sense of what the thermal qualification of the part is and any specific testing that is done.

Here is the general issue that they are seeing:

  1. Soak the unit for 2 hours powered off at -20 C.
  2. Power on the unit.
  3. Perform our device’s built in manufacturing test.  Test passes (further details on the manufacturing test below).
  4. Soak the unit for 1 additional hour at -20 C while powered on.
  5. Perform our device’s built in manufacturing test.  Test passes.
  6. Soak unit for additional 1:45 hours at -20 C (4:45 hours total).
  7. Perform our device’s built in manufacturing test.  Test fails on Bluetooth test.
  8. Note: after removing the unit from the cold soak, the Bluetooth test returned to passing within 10 minutes.

The Bluetooth portion of the manufacturing test performs a Bluetooth LE scan of devices with an expected device within range.  The host processor, AM335X, is running a custom built Debian Linux distribution.  (note: BlueZ is used for the Bluetooth stack)

When inspecting the device in the failure mode (device still at -20C).  They were able to login and communicate from the host to the WL1835MOD, so the UART link looks OK.  At this point, it seems that the issue they are seeing is on the RF side, but that is only an initial hypothesis.  As a last data point, the WiFi portion of manufacturing test performed without problem the entire time (the test scans for active access point and succeeds if one is found).

Thank you in advance for your support!

Errol

  • 0
    TI__Genius 12740 points

    Hi Errol,

    I hope all is well. For Wi-Fi the WL1835MOD uses the SDIO bus. For BT the WL1835MOD uses the HCI buss. The fact that Wi-Fi is working indicates that there is no ISSUE with the SDIO bus. The failure may be related to 2 things.

    1) The HCI buss may have a signal integrity issue

    2) There is an RF issue as you indicated.

    BT output power is lower than Wi-Fi power so if the RF performance shifts over temperature this may be an issue. A few things to look at:

    1) The implementation with the AM335x -> Is it also in the chamber soaking? IS it all rated for the -20C? IF it is outside the chamber, is there a long cable that is connected for communication?

    2) Have you validated your RF antenna match? Is it matched to a good 50 ohm load in this case?

    3) can you do the same test conducted?

    Thanks,

    Riz 

  • 0 in reply to Rizwan Murji
    TI__Genius 12740 points

    Hi Errol,

    I am going to close the issue out over e2e as it has been taken over e-mail.

    Thanks,

    Riz