SN74AXC8T245: DIR Pull-up Resistor Value

joe lindula

Mastermind 6850 points

Part Number: SN74AXC8T245
Other Parts Discussed in Thread: TXU0104-Q1

Hello, I am looking on page 23 of the datasheet for SN74AXC8T245-Q1:

I would like to know how the value of the pull-up resistor on DIR1 is determined?

Last, is it necessary to add 10K on DIR2?

Thank you

Joe

over 1 year ago

+1 Clemens Ladisch over 1 year ago

Guru 243220 points

You need a pull-up or pull-down only if you want to change the direction later. If the directions are fixed, you can connect the DIR inputs directly to V_CC or GND. (Or use a fixed-direction translator like the TXU0104-Q1.)

The value is not really critical; 10 kΩ is commonly used.

0 joe lindula over 1 year ago in reply to Clemens Ladisch

Mastermind 6850 points

Thank you very much.

Logic

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SN74AXC8T245: DIR Pull-up Resistor Value