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SN74LVC1T45: Consultation on SN74LVC1T45

? ??
Prodigy 105 points
Part Number: SN74LVC1T45
Other Parts Discussed in Thread: SN74LXC8T245

Tool/software:

We use SN74LVC1T45 to convert the I/O level from 1.8v to 3.3V and then use the 3.3V I/O to drive a 50Ω load，please help us to confirm whether the SN74LVC1T45 has enougth drive strength to drive the 50 Ω load.

  • 0
    TI__Mastermind 22810 points

    Hello,

    If the plan is to have a static current of 66mA (3.3V/50Ω) going to the 50 ohm load then this part will not work given an absolute max output current of 50mA.

    However, if the plan is to send a signal that's oscillating (i.e. PWM) to the load then this should be fine.

    Regards,

    Josh

  • 0
    Guru 316920 points

    Typically, a 50 Ω driver has an output impedance of 50 Ω and forms a voltage divider with the load. What is the voltage that you need at the receiver?

  • 0 in reply to Clemens Ladisch
    Prodigy 105 points

    We use the SN74LVC1T45 to drive the load through coax，the voltage that the receiver required is 2V above，if we use  50 Ω to form a voltage divider,the load voltage will be below 2V.

  • 0 in reply to ? ??
    Guru 316920 points

    The only way to get a voltage above 2 V with a logic device is to use multiple outputs in parallel. Use the SN74LXC8T245, and connect all eight inputs and outputs together. With a 50 Ω load, this can output more than 3.2 V.

    (You would need a supply with 6.6 V or more to be able to match the driver's output impedance to the cable's characteristic impedance.)