LM5177: Schematic Validation and NFET Selection

Egemen Aksoy

Intellectual 455 points

Part Number: LM5177

Tool/software:

Hello,

We are using LM5177 in our HMI project.

Vin -> 3V-36V

Vout ->5V up to 9.4A

Schematics are attached

Could you please validate the schematic?

Is input and output capacitances suitable for the operation? (For the output side Ecap may not be placed, 22u-10V DC derating is 15u at 5V)

Also could you validate NFETS(Q4,5,6,7) NTMFS4D0N08XT1G is suitable for our design?

NFET specs are

N-Channel 80 V 119A (Tc) 107W (Tc)

Rds max -> 3.5mOhm @ 27A, 10V

Vgs(th) max -> 3.6V @ 133µA

Gate charge max -> 33 nC @ 10 V

Can the Vgs threshold and gate charge characteristics of the NFET cause issues during boost operation?

Also, what voltage does the LM5177 drive the gates of the NFETs with?

Best regards,

Egemen Aksoy

4 days ago

0 Stefan Schauer 4 days ago

TI__Mastermind 48711 points

Hi Egemen,

thank you for using the E2E forum.

Could you please attach the filled out LM5177 Quickstart-Calculator to this thread? This would be the most efficient workflow for us to do a schematic review.

The MOSFET shown above does not fit for the LM5177 - you need to use a logic level MSOFET where the Miller Plateau is in the area of ~ 2.5 - 3 V.\

The MOSFET drive voltage is Vcc which is around 5V - see datasheet for exact values.

Best regards,

Stefan

0 Egemen Aksoy 4 days ago in reply to Stefan Schauer

Intellectual 455 points

Hello Stefan,

I will provide Quickstart-Calculator for LM5177 as soon as possible.

In our component library we also have NVMFS6H836NLT1G

Is NVMFS6H836NLT1G NFET suitable for the operation?

As a logic level mosfet I found BSC065N06LS5ATMA1. If NVMFS6H836NLT1G is not suitable can I use BSC065N06LS5ATMA1?

Best regards,

Egemen Aksoy

0 Stefan Schauer 4 days ago in reply to Egemen Aksoy

TI__Mastermind 48711 points

Hi Egemen,

BSC065N06LS5ATMA1 would work

NVMFS6H836NLT1G has a to high Miller Plateau and does not work.

Best regards,

Stefan

0 Egemen Aksoy 1 day ago in reply to Stefan Schauer

Intellectual 455 points

Hello Stefan,

Thank you for your support.

I found another logic level fet which is NTMFS5C670NL

https://www.onsemi.com/download/data-sheet/pdf/ntmfs5c670nl-d.pdf

Is it okay for the application?

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LM5177: Schematic Validation and NFET Selection