MAX1044 charge pump

[Paul Perry (Frostwave)]

Now that I'm looking at/thinking about that layout I drew up and the circuit... doesn't this not eliminate our problem?  I thought the initial problem was that the MAX1044 will eventually burn out if run at or over it's max input voltage of 10v.  Since this schematic runs the inverting MAX1044 at +10v from the first MAX1044, aren't we still going to encounter the same issue??

I'm sure there are errors in the layout you have, especially if all those crossing tracks are joined at the crosses.
www.maxim-ic.com/getds.cfm?qv_pk=1017 for the MAX1044 data sheet.

No reason why the chip won't work with this strategy, though.
The +5 from the regulator, when doubled, gives the 10, which the second one won't have any trouble with at all. It's designed to run up to 10V input.
But, if you are trying to do it by next weekend.... I hate running to a deadline myself. Personally, I'd build something out of batteries for the short term (but that's just me - Mr Belt&Braces).
Some serious advice though - get a couple more 1044s as spares. Shit happens.

[zpyder]

I'm sure there are errors in the layout you have, especially if all those crossing tracks are joined at the crosses.
www.maxim-ic.com/getds.cfm?qv_pk=1017 for the MAX1044 data sheet.

Well I pretty much copied verbatim from that datasheet the "Voltage Doubler" circuit and the "Negative Voltage Converter with BOOST" circuit - but very quickly.  I'm not particularly worried about errors as I would double/triple check the layout before building it... just wanted to make sure that's what we were talking about.

No reason why the chip won't work with this strategy, though.
The +5 from the regulator, when doubled, gives the 10, which the second one won't have any trouble with at all. It's designed to run up to 10V input.

Hmmm... alright.  This is my primary concern.  The chip is rated with a maximum input voltage of 10V, isn't it risky to run an IC right at it's max voltage??

But, if you are trying to do it by next weekend.... I hate running to a deadline myself. Personally, I'd build something out of batteries for the short term (but that's just me - Mr Belt&Braces).

check that!

Some serious advice though - get a couple more 1044s as spares. Shit happens.

double check!!

thanks
zpyder

[Paul Perry (Frostwave)]

Electronic components often have two "maximum" voltages or currents or temperatures  given - the one that it is perfectly OK to run at forever, the maximum allowable for normal use, and a higher voltage for "momentary" use. (though, for ICs, the general rule is, if you go outside the "allowable operating voltage" you are on your own.)

Bottom line, if the data sheet says you can run something at 10V input, then you can do this. For as long as you like.
But 11 might be a mistake... that's why I went through the hassle of having the +5 reg at the start. That makes sure the doubler can't put out more than 10. Plus the advantage, that you know what it IS putting out. (less a fraction of a volt for losses).

[jaytee]

I can understand your logic trying to keep the output at 10 volts but the rating of 10 volts is for the supply. It should be perfectly ok with a supply voltage of 9 volts even though the output is nearly double this. I realise it doesn't say what the maximum output voltage can be in the datasheet but the most it can do is double it. That's it's job afterall, a voltage doubler. If you look at the datasheet for the ICL7660S it clearly says the max input voltage is 12 volts and you can get up to 22.8 volts when used as a doubler with 12 volts input. The MAX1044 is an almost identical chip just with a lower supply voltage. Unless I'm missing something with this?

[boyersdad]

So if you use the 555 circuit as show a few posts ago, is there noise introduced to the circuit you're powering? I'd like to use this for my PT-80. I have about 50 555's sitting around doing nothing, and would rather use those than a $5 1044 that will fail on me!

How much current can a 555 source?

[Paul Perry (Frostwave)]

So if you use the 555 circuit as show a few posts ago, is there noise introduced to the circuit you're powering? I'd like to use this for my PT-80. I have about 50 555's sitting around doing nothing, and would rather use those than a $5 1044 that will fail on me!
How much current can a 555 source?

Well, the 555 comes in many flavours. The LM555 can source 200mA according to the data sheet, though as a doubler I expect you might get 50mA more likely.
And I expect it would be noisy as all hell. Though you could run it above audio frequencies.
If you use a cmos 555, note the output max current allowed might be less, and the input max voltage will have to be watched closely.

Let's know how you go, if you have a hack at it!

[soulsonic]

Running a 555 at higher frequencies and using proper filtering should deal with any noises. If it's filtered correctly, noise shouldn't be a problem - choices in diodes can affect this as well.

You could put a 9v Zener diode with the '1044. That could help keep it's driving voltage from exceeding 9v, and keep any possible static from damaging it. That might be the real problem here.... the chips could be getting damaged by static.

[boyersdad]

I believe I have LM555's, in an 8pin dip. I have a bunch that I got for free, so I don't mind ruining a few for the cause, lol. I'm going to build up one of those doublers from the handy-dandy circuit page. I don't imagine I will need more supply than about 15mA anyway, so this should work out well.

Think there would be any advantage to increasing the size of the caps on that doubler circuit? Maybe 220mf?

[soulsonic]

I breadboarded the "Negative Voltage Converter" circuit last night and it worked fine. From my experience with 555s, I can say first-hand that they can push enough juice to drive a small speaker, so I'm sure they would be fine for powering pretty much any pedal.

I also did a comparison of the 555 circuit with that of the 1044, and it appears that 555 draws considerably more idle current... about 7mA with the setup I was using. In contrast, the 1044 drew less than 1mA at idle. I tested both circuits using a 270K resistor as a load so it would have something to complete the circuit, but not load it very much.

I'll do some more tests later today... possibly hook a scope up to it to try and see the nature of any noise on the output. Then, I'll build up a simple little opamp booster to test how the circuits compare to each other sound-wise.

[jaytee]

The cmos 555 draws much less current. In the datasheet it's 200uA max. Also it can get closer to the supply rail, I think you lose some voltage with the standard one.

[soulsonic]

The '1044 uses MOSFET construction internally. This probably contributes to its low idle current... but it also proves something else; that it is most likely VERY sensitive to ESD damage. That's probably what's killing these chips; they are likely not properly protected from static discharge. Think about it: the V+ input goes straight into one of the MOSFET switches; that means static discharge at the V+ input should be enough to kill it. Since the V+ is usually connected directly to a battery snap, it is very probably that it could be damaged just by the act of changing batteries. I think this is something we should all chew on.