TPS54678: :

Hello Onur,

You mentioned that your peak load current is 5A in your application.

You should not have any issue with the current limit then. The current limit will only be active if the output current exceeds this 10.5 (typical) value.

The saturation current is only the current value (here 9A) where your inductor decrease of 30%, from 1.5uH down to 1.1uH. 

Let me know if this answered your question.

Thanks a lot!

Regards,

Dorian

Hi Dorian,

Thanks for your answer. 

The only concern I have, if there is a short at the output, 512 times(hiccup), my inductor may face with 11.5A peaks. I can not determine how this will heat-up my selected inductor. 

Hello Onur,

This would be a question to ask SMD inductors.

What I can tell you is that, looking at the datasheet figures 46 & 47, the inductor will face 11.5A condition ~10% of the time.

I would not expect a lot a heat coming from the inductor in this configuration, at least less than 90 C as the curves above are showing.

90 C should be coming from the inductor conducting 11.5A continuously.

You can also evaluate this on the TPS54678EVM, I see that the inductor you want to use has the same size as the inductor on the TPS54678EVM.

Let me know if you have any further questions.

Thanks a lot!

Regards,

Dorian

Hi Dorian,

I am doing simulations with this component at TI Webench tool. For load transient simulations, I am a bit out of my target range. Load Current is at 4.5A and my target is to stay in between 0.825V-0.875V.

Do you have any recommendation. You can see my circuitry and simulation result below.

Hello Onur,

You have several options here, you can either use more output capacitance or tweak the Compensation settings with Ccomp/Ccomp2/Rcomp. 
TPS54678 might not be the best option in our portfolio to achieve best load transient performance, you cam also have a look at the TPS62869/TPS62866 which can be a better choice here and easier to design.

Let me know.

Thanks a lot!

Regards,

Dorian 

Hi,

Changing the supply is my last option here. Adding extra capacitor to the output didn't give me any extra benefit according to Webench tool. Do you think you could help me here with tweaking the compensation settings?

Best Regards,

Onur

Hello Onur,

Here attached you can see the design you can use in order to stay in between 0.825V-0.875V.

WBDesign344_Load Transient-2.pdf

Is there a specific reason not to change part here to a newer device ?

Let me know if you have any questions!

Regards,

Dorian 

Thanks for the update, 

My design is attached. I increased the efficiency a bit more. Here is my circuitry and I would be happy if you have any feedback.

With new power estimations, continuous current will drop to 3.7A Inductor is in range and efficiency will go a bit higher and probably ripples a bit lower.

WBDesign24_Load Transient-19 (1).pdf

Hello Onur,

I haven´t heard back from you.

Do you have any further questions?

Let me know.

Thanks,
Dorian