• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 20 subscribers
  • Views 582 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74LVC125A: about output short current for SN74LVC125A

Vera Mao
Expert 5065 points
Part Number: SN74LVC125A
Other Parts Discussed in Thread: STRIKE,

Hi dear supporting team,

for SN74LVC125ADR, because it is at the brd edge which interface to external, if in lightening stroke,  suppose the output pin is shorted to GND,  could we gurantee the shorted current to GND be smaller than 50mA over whole temp range? if it is exceed 50mA,  is there any internal protection that could shut it off, and when the shorted case is passed, then it could recovered itself?  tks a lot!

  • 0
    TI__Guru* 97046 points
    Hi Vera,
    I'm hoping 'lightening stroke' is a bad translation of 'ESD strike' -- because a true lightning strike would incinerate this device.

    The device does have some innate ESD protection (as defined in the datasheet) however we _highly_ recommend adding external ESD protection if this is an externally facing (connected to the outside of a product directly) device.
  • 0 in reply to Emrys Maier
    TI__Expert 5065 points
    hi Maier,
    thank you for your answer!
    by "lightening stroke" it is a thunder strike. :) customer will have thunder preventer on brd, when it works, it will cause LVC125A output shorted to GND. in case that after the thunder, the thunder preventer keep conducting and recover the circuit, they will request that after the thunder, LVC125A output current be smaller than 50mA, if we still provide higher than 50mA, then the preventer will keep conducting. so whether LVC125A meet this requirement? tks a lot!
  • 0 in reply to Vera Mao
    TI__Guru* 97046 points

    Hi Vera,

    I see.

    The SN74LVC125A is capable of driving 100's of mA at the output -- if it is shorted to ground, then it will likely be damaged due to excessive current.

    The proper method to prevent this is to add a series output resistor to limit the current.  For example, if the customer is operating the device at 3.3V, then to limit the current to 20mA, a resistor value can be easily calculated with Ohm's law:

    R = 3.3/0.02 = 165 ohms