I want to use this chip (ST3232CDR) as an RS232 transceiver. The problem is that I want to power the chip using 2 levels of voltage (3.3V and 5.0V) using a simple jumper, but in the datasheet (http://www.st.com/content/ccc/resource/technical/document/datasheet/group1/40/2c/7f/62/3a/3f/47/3c/CD00002253/files/CD00002253.pdf/jcr:content/translations/en.CD00002253.pdf) page 7, the recommended capacitors values are different according to supply voltage level. How can I solve this problem. Is it okay to same capacitors for the two different voltage levels? or not? PS: I am using this chip as an RS232 transceiver to interface an ATmega32 with db9 connector using UART.
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Unless the big difference in cost hurts you from $0.0015 to $0.008 use the bigger parts. Otherwise test and compare with other models like ST202E – Tony Stewart EE75 Mar 08 '17 at 14:48
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About the capacitors themselves, is it mandatory to use polarized capacitors or simple ceramic capacitors can do the job? – A. Kier Mar 09 '17 at 05:38
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high quality caps low tan delta ought to be used of any type. – Tony Stewart EE75 Mar 09 '17 at 06:09
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If you want to use MLCC, be sure to read up a little about their DC voltage dependency. There should be a couple of questions about it here. – pipe Mar 09 '17 at 09:42
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Just use the higher of the recommended values. For example, as per Table 9:
| Capacitor | Value |
|---|---|
| C1 | 0.1 µF |
| C2, C3, C4 | 0.33 µF |
| Cbypass | 0.33 µF |
Typically, you'd want the lowest possible capacitance for the circuit to function - the lower, the cheaper. This is why they have a table with recommended values. However, using a higher capacitance will not hurt functionality (within reason). You might get a measurably slower start-up time, but the effect would be negligible.
pipe
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