LM5012-Q1: Is there any voltage drop on the output if input voltage and output voltage are same?

Chase Jeong

Genius 5280 points

Part Number: LM5012-Q1
Other Parts Discussed in Thread: LM5012, LM5160-Q1

Tool/software:

Dear TI experts,

My customer considers LM5012-Q1 for their new project.

They use PoE for the input of LM5012-Q1. So the input voltage would be 24V or 48V.

And the output voltage is fixed to 24V.

I think that 48V input voltage would be fine, but if the input voltage is 24V, input and output voltage are the same.

How can I expect the voltage drop if the input voltage and output voltage are same as 24V? Can I find any specification on the datasheet?

- If the voltage drop is too large, Could you recommend other IC which is similar to LM5012 and have no voltage drop with such a situation?

Input voltage is 24V and 48V, output voltage is 24V fixed. and maximum output current is 0.65A. They prefer Automotive qualified parts.

Best regards,

Chase

14 days ago

0 Nityanand Hegde 13 days ago

TI__Intellectual 2510 points

Hi Chase,

With 48V input, 24V output is easily achievable. However 24V input, the output voltage would be roughly ~22.5V considering drops across the FETs and inductor with LM5012. However there are controller like LM5155x which supports above requirements of 24Vin and 24 Vout conditions.

Thanks,

Nitya

0 Chase Jeong 13 days ago in reply to Nityanand Hegde

Genius 5280 points

Dear Nitya,

Thank you for your support.

You mean that all DCDC buck converters which have integrated FET have same behavior like output voltage drop?

And there is the only way to consider DCDC buck controller and use external FET?

Please check this issue. Thanks.

Best regards,

Chase

0 David Baba 13 days ago in reply to Chase Jeong

TI__Mastermind 30420 points

Hello Chase,

Choosing a device with integrated MOSFET, would need to calculated the Efficiency and the losses in the MOSFETs, this is the limitation.

Thanks.

David.

0 Chase Jeong 13 days ago in reply to David Baba

Genius 5280 points

Dear Nitya, David,

Thank you for your support.

I simulated something with WEBENCH, it says that LM5160-Q1 can make 24V output with 24V input. Could you check the result below?

https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=16383B48957484B4

And please confirm that my customer can use this design.

Best regards,

Chase

0 David Baba 13 days ago in reply to Chase Jeong

TI__Mastermind 30420 points

Hello Chase,

According to the WEBENCH the power dissipation in the IC is 1.3W. with a Thermal resistance of ~40C/W you are looking at 52C temp rise above ambient.

You can also double check WEBENCH estimation by using the calculator spreadsheet in the product folder.

FLYBUCK-FLYBACK-DESIGN-CALC Calculation tool | TI.com

Hope this helps,

David.

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LM5012-Q1: Is there any voltage drop on the output if input voltage and output voltage are same?