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TPS1HTC100-Q1: Behaviors when VS shorts to GND

Kazuhiko Hirano
Genius 14908 points
Part Number: TPS1HTC100-Q1

Tool/software:

Hello,

If the power supply voltage is ground fault (0V) while the capacitor is connected to the VOUT pin and the output is on (charge accumulates in the capacitor), my customer thinks that the TPS1HTC100-Q1 behaviors are as follows. Are their understandings correct?

#1 The stored charge of the VOUT capacitor flows backward through the MOSFET to the VS power supply terminal side.
#2 At this time, the MOSFET continues to be in ON state. The MOSFET on resistance value is the RON (REV) value on the data sheet.
#3 At this time, overcurrent protection and overtemperature protection do not work at all.
#4 At this time, to check whether the rating is exceeded, you can calculate the junction temperature using the Transient Thermal Impedance. (If this calculation works, could you please give me the information of Transient Thermal Impedance of TPS1HTC100QPWPRQ1?)

Best regards,

K.Hirano

  • 0
    TI__Mastermind 34905 points

    Hirano-san,

    You understanding is generally correct. 

    Generally, when the supply is in a ground fault, there is also a reverse polarity also. This means that supply voltage would be on ground and 0V would be on supply. In this case, as long as a protection mechanisms are followed from 7.3.4.5 Reverse Polarity Protection then there would be no risk for damage. 

    If we are talking in the case where the output and grounds are still valid, but there is just the supply voltage is 0- then this is a possibility. The best solution here would be to put a diode either on the input side or the output side to block reverse current going through the body diode of the FET. The body diode is not meant to have any significant current/power going through it and as such we do not characterize it or have any calculator tools.

    Best Regards,
    Tim