Other Parts Discussed in Thread: CD74HC4538
I have designed a circuit using the CD74HC4538 using timing values or 15M and 22uF to give a little under 4 minutes duration (not critical, anything between 3.5 and 4 mins is fine) . The datasheet explains that a 51R needs to be added to limit discharge current during power off.
Unfortunately, my PCB manufacturer doesn't stock the 4538 but does have the 123 so I'm redesigning the circuit around that.
The datasheet makes no mention of a maximum value for CX nor does it contain any guidance 're powerdown.
So:
1 - could I use, say, 100F and 5M?
2 - do I need to add any power down current limiting protection?