LM5137-Q1: What is the optimal circuit configuration?

IKUTA

Prodigy 10 points

Part Number: LM5137-Q1
Other Parts Discussed in Thread: LM5137F-Q1-EVM12V

Tool/software:

Dear TI experts,

I am considering a DC-DC step-down controller. The specifications are as follows:

Input voltage：48.0V（24 to 70V）

Output voltage：15.0 ± 0.1V

Output current：max. 40A

Best regards,

Ikuta

25 days ago

0 Timothy Hegarty 24 days ago

TI__Guru 73752 points

Hi Ikuta,

For 15V/40A, a 2-phase design may be feasible if 40A is a transient condition. If it's a steady-state requirement, then consider 4 phases (see the LM5137F-Q1-EVM12V as an example).

Also, if Vin-max = 70V, you can use 80V logic-level FETs (see onsemi family of 80V FETs used in the EVM).

Tim

0 IKUTA 24 days ago in reply to Timothy Hegarty

Prodigy 10 points

Dear Timothy,

Thank you for your support.

I have populated the calculation document with the relevant numerical data.

I would appreciate any feedback or corrections you may have.

The calculations are based on a 4-phase output configuration utilizing two ICs.

Best regards,LM5137-Q1_quickstart_calculator_revB5.zip

0 Timothy Hegarty 23 days ago in reply to IKUTA

TI__Guru 73752 points

Thank you. I will take a look tomorrow and reply.

0 Timothy Hegarty 23 days ago in reply to Timothy Hegarty

TI__Guru 73752 points

Hi Ikuta,

I populated 0.5W as an estimate for the inductor core loss, allowing the efficiency plot to function.

Check if the total Cout is actually 141uF/10mΩ is correct, as the ESR is high.This affects compensation.

Looking at the FETs, you should use higher Rdson for the high-side FET, as it is now too capacitive and giving high switching loss. Also, enter the correct Qg at Vgs = 5V. See the onsemi 80V FETs selected in our EVM as an example.

Regards,

Tim

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LM5137-Q1: What is the optimal circuit configuration?