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TPS54331: EN pin used as enable/disable function

Diego Perez17
Prodigy 130 points
Part Number: TPS54331

Hi,

I have this design, TPS54331 is enabled using the 100k internal pull up of microcontroller and an external 100k pull down. The uC set the pin as input 100k pull up after reset, so TPS54331 is on when the uC is powered. After this uC can disable TPS54331 setting the gpio as output low.

In datasheet EN pin of TPS54331 is used to perform Undervoltage Lockout, setting the pull up to VIN, but do not appears information to use EN pin as enable/disable through other chips like uC powered at lowers voltages.

Is it schematic suitable to perform an enable/disable on the TPS54331?

BR.

  • 0
    TI__Genius 10070 points
    Hi,

    The typical enable threshold voltage is 1.25V. When Ven is higher than 1.25V, the device starts up; when Ven is lower than 1.25V, the device shuts down.

    Shawn
  • 0 in reply to Shawn Nie
    Prodigy 130 points

    hi Shawn Nie,

    I understand this, if I see the EN pin as high impedance input.

    But, datasheet says EN pin is connected to pull up current source that can source 1uA and 3uA. I think there is not a problem if EN pin is used as an Input Undervoltage Lockout, but I want to use EN pin as enable/disable control pin from other power rail much lower than Vin like 3.3v. Also, 3.3v is a sequenced rail, at the beginning this rail is off so I think the current can sink from EN pin of TPS54331 to other unpowered parts.

    My question is, is EN pin of TPS54331 suitable to perform a control enable/disable from other rail lower than Vin?.

    Is there any further information about internal EN circuit? like internal impedance, maximum voltage that can be reach if resistance to gnd is too hight, schematic of this circuit…

  • 0 in reply to Diego Perez17
    TI__Genius 10070 points
    Hi,

    For the question "My question is, is EN pin of TPS54331 suitable to perform a control enable/disable from other rail lower than Vin?" The EN pin is used for Input Undervoltage Lockout, that doesn't mean EN must be connected with VIN via a pullup resistor. Of cause you can enable the device by external signal.
    The resistance of EN to GND is lower than 100kohm, this means the voltage of EN is lower than 100k*1uA=0.1V, it is lower than the threshold voltage.

    Shawn