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Replacement part for NCV887701

Other Parts Discussed in Thread: TPS55332-Q1, LM3481-Q1, LM3481

Hi team,

My customer looks for the replacement part for NCV8877 which is boost converter for start-stop application. Please refer to the follwoing link.

http://www.onsemi.com/PowerSolutions/product.do?id=NCV8877

It operates when the input voltage goes down and it does not work during higer input than target voltage.

TPS433xx-Q1 has similar boost converter, but it also has buck controller. But customer needs only boost converter.

So could you please recommend if we have similar part to NCV8877?

Thanks,

WS 

  • WS,

    The appropriate applications engineer has been notified of your post and will respond accordingly.

    Regards,
  • WS,

    What is the input voltage range required, and what will be the output voltage?

    I'm assuming the input is directly connected to the Battery line, but what is the output voltage? All of the NCV8877xx parts have fixed output voltages (e.g. NCV887700 = 6.8V out), while the majority of TI products will have a feedback (FB) pin to determine that output voltage.

    Also, the NCV8877xx is a Boost controller, meaning the switching FET is external.

    Would the customer consider a Boost converter with an integrated switch?

    For a Boost converter, I would recommend looking at the TPS55332-Q1, which is a highly integrated part with a VERY wide Vin range from 1.5-60 Volts.

    If the customer would prefer a Boost controller, I would recommend looking at the LM3481-Q1, which will operate down to Vin = 2.97V and up to 48V max.

  • Hi Brain,

    Yes, the input voltage is connected to battery directly and so it is nornally 12V and max 40V. The output is 6.8V.
    The output current they need is 2.2A. So I think that they need a controller with external FET.

    And then, Onesmi part is not working during input voltage is higher than target voltage. So it is not working during higher than 6.8V and when it goes donw to 6.8V, it starts operating. How about LM3481-Q1? Is it also not working during the input is higer than target voltage and after input goes down to target votlage, does it starts working?
    Please advise me.

    Thanks,
    WS
  • WS,

    It sounds like you need both Buck & Boost capabilities:

    • Vin>6.8 V, Buck mode operation
    • Vin<6.8 V, Boost mode operation

    Please tell me if customer can use Boost Controller followed by Buck Controller/Converter (2x IC solution) or if they need a Buck-Boost Controller integrated into 1 IC (1x IC solution).

    The NCV887701 datasheet never mentions the words "buck" or "step-down", so I believe ON-Semi would be a 2x IC solution.

  • Hi Brian,

    I'm sorry that you are confused.

    The output is bypass battey voltage during the input is higer than 6.8V. And when the input goes down under 6.8V, the converter works and the output is 6.8V.

    So, Onesmi part is not working during input voltage is higher than 6.8V. When it goes donw under 6.8V, it starts operating and the output is 6.8V. How about LM3481-Q1? Is it also not working during the input is higer than target voltage and after input goes down to target votlage, does it starts working?

    And the recommendation junction temp of LM3481-Q1 is 125'C and then the max ambient temp of customer system is 125'C. So if the ambient is 125'C, what happens? Is not LM3481-Q1 guaranteed for ambient 125'C?

    Please advise me.

    Thanks,

    WS

  • Hi WS,

    Actually the part is rated for Max 150C Tj so it will operate at 125C ambient.

    The LM3481 will not switch if the output is higher than the set voltage. We do have some reference designs specifically for Start-Stop application:

    I hope this helps,

    Florent Boico