+/-15V with MAX1044

[Dimitree]

Hi everyone!
I'd like to know if it is possible to make a +/-15 supply from 9VDC using one or more MAX1044.. I know it is possible to make +/-9V, but +/-15V?
thanks!
Dimitri

[The Tone God]

Datasheet. Hint: voltage range

Andrew

[Dimitree]

ok..it says 10V max..but on geofex it is used to obtain up to 33V (or higher).. So my question is, can I obtain +15V and then -15V?

[The Tone God]

I believe not. You can either voltage multiply or invert. Not invert multiply.

Andrew

[Paul Perry (Frostwave)]

You certainly won't do it with only one MAX1044..
And it's a bit hard even to get +15, because if you start from 9v, you need to be sure you don't exceed 10V input (if you allow wallwart use).
The other thing is, the output impedance is noticeable. (with more current out, voltage sags).
So for some circuits it isn't ideal.
Cheapest & easiest source of +-15, is a 14V AC wallwart , two half wave rectifiers, plus regulators for +15 and -15.

[Dimitree]

I'd like to do this +/-15V supply to insert it in the pcb of a project I'm making.. Unfortunately I can't use a transformer because there is no room on the enclosure.. So what could be another solution?

[DrBoogey]

Maybe a DC-DC Converter like that: http://www.farnell.com/datasheets/112798.pdf

Its a bit expencive but it has +9V input and +/-15V output

[Dimitree]

that is way too expensive..

could this work: http://dsb.tracopower.com/upload/DSBUserFile/CPN_TracoPower/0_tmr3wi.pdf
this model is cheaper.. (about 25 usd)

[frequencycentral]

Hi everyone!
I'd like to know if it is possible to make a +/-15 supply from 9VDC using one or more MAX1044.. I know it is possible to make +/-9V, but +/-15V?
thanks!
Dimitri

Yes it is, using just one MAX 1044 running from a 12 volt wallwart. Give me 5 mins and I will post a schematic.

[frequencycentral]

Here you go:



This is working on my breadboard right now. I've had it running for many hours over a few days.

The opamp buffer keeps the 15 volts from fluctuating.

I'm using a 12 volt 500ma regulated wallwart.

Don't let anyone tell you MAX1044's won't run on 12 volts - they do.

For your circuit:

Circuit +15 volts = MAX1044 30 volts
Circuit earth = opamp buffer 15 volts
Circuit -15 volts = wallwart earth

EDIT: You could add another opamp unity gain buffer for the 30 volt output too I guess.

And be sure to use caps with a higher voltage rating, Mine are all 50 volt I think.

[earthtonesaudio]

Or try a %^&*roft-Walton multiplier for a nice built-in "dynamic voltage sag."
http://home.earthlink.net/~jimlux/hv/cw1.htm

[Dimitree]

wow! thanks frequencycentral! so I can use the MAX1044! Could I do the same thing with a 9V wallwart instead of 12V?
and how I get the -15V? Perhaps I don't need it because the opamps on the circuit are supplied with 30V rail to rail?

I can't understand the second link, earthtonesaudio..but it doesn't matter if I can do that with the MAX1044..
thanks!

[frequencycentral]

wow! thanks frequencycentral! so I can use the MAX1044! Could I do the same thing with a 9V wallwart instead of 12V?
and how I get the -15V? Perhaps I don't need it because the opamps on the circuit are supplied with 30V rail to rail?

I can't understand the second link, earthtonesaudio..but it doesn't matter if I can do that with the MAX1044..
thanks!

Using 9 volts instead of 12 volts will reduce the Max1044 30 volt output to about 24 volts. The output at the opamp buffer will be about 12 volts. That should be enough for most circuits.

If I were you I would breadboard it first and check the voltages on a multimeter.

[snap]

be careful with over 10V input
http://datasheets.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf


http://www.maxim-ic.com/appnotes.cfm/appnote_number/725
http://www.maxim-ic.com/design_guides/en/AD_CONVERTERS_28.pdf

[frequencycentral]

Yeah, I've read the notes. all I can say is that I know from experience that they work at 12 volts over extended periods.

[Dimitree]

could I use my 9V adapter, obtain about 24V, then bring it down to 15V with a 7815? then with another MAX1044 do the same thing but obtaining -15V with a 7915?

[frequencycentral]

Maybe, you could just add two more diodes and two more caps to the MAX output chain to get up to around 33 volts from your 9 volts, then use the resistor voltage divider through the opamp to half it.

However: watch out! Some opamps are rated at only 32 volts across the power rails - such as LM324 quad. RC4136N quad go up to 36 volts. Having said that - I read the 10 volt maximum for the MAX1044 and I'm happy to exceed it!

Anyway: what are you planning to power with this? You may not need to get hung up on absolute voltages.

[Dimitree]

a little project with some TL072..

[frequencycentral]

a little project with some TL072..

They're fine up to +/-18 volts. They would probably be happy with whatever, +/-9v, +/-12v, +/-15v etc.

[Dimitree]

yes..but I'd like to use it with +/-15V.. How many mA would I get using the MAX at around 33 volts?