charge pumps 1 more time

[edad]

  Ive read some posts on the use of charge pumps,and Id like one of you to please explain what it does,Im unclear.
       Im going to build the aby box from geofx ( the 2006 schematic) which I hope is the debugged one???
     It calls for a max 1044 charge pump.Ive also read about the max 660 and a couple of others.
Im looking for the quietest switching possible,and If possible 9 - 18 volt supply.
    maybe  some of the masters here will chime in.  Also where can I get these ,I couldnt find the max 1044 at mouser,help please

[R.G.]

I think the LT1044 is pin compatible.

A charge pump consists of an oscillator to run things, and then a set of four switches in two pairs.  One pair of switches connects the "bucket" capacitor across the power supply from + to -  on one phase of the oscillator, and it charges up to the power supply. When the oscillator switches to the other phase, the first pair of switches turn off, leaving the cap an isolated bucket of charge. Then the second pair of switches turns on. One of them switches to + and one of them to - . If you hook the pump capacitor so its most negative terminal is now connected to + by the second phase + switch, the - side of the cap is pulled up to the power supply, and the resulting + end of the cap is now twice as high as the power supply. If there's a diode up there to let that charge into a second filtering cap, then the "bucket" of charge is dumped into the filter cap at a higher voltage.

Similarly, if you hook the + end of the bucket cap to the switch that connects to the - side of the power supply, the bucket is pulled down, and its most - end is about one power supply voltage lower than the power supply that charged it. If there is a diode and filter cap down there, you can charge that cap to the negative of the original power supply and have a balanced bipolar supply.

It's even possible to pump two caps and do both at the same time. That gets complicated, but it can be done. But the action is to store up a bucket of charge, then either force it up and over the existing power supply or down under the existing power supply where diodes and a secondary filter caps make it into an output voltage.

All of these will make whine in the power supply at the switching frequency because of the big currents drawn when fulling and dumping the bucket.  The 1044 puts this whine up at 80kHz where your audio gear (i.e. your ears...) can't detect it. Otherwise you have to do an IMMACULATE job of wiring the power supply to keep the whine out of your audio.

[stumper1]

http://www.geofex.com/circuits/+9_to_33.htm

The max1044 is usually available at DigiKey.

[O]

Scenario:
-9v Boss adaptor
-FullClone pedal
-me wanting to run the FullClone at 18v

Using this charge pump, as long as I use a 9v regulated adaptor (don't use batteries in my pedals), I should be able to convert the 9v into 18+?

[R.G.]

Not quite. There are always losses, and in this case it's the loss of the forward drop of the diode that keeps the charge in the filter cap once the bucket cap hauls it up there. So if you have a supply of 9.0000 V, you'll lose some in the switches, maybe 50mV, and some more in the diode. If you use something like a 1N5819 Schottky, that can be maybe .2-.3V. With ordinary silicon, it's going to be 0.6-0.7V. But you'll get 17V pretty easily.

[Gilles C]

Just a note about whre to order the IC

http://www.smallbearelec.com/Categories.bok?category=ICs+-+Voltage++Regulators+and+Converters

Gilles

[Processaurus]

note the max 1044 can't handle more than ten volts at its supply pin, or be able to provide more than 10mA.  If either happens it'll probably die.  Using a regulated PS and your circuit it should be safe though.

Anyone know if there a more robust charge pump IC out there with the frequency boost?

[Sir H C]

I doubt it, they just are not nearly as good as inductor based circuits for high current so people just don't make them.  In a syncronous inductor based circuit you need two transistors, and only one is in the path at a time, the charge pump you need 4 and 2 are in the path at a time.  Therefore the two CP devices need to both be twice as big as the inductor ones for the same Rds for the circuit.  That is a lot of extra die to save an inductor.

[R.G.]

Anyone know if there a more robust charge pump IC out there with the frequency boost?

I haven't looked too closely, but I have some dim memory of the LT1054 as being faster, better, more, etc.  Give Linear Technology a look.

The 7662 will go to 20V, but you have to drive it from an external oscillator to get above audio frequency.

Therefore the two CP devices need to both be twice as big as the inductor ones for the same Rds for the circuit.  That is a lot of extra die to save an inductor.

True, but EE's have gone to enormous lengths not to have to cope with inductors. Inductors are smelly, dirty, difficult, and even worse - hard to source in quality and quantity.

[edad]

Ive ordered a max 1044 from smallbear and Ill let you know,but as a second choice is the LT1054 faster and very quiet?

[petemoore]

  Yupp, I just got order confirm for 2 max chips !
  I'm hoping to get that often starved for V's SCReverb project off the batteries and on a power supply, and maybe try a booster/octave with the other MAX supplying @~17v.

[Sir H C]

Anyone know if there a more robust charge pump IC out there with the frequency boost?

I haven't looked too closely, but I have some dim memory of the LT1054 as being faster, better, more, etc.  Give Linear Technology a look.

The 7662 will go to 20V, but you have to drive it from an external oscillator to get above audio frequency.

Therefore the two CP devices need to both be twice as big as the inductor ones for the same Rds for the circuit.  That is a lot of extra die to save an inductor.

True, but EE's have gone to enormous lengths not to have to cope with inductors. Inductors are smelly, dirty, difficult, and even worse - hard to source in quality and quantity.

One thing they have looked at is upping the frequency and using board traces for the inductance. 

[Laus]

I might consider starting a new topic but I dont think that is necessary.

Does the size of the elco's matter? In the exampls 10uF is used. Would it be better or useful to use bigger values like 100uF?
I don't get the whole explanation but how much mA can my Charge pump provide when feeded with a 200mA regulated supply? (9-18V)
thanx!

[R.G.]

Does the size of the elco's matter?

Only incidentally. They have to be big enough to not sag noticeably between charging pulses. The bigger they are, the bigger the switching losses in the charge pump chip. The lower the ESR they are, the lower the overall losses. The things to worry about are all very much second and third order effects. The Maxim and LT datasheets are fat with information about these various considerations.

In the exampls 10uF is used. Would it be better or useful to use bigger values like 100uF?

The law of diminishing returns will keep this from being a huge help. In fact, you can probably lower the 10uF if you select the higher frequencies with the boost pin. The datasheet covers this, I believe.

I don't get the whole explanation but how much mA can my Charge pump provide when feeded with a 200mA regulated supply? (9-18V)

What you feed it with doesn't matter much at all. So it will do about the same. 10ma per charge pump chip is a good working number. The charge pump chip and bucket caps look like an 80 ohm resistor in series with the pumped voltage, so you can model this as pumping 9V to 18V, losing 0.7V in a diode, and then running the 17.3V output through an 80 ohm resistor for the amount of sag it will do. Somewhere over 10ma output, the output voltage begins to sag a lot more.

[Laus]

thanx R.G. I will try and see if it's enough to power a Flipster and a BassDrive. Probably not...18V Wallwarts are hard to find here in NL for a good price.

[R.G.]

It is perfectly acceptable to add more charge pumps in parallel. You get another 10ma per charge pump circuit. The application notes point this out directly.

And here's a thought - power your Flipster with two 9V batteries in series and measure the current it draws from 18V. Do the same with your BassDrive. Add the two numbers. How much current is that? More than 10ma? 20ma?

Then you'd know without building and trying it first.

[Laus]

Good idea! I'll try tomorrow. Let's see what it does when I hit a low B. I'll post my findings for the interest of others.
thnx.

[markusw]

haven't looked too closely, but I have some dim memory of the LT1054 as being faster, better, more, etc.  Give Linear Technology a look.

IIRC, the LT1054 gives you up to 100mA at up to 15V input. 
BTW, it's also available from TI.

Markus

[MetalGuy]

Also let's not forget the ICL7660S which works up to 12V and 20mA - pin to pin analog to MAX1044 with the boost feature included.

[Minion]

You might also consider simply useing a Voltage doubler/Tripler...It should double the available Voltage but half the available current...You can make a Voltage doubler out of a few Diodes and Capacitors but some extra Filtering would be good because of the extra Ripple caused from the Voltage doubler/Tripler....

Just a Thought....