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SN74LVC1G123: Cext to GND

Yuto Sakai
Mastermind 6100 points
Part Number: SN74LVC1G123

Hi,

Is it not recommended to connect Cext and GND?
We recognize that there is no specific description on the data sheet.

Best regards,
Yuto Sakai

  • 0
    Guru 244220 points

    The application note Designing with the SN74LVC1G123 Monostable Multivibrator has a FAQ about this:

    5.6 Can I connect the Cext pin to ground?

    It is best to follow the datasheet recommendations. If your monostable multivibrator recommends not connecting Cext to ground, then do not connect it to ground.

    In some monostable multivibrators the Cext pin is internally tied to ground, but in some it is not. If the datasheet is unclear and the information is required, use an ohmmeter to check the resistance between the two pins. If the resistance reads less than 1 Ω, it is safe to connect both to ground.

  • 0 in reply to Clemens Ladisch
    Mastermind 6100 points

    Hi Clemens-san,

    Checking the SN74LVC1G123 data sheet, there is no clear statement about the recommended connection of Cext and GND.
    Could you advise about Cext and GND connection for this device?

    Best regards,
    Yuto Sakai

  • 0 in reply to Yuto Sakai
    Guru 244220 points

    See the second paragraph ("the datasheet is unclear") quoted above.

    (I do not have this device to test, but I wonder why this would be so difficult for whoever wrote the datasheet and this appnote.)

  • 0 in reply to Yuto Sakai
    TI__Guru* 96591 points

    Hello Sakai-san,

    I can see where your confusion comes from in the datasheet.  There are two images that show the correct connection of the SN74LVC1G123's Cext pin:

    In the timing section, this image shows how we connected the Cext pin for testing the device's timing performance. This is one correct way to connect the device.

    In the applications section, this image shows that the Cext pin is not connected to ground. This is another correct way to connect the device.

    Because the Cext pin is internally connected to ground, either method works the same.