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OPA549 Thermal Shutdown

Zeng LIU
Prodigy 80 points
Other Parts Discussed in Thread: OPA549

Hi,

I'm using OPA549 to operate as a voltage sink. In my design, the power supply of OPA549 is +-5V, and its output is conneced to a DC voltage source through a resistor.  The system works well when the sink current is low. With the increase of sink current, the thermal shutdown will be triggered. However, the voltage between E/S and REF pin is different from the value in the datasheet. In normal operation, the voltage of E/S is 3.5V approximately, and gradually increases with the sink current. When thermal shutdown happens, the voltage of E/S is around 3V, which is much larger than 0.2V given in the datasheet. The test waveform is shown as below. The blue line is the volatge between the E/S and REF, and the green line is the sink current.

So could you tell me why the E/S voltage is different from the value in datasheet, and is there any relationship between E/S and the sink curent?

Thanks!

 

 

  • 0
    TI__Guru 64840 points

    Zeng,

    There is not enough information you provided in your post-specifically what is the voltage on REF pin? In your application using +/-5V supplies, it needs to be between -5V to -3V.  If you need further assistance, please provide the schematic of your circuit showing all nodal voltages and components used.