OPA277: Output short circuit of absolute maximum rating

Hi Mesh,

don't overlook the footnote (2) in the "absolute maximum ratings"!

The short-circuit current is limited to typically 35mA. This current times the supply voltage is the heat dissipation the OPAmp has to handle during a short-circuit. With a +/-15V supply 525mW has to be dissipated during a short-circuit condition, which is quite a lot. With a thermal resistance of 110°C/W of the SOIC package the die will heat up 58K above the ambient temperature.

Now it becomes clear what "continuous" means: If the ambient temperature is low, the short circuit can last longer. But if the ambient temperature is very high, the short-circuit becomes very stressing for the OPAmp and the short-circuit should not last longer.

The short-circuit protection of an OPAmp is like a fire extinguisher. It's something for the emergency case, but nothing for repeated or even planned use. If the output can be short-circuited repeatedly during normal operation, add a current limiting resistor in series to the output of OPAmp. This also serves as an isolation resistor isolating the output of OPAmp from destabilizing capacitive loads.

Kai

Hi Mesh-san,

MESH said:

Does that mean that destruction or deterioration of this device is prevented by the function of a internal protection circuit or the like?

The table and graph below specified how Continuous in output short-circuit is defined. 

1. Isc is only defined in one amplifier per package. 

2. Isc or output short-circuit in continuous is defined within the recommended operating temperature range for a short duration. The IC should withstand the heat dissipation with the short-circuit (not exceeding the maximum junction temperature rating). 

3. The short-circuit op amp should not be self-destructive due to the event for a short duration. The circuit should be self-recovered and operated normally after the short-circuit current condition is removed. Please also see Kai's comments. 

If you have additional questions, please let us know. 

Best,

Raymond