If you have in your „drawer“ a universal 1000V diode in a miniature SOD123FL package, you have a solution for many circuits.
This is an archive article published 28.02.2014. Some information may no longer be up to date and in line with the current state. Please contact us in case of interest.
Small/ bigger, with a lower- or rather with a higher cut-off voltage, solderable by wave or by reflow … these are for example some of the criteria when selecting a universal rectifying diode. However if you already know, that 1A current and a middle speed are sufficient for you, then we can say, that only one type will be sufficient for you in majority of cases - SL1M from company Diotec.
Standard silicon diodes show only a minimal dependency of VF from a cut-off voltage - in opposite to Schottky diodes, where a choice according a cut-off voltage is important in order to reach low losses (as a forward voltage - VF is noticeably higher at types with a higher cut-off voltage).
In other words, if a Schottky diode transfers for example 1A current, there´s a significant difference in a VF between types with a lower cut-off voltage in comparison to types with a higher cut-off voltage. However common silicon diodes don´t have this dependency, thus in general it dosen´t matter, whether we´ll use a „100V“ diode or a „1000V“ diode on a given place (if we don´t use a possible breakdown intentionally). So if can choose between a 400V and 1000V type for a similar price, nothing prevents us to better buy a 1000V type and to have a surety of universal usage - for example even for a direct rectification of a mains voltage. As a result we´ll gain for example a higher resistance to various overvoltages.
SL1M offers such versatility thanks to a very good price and also thanks to its dimensions, because it belongs to the smallest 1A diodes in the market. The only requirement if we want to use a maximum current of 1A is, that it´s necessary to observe a minimal pad dimensions (copper area) of approx. 5x5mm at both sides. This won´t be a problem for the most of applications, as to this area also contribute surrounding solder pads of other components (if they don´t generate heat). Naturally, in this case we mustn´t use at the PCB design a thermal isolation of pads (so called thermals), but only a non-solderable layer (solder resist).