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LM1875: Circuit shuts down after a few seconds of operation, then resumes again after a few seconds ... cycle repeats

3109457
Prodigy 20 points
Part Number: LM1875

I built the circuit as per data-sheet guidelines/values (enclosed pdf file). On feeding an input, I get the output as desired, but the amp shuts down for a few seconds after being in operation for half a minute or so and then again resumes operation. The chip does not get hot so I am at a loss to know how a thermal shutdown can occur as that seems to be the probable cause. Any other ideas ?LM1875-Model.pdf

  • 0
    TI__Expert 6985 points
    Hello! This is very strange if you following exactly the datasheet application. Does it just shut down onece and then never again... or is it continuous?
    Also, uder what input voltage are you operating and what is the value of the load? Please pay particular attention to the DS section on: CURRENT LIMIT AND SAFE OPERATING AREA (SOA) PROTECTION. Thanks, Jeff
  • 0 in reply to Jeff Kohnle
    Prodigy 20 points

    Thank you, Jeff for your reply. As for your question, as stated, the cyle of shutdown-resume repeats indefinitely. I am using a signal generator as the input with about 100-500 mV rms input. As I do not find the chip even getting warm, I am inclined to think it is not a thermal problem. My layout shows the signal and power grounds to be one contiguous area. Could that be the cause ? I also tried to tinker with C2 as 2 x 22 uF in series to give a non-polarized version instead of a 1 x 22uF single capacitor but to no avail. Maybe you can give some more trouble points ..... again, thanks for your help.

  • 0 in reply to 3109457
    TI__Expert 6985 points
    Hello! Yes, your grounds could be the source of the problem. Have you checked them further?
    Thanks, Jeff