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OPA192: Short Circuit Protection Question

Stanley Tang
Prodigy 20 points
Part Number: OPA192
Other Parts Discussed in Thread: OPA2192, OPA4192

Tool/software:

Hello,

So the datasheet says the part can survive an indefinite short (to ground), but I'm trying to understand if this is true over the entire temperature range?

Near 150°C, the part can still sink about 25mA when output is shorted. 

Lets say that my supplies are +/-15V.

So near 150°C, if the amplifier is trying to drive a negative output voltage and the output is then shorted, the part's power dissipation is 225mW. Certainly, this will push the junction over 150°C (ignoring quiescent power dissipation)? Am I missing something?

Thanks.

  • +1
    TI__Mastermind 24428 points

    Stanley,

    • In general, for most modern amplifiers the short circuit limit is designed (and tested) to operate across the specified temperature limit.  The short-circuit limit limits the output transistor drive when excessive current is drawn.  Op Amp Input and Output Swing Limitations explains the circuit in detail.  
    • In the case of OPA192 there is an additional protection mechanism.  The OPA192 has built in thermal protection (see section 8.3.4).  For this device, if the die becomes too hot, the output drive is turned off two reduce power dissipation.  Once the temperature drops, the output will be turned back on.
    • The thermal protection is not incorporated into all amplifiers.

    I hope this helps!  Best regards, Art

  • 0 in reply to Art Kay
    Prodigy 20 points

    Hi Art, Thanks for the response, that helped.

    A follow up question.

    So for the multi amp packages, OPA2192 and OPA4192, if one amplifier shorts to ground and goes into thermal protection, does that cut power off to the entire chip or just the amplifier that is shorted?

    Stanley

  • +1 in reply to Stanley Tang
    TI__Mastermind 24428 points

    Stanley,

    Good question.  Since all the op amps are on the same die and the die is at a relatively uniform temperature they all should shut off.  Shut-off in this case means that the output is disconnected from the load.  I suppose it is possible if there were a significant temperature gradient across the die that one output would remain on while others would be disconnected, but in general I think the die would be at a relatively uniform temperature.  

    Best regards, Art