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TPS92640: TPS92640 UDIM Schottky diode

Eric Shen42
Expert 2750 points
Part Number: TPS92640

Dear TI Team:
    What is the function of the Schottky diode connected with UDIM?

    Thanks!

Regards!

Eric Shen

  • 0
    TI__Mastermind 28655 points

    Hello Eric,

    The main function is to allow UVLO to function when PWM is high, it is a multi function pin.  If there was no diode the PWM connection would not allow UVLO to function from the three UDIM resistors since PWM would take over (if it is being used).

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Expert 2750 points

    Hi  Irwin:

        Thanks for your reply!

        My customer PWM input is  5V level , 2KHz, 

    1, If the PWM signal is connected to the negative (positive is connected to UDIM) of the schottky pole, how does the PWM signal input the UDIM PIN?

    2, Why choose schottky diode, how to choose the schottky diode specification?

    Thanks!

        

  • 0 in reply to Eric Shen42
    TI__Mastermind 28655 points

    Hello,

    1)  If a 5V PWM is applied the common or return ties to the circuit common or ground.  The positive going PWM ties to the PWM (cathode of the diode).  When PWM is low the diode conducts pulling UDIM below 1.276 minus the hysteresis of UDIM turning off the TPS92640.  When PWM is high UDIM is pulled high by the UDIM resistors (diode is, most likely, reverse biased and not conducting).

    2)  The diode is not that critical for 2 KHz PWM.  They can use a BAT56, BAS40, or even a 1N4148 (not a Schotty diode) or anything similar.   It just has to be able to pull UDIM below the UVLO threshold, including the hysteresis.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Expert 2750 points

    Hi Irwin:
       Thanks! 

    Regards!

    Eric