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SN64BCT25244: Level translator/line driver

Sumia Hassainar
Prodigy 80 points
Part Number: SN64BCT25244
Other Parts Discussed in Thread: SN74LVC8T245

I am trying to use  SN64BCT25244DW as a level translator as well as  driver. I have connected this to 5V VCC. Input level is 3.3V. From the datasheet i found that ViHmin is 2V. 

My assumption during design was that the output will be 5V. But i am getting only 3.3V at output.

In the datasheet for Voh only miniumm vlaue is provided as 2V.But typical and maximum value not given.

Please advice  whether i can use this for my design.

  • 0
    TI__Genius 16725 points

    Hello,

    The device you are using is a TTL compatible device. This means that the output pin as you mentioned only has a VOH min requirement of 2V. This is why your output is only 3.3V. The device is working as it should.

    Do you need the 25Ohm line impedance? I would recommend using the SN74LVC8T245 for level shifting from 3.3 to 5V.

    Thanks!

    -Karan

  • 0 in reply to Karan Kotadia
    Prodigy 80 points

    As Vcc is tied to 5V, the output should be 5V , when  input>2V, right? but i am getting an output voltage <4V(3.9V).

    I need to drive a load of 50 ohm impedance receiver.When i tried to load 50 ohm resistor at output, the output  voltage  dipped to 3.4V.

    Please suggest a part which can take 2-3V at input and  output should be  5V at   50 ohm impedance load.

  • 0 in reply to Sumia Hassainar
    Guru 256770 points

    There are at least two diode drops between VCC and the output:

    (BCT is a BiCMOS family and has additional MOSFETs, but they are rather weak and have an effect only at low output currents.)

    There is no logic device with an infinitely low output impedance. The strongest output drivers can be found in the LVC family; for eight channels, Karan already suggested the SN74LVC8T245.