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SN74LVC16245A: SN74LVC16245A and SN74LVT16245B output status undere operation supply level

Jade Goo
Intellectual 1940 points
Part Number: SN74LVC16245A
Other Parts Discussed in Thread: SN74LVT16245B

Hi Team,

Customer designed SN74LVC16245A and SN74LVT16245B with always enable status. (/OE tied to low)
SN74LVC16245A minimum operation supply is 1.65V and SN74LVT16245B minimum operation supply is 2.7V.
However each device show input voltage level even if supply voltage level under minimum range.
For example, 900mV for SN74LVC16245A and 2V for SN74LVT16245B.
Ecah device output level are 900mV and 2V still supply level 900mV and 2V.
Woudl you let me know why these low voltage level can monitoring at output of SN74LVC16245A and SN74LVT16245B?
Thank you.

Best Ragards,
Jade

  • 0
    Guru 276440 points

    The datasheet says that

    functional operation of the device at … conditions beyond those indicated under Recommended Operating Conditions is not implied.

    There will be a certain safety margin to ensure that the device works at the guaranteed minimum voltage even under the most adverse conditions. However, when you go outside the recommended operating conditions, there are no guarantees, neither that the device works, nor that the device does not work.

  • 0 in reply to Clemens Ladisch
    TI__Intellectual 1940 points
    Hi Clemens,

    Does it mean, SN74LVC16245A and SN74LVT16245B might be start the operation before VCC reach to minimum supply operation level?
    I and customer thought minimum supply level is some kind of threshold supply level for operation and never active before reach the minimum supply level.
    Please let me again, if I misunderstanding about minimum operation range.
    Thank you.
  • 0 in reply to Jade Goo
    Guru 276440 points

    They might start operation, but they might also start outputting random values.

    The LVC datasheet says:

    To ensure the high-impedance state during power up or power down, OE should be tied to VCC through a pullup resistor.

    The LVT datasheet says:

    When VCC is between 0 and 1.5 V, the devices are in the high-impedance state during power up or power down. However, to ensure the high-impedance state above 1.5 V, OE should be tied to VCC through a pullup resistor.