TPS53681: load transient question

user4811888

Part Number: TPS53681

Hi TI,

I see that there's a proportional path named ‘ACLL’ in compensator, being combination with integration 'INT' path, together as 'PI' control in loop. Changing KP/KI can shape loop gain curve easily.

However, it is well-know that 'ACLL' has its own definition from processor vendor, when 'DCLL' equals to zero, ACLL(transient load-line) can be used to describe ΔV/Δi during transient.

This physical meaning is also named AC droop somewhere.

My question is:

When loop is always linear at load transient, can I directly calculate that undershoot//overshoot ΔV = ACLL*Δi ?

over 4 years ago

0 Matt Schurmann over 4 years ago

TI__Genius 11095 points

No, this relation will not generally hold. You can think of the ACLL in the TPS53681 control loop as controlling the gain of direct voltage feedback vs. current feedback. If ACLL = 0, for example, the loop would be a pure voltage mode controller. The ACLL is added to the loop for speed during high speed transient events, as the inductor current (Isum) is slew-limited by the inductor value chosen.

0 user4811888 over 4 years ago in reply to Matt Schurmann

Intellectual 530 points

So DCLL has very clear physical relation, but ACLL here doesn't. I can only take ACLL as one gain parameter in loop(like Kp in PI).

A little bit confusing if both using load-line definition maybe. Thank you for answering!

0 Matt Schurmann over 4 years ago in reply to user4811888

TI__Genius 11095 points

Yes, that is correct.

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TPS53681: load transient question