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TMP461: VIL spec in datasheet vs I2C spec

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Replies: 3

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Part Number: TMP461

Hi!  I have a customer looking to use the TMP461 with a question on the VIL spec in the datasheet.  Would you be able to help shed some light on below question from customer?

I have a question about the TMP461 data sheet. The Serial Interface low level input voltage. The spec says 0.45V max, but the I2C spec states this should be 0.8V max. Can you verify the data sheet is correct? We are using it in an application where the master has a 0.4V Voh max, so we would have only 0.05V of noise margin. 

Thank you,

Meredith

  • Dear Meredith -

    Here is screen shot of I2C spec. with the notes 1 and 2 which apply to these rows.

    please note this is 0.3 * operating voltage (VDD) for VIL max and 0.7 * VDD for VIH min

    [1] Some legacy Standard-mode devices had fixed input levels of VIL = 1.5 V and VIH = 3.0 V. Refer to component data sheets.
    [2] Maximum VIH =  VDD(max) + 0.5 V or 5.5 V, which ever is lower. See component data sheets.

    BR-

    Josh

  • In reply to Josh Wyatt:

    Thanks Josh!  Follow-up questions....

    So for a VDD=3.3V, the I2C spec has Vil (max) = 0.99V, which makes the TMP461 spec of Vil (max) = 0.45V even further out of spec that what I described? Or is there a scale factor since the TMP data sheet is for VDD=1.7V to 3.6V? Even at VDD=1.7V, the I2C spec would be at 0.51V. So is the TMP part out-of-spec w.r.t  the I2C spec?

    Thanks,

    Meredith

  • In reply to Meredith Turner:

    Meredith - 

    the I2C standard has VIL set for 0.3*VDD, and you are right 0.3*3.3VDC = 0.990...but, if the part spec limit for VIL max is 0.45V, then its inside the I2C spec still. 

    BR-

    Josh

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