LM5146: If I need three different DC output converting from the same input dc power supply circuit, what am I supposed to pay attention to?

Good morning, Tim!

Many thanks for your design recommendation. 

Based on my understanding of your recommendation, you suggest that I apply two types of chip of the power board: one is LM70880 and the other is LM5146/LM5145, do you?

But, could you please explain a bit about the first suggestion, why using LM70880 to substitute LM5146 for 3A & 8 A design, why need SYNCOUT to synchronize the other output channels? 

Thank you so much.

Yours Sincerely,

Nicole

August 29 2025

Good morning, Tim!

I used the SIMPLIS model of LM5146 you supplied to me to work on two regulators( 5V @ 10 A, 12 @ 8 A) working under the same input power source. The attachment are the schematic and the adjustment parameters which I used when I created 12V regulator based on your 5V model. 

I don't know why the outcome of the simulation for the two output voltages is wrong. Probably, I oversaw some parameters to set them probably. Would you please give me some advice ?

LM5146 5V 12V 250kHz two regulators.rar

Best Regards,

Nicole

Sep 2nd 2025

Hi Nicole,

Do the models work independently?

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Tim

yes, I think so. You can see in the schematic, these two regulators have independent own circuits except the input. They just share the same input dc power.

 I connected SW pin to different value of the inductor, and set the compensator circuits with according value components. That's what I did. As for the model self, I did not do any modification because I don't know how and what's the principles to build the model. I just simply copied yours. 

However, can I deduce that the reason for the  inappropriate result comes from the model ?

Thanks a lot, Tim!

Have a nice day!

Nicole

Sep. 3 2025