TRSF3232E: how to choose capacitor C1, C2, C3 and C4 value?

Hi Max,

The recommended datasheet values were chosen to be able to provide a suitable voltage under typical loading conditions and minimize switching ripple.  They are not the only values that can work, though.  Other values can be OK to use, they just may give slightly different performance (faster/slower switching, higher/lower ripple, etc.).  To get a better idea how different capacitor values impact the circuit operation, you can reference this blog:

https://e2e.ti.com/blogs_/b/analogwire/archive/2018/06/28/how-the-rs-232-transceiver-s-regulated-charge-pump-circuitry-works

You can check the performance of the chosen values by probing the V- and V- rails on an oscilloscope to verify they are generating the proper voltages when the DOUT lines are in either high or low states.

Regards,
Max