I need to create a delay in my circuit (about a second) and I'm wondering what are the advantages/disadvantages of using a 555 Timer to create a delay vs using a specialized delay IC like the LTC6994? This is the datasheet for the LTC6994: (http://cds.linear.com/docs/en/datasheet/699412fb.pdf)
A 555 is about 1/10 the price, but accuracy will likely be less. It also has a plethora of 2nd sources.
The LTC6994 may be lower power, and has most likely higher accuracy.
Of course you could use a microcontroller and do better than either of the above in everything but cost, where the 555 still wins.
I doubt that either the 555 or LTC6994 are really great solutions. It may help if you just list the requirements you need to do for your application:
- Sense a button press (are there any further limitations here such as button bounce or if you hold the button down for over 30 seconds?)
- Start a 30 second timer (how accurate? Will you have to adjust it?)
- Set the power on signal (is this an RS flipflop or some other latching logic signal)
- Is there a power off? (button? Timer? Do you press the same button again? Or hold it down for a time period like a PC power button? Or press a second button? etc)
The 555 is certainly cheap but you'll end up paying more for the components around it, especially if you need a potentiometer to adjust the time and a logic chip to hold power on state. Total cost will probably run out to $1.50 if you have an RS latch.
The LTC6994 is a great chip but not really designed for such a simple application. You'd probably end up in the $4+ range.
As Sphero so correctly pointed out you may be better considering a 6-8pin MCU like an ATTiny10 SMT (really nice because they do QTouch cap switch sense, and don't require a crystal) for < $0.90.
Once you have the skills to use the minimal MCU solutions you may hardly ever touch Logic chips again, so it's skills worth having.