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LM5156H-Q1: Device solution recommendation

Daniel Wang (auto)
Expert 4920 points

Part Number: LM5156H-Q1
Other Parts Discussed in Thread: LM5156, LM5122

Tool/software:

Hello team,

We got a socket to replace NCV8871-Q1, now the work condition is VIN: 3.5V-45V, VOUT: 10V@1.5A.

When VIN is lower than 10V, the device need to work in boost mode, when VIN is above 10V, it's required VOUT=VIN, which means FET need to keep always on state.

I noticed LM5156 has the limitation of max duty cycle, cannot achieve 100%, so do you have better solutions?

Thank you!

  • 0
    TI__Mastermind 24715 points

    Hi Daniel,

    Thanks for using E2E.

    As LM5156 is a non-synchronous boost controller, the device will in case of Vin>Vout stop switching and automatically be in "always on" mode because of the rectifier diode.

    The output voltage in this case will be the input voltage minus the diode drop.

    So LM5156 is suitable in this case.

    Best regards,

    Moritz

  • 0 in reply to Moritz
    TI__Expert 4920 points

    Hi, Moritz,

    Thanks for your explanation.

    I want to check if LM5123 is available for this case, because LM5123 is in customers' system, but LM5156 is not.

    I searched the datasheet, and found LM5123 can support 100% duty cycle when Vout exceed OVP, but what customer want is: Vout is fixed 10V, Vin= 3.5~45V, high side switch keep on constantly when Vin beyond is 10V.

    Kindly ask your opinion, thanks!

  • 0 in reply to Daniel Wang (auto)
    TI__Mastermind 24715 points

    Hi Daniel,

    LM5123 has a bypass mode and could support what the customer wants, however the max voltage of the input pins is limited to 42V.

    Another possibility for a synchronous solution would be LM5122.

    Best regards

    Moritz