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SN74BCT756: II and Input current range

Mark Qu
Prodigy 10 points
Part Number: SN74BCT756
Other Parts Discussed in Thread: SN74LS244

Hello Ti experts,

I am trying to interpret some datasheets.

Consider please the SN74BCT756 bipolar CMOS datasheet, under 'Absolute Maximum Ratings':
Input current range, II . . . . . . . . . . . . . . . . . . . . . . . . –30 mA to 5 mA

and under 'Recommended operating conditions':
II  Vcc = 5.5 V   VI = 7 V . . . . . . . . . . . . . . . . . . . . . . . . 0.1 mA MAX                                          

The first use of II seems to imply that connecting an output (IOL = 64 mA) directly to an input (-30 mA max)
requires a series current limiting resistor. Is this a correct interpretation?

The second usage of II, grouped as it is with IIH and IIL, seems like common bipolar leakage currents.

'Input current range' is not specified in SNx4S24x / SNx4LS24x (e.g. SN74LS244) datasheets. Is it because of
differences between LS/S and BCT?

Thank you for any comment.

  • 0
    Guru 272510 points

    There is no II specification in the "recommended operating conditions" table.
    There is an II specification in the "electrical characteristics" table; this is indeed a leakage current.

    To exceed the absolute maximum ratings of the BCT input, you would need to apply an invalid input voltage. There might be an implied statement "you can exceed the input voltage if you limit the current".

    The LS datasheet has no absolute maximum ratings for the input current because the input voltage limits ensure that the current stays low enough.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Thanks, I see now what they are trying to convey