MAX1044 charge pump

[zpyder]

Some of you are familiar with the MAX1044 charge pump IC (http://www.geofex.com/circuits/+9_to_-9.htm).

The MAX1044 can be used to get a bipolar +9v/-9v power supply using only one battery (or adapter).  Apparently the TLC7660CPA, LMC7660, and NJU7660D also do this, though I've only used the MAX1044.

I have been using a MAX1044 in a pedal for a while and now the pedal has failed.  I have pulled the MAX1044 out and protoboarded a test circuit for it (exactly the first schematic at http://www.geofex.com/circuits/+9_to_-9.htm).  I'm not getting what I expect.  I'm running the circuit with an adapter that's giving me +9.6v.  At pin 5, instead of getting -9.6v, I'm getting around +2v.  I have another MAX1044 (which has been used before), so I popped the other in and that one gives me about +3.2v at pin 5.  The results are repeatable as I tried them both many times.

It seems both of my IC's are failing      I've checked and double-checked my circuit (it's pretty simple)....

Has anyone experienced a MAX1044 failing before?
Has anyone ever tried the TLC7660CPA, LMC7660, or NJU7660D and with what kind of success?

This kinda sucks - I've got a gig tomorrow and no more charge pumps

Thanks!
zpyder

[Processaurus]

Has anyone experienced a MAX1044 failing before?

Yeah, it's been the only one of my pedals to break once it was built & debugged  .  Basically they aren't meant for running as high as 9v, because 10v can kill them, as can drawing more than 10mA (20mA total for the pedal, since the charge pump is doing half the work).

I'm going to try the LT1054 next time I need a +/- supply.

[zpyder]

ahhh shite.... now I see on the datasheet that 1.5 - 10V is indicated.  same/similar with LMC7660 and NJU7660D.  crapness. The LT1054 indicates 3.5 - 15V.  Still kindof cutting it close (especially if you use adapters with higher than 9v output), but better.

R.G. - maybe want to add the LT1054 to your page there on the MAX1044 and alternatives?

So, here's an interesting question:

Would it be possible to use 2 MAX1044's (etc.) in parallel somehow, running at half-supply voltage, to remedy the problem?  Perhaps set up a voltage divider to get half-supply, feed it to two MAX1044's, and then somehow (this part I don't know how to do at all) sum the voltages back together!?!?!?  Would not be cheaper than an LT1054, but would give more headroom if possible.

at least now I know confidently what went wrong with my pedal... and I'll be buying some of those LT1054's as well.  2 bucks a pop at mouser, unfortunately not in time for the show tomorrow.

thanks!
zpyder

[jaytee]

The ICL7760S is rated up to 12 volts.

[Solidhex]

  I checked out this thread because I had recently been looking at the general guitar gadgets Geofex a/b/y amp switching project and recognized the MAX1044 charge pump mentioned in it. Have a lot of people out there experienced failure with it? Is there an alternative part to use that would handle the job better but not have any of the audio "whining" mentioned with the 7660? I'd really like to get a good amp switcher but need one I could depend  on when I'm on the road!

--Brad

[Paul Perry (Frostwave)]

I know it's a mess, but.......
when I need a stable +-9v approx system. I run the 9v nominal input to a low dropout +5 reg.
Then the +5 goes to a 7760 or similar, that gives you +9, but pretty stable.
Which you can invert with another 7760, if you need the +-9, and if that gives you enough current.
Not cheap or simple, but it's reliable, and still works OK with your battery down to 6.5V. - or a plugpack from +6.5 to more than 16 volts.

[moro]

So would the LT1054 be a better choice for the +18V circuit as well?

[zpyder]

I just noticed that on the LT1043 datasheet the output voltage is listed as –4.7/–5/–5.2 V MIN/TYP/MAX.  Input is listed as 3.5 - 15 V...

So am I reading correctly that I'm not going to get more than ~-5VDC out of this thing?

zpyder

[zpyder]

I run the 9v nominal input to a low dropout +5 reg.

ok...

Then the +5 goes to a 7760 or similar, that gives you +9, but pretty stable.

how do you wire a 7760 to convert +5v to +9v?  I went through the datasheet but couldn't find an explanation I could understand.

Which you can invert with another 7760, if you need the +-9, and if that gives you enough current.

so you run the second 7660 off of the same +5v and get -9v at output, right?  makes sense, but again, how does one wire this up?

What's the equation and circuit?

thanks,
zpyder

[MetalGuy]

It looks like you're pulling too much current that's why the voltage drop is so big. Try the 7660S - it's rated for higher voltage and current.

[Paul Perry (Frostwave)]

Zp7yder, what I meant was this:

The +5 regulator gives the stable +5.

Then the regulated +5 goes to the first 7660, which is wired up as a doubler, to give you the +10.

Now, that's your +10 - but you also run this +10 to another 7660 wired as an inverter, to give -10.

Typical circuits here: http://www.catsemi.com/products/CAT660.asp
(don't be confused by the 5.5V max on the units in this datasheet, if you use a 7660  or 7662 you will be OK, the circuitry is the same).

[g3rmanium]

Is there an alternative part to use that would handle the job better but not have any of the audio "whining" mentioned with the 7660?

I've been using the XP Power IA0515S DC/DC converter as the power source of my X² squarer. They work well but eat up lots of current.

[Processaurus]

I just noticed that on the LT1043 datasheet the output voltage is listed as –4.7/–5/–5.2 V MIN/TYP/MAX.  Input is listed as 3.5 - 15 V...

So am I reading correctly that I'm not going to get more than ~-5VDC out of this thing?

zpyder

I saw that too, but I'm not sure what the deal is, I'll let people know when I get a chance to fiddle with the ones I got from Digikey.

[zpyder]

Paul-



Kind of a sloppy layout, but is this what you're talking about?

And what values for C3, C4??

cheers,
zpyder

[Paul Perry (Frostwave)]

I've been using the XP Power IA0515S DC/DC converter as the power source of my X² squarer. They work well but eat up lots of current.

Thanks for the headsup on the XP series, Johann! Been looking for something like this for a while..
just how much current DOES it use?

[Paul Perry (Frostwave)]

is this what you're talking about?
And what values for C3, C4??

Yeah, that's the idea.
I havn't checked the connections, but that's the idea all right.
I'd try 100uF for those caps.

best, paul perry

[zpyder]

anyone know a US distributor for the IA0515S?

[zpyder]

Paul-

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??

trying to figure this all out so I can order my parts and get my board up and running for next weekend's gig.

thanks
zpyder

[CGDARK]

anyone know a US distributor for the IA0515S?

http://www.newark.com/jsp/search/productdetail.jsp?SKU=38K2299&CMP=AFC-QO1721829242

[soulsonic]

Um... what about just using a 555? There's some real simple circuits for voltage doubling and bipolar-supply-making that use a 555. The 555 already has a proven track record for reliability in 9v powered devices.

You can see an example here at the bottom of the page under the heading "DC to DC Converter":  http://members.shaw.ca/roma/six.html