LM2576HV: Peripheral selection

Michael Priven

Part Number: LM2576HV
Other Parts Discussed in Thread: LMR36015, LM22672

Hi,

I would like to do dc/dc buck conversion:

36-40V to 12V, @0.6-1.5A
12V to 3.3A, @ 0.2-1A (12V comes from the previous dc/dc)

I tried datasheet, evaluation board schematics and Webench they all give different suggestion for input and output capacitor and the inductor

Please assist with peripheral selection, I'm also open for other dc/dc options

Michael

over 6 years ago

0 Katelyn Wiggenhorn over 6 years ago

TI__Genius 11040 points

Hello,

I would recommend using the datasheet recommendations or EVM recommendations as a starting point.

I would also recommend evaluating the LMR36015 for this application. This is a 60 V, 1.5A device. www.ti.com/.../lmr36015.pdf

Best Regards,
Katelyn

0 Michael Priven over 6 years ago in reply to Katelyn Wiggenhorn

Prodigy 190 points

Hi Katelyn,

Thank you for replay.

I'm looking for voltage-mode buck converter (I forgot to mention), and the part you suggested is current mode.

How to select inductor for application with changing current? by maxim or minimum?

Does bigger capacitor are better?

Do I need add pi filter?

Best Regards,

Michael

0 Katelyn Wiggenhorn over 6 years ago in reply to Michael Priven

TI__Genius 11040 points

Hello,

The 40V input, voltage mode buck converters have a maximum current of 1A or 0.5A. One option would be the LM22672.

For the current mode control, the inductor is chosen based on the maximum load current. The recommended capacitance is listed in the datasheet. For this specific device it will range between approximately 44uF - 66uF. You do not need a pi filter for a current mode control device. You will need a standard LC output.

Please let me know if you have any additional questions.

Best Regards,
Katelyn

0 Michael Priven over 6 years ago in reply to Katelyn Wiggenhorn

Prodigy 190 points

Hi,

Don't you think that 42V is marginal for 40V input?
What about LM2591HV-ADJ?

Thank you,
Michael

0 Katelyn Wiggenhorn over 6 years ago in reply to Michael Priven

TI__Genius 11040 points

Hi Michael,

This depends on what the variance needed on the 40V input. The LM2591HV-ADJ will also work for 1 A load.

Best Regards,
Katelyn

0 Michael Priven over 6 years ago in reply to Katelyn Wiggenhorn

Prodigy 190 points

Hi Katelyn,

Looking on the inductor selection diagram (Figure 31), and Et calculation, my result is - 56Vus, but there is no inductor value in this region.
Can I assume 330uH (according to AN-1197)?

Best Regards,
Michael

0 Katelyn Wiggenhorn over 6 years ago in reply to Michael Priven

TI__Genius 11040 points

Hi Michael,

Yes, you can also use the AN-1197 to calculate the inductor, and the 330uH should work.

Please let me know if you have any additional questions.

Best Regards,
Katelyn

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LM2576HV: Peripheral selection