What do these ratings mean when it comes to reading datasheets for Schottky and how do you pick a diode based on these ratings:
Current, Forward, Continuous
Voltage, Repetitive Peak
Voltage, Forward
For example, I have a 12V / 3A line that i would like to put a Schottky diode on to prevent backflow but have no idea what any of the above ratings have to be so that i get the right one.
Forward continuous current is what you might regard as the maximum current you are allowed to pass through the diode continuously given what the data sheet says (small print) about heat sinking requirements. This is a thermal specification as opposed to peak forward current (sometimes ten times higher than continuous) which is a "fusing" type of specification.
Repetitive peak inverse voltage is the blocking voltage that the diode can withstand when reverse biased.
Forward voltage is the volt drop across the diode when forward biased and is always specified at a forward current. For a Schottky diode this can be in the range 0.3 to 0.6 volts typically.
The power ratings are based on not only how much current, but how much time the current will be flowing through the diode.
Because a diode receiving a pulsed current will dissipate less power (the time average of the current will be lower) the package will be able to handle a higher pulsed current
If you have a continuous current then the power rating of the package needs to be more than what the diode is dissipating.
For a diode the equation is this: $$ P_{dissapated} = V_{drop}*I$$
and this needs power needs to be lower than what the package can handle.
Here is a good reference on how to calculate these values
