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TPS7A66-Q1: behavior at over current

K.Hamamoto
Guru 12155 points
Part Number: TPS7A66-Q1

Hi

I have a question about the behavior at over current and short-circuit state. How does this device operate at the OC and SC?

(e.g. latch-off type or dropping type ?) 

There is no information about at those situation on the datasheet.

Regards,

Koji Hamamoto

  • 0
    Guru 140200 points

    Hi Koji,

    table 1 in section 7.4 of datasheet says that in an overcurrent condition the output isn't "disabled" but is in "current limit operation". This would mean that the chip can show a drop of output voltage in order to limit the output current. In section 6.5 you will find the specified "output current limit".

    Kai

  • 0 in reply to kai klaas69
    Guru 12155 points
    Hi Kai,

    Thank you for your prompt reply.
    "Current limit operation" mean a dropping type over current protection. Is that correct?

    How about short-circuit protection behavior ? Is this behavior is same as over current?
    If it so, this device operate to limit the short current (500mA max) until be thermal shutdown. Is my understanding correct?

    Regards,
    Koji Hamamoto
  • 0 in reply to K.Hamamoto
    Guru 140200 points
    Hi Koji,

    it's rather simple to limit the output current of a regulator. But it isn't simple to handle an overtemperature situation, because the internal circuit begins to work improperly then. So, it's wise to disable the internal circuitry when the chip temperature becomes too high. But there's no need to disable the voltage regulator in an overcurrent situation.

    In an overcurrent situation the output voltage drops down, in order to reduce the output current. In an overcurrent situation the output voltage need not to drop down to 0V. But you will no longer have the nominal output voltage. In a short circuit situation, on the other hand, the output is pulled to GND by the external circuit.

    If the overcurrent condition or the short circuit condition lasts longer, then the chip temperature can finally become so high that the overtemperature disabling can be activated.

    Kai
  • 0 in reply to kai klaas69
    TI__Expert 7015 points
    Hi Koji,

    Kai is correct. During the over current situation the LDO changes from supplying a constant voltage to providing a constant current. If the output current demanded is too high the output voltage of the LDO will be determined by the (current limit)*(load resistance).

    If the output is shorted to GND there is a greater chance that the LDO will go into thermal shutdown as there is increased power dissipation on the regulator. Once the temperature gets to high the LDO will shutoff until it cools down, if the LDO is still shorted the LDO will continue to cycle in and out of thermal shutdown until the fault condition is cleared.

    Regards,
    Mark
  • 0 in reply to Mark Sellers
    Guru 12155 points
    Hi Kai-san and Mark-san,

    Thank you for the information.
    I understood that this device continues to limit the current until the thermal shutdown triggered.

    Regards,
    Koji Hamamoto