Hi Team,
My customer would like change their solution from SN74HC245 to SN74AHC245 because Vsignal may larger than Vin.
And below are the questions that we would like to check.
1. Could SN74AHC245 support 5V -> 3.3V voltage translation?
2. Because there is no top zener diode on SN74AHC245, do we need to concern its schematic design? or just the same as SN74HC245?
Regards,
Roy
Hi Roy,
The SN74AHC245 is a direct replacement for the SN74HC245 in the vast majority of applications.
If all you're interested in is getting rid of the positive clamp diode on the input, then this is a good solution.
If your input voltage is 5V and the supply is 3.3V, then the device will properly convert the output to 3.3V so long as the input signal is above VIH for a 'HIGH' and below VIL for a 'LOW'. To be sure that you can exceed VCC, you can check the datasheet:
The above highlighted spec indicates that the input voltage can be up to 5.5V, independent of the supply. You can read a bit more about this here: [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?
