I want to use LM78xx for various applications. What I am concerned about is its failure modes.
1. Failure to Short
Not shorting Vcc to ground!! I mean shorting V_input to V_output.
Assume that you have a delicate and expensive piece of electronic equipment that works with 5V. You are using LM7805 to reduce voltage from 12~13VDC to 5VDC. For some reasons your LM7805 fails to short and your delicate electronic device sees the 12VDC instead of 5VDC and fries. I have seen this all around the web. How to protect against this?
2. Failure to Open
It is not as critical as the failure to short. It can happen as a result of over temperature (temporary) or permanent failure. What are the other things that can trigger this?
3. Reverse Bias & Reverse Discharge
I have seen that too big an output cap can cause reverse current going back to input. It is recommended to add reverse discharge diode protection. What else can cause this kind of reverse bias voltage?
From Various datasheets:
With the LM7805, the output capacitor should not exceed 1mf, as larger values could damage the 7805 due to backfeeding of current when power is switched off.
When a surge voltage exceeding maximum rating is applied to the input terminal or when a voltage in excess of the input terminal voltage is applied to the output terminal, the circuit may be destroyed.
Does the diode on the above picture also protect against flyback current of an inductor? Or is it better to add a separate diode across the inductance load?
5. What else?
What are the other possible causes of LM78xx failure?