Must capacitors used with MAX232 devices be polarized ?

[dxpwny]

I saw a previous question similar to this, though I don't think it addressed polarity.

I have some tantalum caps which don't appear to be polarized - are they fine to use with the MAX232 type devices ?

 

[FvM]

I have some tantalum caps which don't appear to be polarized

Unlikely. Either they are not tantalum electrolyte type or you didn't yet understand the marking.

Appart from this point you can always use non-polarized capacitors (e.g. ceramic or film) in place of polarized.

 

[dxpwny]

I assume it must not be - there is no +/-. How else might polarity be noted ? Marking on one side reads "102 AFN", then "270 AIJ" on the other.

 

[D.A.(Tony)Stewart]

Why do you have a series cap in RS232? unless this is for a charge pump IC then I understand. But these typically use 0.1uF

FYI it is ok to have 10% of rated voltage in reverse on e-caps.

 

[dxpwny]

Sorry - should have been clearer - yes it is for the charge pump.

 

[FvM]

Electrolytic capacitors don't necessarily have a plus sign, a bar marking the anode terminal is quite common.

102 means usually 1 nF, if so this won't be a tantalum electrolytic capacitor.

Standard MAX232 requires 1 µF charge pump capacitors.