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DP83848YB: DP83848YB - Communication lost at high temperature (>40°C)

Davide Di Venti
Prodigy 10 points

Part Number: DP83848YB

Tool/software:

Starting electronic from ambient temperature to high temperature (20°C-70°C), communication still works. Conversely, starting at high temperature (~70°C) causes a breaking communication. To enable communication, starting electronics once temperature is at room temperature is necessary (waiting or with a -45°C refrigerant spray). 

When starting at high temperature (>40°C), adding a second ceramic capacitor of 10uF (16V-0805) in parallel at PFBOUT (pin 19) and ground allowed better behaviour about communication breaking. Is the solution? Do you have any remarks to optimize the result? 

In datasheet, you are precising that a tantalum 10uF capacitor is preferred, probably because you encountered poor performance? it is related ?

  • 0
    TI__Mastermind 43325 points

    Hello,

    Please note that DP83848 is an older part and support is strictly limited to existing documentation.

    We have characterized that part to perform with the desired PF network of 3x 100nF || 1x 10uF tantalum. Is your current design following datasheet recommendations?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    Prodigy 10 points

    Hello Gerome,

    Yes, the entire architecture around the PHY strictly follows the reference design. This device works perfectly in several of our projects, but this specific board shows the described behavior once it gets warm.

    My question is: can I safely use a ceramic capacitor instead of a tantalum one on the PFBOUT node?
    As mentioned in my previous message, I am currently using 10 µF ceramic capacitor. I cannot use tantalum or polymer capacitors because of long-term aging and reliability concerns in our application.

    Is the PFBOUT bias stability the only critical factor at high temperature, or could other internal blocks of the PHY also impact communication when starting at elevated temperature?

    For reference, my 3.3 V supply is very stable across all temperature ranges, and the military-grade EP version shows the same behavior.

    Any advice, even informal, would be very helpful.

    Best regards,

    Davide

  • +1 in reply to Davide Di Venti
    TI__Mastermind 43325 points

    Hello,

    There is very limited support available for this device unfortunately. It could be possible that the specific differences between a tantalum and ceramic capacitor are being stressed by temperature. 

    Another basic check; how is the clocking and control lines (like RESET) looking versus this temperature variable? Perhaps the device may be okay, but the clocking, which is an important subsystem for the PHY, is affected.

    Sincerely,

    Gerome