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TPS54386 operation with max duty cycle

Sosun Duan
Intellectual 895 points
Other Parts Discussed in Thread: TPS54386, TPS54383

Hi, Dear

Datasheet said that if TPS54386 works in max duty cycle, and could not suport enough power for output, it will trigger UV comparator and goes into shut down and restart cycle. So does it shut down two channel output or only one channel with UV output? thanks.

This part is used in Car GPS power system, and it is powered by 14V battery, and has 8V and 3.3V outputs. when the battery voltage drops to near or below 8V, it will work in max duty cycle on 8V channel.

Thanks.

  • 0
    TI__Guru 56925 points

    Sosun Duan,

     

    Per the previous section on page 26 of the datasheet - under Output Overload Protection - Under Voltage (UV) fault turns off both PWMs and attempts a restart.  This is to ensure any programmed sequencing is maintained.

    The UV detector has an 85% threahold (VFB has to drop 15% from the nominal operating point)

    The TPS54386 has a minimum max duty cycle of 85%, so if VIN drops to 8V, Vout may drop sufficiently to trigger UV protection on the ouptut and force a restart.

    The TPS54383 has a minimum max duty cycle of 90%, which would allow operation down to 7.55V