The EIA 232 datasheet calls for 1ufd capacitors across C1+ C1- and C2+ C2-.

They don't show a polarity so I assume they are just 1ufd caps?


They show the polarity of the caps for VS+, VS- and VCC.

I don't have any 1ufd regular caps on hand, just several 1ufd tants. Is there any reason I can't use them for everything?

 

The polarity is the + & - on the pins, as long as they are at least 16V they should work fine.

 

The polarity is the + & - on the pins, as long as they are at least 16V they should work fine.

Yep I have the pinout thing down and my tants are 50V so I guess I am good.

Thanks!


I did some checking, the tants are a bit more expensive than the cerramic disks but I have the tants and I would have to order the regular caps.

 

Yep I have the pinout thing down and my tants are 50V so I guess I am good.

Thanks!


I did some checking, the tants are a bit more expensive than the cerramic disks but I have the tants and I would have to order the regular caps.

Do I have to use 1ufd?

I found this here where he uses .1ufd and I have bunches of those. But the datasheet calls of 1ufd which is really curious.

 

Depends on the part. Some can use 0.1 others 10uF. It's in the datasheet.

 

Depends on the part. Some can use 0.1 others 10uF. It's in the datasheet.

Is the EIA232 a generic part #? I have seen 2 EIA232 projects with .1 ufd.

 

Ah yes here is what the datasheet says:


Nonpolarized ceramic capacitors are acceptable. If polarized tantalum or electrolytic capacitors are used, they should be
connected as shown. In addition to the 1-μF capacitors shown, the MAX202 can operate with 0.1-μF capacitors.

So EIA232 is generic?

 

Ah yes here is what the datasheet says:


Nonpolarized ceramic capacitors are acceptable. If polarized tantalum or electrolytic capacitors are used, they should be
connected as shown. In addition to the 1-μF capacitors shown, the MAX202 can operate with 0.1-μF capacitors.

So EIA232 is generic?

No it is not a part. EIA stands for Electronics Industry Association. It published a specification called RS-232 with several revisions.

Maxim, a semiconductor company, makes a family of chips, of which the MAX232 is one of the widely used members.

 

The deal here is that if an electrolytic is used a higher ESR is expected thus the higher value specified. 0.1 in ceramic or film would be fine and a lot cheaper than 1 uF which are rarely seen in less than 50V.

Some people don't realize that to keep an electrolytic capacitor in a "survival state" it should be seeing at least half of its rated voltage such that it can maintain it's qualities but still be rated high enough to handle any spikes. In other words a 16V cap on a 12V circuit may be fine if it's regulated but should be a 25V or 35V if it's not. If you put a 100V rated cap in there the darn thing will lose it's capabilities over a shorter order of time.

If this fact isn't in the e-book it should be.

 

The deal here is that if an electrolytic is used a higher ESR is expected thus the higher value specified. 0.1 in ceramic or film would be fine and a lot cheaper than 1 uF which are rarely seen in less than 50V.

Some people don't realize that to keep an electrolytic capacitor in a "survival state" it should be seeing at least half of its rated voltage such that it can maintain it's qualities but still be rated high enough to handle any spikes. In other words a 16V cap on a 12V circuit may be fine if it's regulated but should be a 25V or 35V if it's not. If you put a 100V rated cap in there the darn thing will lose it's capabilities over a shorter order of time.

If this fact isn't in the e-book it should be.

So even if the datasheet calls for 1 ufd and specifically mentions a version of the chip that uses .1 ufd a .1 ufd will still work?

BTW this is for a very limited distance not more than 6 feet or so. Just enough to make it from my PIC to my PC.

Interesting to know about electrolytics. I was not aware of that thank you. I know have a PSU to resdesign and build.

 

A good 0.1 will be fine, seems it's been a capacitor night, doesn't it?

Personally I keep these around at all times because they're easy to use. The pic is misleading, they're very tiny, almost like little beads:
http://www.mouser.com/Search/Produc...5TAvirtualkey64600000virtualkey80-C410C104K5R