On Fri, May 25, 2018 at 05:18:09PM +0200, Philipp Zabel wrote: > On Fri, 2018-05-25 at 15:52 +0100, Mark Brown wrote: > > On Fri, May 25, 2018 at 01:42:53PM +0200, Marco Felsch wrote: > > > Also the formula for the delay time (t = C × 25,000/3.5) depends only on > > > the capacity size. > > Why not just have the user specify the capacitance of the capacitor on > > the rail which they can directly read from the schematic rather than > > forcing them to do the calcualtion? That seems a bit clearer and more > > user friendly (plus if someone decides the spec was wrong it's easier to > > roll out fixes). > The exact capacitance may not be known or vary above the nominal value > because of cheap components, and the formula from the datasheet is just > a guideline. That variability is going to apply just as much to the charge time calculations/measurements as it is to the initial capacitance value - the results are going to be very much garbage in, garbage out. > I'd expect the usual method to set this delay to be semi-empirical: > "start from the value calculated from datasheet and schematics and then > increase until no more audio artifacts on a representative sample of > boards". > I think it is be better to specify a delay that works than a bogus > capacitance value that happens to correspond to a delay that works. If this is varying so drastically per board/system that it's relevant then we're already into problematic territory. For most devices we just have a number for the part, not something that varies so wildly that each system needs to configure it.
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