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TAA5242: VIH, VIL spec

Toshiro Imi
Expert 7660 points

Part Number: TAA5242

Tool/software:

Hello,

Our customer has a simple question about digital IO VIH, VIL specification. He mentioned that VIH, VIL definition is slightly different from IOVDD=1.8V and IOVDD=3.3V condition., that means VIH is defined fixed 0.8V max at 3.3V IOVDD whereas 0.35 x IOVDD max at 1.8V IOVDD depending on IOVDD, VIL is defined fixed 2V min at 3.3V IOVDD whereas 0.65 x IOVDD min at 1.8V IOVDD depending on IOVDD.

 Could you please let us know the reason the spec definition differences.

Best regards,

  • 0
    TI__Genius 9010 points

    Hi Imi-san,

    The datasheet specifications for the VIH/VIL levels are based on the design of the I/O block used in the device, with the VIH/VIL specifications at 1.8V ensuring sufficient margin for device operation at this IOVDD level.

    Thanks and Regards,

    Lakshmi Narasimhan

  • 0 in reply to Lakshmi Narasimhan Badrinarayanan
    TI__Expert 7660 points

    Hi Lakshmi-san,

    Thank you for your feedback. 

    But the customer's question is why the datasheet specify VIL=0.8Vmax, VIH=2Vmin at IOVDD=3.3V but specify VIL=0.35xIOVDD max, VIH=0.65xIOVDD min at IOVDD=1.8V not VIL=0.63Vmax, VIH=1.17Vmin.

    We usually specify threshold by either fixed number or voltage ratio, but TAA5242 datasheet specify by both.

    Do you have any reason why VIL,VIH of AVDD=3.3V are specified by fixed number but VIL,VIH of AVDD=1.8V are specifiled by IOVDD ratio ?

    Best regards,

  • 0 in reply to Toshiro Imi
    TI__Genius 9010 points

    Hi Imi-san,

    In the datasheet, there is a "Recommending Operating voltage range" for each IOVDD. For example, at "3.3V IOVDD operation", the range is 3V - 3.6V.

    Basically, at "3.3V IOVDD operation", the VIH/VIL of 2V/0.8V holds for the recommended operating voltage range. However, at "1.8V IOVDD operation", this is not applicable. For example, if the IOVDD voltage is 1.9V, the device is still in "1.8V IOVDD operation" condition, but VIH needs to be 0.65 * 1.9 = 1.235V, and not 1.17V. Hence the specification is such.

    Thanks and Regards,

    Lakshmi Narasimhan

  • 0 in reply to Lakshmi Narasimhan Badrinarayanan
    TI__Expert 7660 points

    Hi Lakshmi-san,

    Thank you for your reaply.

    I understood that  VIH, VIL are not so large impact on 3.3V IOVDD range, but impact on 1.8V IOVDD. This is the reason 1.8V VIH, VIL are defined by IOVDD ratio.

    best regards,

  • 0 in reply to Toshiro Imi
    TI__Genius 9010 points

    Hi Imi-san,

    Thank you for the confirmation. I will now proceed to close this thread.

    Thanks and Regards,

    Lakshmi Narasimhan