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Serial Port Capacitors

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hisham.i

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Hello...
I did a circuit for sending serial data to the computer, so i used max232 ic.
I used 1uf non polarized capacitor for the max232, but i figured out that in the datasheet they are polarized capacitors.
Do i have to change the capacitors or they will work fine?.. anyone has explanation on the role of these capacitors?
 

ckshivaram

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you have to change it to get better efficiency... and its always better to go with design and proven values as they work as charge pump and have to swing the voltage in both + and - values which non polarized cannot do.
 

robotop

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Hello...
I did a circuit for sending serial data to the computer, so i used max232 ic.
I used 1uf non polarized capacitor for the max232, but i figured out that in the datasheet they are polarized capacitors.
Do i have to change the capacitors or they will work fine?.. anyone has explanation on the role of these capacitors?

Hello, the circuit can work with non-polarized capacitors. The capacitors are used to generate the voltage for EIA level (positive and negative supply) starting from single 5V.
 

IanP

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Forget about voltage swings and all that nonsense ..
The main reason why polarized capacitors were recommended was their low ESR (equivalent series resistance) as the output resistance of a charge pump is directly proportional to ESR of used capacitors ..
I don’t know what type of non-polarized caps did you use, but if they are [RB] bipolar, for example, they are as good (if not better) as standard electrolytic (polarized) caps ..

IanP
:wink:
 

ckshivaram

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keith1200rs

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I think the only reason the data sheet shows polarized capacitors is because when the chip was developed that was the only sensible option. Since then large value ceramics are available so it is fine to use those.

Keith
 

dr pepper

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You can use non polarised caps in place of polarised ones for most circuits, the other way round is when you'll get problems.
 

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