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Input impedance of SN74CB3Q330x / TS12A451x

Gibson Kim
Prodigy 420 points
Other Parts Discussed in Thread: SN74CB3Q3306A, SN74CB3Q3305, TS12A4515, TS12A4514

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

  • 0
    Guru 243220 points

    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.)

  • 0 in reply to Clemens Ladisch
    TI__Prodigy 420 points
    Thanks for quick answer.

    Thanks, Gibson
  • 0 in reply to Gibson Kim
    TI__Prodigy 420 points
    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
  • 0 in reply to Gibson Kim
    TI__Guru* 96591 points
    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.