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ADSP-21375KSWZ-2B temperature testing issue

Hello,

    My customer applied ADSP-21375KSWZ-2B for their product. During the system power-up and re-boot stage, MCU will config ADSP-21375 by SPI interface.

There is a phenomenon about this problem:

When the system is in normal working mode, the Customer uses a hair drier to increase the environment temperature to +55 degree centigrade. Everything is ok when the temperature reached +55 degree centigrade. Then they powered down and restart the system at +55 degree centigrade, they found the SPI interface of ADSP-21375 didn't worked correctly so that MCU could not configure our DSP and the system will work down. They tested the SPI signal by oscilloscope, MCU could send out the SPI signal correctly, but ADSP-21375 didn't respond correctly.

    Would you please help to extend some suggestion about this problem? Thanks!

  • Since the part was operational before the reboot, I would look at several items:

    1. Flash Device. This is used during boot and not afterwards. This could be the problem but actually not so likely.

    2. Are you using a crystal? I have seen crystals that did strange things versus temperature however still not likely given that the system was operational before reboot.

    3. My favorite theory would be that the PLL is having trouble relocking. Later SHARCs have a fairly elaborate PLL set up procedure. You may be able to experiment with this possibility. Is there a 1M resistor across the crystal?

    4. Check the core supply voltage as well. You may want to tweak this a little. You didn't mention the core clock frequency that the part was supposed to operate at.

    5. Is reset# time too short?

    55C is not that hot, but I wonder how they determined that was the actual temperature.  Maybe the die really is much hotter than they think given the hair dryer is not the most precise test apparatus. If the die gets too hot, I think the PLL might be susceptible as well as other parts of the device. Maybe the leads of the part are increasing die temperature more than a normal temperature rise.

    Al Clark

    www.danvillesignal.com

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    EZ Admin