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TLV1821: VOH and VOL level

Asha C
Intellectual 385 points
Part Number: TLV1821
Other Parts Discussed in Thread: TLV1812

Hello,

We are TLV1821 comparator which is open drain as per 9.1.1.1 operation mentioned in schematic , like without hysteresis and a basic  comparator. What is the VOH and VOL in this case?

We are connecting 6.25V to Vcc and IN+ varies from 0 to 3.3V with Vref 2.5V. Could you please let know the VOH and VOL Level for the same!

  • 0
    TI__Guru 63416 points

    Hello Asha,

    Shorting the inputs together is theoretically a "indeterminate" condition, as neither input is higher than the other.

    But in reality, the internal offset voltage will make the decision, as the offset can be up to ±4mV. So there is a 50% chance of the output going high or low.

    Normally, if the inputs are very close, then there will be a region that the comparator will "chatter" on the internally generated noise - this is normal expected comparator behavior and not a failure.

    This is why hysteresis is added to ensure a smooth transition through the threshold zone. See section 8.4.4 and 9.1.1.3 in the applications section of the TLV1812 datasheet for more information on Hysteresis.

    Hysteresis is usually used where the input moves *slowly*, such as temperature monitoring or battery charging. If the change between 0V and 3.3V is fast, then there should not be an issue.

    The output will always be either be low (VOL) or the pull-up voltage (VOH). Comparator outputs should never go "linear".