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LM5050-1: GATE control circuit question

Ann_Lien
Genius 14430 points
Part Number: LM5050-1

Hi expert,

My customer is asking for below circuit operation. We can know 2A MOSFET is for two conditions to tie GATE and SOURCE together, one is OFF pin is high and one is reverse current occurred. But for 35uA/30uA/30mV/two BJTs, may we know how it work for below circuit? Thanks a lot!!

Best regards,

Ann Lien

  • 0
    TI__Genius 16305 points
    Hello Ann,

    The highlighted portion of the block diagram shows the amplifier that does the job of regulating forward voltage drop to 22mV.
    The amplifier measures the Vds drop across the external MOSFET and controls the gate voltage with 30uA sourcing current.

    To maintain 22mV across Vds of external MOSFET, Gate voltage is controlled. For example, for a 2.2mohm FET (datasheet specification at Vgs 4.5V), at 10A, Gate voltage will be at 4.5V. For currents higher than 10A, gate voltage will be increased depeding on the MOSFET Vgs Vs RdsON characteristics.
    For currents lower than 10A, gate voltage will be reduced depending on MOSFET characteristics.

    Let me know if this answers your question.

    Regards,
    Kari.
  • 0 in reply to Karikalan Selvaraj
    TI__Genius 14430 points
    Hi Kalikalan,

    Thanks for your great help on it!! May i have one more question on 30mV? What is the purpose for 30mV? Thanks a lot!!

    Best regards,
    Ann Lien
  • 0 in reply to Ann_Lien
    TI__Genius 16305 points
    Hi Ann Lien,

    30mV is referring to the 22mV forward regulation of source-drain.
    -8mV is offset of the internal amplifier and so 30-8mV is 22mV.

    Regards,
    Kari.