Charge pump capacitor for TRS3232E? (compare with MAX3232E)

Alex,

Both TRS3232E and MAX3232E use the same capacitors.

The capacitors suggested vary based on VCC voltage.

What VCC voltage do you plan to use?

Hello,

I'm considering to use the TRSF3232E.
I understand that Voltage of the external capacitor is the same as the VCC, it's OK?
The reason is the following sentence.

> datasheet SLLS825 DESCRIPTION/ORDERING INFORMATION
The charge pump and four small external capacitors allow operation from a single 3-V to 5.5-V supply.

Is There problem with no margin of voltage?

Best Regards,

sopatopa

Sopatopa,

C1 voltage is same as VCC

The other capacitors can see up to double VCC or 8V, whichever is less.

Hellow Ronald Michallick

Thank you for your reply.

Best Regards,
sopatopa

Hi Ron,

What is the consideration point regards VCC of 3.3V or 5V for the charge pump cap? Lower VCC can use smaller cap? 

Thanks

Regards,

Alex

Alex,

Charge pump tries to make a regulated +/-5.5V supply. The charge pump is set up as a doubler.
At 3.3V a large percentage of the doubler is needed. (3.3V *2) - 5.5V = 1.1V over charge (some of that lost in conversion)
At 5V, less boost is required. (5V *2) - 5.5V = 4.5V over charge (this would result in too much ripple voltage)
It is the ratio of capacitors that matters most.
It is OK for 3.3V to use all the same capacitors.
At 5V, C2,C3,and C4 are increased so that doubler will have a lower boosting voltage to prevent over voltage.