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About Output inpedance of SN74LVC04A

Guru 18070 points
Other Parts Discussed in Thread: SN74LV04A, SN74LVC04A

Please let me know about LVCMOS output inpedance(Zo) of SN74LV04A.

【Background and condition】

・SN74LVC04A using for clock driver(50MHz)

・Inpedance matching of this pattern is 40~50Ω

・Output side is connected 22Ω-danping for waveform shaping.

⇒Customer want to know these circuit is maching or not.

Best regards,

Satoshi

  • Hi Satoshi-san,

    A 50 ohm load on this part will exceed the part's drive capability (max of ~12mA at 3.8-V Voh)

    My math:

    Vo / Rload = Imax (maximum output current required)

    5V / 50ohm = 100mA

    If Voh were to dip to 3.8V (lowest value listed on datasheet),

    3.8V / 50ohm = 76mA

    Since the part can only output ~12mA max, I would recommend looking into a different solution.

    Can you tell me more about your application?

  • Correction*

    The output will have to source half of what I listed, but 50mA and 38mA are still much higher than what the device can handle.