Shop OBEX P1 Docs P2 Docs Learn Events
Max232A problems. — Parallax Forums

Max232A problems.

GICU812GICU812 Posts: 289
edited 2008-10-13 07:14 in General Discussion
I need to convert an output from 3.3v to 12v.

I dont know if the 232 will work with 3.3v, but I can convert to 5v if neccessary.

My problem is im only getting 4.6v on the voltage doubler output. I havent hooked anything else up yet, but I thought it was supposed to output 10v+ at all times.

I have 4.8-4.9v on the VCC pin, and ground hooked up

I have connected the capacitors as here http://www.datasheetcatalog.org/datasheet/maxim/MAX220-MAX249.pdf
page 17

I have .1uf ceramic caps on the voltage doubler and -10v generator, and 10uf on the others, as I only had 2 .1uf caps.

Is this the problem? Does anyone have a better solution to get 12v out of a 3.3v MC? This is logic circuitry, so I dont need large currents.

Thanks.

·

Comments

  • LeonLeon Posts: 7,620
    edited 2008-10-13 06:03
    I've had the 5V MAX202 working at 3.3V in an emergency. The 3.3V MAX3232 would be better, of course.

    That 4.6V might be right, from 3.3V. I'll check one of my boards with a MAX3232 at 3V, and see what I get.

    Maxim makes some little voltage booster chips that might give you 12V, or you could build a little boost converter using a Nat Semi Simple Switcher chip or something like it.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • GICU812GICU812 Posts: 289
    edited 2008-10-13 06:25
    Nah, sorry, what I meant is i'm feeding it 4.9v on the VIN, its outputing 4.6ish on the doubled pin.

    My logic switching is going to be done on 3.3v.
  • LeonLeon Posts: 7,620
    edited 2008-10-13 07:14
    That sounds wrong.

    Do you get the same voltage (-ve) on the other capacitor?

    Have you got the polarised capacitors the right way round?

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
Sign In or Register to comment.