Oh and just to share some stuff I've been reading in my own research into this.. I found a document from TI which indicates it's possible to put a resistor in series with a ceramic cap to replace a tantalum.
I found a document from TI which indicates it's possible to put a resistor in series with a ceramic cap to replace a tantalum. But I've also found something from Micrel which indicates I should just cut the farads in half.
So now I'm thinking about using this TI, or Micrel, but they both want 10uF ceramic caps:
Tantalum has much higher ESR than a Ceramic. So TI is saying that their regulator is sensitive to the ESR of the cap. If it is too low, the regulator will be unstable.
Are you sure? That's not what the datasheet from TI says:
"The recommended load/decoupling capacitance is a 10uFtantalum or a 50uF aluminum." It specifically mentions it wants a capacitance with high ESR. The only time ceramic is mentioned is on the output, in parallel with an electrolytic.Micrel says: "in fact, extremely low ESR capacitors may contribute to instability. Tantalum capacitors are recommended..." Neither seem to be suggesting a ceramic-only solution.
If you don't need to worry about extreme temperature ranges, Aluminum Electrolytics are a cheap alternative to Tantalum. Or as suggested, a small 1 or 2 ohm resistor in series with the ceramic.
If you do choose a Tantalum (or Electrolytic) make sure you pick a rated value at least 2X the high transient spike the cap will see.
This is because when a tant cap fails it fails short circuit and that is a fire risk.
If you ever want to get a circuit UL approved they will not allow the use of this sort of capacitor in this situation.
All caps can fail short.
So tantalum isn't the only cap that can fail short and it isn't the only one that can ignite.
I have never heard this to be the case.
Tantalums don't fail over time.
it is extremely unlikely to fail during its life
the chance of failure is almost zero.
If you need 5V regulated input, make an input for 5V regulated DC, and don't worry about it in your circuit. Let the wall wart regulate and filter and provide your 5V.
Is it fair to say that, after the initial test and burn-in, a tantalum capacitor has an expected life that's more than double that of an aluminum electrolytic, assuming the device is operated within "normal" temperature and load ranges
The problem is that what you get in terms of reguation from a standard "regulated" wall wart may be less than desired.