• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 14 subscribers
  • Views 1012 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

SN54LVTH244A-SP: ABS MAX RATINGS

Selwyn Khaw
Prodigy 90 points
Part Number: SN54LVTH244A-SP

abs max rating lists "current into any output in the high state, Io" only for Vo > Vcc (Note 2).  Is there abs max rating for high state current when Vo < Vcc?

  • 0
    TI__Guru 62930 points
    If Vo < Vcc, then current will not flow into device output. In this case the device output will be sourcing current.
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Prodigy 90 points
    Agreed. Is there abs max rating for the case when Vo < Vcc, and the device output is sourcing current. I am auditing a design that inadvertently short circuited this output to ground .. thru a resistor.
  • 0 in reply to Selwyn Khaw
    TI__Guru 62930 points
    Understand.
    This is not explicitly specified in the absolute max section.
    Typically it would be recommended to keep currents to within levels for VOH/VOL under a load condition.

    However, these outputs are very robust, and can handle larger currents than specified in the recommended operating conditions.
    I checked with the commercial team, and the recommendation was to insure that the current did not cause excessive heating greater than the absolute max temp of 150 for Tj.

    I checked the datasheet, and it seems the ceramic devices thermal information is missing.
    I will need to request them to be generated so we can estimate the thermal temp increase.

    Do you have a current value from the series resistance to ground? What package are you using?
    What ambient temperature? How many concurrent outputs? What voltage?

    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    Prodigy 90 points

    CFP packages

    Here are details of fault condition.  54LVTH16245 driving HI state into 24.9 ohm and 33.2 ohm resistors, which then connect to 54LVTH244 driving LO state .. these two outputs contend thru the two resistors.

    Board max temp = 84C.  Tj (54LVTH16245) = 86C, Tj (54LVTH244) = 91C from detailed thermal analysis.

    Vcc = +3.3V for both devices.

    From load line analysis using typical IBIS model I-V curves, I get 40 mA current.

    The resistors will be removed and replaced.  I seek to determine if the drivers are OK for use-as-is.

  • 0 in reply to Selwyn Khaw
    TI__Guru 62930 points
    Selwyn,
    I was able to obtain the modeled thermal values for this device/package combination.
    Result- Theta JA-High K (standard datasheet value): 119.3
    Result-Theta JC, top (standard datasheet value): 71.9
    Result-Theta JB (standard datasheet value): 110.7
    Result- Psi JT (standard datasheet value): 48.1
    Result- Psi JB (standard datasheet value): 97.6
    Result-Theta JC, bottom (standard datasheet value): 13.9
    Modelling Assumptions: Package body NOT solder to PCB. No PCB via.

    If you re-run your thermal analysis using appropriate thermal values above, and junction temperature is less than 150c, then you will not be exceeding the absolute max conditions. Long term exposure to this could affect reliability.
    If the junction temp is less or equal to 125c, then you should not see any reliability impact from this condition.
    Regards,
    Wade