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LM5170-Q1: About LM5170 how to drive back to back mosfet.

Jeff_Liu
Prodigy 150 points
Part Number: LM5170-Q1
Other Parts Discussed in Thread: TIDA-01168, LM5170,

Hi

In the TI Design of TIDA-01168,the pins of BRKS and BRKG in LM5170 is used as the gate drive of the back to back mosfets in page 23.

But I do not understand how it drive the mosfet?

Such as when BRKG is High and BRKS is low,the mosfet is drived,but at the same time the voltage of BRKS is equal to KL30,will the voltage of BRKS larger than BRKG and caused the mosfets opend again?

  • 0
    Prodigy 150 points

    [quote user="user5138648"]

    Part Number: LM5170-Q1

    Hi

    In the TI Design of TIDA-01168,the pins of BRKS and BRKG in LM5170 is used as the gate drive of the back to back mosfets in page 23.

    But I do not understand how it drive the mosfet?

    Such as when BRKG is High and BRKS is low,the mosfet is drived,but at the same time the voltage of BRKS is equal to KL30,will the voltage of BRKS larger than BRKG and caused the mosfets opend again?

  • 0 in reply to Jeff_Liu
    TI__Guru* 78150 points

    Hi,

    Thank you for posting.  Please refer to the LM5170-Q1 datasheet Sec 8.3.16, and also the IC block-diagram.  The BRKG is a current source with voltage clamp at 12V to BRKS.  The current source is supplied by the VIN pin, which is supposed to be higher than  KL30 rail voltage.  Note that the TIDA -01168 is intended for the 48V-12V system.  

    Thanks,

    Youhao