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OPA541: OPA541 paralled operation circuit

Seokbong Kim
Prodigy 10 points
Part Number: OPA541

Tool/software:

hello.

I configured a paralled operation circuit with reference to Figure.15 in the Application of OPA541.

+VS: +6V, -VS: -6V

R1: 10K, R2: 10K

I set the input power to -1V and set the 5A in the loader instrument, it will be 1V/5A setting in the output.

Current Sharing of Master Opa541 and Slave Opa541 work well

but

I set the input power to +1V and set the 5A in the Loader instrument (polarity change), the output is -1V/-5A setting.

Current Sharing of Master Opa541 and Slave Opa541 do not work well.

The Master OPA Output Voltage starts with -1.45V and Slave -1.0V, and after about 30 seconds, it changes the same to 1.0V and 1.0V.

I want to check if this is normal.

And additionally 10A output is not available on SOA in that paralled operation circuit(+6Vs, -6Vs, 1Vout)? Is it possible up to 7A?

  • 0
    TI__Genius 12396 points

    Hi Seokbong,

    This delay may be caused by the a few reasons. Is the load purely resistive, or is it also capacitive/inductive?

    C1 and C2 sometimes require optimization to ensure proper circuit operation. Would you be able to remove the components for a quick test on your board.C2 can especially cause problems sometimes for parallel circuits like this. 

    Does the amplifier set to -1V faster if you reduce the current load?

    Thanks,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 10 points

    This delay may be caused by the a few reasons. Is the load purely resistive, or is it also capacitive/inductive?

    -> My loader instrument set Resistive

    C1 and C2 sometimes require optimization to ensure proper circuit operation. Would you be able to remove the components for a quick test on your board.C2 can especially cause problems sometimes for parallel circuits like this. 

    -> tested C1, C2  but the results are same

    Does the amplifier set to -1V faster if you reduce the current load?

    -> Yes. The speed was fast on the low current.

  • 0 in reply to Seokbong Kim
    TI__Genius 12396 points

    Hi Seokbong,

    Thanks for the details here. 

    Do you have bypass capacitors on the supply rails of the amplifier? 

    Layout like this will provide a low impedance path for transient return currents to pass back to the supply pins of the device. 


    A good place to start would be taking scope shots with low current and full load at a few points on the circuit. These scope-captures will help me understand what parts of the circuit are operating as expected.

    If possible, could you please place probes at the following nodes:

    Vin

    IN- U1

    Vout U1

    Vout U2

    Seeing the transient response at these nodes will help us possibly understand what is going on. 

    Thanks,

    Jacob

  • 0 in reply to Jacob Nogaj
    Prodigy 10 points

    Thanks. Jacob.

    spcope captures here.

    load set 6A, then U1 vout is -1.4V and U2 vout is -1.2V.

  • 0 in reply to Seokbong Kim
    TI__Genius 12396 points

    Hi Seokbong, 

    Thanks for the scope shots, I appreciate you taking this data for me. 

    I cannot tell if U1 Vout and U2 Vout are really 200mV different, but I can clearly see that there is a time delay associated with the realization of the final value. 

    As I see it, it looks like the output first goes to -.9V for U1 out and U2 out, then after about 4 seconds goes to -1.4V. Do you see things the same or different?

    Thanks,

    Jacob