LM5146: Design review

Sarumathi R

Intellectual 480 points

Part Number: LM5146

Hi Team,

We have selected LM5146 part for our below power application.

50V to 12V converter

50V to 28V converter

Herewith I have attached the schematics for your reference.

Kindly review the same and provide your valuable comments.12V-and-28V.pdf

Note: Input and output details are mentioned in the schematics pdf.

over 2 years ago

0 Timothy Hegarty over 2 years ago

TI__Mastermind 49207 points

Thanks, Sarumathi.

Please send completed LM5146 quickstart calculator files for these two designs so we can easily review compensation, component power losses, etc.

Regards,

Tim

0 Timothy Hegarty over 2 years ago in reply to Timothy Hegarty

TI__Mastermind 49207 points

Here are some comments on the schematic:

Use 60V or 80V FETs for the high-side position (no need for paralleled 100V FETs in a 10A design).
Sweet spot for efficiency-size tradeoff is 300-400kHz.
Remove components on LO -- not required.
Add boot resistor (e.g. 2.2Ω) to control high-side turn-on speed (if needed for EMI).
Connection errors at SW to PGOOD, VCC, etc.
RC snubber goes across low-side FET, e.g. 2.2Ω and 220pF. It should not be required if layout is correct -- see app note SNVA803.

Regards,

Tim

0 Sarumathi R over 2 years ago in reply to Timothy Hegarty

Intellectual 480 points

Hi Tim,

Thanks for the quick response.

Please find the calculator for the both designs.

LM5146-Q1 Quickstart Tool r2 - 50Vin 28Vout 10A 500kHz.xlsm LM5146-Q1 Quickstart Tool r2 - 50Vin 12Vout 13A 400kHz.xlsm

Note: We copied the design from webench.

Herewith I have attached that design also.

WBDesign18_28V.pdf WBDesign17_12V.pdf

+1 Timothy Hegarty over 2 years ago in reply to Sarumathi R

TI__Mastermind 49207 points

Hi Sarumathi,

The quickstart files look good. Just make sure the derated value for Cout is entered as this affects compensation. Also, the current limit is tight on the 12V/13A design - it should be set at ~150% of full load to give margin for transients, Rdson variation, etc.

Note that there is a SYNCOUT signal in the LM5146 that can be fed to the SYNCIN of a second regulator to achieve synchronization. The phase is shifted 180 degrees, so it provides input ripple cancellation.

Regards,

Tim

0 Sarumathi R over 2 years ago in reply to Timothy Hegarty

Intellectual 480 points

Thank you Tim for you valuable comments.

0 Timothy Hegarty over 2 years ago in reply to Sarumathi R

TI__Mastermind 49207 points

No problem, thanks for submitting on e2e.

Power management

Power management forum

LM5146: Design review