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SN74LVC2G17: Pull down resistor at input

Anubha Gupta
Intellectual 1840 points
Part Number: SN74LVC2G17

Hello e2e team, 

I am using the SN74LVC2G17 buffer in my design and connected the PWM inputs as follows via the pull down resistor 10k ohm --> 

The issue is when I give the supply 3.3V, the pin 2 (of both J17 and J18) both are somehow pulled up (~2.3V) instead of getting tied by GND via pull down resistors. I see the PWM input wave going from 2.3V to 3.3V instead of 0 to 3.3V --> level shift. 

Could you please tell me what could be the possible source of error here ? I even tried replacing the 10K resistor value with 1k and 100k but still no change.

Thank you,

Anubha

  • 0
    Guru 295240 points

    Does the problem vanish when you disconnect pin 1/3?

    Overvoltage (above 6.5 V) could have damaged the inputs. The schematic does not show any ESD protection.

  • 0
    TI__Genius 16400 points

    Hi Anubha,

    Is this just a schematic or is there a PCB layout?

    If you disconnect the PWM input and J17/18, then leave the 10k resistor connected to GND on the input, do you see 0V at the input? 

    As Clemens asked, does the problem go away when you disconnect pin 1/3? 

    Regards,

    Sebastian