• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 23 subscribers
  • Views 511 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.

SN74LVCA125A-EP

Aaron Spaete
Expert 4667 points

Team,

Question from my customer.

According to the component datasheet the absolute maximum negative voltage ratings of the buffer can be exceeded if the max input current is not exceeded. I'm wondering if the positive input voltage ratings can be exceeded in a transient situation (<100us) as long as the input current is not exceeded? The specific application of this buffer is at a card boundary that will be exposed to DO160 lightning. I hope to use it with a tranorb that limits the max voltage at the input to the buffer to 13V through a 150 current limiting resistor.

Regards,

Aaron

  • 0
    Prodigy 100 points

    You may want to use two resistors, one that limits the current/voltage to the TVS and then a resistor between the TVS and the buffer. Or use a big TVS that can handle the Peak Pulse Power up front and then a single resistor between the limited 13V and the buffer. Either way, I would not have the "naked" 13V straight to the buffer. This is what I have done in the past for Do-160 indirect lightning requirements using IC's. Watch out for negative spikes as well so consider using a uni-polar TVS to clamp negative at a single diode drop.

  • 0 in reply to James Fuerherm
    TI__Expert 7055 points

    What is the supply voltage of the buffer for the test?  For a 13V clamp voltage, 5V VDD supply, and 0.5V ESD protection clamp to VDD, then you should see I_in = (13V-5V+0.5V) / 150ohms  = 56mA into the buffer.  That's more than the ABS MAX specifiction for the buffer.  I suggest a larger resistor value to prevent damage from current flowing into the buffer.  I would probably use 1kohm or more to be safe.

    Thanks,

    Jake

  • 0 in reply to Jake Salmi
    TI__Guru 62930 points

    Aaron,

    Since the device only indicates a negative voltage IIK specificaton, this implies that it does not have an ESD diode to VCC.

    Under this case, the abs max VI limit (6.5v) must be adhered to.

    There is an app note titled: "Understanding and Interpreting Standard-Logic Data Sheets"  http://www.ti.com/litv/pdf/szza036b

    See page 29 for IIK definition and ESD diode determination.

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    TI__Expert 7055 points

    Wade - thanks for the correction!