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temperature on case ...

samuele^_^
Prodigy 170 points

Other Parts Discussed in Thread: TMS320F2808

Hi!

I'm currently using TMS320F2808 DSP, and I'm experiencing some troubles with temperature measured on the case, that rises up to 80°C from 25°C room temperature...the machine could then work at 50°C room temperature, that is 105°C on the DSP case!!!

The periferals used are only PWM1,2,3 and SCI-A.

Are there some tricks in order to obtain a lower temperature? Switching off all the periferals clocks that are not used is a possible solution?

ThanX

samuele

  • 0
    TI__Guru 57255 points

    Samuele,

    Yes, it is possible and encouraged to turn off of peripheral clocks if you will not be using them.  This results in power savings and should also reduce the temperature increases that you are seeing.  You should take a look at the PCLKCR0, PCLKCR1 and PCLKCR2 registers in the F280x System Control and Interrupts User Guide (spru712).

    You may also want to check to see how unused GPIO are being used.  Ideally, unused GPIO would be configured as GPIO inputs and tied high by their internal pull-up resistor.  If you're interested, more tips can be found in the Hardware Design Guidelines App Note (spraas1)

    Even with all the peripherals on, the temperature rise seems high to me.  In addition to trying out some of the above, I would also check that the MCU is getting good stable power and that it is being grounded well. 


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Prodigy 170 points

    thank you Brett!

    I turned off all the clocks I'm not using, but with a room temperature of about 45°C the temperature on the case of the DSP is still above 82°!

    By the way, is there any protection (reset) against over-heating?

    The power is stable, but I have some doubts about the ground loop, since we have an analog ground for the DSP acquisition and a digital ground, connected together in 1 point...

    Soon we'll have a new board with 1 single ground plane, maybe it will bring some benefits :-)

    thanks!

    samuele

  • 0 in reply to samuele^_^
    TI__Guru 57255 points

    Samuele,

    Hmm, that still seems high, but not terrible anymore.  If it were me, I might try to replace the MCU with a new F2808.  ESD or something else may have happened during development on this device.  Nothing is more frustrating than trying to debug an issue that shouldn't really be there.  Just a thought...

    Having one ground may solve your issue, but it shouldn't be necessary.  The key thing is that the ground plane or net has good access to the GND pins and isn't being choked off by thin traces.  Also, if there's a good GND connection, heat will also flow through these traces :).

    On the F2808 (F280x family) there is no provision for an over-temperature reset internally.  You'd have to handle this externally.


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Prodigy 170 points

    ok, I powered only the board with the DSP, in an oven with an internal temperature of 50°C, and the temperature on the case rose up to 70°C, that is a 20°C delta, that's ok....the problem is then when the machine work with the load (300A output...), that probably creates a very noisy environment. So the cause of the problem is definitely the ground loop, as you suggested, and that's not a good news :-/

    I think we're going to change the board layout.........

     

    thank you for your support :-)

     

    samuele pierobon