LM5169: review of layout and schematic

Zixu Wang

Part Number: LM5169

Hi Team,

My customer is using LM5169. Vin_normal=72V, Vin_max=84V. Vout=15V. Iout_normal = 115mA. Please help to review its schematic and layout.

From my point of view, the value of Cin is not big enough, which could cause risk for normal operation.

For more comments of the whole design, I would like to hear from your advice!

BRs

Zixu

over 2 years ago

+1 Marshall_Beck over 2 years ago

TI__Mastermind 35210 points

Hello, Zixu.

I reviewed the schematic and the layout and it appears OK to me, minus the one point you made on input capacitors.

I agree the input capacitance is low.

Per the datasheet, we advise: " A minimum of 2.2 µF of ceramic capacitance is required on the input of the LM516x regulator, connected directly between VIN and GND." Currently, the schematic shows < 1uF effective,

Otherwise, looks OK.

0 Zixu Wang over 2 years ago in reply to Marshall_Beck

TI__Expert 8100 points

Hi Marshall,

Thanks for your reply. One more question: What kind of risk could happen for LM5169 for such low value Cin?

Could LM5169 shutdown when sourcing large current under such condition?

BRs

Zixu

0 Marshall_Beck over 2 years ago in reply to Zixu Wang

TI__Mastermind 35210 points

Hello Zixu, if Vin is well-stabilized (by CIn) then, the output could be somewhat unstable, as the device would be undergoing a constant line transient.

0 Zixu Wang over 2 years ago in reply to Marshall_Beck

TI__Expert 8100 points

Hi Marshall,

Could you please clarify what is "Constant line transient"? And I am confused that why output could be unstable if Vin is well-stabilized?

BRs

Zixu

+1 Marshall_Beck over 2 years ago in reply to Zixu Wang

TI__Mastermind 35210 points

I misspoke, I meant to say if Vin is not well-stability (by CIn).

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LM5169: review of layout and schematic