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SN74CBT3384A: Some voltage on Input pins when VCC not powered

Genius 15750 points
Part Number: SN74CBT3384A
Other Parts Discussed in Thread: SN74CBT3384C

Hello,

I have a question for SN74CBT3384A.

Input voltage range of absolute max is defined as just “-0.5V to 7V” without any relation to VCC.
Doesn’t it really depend on VCC?

My customer is considering to use this device and some voltage less than absolute max is input although VCC is not powered when the system goes to kind of low power mode.
Is it allowed? Isn't the device damaged?

Regards,
Oba

  • Oba,

    It is not recommended to have a voltage on the signal path without Vcc present.  This device doesn't have powered off protection feature so there could be risk that the voltage on the signal path will backpower the device and turn on the switch. 

    If you would like a device that ensures signal path isolation when Vcc= 0V you can use a device with powered off protection like the SN74CBT3384C. This device includes a leakage spec when Vcc= 0V that <10uA will pass through the switch even if 5.5V is on the input pin.  

    Thank you,

    Adam