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SN74AVC4T774: SN74AVC4T774 vs SN74AXC4T774 Ioz leakage current characteristics

Nicolas PERRIN
Prodigy 10 points
Part Number: SN74AVC4T774
Other Parts Discussed in Thread: SN74AXC4T774

Tool/software:

Dear TI support team,

Could you provide me SN74AVC4T774 and SN74AXC4T774 Ioz polarity and value depending on junction temperature ?

We found an issue on our design that depends on leakage current of TI voltage translator and temperature of our system.

We use TI voltage translator to translate SPI signals from 1.8V to 3.3V.

When voltage translator is in high impedance state (OE# = 3V3), we observe different behaviour on pin #2 (A2) between SN74AVC4T774 and SN74AXC4T774 

SN74AVC4T774 does not work at high temperature while SN74AXC4T774 is working fine under same condition.

We use following schematic :

Best regards,

Nicolas PERRIN

  • 0
    TI__Mastermind 22790 points

    Hello Nicolas,

    Thanks for reaching out. What leakage current are you observing on both AXC4T774 and AVC4T774, and at what temperatures are you running these tests?

    Regards,

    Josh

  • 0
    Prodigy 10 points

    Hi Joshua,

    I am running test between 25°C and 100°C.

    I know there is an issue in my design that would be triggered by a positive current going out of pin A2 of the level shifter.

    In both cases level shifter is in high impedance state, by setting OE# pin to 3.3V.


    When I assemble AVC4T774 on a PCB, I do not see the issue at 25°C, but issue happen between 50°C and 100°C.

    When I assemble AXC4T774 on the same PCB, I cannot observe the issue.


    I would like to get leakage currents data from TI to confirm that my lab observations are correct.

    Regards,

    Nicolas PERRIN

  • 0 in reply to Nicolas PERRIN
    TI__Mastermind 22790 points

    Hello Nicolas,

    Could you clarify the leakage current you are seeing on the AVC4T774 that's causing issues to your system? Is the Ioz value not within the datasheet spec?

    Note the recommended operating temperature of the AVC4T774 is -40C to 85C. Parameters like Ioz are tested under the recommended conditions.

    Regards,

    Josh

  • 0 in reply to Joshua Salinas
    Prodigy 10 points

    Hello Joshua,

    I am not saying that leakage current is not  inside datasheet spec.

    I just see different behaviour on my PCB.

    What I observe is that Ioz is lower on AXC4T774 than AVC4T774 but datasheet says the opposite.

    Could you provide me a curve for Ioz between -40°C and 85°C for AVC4T774 and AXC4T774 ?

    Regards,

    Nicolas

  • 0 in reply to Nicolas PERRIN
    TI__Mastermind 22790 points

    Hello Nicolas,

    When you compare both datasheets, the AXC4T774 has the lower Ioz current so your observation is correct. The difference between AXC and AVC Ioz at max conditions is 1uA. Additionally you mention the leakage current you see is not outside the datasheet spec.

    I would recommend going with the AXC family since it's built in a new process technology and has integrated static pull-down resistors which more than likely is helping lower the leakage current you are observing. 

    Regards,

    Josh