[SOLVED] Capacitor in RS232 chip

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vishweshgm

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I am designing RS232 communication chip using SP3232 chip
Datasheet - SP3232
Datasheet typical circuit is as below :


I am having question about the capacitor used. These are all electrolytic. Why?
When I googled for example ciruits I found it is being used both ways polarised and non-polarised. These are called charge pump capcitors and my question is that if non-polarised SMD 0.1uF capcitor be used instead?
 

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You can use non-polarised ones if you wish. The polarity is only marked so if you used a polarised capacitor you would know which way to connect it. Otherwise, the polarity wouldn't be obvious given that the device internally generates some negative voltages.

Brian.
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Hi,

I´d say: you can always use a non polarized insted of a polarized one. (Not the other way round)

Unless the datasheet gives some dedicated requirements on the capacitors. Thus you need to carefully read the datasheet.

****
Known issues:
* ceramics capacitors usually have very low ESR. Some circuits (usually linear regulators) can´t handle these low ESR.
(But I dot think SP3232 is critical in this. But I did not read the datasheet)
* ceramics (Z5U, X5U...) vary the capacitance with applied voltage. Be surre to use the correct cermics type. (X7R should be suitable. Use capacitors with higher voltage rating than your application needs)
* ceramics capacitors suffer from piezoelectric effect. They may cause audible noise.


Klaus
 

    vishweshgm

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You can use non-polarised ones if you wish. The polarity is only marked so if you used a polarised capacitor you would know which way to connect it. Otherwise, the polarity wouldn't be obvious given that the device internally generates some negative voltages.

Brian.
 
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