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LMQ644A2-Q1: Webench Question

brandon weatherly

Prodigy 20 points

Part Number: LMQ644A2-Q1

I tried to model this component in Webench:

Output Type: Single, dual-phase

Input: 9 - 16V

Output: 12A max @ 3.3V

1.) The resulting schematic shows FB1 being left open. Why is not being tied to ground, as per data sheet instructions for a 3v3 output? I don't know if I can trust anything else being showm in the schematic now.

2.) I need correct compention component values for a device beign configured as a single output 3v3 and another device being configured as a single output 5v. Both devices will have 12A outputs (6A per phase)

0 Sourish Nandy 22 days ago

TI__Expert 6960 points

Hello Brandon,

Thank you for the query!

Can you kindly tell me what the switching frequency is you want the device to operate at?

Thanks and Regards,

Sourish Nandy.

0 brandon weatherly 22 days ago in reply to Sourish Nandy

Prodigy 20 points

f = 2.1 MHz

0 Sourish Nandy 22 days ago in reply to brandon weatherly

TI__Expert 6960 points

Hello Brandon,

Thanks for the clarification.

Thanks and Regards,

Sourish Nandy.

0 Sourish Nandy 22 days ago in reply to Sourish Nandy

TI__Expert 6960 points

Hello Brandon,

Here is the QuickStart calculator for both the cases you asked for:

1641.LM(Q)64480_A0_A2_Quickstart_Tool_Brandon_3V3.xlsm

1641.LM(Q)64480_A0_A2_Quickstart_Tool_Brandon_5V0.xlsm

Make note that the procedure for fixed output was not taken during the making of the QuickStart calculator resulting in use of feedback ladder there.

It is the same case even with the Web Bench model too.

You can go ahead and use the method to fix the output of the convertor as follows:

The rest of the connections remains the same as explained in the datasheet and given in the QuickStart calculator.

You can use the attached calculators as reference to your case and tune to your application parameters.

Hope this helps!

Thanks and Regards,

Sourish Nandy.