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SN74LVT245B: Sink source current limitation

user1863281
Prodigy 20 points

Part Number: SN74LVT245B
Other Parts Discussed in Thread: SN74LV244A

Hi,

I would like to know what is the output continuous current limit of the SN74LVT245B to not affect the device reliability (in the recommended operating condition)?

Thank you.

Pier

  • 0
    TI__Guru* 97696 points
    Hello,

    We will have to look into this when we return to work on Monday.
  • 0
    TI__Guru* 97696 points

    Hello again,

    The recommended maximum values for IOH and IOL are:

    IOH = -32 mA

    IOL = 64 mA

    The datasheet doesn't include any information regarding output continuous current, so I can't guarantee anything on that, however my recommendation would be to limit current to 70mA total through Vcc or Ground to maximize reliability.

    There is an application report on this family of products that has a little more detail, but I found no mention of a total current limit.  LVT Family Characteristics

  • 0 in reply to Emrys Maier
    Prodigy 20 points

    Hello Emrys,


    Thank you very much for your answer. I saw that the information in the datasheet was limited to Ioh = -32mA and Iol = 64mA, but your recommendation to limit the current to 70mA total through Vcc or Ground is useful. Thank you also for the literature regarding the LVT Family Characteristics.


    Best regards,

    Pier-Emmanuel

  • 0 in reply to user1863281
    Guru 21685 points

    Hi Emrys,

    You commented to limit the Icc to 70mA, then where did you quote 70mA? I can't find the value of 70mA and any limitation about Icc in datasheet. I guess that it should be resulted from maximum power dissipation or junction temperature, but I can't find Cpd parameter to calculate power consumption.

    Your help will be appreciated.

    Best Regards,

    Satoshi / Japan Disty

  • 0 in reply to S.Satoshi
    TI__Guru* 97696 points
    Hello Satoshi-san,
    This value is not in the datasheet. The limitation on this is not only related to the thermal issues. It also is related to multiple factors inherent to the construction of semiconductor devices.

    I had to base my answer on several factors. The maximum current through Vcc or ground is typically double that of a single channel. The maximum I_OH recommended for this device (in the Electrical Characteristics table under 'V_OH') is I_OH = -32mA. I would have recommended 64mA as a maximum if I had no other information, but 70mA is the lowest standard maximum value for similar parts that I found in our database, so I increased my recommendation to match.

    It's likely that this part will function with up to 128mA on the ground side and 70mA on the Vcc side, however without hard data, I went with the conservative estimate for an answer.
  • 0 in reply to Emrys Maier
    Guru 21685 points
    Hi Emrys,

    Thank you for your comment. You commented that "The maximum current through Vcc or ground is typically double", so can you chose example device that has maximum Icc in datasheet? I'd like to see it for my understanding.

    Best Regards,
    Satoshi
  • 0 in reply to S.Satoshi
    TI__Guru* 97696 points
    The SN74LV244A would be one example. It lists a continuous output current from one channel as 35mA max, but has a limit of 70mA max through Vcc or ground.
  • 0 in reply to Emrys Maier
    Guru 21685 points
    Hi Emrys,

    Thank you for your comment. This will be helpful for my understanding.

    Best Regards,
    Satoshi