7660 for neutron charge pump

[scaesic]

what is the difference in using ICL7660 ACPA or ICL7660 SCPA, if any?

[Ry]

I don't have time to look at the data sheet right now, but be aware that the 7660 is really noisy and can add audible bleed through to your circuit.  I messed around with that chip for a while and finally gave up and went with the MAX1044 (a bit more expensive, but it will save you a headache).

[cd]

In a pinch, make an oscillator out of the audio frequency range from a 555 timer and drive the 7660 from that.  No bleed thru.

[waldo041]

http://geofex.com/circuits/+9_to_-9.htm

i don't know the difference, but this is a good read from the search function if you plan on using them for a charge pump.


peace,
waldo

[scaesic]

well, thats great aslong as the pin out of the max1044 is the same

[Ry]

In a pinch, make an oscillator out of the audio frequency range from a 555 timer and drive the 7660 from that.  No bleed thru.

Brilliant!  I feel stupid for not thinking of that...of course, it is adding another chip, but it will work with the half dozen 7660's I have sitting around.

Thanks for the tip!

[stm]

Even more, with a CMOS 555 astable oscillator plus two diodes and two capacitors you can get -8.5V or +17.5V with at least 10 mA current capacity using inexpensive and easy to get components.  No need for a ICL7660 or MAX1044 if you can live with the slight voltage drop at the output secondary voltage output.

[Morocotopo]

Hi, this loks cool. I´ve been reading about charge pumps and +/-9V, here in Argentina the MAX chip is unavailable, but the 7660 I can buy. Since i don´t know anything about 555´s or oscillator (astable or not ) or driving a 7660 with a 555, it would be nice if you could post a schematic/diagram of this, so that I can try it, or tell me where to find some more info about this (I´ve already read the articles in different pages, like GEO, Runoffgroove, etc. but I think none of them adresses this particular idea(s))

Thanks in advance

[redeffect]

Heres a vote for the MAX1044. The amount of aggrivation you save vs. the couple of extra $$ is well worth it.
Peace of mind is priceless.
red

[Morocotopo]

Look what I found in some old japanese circuit...


Could this be useful for getting higher voltage from 9V? What do you think?

[stm]

For an example you can look at thesesites (just used the keywords 555 and INVERTER in Google).

This is a simple circuit. R3 and Q1 are not neede for your purpose.
http://www.compuphase.com/electronics/inv555.htm

And this circuit is quite straight:
http://www.aaroncake.net/circuits/vinvertr.htm

The tips here are:

Make sure the oscillating frequency is 20 kHz or higher.
Try using shottky diodes if available for minimum voltage loss n the inverted voltage (you get around 0.6V less with shottkys, and around 1.2V less with silicons.  Germaniums are not recommended due to their higher series resistance).
You need a CMOS 555, not a bipolar one.

One final note:

If you can afford a MAX1044, go and use it.  On the other hand, if you live in a place where you cannot get it without importing it, then other alternatives like this might be attractive.  The CD4049/69 option is also a good one.

[stm]

Regarding the CD4049, you need to do the following changes to make it a negative voltage inverter:

1) Reverse polarity of both diodes
2) Reverse capacitor polarity
3) Connect the leftmost diode to GND instead of Vcc (now the cathode or the line-marked leg go to GND)
4) Please notice the output inverter is actually composed of the remaining four gates of the chip in parallel, i.e. two gates for the clock and four gates as the driver.

I tend to like this CD4069 inverter better than the 555 option.

[Morocotopo]

Thanks STM for the reply!
So, the 4049 circuit would work as it is presented in the files, no mods needed? It wouldn´t bleed into the audio like the 7660 ones? Since it already has a PCB, I might go with this one when I need to "upvert" voltage...
Oh, and, how about switching the negative voltage with the in jack, would that work with this circuits? I seem to recall that someone in an article (R.G?) advised against it...

[Morocotopo]

This forum´s  so coool! So you could get, with your suggested mods, +/- 16-17 V, right?

[stm]

The circuit as presented provides +16 to +17V.
The suggested changes turn it into a voltage inverter, thus obtaining roughly -8V from a 9V battery.
Using shottky diodes like 1N5819 is advised for minimum voltage loss.
The oscillator whine will depend in the frequency of the oscillator. You should aim for 20 kHz or higher, which is in accordance with the presented schematic.  I wouldn't go too much further than 30 kHz since sitching losses will reduce circuit efficiency.

[Morocotopo]

Thanks stm, you are so nice to answer and teach the less informed...
I just realized that I completely hijacked the thread I´m sorry scaesic, I hope some of it is of use to you.

[scaesic]

so'ok
What i really want to know is can i swap the 7660 for the MAX1044 in the geo neutron pcb?

[col]

Check the spec sheet for the version you have. I have used 7660 for other circuits that needed a +9v and -9V with success. The version of the 7660 you need has the option to speed it up by adding 9v to pin 1 (like the MAX1044) to take the buzz out of the audio range. I think it has the same pinout as the MAX1044 so it should be a straight swap. You will need to check the letters in the suffix as not all 7660s have this option and I can't remember which one does. I replied to another post with this info some time ago so a check for the 7660 might turn that up and give you the info you need.
BTW you don't get -9v, it's more like -8v. The circuit for using a 555 to get the same result is in the Babani book for that chip if that's any use to you.
Please post how you get on with the Neutron as I was looking to build one. What are you using for the optocouplers?

good luck,

Col

[scaesic]

cool, i really want to encorperate the charge pump so i can use it with my power-all wall wart, but i might leave it for a later date and just use two batteries.
i'd planned on using option 3 for the optocoupler. the vtl5c3 is one option which banzai sell. I still need to order an enclosure/optocoupler and possibly the 7660, i'll let you know how it goes.

[Paul Perry (Frostwave)]

Something to note, charge pump chips being CMOS, are prone to destruction if their maximum input voltage is exceeded. Which can happen sometimes wiht a lightly loaded wallwart. Always look at th data sheet for the one you are using & think about whether there is a risk. (Fortunately, some at any rate withstand REVERSE power... don't ask me how I know this and don't depend on it!)