LM5155: Schematic Review

Henry Wang3

Genius 3345 points

Part Number: LM5155
Other Parts Discussed in Thread: LM5122

Hi Sirs,

My customer is developing a board for LM5155 for 12V-in to 13V-out with 10A output current.

Could you please help to check and advise the schematic?

Thanks for your support.

over 4 years ago

0 Brigitte over 4 years ago

TI__Guru 65310 points

Hello Henry,

Please specify the minimum and maximum value of the 12V input voltage.

Best regards,
Brigitte

0 Henry Wang3 over 4 years ago in reply to Brigitte

Genius 3345 points

Hi Sir,

The input voltage maximum value is 12V.

0 Brigitte over 4 years ago in reply to Henry Wang3

TI__Guru 65310 points

Hello Henry,

What is the minimum input voltage?

Best regards,
Brigitte

0 Henry Wang3 over 4 years ago in reply to Brigitte

Genius 3345 points

Hi Sir,

The minimum input voltage is 12V too.

+1 Brigitte over 4 years ago in reply to Henry Wang3

TI__Guru 65310 points

Hello Henry,

It is not possible that a power source delivers 12V without any change. So I assume 11.5V to 12.5V for the review.

Generally for 10A output current, I would recommend to use a synchronous controller like LM5122 as the power dissipation in the diode is in the range of 0.58V*10A =5.8W . If you do not take specific care on the power dissipation, I think you might not find a diode that will survive.

The inductor and the transistor do not have any margin. I expect both will get very hot.

Softstart happens in 2.5ms. Please check the inrush current.

Why is UVLO set to 5.8V if the minimum input voltage is 12V?

The compensation does not fit, please try Rcomp = 494 ohm, Ccomp = 47nF and Chf = 1000pF.

If PGOOD is not used anywhere else, there is no pullup resistor needed.

I recommend to add a gate resistor.

Best regards,
Brigitte

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LM5155: Schematic Review