Quick charge pump question

[slashandburn]

 I have a few projects lying around that ask for 18V+, I ordered 555's and ICL7660S, not realising that one of said projects (Randall Preamp) asks for 24V rather than 18V. The easiest route seems to be shooting for 25V with a MAX1044 or TC1044.

Can I get up to that with a 7760 or a 555 or are my options basically suck it and order more IC's or settle for ~17.5V?

[Kipper4]

Google the part model for the data sheets and tell us if the parts you intend to use can do what you want....

You've been here a while now.

Once you publish your findings I might learn something too.

[slashandburn]

DOH! I swear I'd checked them. Evidently not.

So the Maxim chip and the 7660 are pin for pin, drop in replacements?    Well that was unexpected.   I guess that problem is solved.   

I must not have seen it for looking. Cheers Rich!

[amptramp]

This sounds like a lot of risk of introducing switching noise to eliminate the solution of two 9 volt batteries in series.

[slashandburn]

Most likely Ron! You make a very good point, it would probably make a lot more sense to try the circuits at 18v using a more straightforward method like two batteries before committing to building 2 or 3 different types of charge pump.    I cleared some space in my drawer of shame, I guess I must subconsciouly be in a rush to fill it back up with more ill-conceived  projects.

I'm still a little baffled with this MAX1044/ICL7660S business though. The data sheet (that they share) seems to imply they're pin compatible but all my other reading gives the impression they're totally serperate entities.  I'm less sleep deprived than yesterday so I'll have have a closer look. So far all I think I know is that if I use the 7660 I need to be sure to get the S prefix in order to bump the oscillating frequencies up out of the audible range. Other than that I probably know less than nothing.

[amptramp]

It's not just a case of it being more straightforward and less noisy, you have the unalterable power equation that if you need 18 volts at 5 mA, and you are running from a 9 volt source, the 9 volt source would have to put out 10 mA plus extra to handle the inefficiencies of the inverter.  If you are running off batteries, the overall battery consumption would be less with the two batteries in series because there would be no inefficiencies.  And as a bonus, no noise.  A stompbox that would need replacement of a single battery every 10 gigs might get away with replacement of two batteries every 25 gigs.

[slashandburn]

That's something else I hadn't considered. That said only one is likely to have enough space left in the enclosure for two batteries. Thankfully that's the flanger that only asks for 18v. The other one asks for 24v and while I could likely easily get away with 18v (it's reported to be usable even at 9v, I assume at a cost of headroom) I can't imagine having space left for 2x 9v if it makes it as far as getting its own enclosure.

As usual I'm putting the cart before the horse.  If it wasn't for the flanger I doubt I wouldn't bother pissing about much with 18v. It just ties in with the Randall Pre's I've also been wanting to compare which were originally running at 24v.