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SN74LVC8T245: SN74LVC8T245- Query Regarding Datasheet(Noise margin)

Ananthesh Acharya
Intellectual 535 points
Part Number: SN74LVC8T245

Hi,

I am using SN74LVC8T245 level translator for the voltage conversion  VCCA= 3.3V & VCCB=5V .

Anywhere in the datasheet VOH and VOL level for  3.3V to 5V is not mentioned.
The values are suggested only till 4.5V for VCCA and VCCB levels.

Can you suggest the VOH(min) and VOL(max) values for VCCA=3.3V to VCCB=5V & vice-versa?

Thank you in advance.

With Regards,
Ananthesh

 

 

  • 0
    TI__Guru* 97046 points

    Hello Ananthesh,

    The 3V and 4.5V values are indicative of the worst case for a 3.3V or 5V supply (one that is out of tolerance by about 10%). When designing an electronic system, it is highly recommended to design for the worst case. Unless you have a mythical power supply that never wavers below 3.3V or 5V, I would recommend using the given values for VOH and VOH.

    VOH(5V) = 3.8V

    VOH(3.3V) = 2.4V

    VOL(3.3V and 5V) = 0.55V

  • 0 in reply to Emrys Maier
    Intellectual 535 points

    Hi Emrys,

    Thanks for your quick reply.

    These are the values when VCCA=VCCB right?
    But in our case VCCA= 3.3V and VCCB=5V .VCCA not equal VCCB(not acting as buffer).

    Can you suggest the value when it is different(VCCA and VCCB are different and acting as level translator).



    With Regards,
    Ananthesh

  • 0 in reply to Ananthesh Acharya
    TI__Guru* 97046 points

    Hi Ananthesh,

    The VOH and VOL will be relative to the supply of the side at which you are measuring the output. Having different supplies will not change the output VOH and VOL.

    In short, if your output is driving 100μA at 5V, use 4.9V as the VOH and 0.1V as the VOL. If your output is driving 100μA at 3.3V, use 3.2V as the VOH and 0.1V as the VOL.

  • 0 in reply to Emrys Maier
    Intellectual 535 points

    Hi Emrys.

    Thanks for your support.

    This will  solve my problem.

    with Regards,
    Ananthesh