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TXS0108E: Clarification on the VILmax and VIHmin spec’

Randhir Kalsi
Expert 4545 points
Part Number: TXS0108E
Other Parts Discussed in Thread: TXS02612, LSF0108

Hello team,

Hope you are well. Customer is requesting to get me some clarification on the VILmax and VIHmin spec’s for the following parts? 

TXS0108E

TXS02612

 

Both of these parts appear to have extremely tight input spec’s ( eg. VILmax = 0.15v and VIHmin = 1.4v or 1.6v for VCC = 1.8v ) which means that these parts aren’t spec’ed to work with almost any FPGA LVCMOS output ( typ. VOLmax = 0.45v and VOHmin = 1.35v for VCC = 1.8v ).  I know they work at room temperature, seen these parts used on various commercial FPGA based products, but need to ensure that will work over temperature.  Thus, I need clarification because the input spec’s for the parts.

  • 0
    TI__Mastermind 29955 points

    Hello Randhir,

    The Vil spec is a guarantee that if the input voltage is less than 0.15V, the output voltage will be less that 0.4V. In reality, Vil can be higher than that, but your corresponding Vol will also increase due to the fact that the TXS acts as an open switch when passing a low. Basically, the output will be equal to the input voltage plus the voltage drop across the internal pass transistor when passing a low. As an example, here is a plot I made comparing Vol and Vil for the TXS0108E.

    The Vih parameter is also very conservatively spec'd. In reality, Vih occurs whenever the internal pass transistor turns off, which is usually around VCCI / 2. However, because the datasheet is spec'd as it is, we cannot make any guarantees that it will work for any values below what is published in the datasheet. 

    Unfortunately, all I can tell you is that you will likely be able to get away with the typical LVCMOS Vol and Voh specifications but I cannot make any guarantees when you decide to operate outside of the datasheet parameters. Also, I have tested the Vil vs Vol over -40 C to 65 C and the difference based on temperature is negligible. 

    If your application requires bidirectional translation, perhaps you may want to look at the LSF0108 instead. It is a passive bidirectional translator so it does not have any Vol or Vil spec requirements.