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SN74GTL1655: The device status when there is no VREF

Nick Dai
Expert 4240 points

Part Number: SN74GTL1655

Hi Team,

     What's the input and output signal status when the VREF of SN74GTL1655DGGR was decrease to ground? Will the device output any error signal?What's the high and low voltage judgement level if the VREF is zero?

Best Regards,

Nick Dai

  • 0
    TI__Guru* 97046 points
    Hi Nick,
    The SN74GTL1655 is an analog device - there no processor or error monitoring included inside.

    If the inputs of the device are not within the recommended limits of the datasheet, we cannot guarantee what the output will do. For the case of Vref, the recommended operating conditions are very limited - from 0.74 to 1.1V (depending on the operating mode).

    Since the Vref signal is going to the input of a comparator, it would not be unreasonable to assume that putting 0V into Vref would cause the comparator output to always be HIGH - but since the B-side input could also be 0V, there's no way to know which signal would be determined as larger by the comparator (due to input offset voltage). The short answer is - the output is unstable in this state and we recommend operating the device within the datasheet Recommended Operating Conditions.