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LP8860-Q1: Hi, I have a question about the diode in lp8860-Q1.

Yunsik Chung
Intellectual 1150 points
Part Number: LP8860-Q1

Hi, i was studying about lp8860 LED driver and i got curious about the reason of using shottky diode above picture.

I think if we use MOSFET instead of diode, there must be less voltage drop, so we can achieve better efficiency.

I know that it's way cheaper to use diode than MOSFET, but i am wondering if there is any electrical reason related to LED driver.

Also, i wonder if there is any TI product using MOSFET instead of diode.

Thanks,

Best regards,

Yunsik

  • 0
    TI__Genius 15776 points

    Hi Yunsik,

    In cluster LED driver， we focus on cost far above efficiency because it's a low power application.

  • 0 in reply to Frank Qiu
    TI__Intellectual 1150 points

    Thank you for your reply frank!

  • 0 in reply to Frank Qiu
    TI__Intellectual 1150 points

    Hi, frank

    Can you explain it to me more in detail?

    I did power consumption calculation for shottky diode(TJ15S06M3L), P channel mosfet (RBR15BM60AFH).

    They are both 60V, 15A device.

    You said LED driver is a low power application, I wonder from what level of power this power consumption difference of two devices has to be considered.

    Also, how much shottky diode is cheaper than mosfet? When i searched in mouser i could not find big cost difference.

    Lastly, is there any advantages of using shottky diode than mosfet in led driver except the cost?

    I always appreciate your kind replies of my element question.

    Thanks,

    Best regards,

    Yunsik

  • 0 in reply to Yunsik Chung
    TI__Genius 15776 points

    Hi 

    When you use MOSFET as a SR

    1.The consumption is not only conduct loss(as you calculate) but also driving loss, switching loss and so on. So your loss compare is not fair.

    2.The cost of SR is not the device itself.You should add a driving IC and some extra resistances and capacitors.