LM5145: Schematic review

CHO SR

Genius 3285 points

Part Number: LM5145
Other Parts Discussed in Thread: CSD19534Q5A

Please review the customer's schematic

And attached a calculator.

201013_Main_Power_LM5145 Schematic.pdf

201013_LM5145 Calculator r12-7.xls

over 3 years ago

0 CHO SR over 3 years ago

Genius 3285 points

Sorry.

The schematic has been updated.

Schematic changes : Capacitor ESR value

0 Frank De Stasi over 3 years ago in reply to CHO SR

TI__Guru 63275 points

Hello

Sorry for the delay in responding.

We will get back to you shortly.

Thanks

0 Timothy Hegarty over 3 years ago in reply to Frank De Stasi

TI__Guru 57152 points

Hi Cho,

Thanks for sending the files. Here are some comments:

1000uF seems excessive for an output cap, why so high? It will provide very little filtering at the switching frequency of 300kHz (high ESR and ESL). Also, check if ESR varies over temperature as this will affect compensation.
Consider using a 5 x 6mm FET for the high side, e.g. CSD19534Q5A 100V NexFET, for better thermal performance at 10A load.
BSC117N08 is somewhat high Rdson for the low-side FET given the 25% duty cycle.
SYNCIN already has an internal 20k to GND (consider adding an option to pull high to enable FPWM if needed).
Consider adding an input EMI filter (not sure if you need the NTC resistors, most designs do not include those).

Regards,

Tim

0 CHO SR over 3 years ago in reply to Timothy Hegarty

Genius 3285 points

Hi Tim,

Thank you for replay.

Please review the revised information.

1. The customer has decided to change to 470uF at present. Is there any problem with using 470uF?

2. Change to calculator recommended product.

High side : BSC117N08NS5

Low side : BSC037N08NS5

3. Changed to BSC037N08NS5.(Rdson 3.7)

4. It deleted 20k and filled it out as an option.

0 Timothy Hegarty over 3 years ago in reply to CHO SR

TI__Guru 57152 points

Sounds good, Cho. These 80V Infineon FETs are also used in the EVM.

Please send an updated quickstart file and latest schematic if you need further review.

Regards,

Tim

0 CHO SR over 3 years ago in reply to Timothy Hegarty

Genius 3285 points

Sorry, I chose the wrong column.
So I revised the replay.

0 Timothy Hegarty over 3 years ago in reply to CHO SR

TI__Guru 57152 points

Cho,

Let me know if you need further help with a review, If so, send on the latest files to review (quickstart and schematic).

Regards,

Tim

0 CHO SR over 3 years ago in reply to Timothy Hegarty

Genius 3285 points

Dear Tim,

The customer decided to proceed with the board test.

I will complete the column and ask you again if there is a problem with the test.

Thank you for your support.

0 Timothy Hegarty over 3 years ago in reply to CHO SR

TI__Guru 57152 points

Ok, Cho. I will close this thread for now.

Regards,

Tim

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LM5145: Schematic review