LM74900-Q1: Design review - Power management forum - Power management

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Shrey Gupta

Prodigy 125 points

Part Number: LM74900-Q1
Other Parts Discussed in Thread: LM74900

Good morning,

I have completed calculations and designed a hotswap and ideal diode using the LM74900 IC for 60V, 20A, and 60V, 100A applications. I'm looking for someone to review my design and calculations, suggest any necessary changes, and provide feedback. Your insights on how to enhance the efficiency of my design would be greatly appreciated. I am ready to share the relevant documents over private chat.

Thank you.

over 1 year ago

0 Shiven Dhir over 1 year ago

TI__Mastermind 49735 points

Hi Shrey,

Please share the design.

Regards,

Shiven Dhir

0 Shrey Gupta over 1 year ago in reply to Shiven Dhir

Prodigy 125 points

Hi Sir,

I've sent the design through a private chat. Please review it and suggest any changes. Also, help me on how to enhance the efficiency of my design?

Thank You

0 Shiven Dhir over 1 year ago in reply to Shrey Gupta

TI__Mastermind 49735 points

Hi Shrey,

Are you concerned with the power dissipation across the FETs?

I think it looks fine.

Regards,

Shiven Dhir

0 Shrey Gupta over 1 year ago in reply to Shiven Dhir

Prodigy 125 points

Hello sir,

Yes sir, I am worried about the power dissipation across the FET. In my calculations, I used six FETs for my 100A design. I'm hoping this won't significantly impact the efficiency.

Thank You

0 Shiven Dhir over 1 year ago in reply to Shrey Gupta

TI__Mastermind 49735 points

Hi Shrey,

I am unsure what you mean by efficiency here. I think higher number FETs will improve your power budget and hence efficiency of the system. Which you have already implemented.

Regards,

Shiven Dhir

0 Shrey Gupta over 1 year ago in reply to Shiven Dhir

Prodigy 125 points

Hello sir,

I'm concerned about the PCB board's temperature. In my calculations for 60V, 100A, the FET junction temperature reaches 97 degrees Celsius during steady state. Is this acceptable?

Thank You.

0 Shiven Dhir over 1 year ago in reply to Shrey Gupta

TI__Mastermind 49735 points

Hi Shrey,

97 degrees is acceptable, just in case you want to want lower temperature, you can work on using heat sink or thermal paste (basically reducing RthetaJA) Instead of adding more FETs. Since adding more FETs keep increasing the turn on time.

Regards,

Shiven Dhir

0 Shrey Gupta over 1 year ago in reply to Shiven Dhir

Prodigy 125 points

Hello sir

Is there any other concerns I should be aware of, aside from the turn-on time, when I increase the number of FETs in parallel, sir?

0 Shiven Dhir over 1 year ago in reply to Shrey Gupta

TI__Mastermind 49735 points

Hi Shrey,

1. You will have to scale up your charge pump cap according to the equation mentioned in the datasheet.

2. Your AC superimposed performance will be affected.

Other than that, there are no major concerns. Although I would say, 1W of PD across the FETs is very acceptable.

Regards,

Shiven Dhir

0 Shrey Gupta over 1 year ago in reply to Shiven Dhir

Prodigy 125 points

Hello sir,

I've taken note of your comments. I will share my design in a private chat, including both the schematic and PCB, for your review. Please suggest any modifications that might be necessary.

Thank you so much for your assistance, sir.

0 Shiven Dhir over 1 year ago in reply to Shrey Gupta

TI__Mastermind 49735 points

Hi Shrey,

I will review and get back to you by EOD Thursday.

Regards,

Shiven Dhir

0 Shiven Dhir over 1 year ago in reply to Shiven Dhir

TI__Mastermind 49735 points

Hi Shrey,

In the schematic shared, I see you have two soft-start circuits, which one are you using? Also can you fill-out this excel and share with me.

FET-INRUSH-SOA-CALC Calculation tool | TI.com

Regards,

Shiven Dhir