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  • TI Thinks Resolved

Input impedance of SN74CB3Q330x / TS12A451x

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Replies: 4

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Hi,

Can you please confirm if INPUT of SN74CB3Q3305 or SN74CB3Q3306A is high Z when,

1) Vcc=0V

2) Vcc=3.3V but OE/=high (disabled)

I see only max Vcc level difference between SN74CB3Q3305 and SN74CB3Q3306A. Is there any other noticeable discrepancies?

Same question for TS12A4514 or TS12A4515. Their IN pin is in high Z when V+ is 0V?

Is there any other noticeable discrepancies between TS12A4514 and TS12A4515?

Thanks in advance for your advice.

Thanks, Gibson

  • The A/B pins of the SN74CB3Q330x are Hi-Z when disabled or powered off.

    The TS12A451x have protection diodes to Vcc, so you must not apply voltages to COM/NO/NC when powered off. (The difference between -4 and -5 is only whether they are normally open or closed.)

  • In reply to Clemens Ladisch:

    Thanks for quick answer.

    Thanks, Gibson
  • In reply to Gibson Kim:

    Please let me have one additional question:

    Do you have measured leakage current value in each cases below? Is the leakage current same at each case?
    1) power off and A/B =3.3V
    2) disabled (OE# =HIGH) and A/B=3.3V

    Thanks
  • In reply to Gibson Kim:

    Hi Gibson,

    For the TS12A devices, as Clemens mentioned, don't apply 3.3V to the inputs when the supply is < 3.3V. The current will be huge and will damage the device. Otherwise, the leakage current specs are listed on the datasheet and are rather detailed. Do you have a question about one in particular or are you having trouble determining what those values mean?

    For the SN74CB3Q devices, the leakage when the supply is 0V is called "I_off" and is listed as 1uA max on the datasheet. The leakage for when the switch is disabled is called "I_OZ" and is also 1uA max on the datasheet.


    Looking for a low voltage translator? Check out the AXC family that supports 0.7V to 3.3V translation!

    The Logic Minute training page has videos on many interesting topics that all are kept shorter than 5 minutes.

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