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SN74CB3Q3257: Difference between SN74CB3Q3257 and SN74CBTLV3257

Anders Yang
Prodigy 570 points
Part Number: SN74CB3Q3257
Other Parts Discussed in Thread: SN74CBTLV3257

Hi there,

 

What's the detailed difference between SN74CB3Q3257 and SN74CBLV3257.

The reason I am asking is that we observed some signal quality issues(solid failure) with SN74CBLV3257, while with SN74CB3Q3257 it is error free. So I am wondering if there are any difference between these two parts on the signals passing by.

 

Some more info here:

In our design, VCC=3.3V and failure rate become higher if we apply voltage margin to 5%.

And the select pin is always high.

  • 0
    TI__Genius 9132 points

    Hi Anders,

    Are you referring to  SN74CBTLV3257? Can you share details on what kind of fails you are getting and what signal you ? 

    The CBTLV has <=200Mhz BW and CB3Q has 500Mhz BW .

    The CBTLV is rail to rail output ;with 3.3Vcc , only 0V to 3.3V i/O can be passed through whereas CB3Q is beyond rail to rail output where with 3.3Vcc, 0-5V I/O can be passed through. This could be the reason you are getting the fails.

    Please take a look at the App note "CBT-C, CB3T, and CB3Q Signal-Switch Families" that has more details on the difference between the CB3T, and CB3Q families.

    Thank you,

    Saminah

  • 0 in reply to Saminah C
    Prodigy 70 points

    Hi Saminah,

    Yes, it’s SN74CBTLV3257.

    It is used as a SPI mux, the signal frequency is below 20MHz. So the BW should not be the problem.

    And i checked the datasheet of SN74CBTLV3257, the max input voltage is 4.6V. In our design the max Voltage is below 3.5V.

    There is a flash as the slave, we got the failure when we perform a write/read test.

    We did some experiments and find the failure is on the CS signal, and it is very sensitive to the capacitance.

    So I am wondering if these two parts have a difference of the capacitance characteristic under on state.

     

  • 0 in reply to user6140999
    TI__Genius 9132 points

    Hi Anders,

    Please use the SN74CB3Q3257 for your application as it offers low CN capacitance (10.5pF) compared to SN74CBTLV3257.

    Thanks

    Saminah