Dear Technical Support Team,
About "Figure 6. Typical Operating Circuit and Capacitor Values" on datasheet page 11.
When + 5V ± 5% is applied to VCC(Power Supply voltage) , what is the maximum voltage applied to C1, C2, C3 and C4?
We are investigating the validity of the withstand voltage of the capacitor model numbers selected for C1, C2, C3, and C4.
Best Regards,
ttd
Hi ttd,
I have attached an app note here that describes the structure of the charge pump, and how capacitors C1, C2, C3, and C4 are used to generate RS232 output voltage.
C1 theoretically sees a maximum voltage of VCC. Once C1 is charged to a VCC, SW1 & SW2 flip. C1 already charged to VCC now has a different reference to VCC. V+ will charge up to 2*VCC. This means that C3 and C2 both potentially see max voltage of 2*VCC. Once C2 is charged, it also switches over via switches SW3 & SW4, where V- will be at a potential of -2*VCC meaning C4 = -2*VCC.
Max voltages:
C1 = + 5V ± 5% V
C2 & C3 = 2 * (+ 5V ± 5% ) V
C4 = -2 * (+ 5V ± 5% ) V
Output voltage of the TRS3223E still is around +-5.4V swing. This is regulated by the switching frequency feedback system as described in the app note.
Regards,
Tyler
Hi Tyler,
Thank you for your reply.
I have question about "C1 = + 5V ± 5% V".
According to the following blog, C1 connects V＋, then "2 * (+ 5V ± 5% ) V" is applied to C1?
Should I choose withstand of C1 about over 10V or 16V?
e2e.ti.com/.../how-the-rs-232-transceiver-s-regulated-charge-pump-circuitry-works
Best Regards,
ttd
