Can you stack charge pumps for more output current?

[TOPLEL]

Can you stack charge pumps for more output current?

Like this:


(image taken from beavisaudio.com)

(background info: i have lots of 7660 ICs but i have zero LT1054 ICs (they are very expensive here and shipping from ebay takes like a month) and i thought about substituting the LT1054 in a diy ADA Flanger with some 7660S)

[hex_void]

I don't think it's a good idea because there are no 2 perfectly identical ICs. If you stack them at least one of them will get fried since the output transistors won't switch at the same time.

[Paul Marossy]

Stacking opamps is sort of akin to paralleled triodes, but I don't think it would work with charge pumps as they are completely different animals.

[R.G.]

No, you cannot (successfully, at least) stack them like the picture of opamps, unless you're very lucky.

However, you CAN parallel them for more power. See  http://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf, page 11, "Paralleling devices".

[Mark Hammer]

But these things are clocked.  Any chance of audible heterodyning?

[TOPLEL]

No, you cannot (successfully, at least) stack them like the picture of opamps, unless you're very lucky.

However, you CAN parallel them for more power. See  http://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf, page 11, "Paralleling devices".

looking at that pic in the datasheet it seems like that PIN 1,3,5,6,7,8 can be soldered together and only pin 2 and 4 needs to be separated. (and have it's own caps) (i can bend those legs away from the chip's legs underneath like in the pic in the first post)

Am i right?

[R.G.]

But these things are clocked.  Any chance of audible heterodyning?

Yes. However, they are all dumping into a single big filter cap that's sized to squash the ripple. Heterodynes may mean it should be bigger. OK, can do.

A subtler consequence of this is that you may well need a big filter/bypass cap on the INPUT to prevent heterodynes being reflected back through the power supply lines. I consider that under the heading of "circuit hygene", but beginners often forget that even if there is no power supply bypass cap shown, they should always be there.

looking at that pic in the datasheet it seems like that PIN 1,3,5,6,7,8 can be soldered together and only pin 2 and 4 needs to be separated. (and have it's own caps) (i can bend those legs away from the chip's legs underneath like in the pic in the first post)

Am i right?

If any two points are to be connected together, they can be connected vertically as well as horizontally. However, vertically is less mechanically stable. I was (in)famous among my engineerling friends and associates for generating so-called "hanging garden" circuit prototypes, with the circuit constructed with *no* underlying circuit board at all, just the component leads and solder joints holding the mess together. They would periodically (and quietly!) bend two points into contact, or break a solder joint just to keep me humble. Any 3d realization of the schematic, with all the connections made and no non-schematic connections made, will work electrically. But once you have done that, the result has to live in the real (mechanical world).

Solder cold flows, and cracks. Shorts happen.

[PRR]

> so-called "hanging garden" circuit prototypes, with the circuit constructed with *no* underlying circuit board at all, just the component leads and solder joints holding the mess together

The cover of this book is a working electronic thermometer (note the dangling LEDs reading "72").


http://www.amazon.com/Science-Analog-Circuit-Design-Engineers/dp/0750670622

[Cliff Schecht]

I haven't read that book Paul, I might order a copy. That's pretty funny about the front cover.

When I was a young'n my dad would take into the lab at wherever he was working and let me play with the soldering irons and play games on the computers and such. I remember specifically about one place that always had these huge balled up messes of components cobbled together with leads everywhere. They would be hanging from plastic coat hangers and have banana clips going everywhere. My dad finally explained that this guy absolutely refused to use any sort of breadboard/perfboard to build circuits out of pure stubbornness (and probably a healthy mix of voodoo electronics). These things were bigger than your head and of course looked terrible but apparently worked for the most part. But it still sucks to be the engineer AFTER him that has to figure out what is going on with this ball of electronics inevitably breaks/fails.

It's hard enough to debug with two dimensions, why add a third?

[R.G.]

I tend to debug in four dimensions. I usually can't remember what my last few changes to the circuit were...

[TOPLEL]

But these things are clocked.  Any chance of audible heterodyning?

Yes. However, they are all dumping into a single big filter cap that's sized to squash the ripple. Heterodynes may mean it should be bigger. OK, can do.

A subtler consequence of this is that you may well need a big filter/bypass cap on the INPUT to prevent heterodynes being reflected back through the power supply lines. I consider that under the heading of "circuit hygene", but beginners often forget that even if there is no power supply bypass cap shown, they should always be there.

looking at that pic in the datasheet it seems like that PIN 1,3,5,6,7,8 can be soldered together and only pin 2 and 4 needs to be separated. (and have it's own caps) (i can bend those legs away from the chip's legs underneath like in the pic in the first post)

Am i right?

If any two points are to be connected together, they can be connected vertically as well as horizontally. However, vertically is less mechanically stable. I was (in)famous among my engineerling friends and associates for generating so-called "hanging garden" circuit prototypes, with the circuit constructed with *no* underlying circuit board at all, just the component leads and solder joints holding the mess together. They would periodically (and quietly!) bend two points into contact, or break a solder joint just to keep me humble. Any 3d realization of the schematic, with all the connections made and no non-schematic connections made, will work electrically. But once you have done that, the result has to live in the real (mechanical world).

Solder cold flows, and cracks. Shorts happen.

I've made a CMoy amp explode in the past because of going point-to-point, i think should really just buy that damn LT1054.