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Level shifter SN74AVC16T245, SN74AVC4T774 - Leak voltage

Kawai
Guru 19775 points

Hello Team,

Please allow me to ask you if there is a possibility to have a leak voltage on power pins (VCCA or VCCB), when signal is input to the A side or B side input before power up (No VCCA and VCCB)?

I believe there is no ESD protection diode on top side for signal input pins, so I believe there would not be a leak voltage from signal line to VCCA or VCCB.

Best Regards,

Kawai

  • 0
    TI__Guru* 96591 points

    Moving to voltage translation forum for support.

  • 0
    TI__Intellectual 2530 points
    Hi
    Both parts have VCC isolation feature that ensures if either VCC input is at GND, both ports are then in the high-impedance state.
    Thanks
  • 0 in reply to Jennifer Joseph
    Guru 19775 points

    Hi Jennifer-san,

    Thanks for your support. Please allow me to ask you a little more.
    I understood that Ax and Bx pins are Hi-Z when either of VCC input is at GND (Not powered).

    Customer would like to know if there would be a leak voltage from signal pins (Ax or Bx) to Power pins (VCCA or VCCB)
    From the datasheet, it seems that there is a ESD protection diode to VCCx pin when EN pin is set to High.

    [Q1]
    Would there be a leak voltage from Ax or Bx pins to VCCA or VCCB pins, when VCCA and/or VCCB is not applied with EN=High ?

    [Q2]
    Would there be a leak voltage from Ax or Bx pins to VCCA or VCCB pins, when VCCA and VCCB has some kind of voltage applied with EN=High ?

    [Q3]
    Can you say there is no leak voltage as long as EN pin is kept Low ? Ax and Bx output pins would be Hi-Z and NO ESD diode to VCCx.

    Thanks in advance.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Intellectual 2530 points

    Hi Kawai-san

    I have sought designer's help on this. I will get back to you soon.

    Thanks

  • 0 in reply to Jennifer Joseph
    TI__Intellectual 2530 points

    Hi Kawai-san

    From the datasheet, it seems that there is a ESD protection diode to VCCx pin when EN pin is set to High.

    The schematic of the ESD on page 54 shows only connection to ground, it does not to have a diode to supply.

    [Q1]

    Would there be a leakage ( voltage) from Ax or Bx pins to VCCA or VCCB pins, when VCCA and/or VCCB is not applied with EN=High ?

    No leakage path. There is a CDM clamp with back to back diodes to VCCA. In addition, the output buffer connected to the pin has a diode to the charge pump and when disabled there is no path to supply.

    [Q2]

    Would there be a leak voltage from Ax or Bx pins to VCCA or VCCB pins, when VCCA and VCCB has some kind of voltage applied with EN=High ?

    No. The EN pin does not have a path to supply and A or B does not leak to VCCA or VCCB.

    [Q3]

    Can you say there is no leak voltage as long as EN pin is kept Low ? Ax and Bx output pins would be Hi-Z and NO ESD diode to VCCx.

    Yes

     

    Thanks

  • 0 in reply to Jennifer Joseph
    Guru 19775 points

    Hello Jennifer-san,

    Thanks for your cooperation supporting these device. I understood that there is no leakage path from Ax/Bx pins to VCCA/B pins.

    I just could not find the schematic which you had mentioned "ESD on page 54". Could you tell me which document you were looking at ?

    Thanks and Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Intellectual 2530 points
    Hi Kawai-san

    Please send me your email address and I can send the schematic page to you. It is from internal design review document.

    Thanks
  • 0 in reply to Jennifer Joseph
    Guru 19775 points

    Hello Jennifer-san,

    Thanks for your support.


    Thanks and Best Regards,
    Kawai