circuit-designcircuit-protectiondiodesschottky
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.
Peak Repetitive Reverse Voltage is the "guaranteed" normal reverse voltage across the diode without causing it problems like breakdown - notice that further down it states that peak reverse current is between 5uA and 50uA (at temperature) for this reverse voltage (same as blocking voltage)
Ta is ambient temperature.
The maximum rating on dv/dt is just that- do not exceed it if you want your design to be reliable. Older diodes were good for as little as 2kV/us but most are now okay with 10kV/us. Of course the actual ability to withstand dv/dt may be higher but that is all you are guaranteed, so stay within it.
The capacitance of all diodes varies with the voltage across it- minimum at the rated reverse voltage and higher with positive bias (though it is in parallel with the conduction of the diode). Diodes characterized for this are called varactor or varicap diodes, but all diodes have this characteristic.
Beware if this is important to you and the number is specified at a much higher voltage than where you are using it.
Schottky diodes do not directly have reverse recovery time as do conventional diodes (though the protective structures can have some similar effect), so the capacitance may be your main speed consideration. Here is the 1N5819 capacitance curve from the datasheet:
Best Answer
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.