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OPA541: Current limit and resistance lmit

Shuji Ishiwata
Mastermind 7035 points
Part Number: OPA541
Other Parts Discussed in Thread: OPA549

Hi All,


I have a question about OPA541AP.


When used with RCL = 0.2Ω, I think ILIM will be about + 3.3A.

As a result of evaluation on the customer's board, it was 2.3A
Also, the output voltage and output current are decreasing.
Will it be within the guaranteed operation range?

I understand that ± 10% fluctuates due to the inflow of output current.
I also understand that the output current fluctuates depending on the temperature.

How much semiconductor variation does the device have?


Best Regards,
Ishiwata

  • 0
    TI__Guru* 93105 points

    Ishiwata-san,

    The OPA541 is one of our earlier power op amp developments and the current limit function is not precise. You may notice that there are not any current limit specifications listed in the Electrical Characteristics table. The actual current limit of a particular device will be a function of its transistor base-emitter voltages (VBE) and the external current limit resistor accuracy and its behaviors.

    Both the temperature dependent transistor VBE and current limit resistor's accuracy and temperature coefficient affect the point where limiting occurs. Figure 8. the Current Limit vs Resistance Limit vs Temperature graph gives some idea just how much the current limit range can be affected by temperature. Section 8.1.1, Current Limit, in the datasheet provides a good explanation of the current limit function and behavior.

    If you need tighter current limit control and its other parameters meet your application's requirements the OPA549 uses a different, more predictable current limit design that is voltage reference based. The high output current does not flow through the current limit resistor decreasing circuit power dissipation, voltage drop, and the physical size of the resistor.

    www.ti.com/.../sbos093e.pdf

    Regards, Thomas

    Precision Amplifiers Applications Engineering