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TSX0108E

Ignacio Linares
Expert 1655 points
Other Parts Discussed in Thread: TXS0108E

My customer is asking the following question:

 

I have a question on the specifications for the Texas instruments TXS0108E component.

 

The part is being used with 3.3V on the VCCA rail and 5V on the VCCB rail. My issue is with the recommended input and output voltage levels. According to the datasheet the following levels are recommended:

 

A side (3.3V side)

 

                                  Min                                                                      Max

Vih          Vcci-0.2 = 3.3V-.2  = 2.9V                                              Vcci = 3.3v

 

Vil                           0V                                                                           0.15v

 

Voh                                                                                                        Vcca * 0.67 = 3.3v * 0.67 = 2.21V

 

Vol                                                                                                         0.55V

 

 

B side (5V side)

 

Vih         Vcci-.4V = 5V - .4 = 4.6V                                                 5V

 

Vil                           0V                                                                           0.15V

 

Voh                                                                                                        Vccb – 0.67 = 4.33V

 

Vol                                                                                                         0.55V

 

 

It kind of an unusual part, so I may be misinterpreting the datasheet, but I can’t locate the problem. The input voltage level requirements for either side cannot be guaranteed by any standard logic family under their recommended load ranges.

 

Please take a look and see what you think.

 

  • 0
    TI__Genius 9085 points

    The VIL recommended is to ensure that the VOL specs are accurate with the worst case conditions (across temperature) and the listed load current.

    The device will operate correctly even with higher VIL, but the VOL may be higher depending on the operating conditions. 

     We have many customers successfully using these TXS devices in their applications. 

    If given the operating conditions, we could do a quick simulation to determine device performance in a specific application. 

  • 0 in reply to Hattie
    Prodigy 5 points

    I agree that the input specs are not at all compatible with what standard cmos or TTL logic could achieve.
    CMOS is usually 30/60% of Vcc for a LOW/HIGH.
    TTL is tighter I believe, but neither are VCCi – 0.4V.

    However, it does say its made for OPEN DRAIN applications, so does this mean its expecting an open drain to be driving the inputs?
    There is a pullup shown on the input, and in this case the pullup WOULD achieve VCCi-0.4V, actually VCCi it would get to.

    So it does not appear this part is made for logic level inputs, but open drain driving the inputs.