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SN74LXC8T245-Q1: Need for external pull-ups on control inputs

Kshitish Gadre
Prodigy 60 points
Part Number: SN74LXC8T245-Q1

I understand from the datasheet that SN74LXC8T245-Q1 has weak internal pull-downs of 5-MΩ, which set the default direction of the device from B to A and keeps it enabled all the time. But I want the device to be normally disabled and the direction set from A to B at all times. So can I use external pull-ups? Will it affect the functionality of the control pins and ultimately, the device, in any way, if I connect any external pull-ups. The internal pull-downs and my external pull-ups will form a voltage divider, will that cause any voltage level issues for the control pins?

Thanks,

Kshitish

  • +1
    TI__Expert 7730 points

    Hello Kshitish,

    There shouldn't be any issues with adding an external pull-up to the DIR and OE pins. A 4.7kΩ or 10kΩ pull-up would work fine to disable the device and set the direction from A to B. Since the pull-down resistor is weak (5MΩ) there wouldn't be much of a voltage divider and you would get roughly 3.3V.

    Regards,

    Josh