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SN74LVC07A inquiry

Hiroshi Sato
Expert 2590 points

Hello,

The attached waveform I got from our customer and he has a question.

He think that due to Ioff function, LVC07A output goes high even when Vcc is 0.6V but he does not know it has no problem with the Vin is  0.6V.

He hopes LVC07A outputs continuously high as attached waveform, are his circuit and device selection and understandings correct ? 

Please check this and post your comment.

Thanks and best regards,

Hiro

LVC07Ainquiry20150904.pptx 

  • 0
    TI__Guru 62120 points
    Hi Hiroshi San ,

    This device is open drain buffer and it requires pullup on the outputs to go high . The device can pull down the output low and can sink in current but cannot sources current on it own .
    With input high the output must pull high using the pullup resistor to 3.3V .
    The Ioff feature enables to have input and output voltages at more than Vcc while device is turned off or Vcc at 0V and still be protecting the device.
    The Ioff circuit usually would start in around 0.5V I assume but I will be checking it in the lab for one of the part shortly next week .
    The CPU output has pullup too but is it open drain ? If it cant support 1.8mA drive then the input can be held high to the device .