OPA549: The design review for OPA549

Hi Zhang,

What is VIN_OPA in this schematic? Is this OPA549_VSET_4?

What is your V+ connection?

You have implemented your current limit circuitry correctly, but it is important to remember that the current limit is only used in instances where the amplifier is exiting linear operation.

Is this a voltage controlled voltage source?

This circuit looks to have a DC gain of 1+ (10k/5.1k) 

The interesting thing is that I see your output is changing as ILim is changing. This means the amp is wanting more output current. 

The figure you sow is actually the claw curve. This can depend on ILim, but as we discussed earlier, ILim should only be activated during non-linear operation.

What is connected to the output of the OPA549?

Thanks,

Jacob

Hi Jacob,

1. The VIN_OPA is the input voltage(The V_BB pin);

2. The V+ is connect to Buckboost and it can be regulation voltaget;

3. The change in output voltage is due to the fact that the reverse current is set to 5V while our source is set to 4V.

     At this time, the reverse current flows back through the lower tube of the OPA. As the voltage sampling point is located at the back,

     there is impedance in the path, resulting in loss from the output of the operational amplifier to the port output.

Hi Zhang,

I think I understand now. You want to know why BB is consuming 7A and OPA I set is only at 4.3A, Correct?

What is the efficiency of your buck-boost converter?

Can you measure the current flowing into the V+ pin?

Thanks,

Jacob

Hi,

Please refer to below waveform:

1. The direct reverse injection testing, the PIN3 is red line and the PIN4 is the blue line:

2. Fixed the PIN4 voltage to 1.384V, the output voltage is 3.99V:

3. Fixed the buck boost voltage to 9V, the red line become thicker and the blue line lift up:

4. The schmeatic diagram:

5. We need to know why the amplifer stable forward current output is 7A max. and the stable reverse current output is only 4A,

and the current waveform is oscillated when the output current more than 4A, thanks.