LM70880-Q1: Parallel Design

Aaron McIntosh

Part Number: LM70880-Q1

Tool/software:

Hello,

I was looking at suitable buck converters for an application of up to 48V input voltage, 12V output voltage at 15A. I identified using LM70880-Q1 in parallel as my only option. After reviewing the datasheet I am still a little confused as to how I would design the component in parallel, as from what I have seen, neither Webench or the Quickstart calculation tool support parallel modelling unless I am mistaken. Would I be able to be provided an example design for my application or a similar design that I could use as a reference?

Thank you.

11 months ago

+1 Ben C 11 months ago

TI__Guru 56345 points

Hi Aaron,

Below is a picture showing dual LM70880-Q1 setup. Please let me know if there are any questions.

Ben

0 Aaron McIntosh 11 months ago in reply to Ben C

Prodigy 90 points

Hi Ben,

Thank you, I appreciate it.

0 Ben C 11 months ago in reply to Aaron McIntosh

TI__Guru 56345 points

Hi Aaron,

No problem. Glad to be of help. :-)

Ben

0 Aaron McIntosh 11 months ago in reply to Ben C

Prodigy 90 points

Hi Ben,

Does the note in the simulation model file saying the CNFG pin is not modelled mean I will not be able to create any meaningful parallel mode simulation results using Pspice for TI? I briefly attempted to anyway but was met with multiple errors, some of which I included in the attached image and have been unable to fix so far.

Thank you.

+1 Ben C 11 months ago in reply to Aaron McIntosh

TI__Guru 56345 points

Hi Aaron,

Yes, the model does not support dual mode operation.

We are aware of the issue with the PSpice model that is found on TI.com is not working.

We will be updating the model and hopefully the working model will be available by early next week.

Ben

0 Aaron McIntosh 11 months ago in reply to Ben C

Prodigy 90 points

Hi Ben,

So will I only be able to validate parallel circuit designs and obtain efficiency estimates for the application if I physically obtain the components and conduct bench tests or is there any other alternatives?

Thank you.

+1 Ben C 11 months ago in reply to Aaron McIntosh

TI__Guru 56345 points

Hi Aaron,

I don't think there is another alternative. The main engineer is out of the office at this time but once he is back, I can ask him. He will be back on Monday of next week.

Ben

0 Aaron McIntosh 10 months ago in reply to Ben C

Prodigy 90 points

Hi Ben,

As I cannot simulate it, will you please review the below design?

Thank you.

+1 Ben C 10 months ago in reply to Aaron McIntosh

TI__Guru 56345 points

Hi Aaron,

Here are a few comments that I have:

Please add 0.1uF capacitors as close as you can to both VIN pins for high-frequency bypass
Depending on your output load transient characteristic, the amount of output capacitance on the schematic can support a 60% load step, if using TDK C3225X7R1E226M250AB capacitors.
What inductor do you plan to use for this design? A suggestion is Coilcraft XGL1060-682 inductor
Make sure the Cboot and Rboot circuit is connected to SW4 (pin #5)
I didn't see a connection to the BIAS pins for both parts. You can have the BIAS pins connect to VOUT (12V)
Please see attached quickstart calculator for loop compensation values.

LM70XX0_quickstart_calculator_A0_Aaron_M.xlsm

Ben