capacitancefrequencyschottky
In datasheets they write '1 MHz' in the capacitance vs voltage figures. For example:
I suppose it is some sort of a standard to measure the capacitance at 1 MHz, but is there a dependence of the capacitance on the frequency or is it just the dependence on the reverse voltage?
I think your second app note from ECS explains it: it is the frequency the crystal oscillates at when put into an (parallel) oscillator circuit, with the load capacitance specified by the manufacturer. (see page 85, "load capacitance")
This means you are right in that the frequency depends on the load capacitance - which is why it is specified in the data sheets.
But there are also crystals which are used in series oscillator, the you have no capacitance, and the specified crystal frequency is the series resonant frequency (fs).
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
The supplier has to measure capacitance using an oscillator and, that oscillator has to use a certain frequency. Given that a nominal value of 30 pF at 1 MHz implies a capacitive reactance of 5305 Ω, it's a fairly easy thing to measure.
For instance, if 1 kHz were used, the reactive impedance would be over 5 MΩ and, simple measurement techniques would be susceptible to diode leakage currents (these are quite high on Schottky diodes).
So, in a nutshell, stating the frequency as being 1 MHz is a means of giving confidence in the measurement method because you wouldn't want to use a frequency ten times lower (or worse) because of "other effects" such as leakage current.
I don't think there are any significant effects on capacitance related to frequency but, the higher you go (up to a certain point where transmission-lines effects take place), the more accurate the measurement is.