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OPA548EVM: OPA548 Eval Board Stuck in Thermal Shutdown

Reid Kovacs
Prodigy 10 points
Part Number: OPA548EVM
Other Parts Discussed in Thread: OPA548

I recently purchased the OPA548EVM eval board. Upon arrival, I took it out and began to set it up. After reviewing the datasheet, I connected the rails (AVDD, AVSS, GND) with +/- 6V and expected to see the power indicator LED (greed LED). However, upon starting the power supplies, the eval board indicated a thermal shutdown (red LED) so I immediately turned off the supply. The OPA548 did not seem warm at all. I ordered two of the boards, and I have found the same result with both. I tested the power supplies to ensure they they are supplying the expected voltages. I also noticed that when the inverting and non-inverting input pins on the OPA548 package are pulled low no matter what is selected with the eval board jumpers.

Is there an obvious issue that would cause the thermal shutdown pin to trigger without excess heat?

  • 0
    Guru 140200 points

    Hi Reid,

    there's a +5V regulator on the board powering all the LEDs which needs an input voltage of at least +7V to work properly. Looks like your +6V supply voltage is too low.

    Kai

  • 0
    Prodigy 10 points

    Hello Kai, thank you for the suggestion. Since posting this I have also tried with +/- 10V rails and I had the same result. In both cases I measured the output of the 5V regulator to be within 20 mV of 5V.

    Is there anything else that might be causing the thermal shutdown to trigger? 

    best,

    Reid

  • 0 in reply to Reid Kovacs
    Guru 140200 points

    Hi Reid,

    how have you set all the jumpers?

    Kai

  • 0
    Prodigy 10 points

    Hi Kai,

    I have tried a few configurations and the light is still triggered:

    1. The configuration described in the manual for non-inverting output with dual rails then with single rail.

    2. The configuration described in the manual for inverting output with dual rails then with single rail.

    3. Both inputs connected connected to ground. 


    best,

    Reid

  • 0 in reply to Reid Kovacs
    Guru 140200 points

    Hi Reid,

    can you measure the voltage at TP8? During shutdown it should be 300...400mV more positive than the negative supply voltage. During normal operation, on the other hand, it should be about 3.5V more positive than the negative supply voltage. See section 7.3.3 of datasheet.

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 55091 points

    Hi Reid, 

    Please follow Kai's suggestions, and measure the TP8 voltage with respect to V- rail.

    In addition, please increase the supply rail above 7Vdc for LDO. Please apply +/-10Vdc to +/-12Vdc to check out the EVM.  

    If you have additional questions, please let us know.

    Best,

    Raymond