Olin Lathrop wrote:
> Vitaliy wrote:
>> Olin, you haven't read the datasheet yourself, have you? It says
>> nothing about not using electrolytics.
>
> We're talking about power supply "bypass" or "decoupling" caps.

The OP was specifically asking about a decoupling cap for a MAX233A.


>  Basic
> electronics should be enough to assume that electrolytics are not suited 
> for
> this application unless the datasheet specifically says so, and I expect 
> it
> doesn't.  There is really no place left today for a 1uF electrolytic
> capacitor.

This is completely backwards. If Maxim doesn't want us to use electrolytics, 
they should explicitly say so.


>> It says nothing about "low ESR", either. Any cap will do.
>
> It may not say anything about ESR, but this gets to the level of obvious
> unless the datasheet specifically says otherwise.

Most datasheets would specifically tell you whether a low-ESR cap is 
required. For instance, Microchip goes to great pains to explain this when 
it matters (I recently read an entire app note devoted to this issue).


> At some point they have
> to rely on the person reading the datasheet to know at least a little 
> about
> electronics.  Keep in mind that even though a electrolytic would not be
> violating the datasheet if taken literally, neither would a ceramic, and
> there are plenty of good reasons to use a ceramic instead of a 
> electrolytic
> in this case.

If it ain't forbidden, it is permitted. If a non-electrolytic low-ESR cap is 
required, it is the manufacturer's responsibility to tell me so. This has 
nothing to do with my level of knowledge of electronics. The IC in most 
cases is a black box, and I trust the mfr to tell me what to hook up to it.


>> You guys seem to forget that these are level shifter circuits, not
>> microcontrollers. The cap is there simply to keep the voltage on
>> RS232 from going too far below 10V, for the duration of the bit.
>
> It's a digital circuit that has switching transients and two or three 
> charge
> pumps.  Unless the datasheet explicity says otherwise, the assumption 
> should
> be that good power supply bypass is required.  The fact that they 
> explicitly
> call for 1uF should be a big clue that something there matters more than
> usual.

I would have no problem if you said that SW should just buy a bunch of 
ceramic 1uF caps, and forget about the whole thing. But woe unto you, for ye 
lade newbies with burdens grievous to be borne unnecessarily.

Vitaliy 

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