SN74AHCT08: SN74AHCT08

Paul Chan

Part Number: SN74AHCT08
Other Parts Discussed in Thread: SN74HCS08

Tool/software:

Hi, I am using this quad AND gate as shown below. In the application, the VCC pin is tied to ground and the GND pin is tied to -3.45V as I'm using negative logic. My question is, how should I terminate the inputs and outputs of unused logic gates for this part.

4 months ago

+1 Clemens Ladisch 4 months ago

Guru 277650 points

Unused outputs should be left open. Unused inputs must have a valid voltage, either high or low.

Please note that AHCT devices do not allow a supply voltage of 3.45 V. And the low-pass filter at pin 4 violates the Δt/Δv limit. Better use the SN74HCS08.

0 Malcolm Lyn 4 months ago

TI__Mastermind 19200 points

Hi Paul, you can connect unused inputs either to GND or to the -3.45V pin and leave the outputs floating.

Logic

Logic forum

SN74AHCT08: SN74AHCT08