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TXB0304: 5-3.3V level converter

Terry Hendrix
Prodigy 70 points
Part Number: TXB0304
Other Parts Discussed in Thread: TXB0104, LSF0204, LSF0108, SN74CBT3384A, TXS0104E

I need to use the TXB0304 in a 5-3.3V application.
Max operating voltage is listed a 3.6V
How does the higher voltage affect operation and reliability?
End product is use in office environment. ~22c.

I've tried the TXB0104 but in the application it only drives the B side (+5) to 2V because of termination on customers CPU card.

The TXB0304 drives it to 4.3V.... and their application works.

Thanks.

  • 0
    Guru 245050 points

    Allow me to quote section 6.1 of the datasheet:

    Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.

    Are you converting from 5 V to 3.3 V, or in both directions?

  • 0 in reply to Terry Hendrix
    Guru 245050 points

    What is that termination?

    Is there a direction control signal for the bidirectional lines?

  • 0 in reply to Clemens Ladisch
    Prodigy 70 points

    no resistor termination..

    Winsystems builds an analog board for the PC104 bus 5 Volt logic. My customer uses that and a LOGIC-PD PXA270 SOM with a 3v bus. The customer builds a carrier for both bards with 74CBT3384 to do the 3.3V <> 5V conversion. I have recently redesigned my board because of parts obsolescence and using a LFS0204. Works fine on all my CPUs. Does not work on the customers application. I observed the data bus during IOR from my analog card and the "high" bit only rise to 1V

    Found the XBT0304 and installed it in place of the LSF0204 and every thing works great.

       Then I saw it was only good to 3.6V so I got some BXT0104. The data only rises to ~2V

    The output impedance of the 0304 is lower and over powering the current source else where in the system.

    So, I've been running the 0304 at 5V for 48 hours and it hasn't blown up yet. I'm just wondering how  must the relibalty drops running at 5 volts. I think the at 3.3 the FIT number is 0.5 If it jumped to 100 that would be ok by me...

  • 0 in reply to Terry Hendrix
    Guru 245050 points

    TXB level shifters have extremely weak outputs and cannot be used with pull-up/-down resistors or long traces or cables.

    The SN74CBT3384A is not obsolete. If you do not want to use it, use another level shifter based on passive switches, like the TXS0104E or LSF0108.

  • 0 in reply to Clemens Ladisch
    Prodigy 70 points

    Again, this is a existing product, it's been around for ~15 years. Since it's our redesign that's failing, I have to fix it even though the problem is with the customers motherboard.

    As I see it I've got to options.

    Replace 4 LFS0204 with TXB0304 or add pullups on my IO card.

    I chose replacing the part, knowing that it will not last as long as normal.

    I'm just trying to come up with some derating factor for the FIT so I can purpose it as a solution to the end customer.

     

  • 0 in reply to Terry Hendrix
    TI__Mastermind 42700 points

    Hey Terry,

    There is no derating factor for FIT that we can provide when operating outside there commended data sheet range. This is a risk the end customer will have to take if this is the only solution you have going forward.