Q: Charge pump suitability

[Mark Hammer]

Realizing I had a plethora of suitable LDRs, and some nice slender yellow LEDs, not far from the 540nm peak sensitivity of the LDRs, I figured I'd throw together an expanded version of the Craig Anderton/EPFM optical phaser.  I expanded it to 6 stages from the stock 4.  The EPFM book states that current consumption is +/-15ma for the stock 4-stage circuit.  I used a pair of LM4136 quad op-amps for the audio path, but opted for an LM358 for the LFO subcircuit (a traditional low-current choice to minimize ticking).  The LEDs are not especially bright (a 1k8 current limiting resistor and a 9V battery did not yield gobs of illumination), but I'm only using one per pair of LDRs, instead of the 4 CLM6000s the original calls for.

I'm trying to build it into one of the pre-drilled powder-coated 125B enclosures I got from Tayda.  I can easily fit the perfed circuit boards (all the optical stuff is on a separate daughter-board) and many controls (5 pots and a toggle) into the enclosure, but there is no room for a pair of batteries.  No problem if it was a 9V-powered circuit, but it requires +/-9V so a charge-pump-inverter is called for.

My question is regarding what charge pump will be able to handle the current-requirements.  I'm assuming the additional stages may demand more current, and that overall consumption may exceed what a MAX1044 or ICL7660 can deliver.  I do have a JRC7660D sitting in the parts drawer, in addition to a pair of MAX1044 chips, but can't seem to locate a datasheet for that specific chip.  Can anyone either confirm for me that the JRC7660D can handle those current requirements, or simply point me to a datasheet?

[Nitefly182]

LT1054 would be a solid option if you have current concerns.

[cloudscapes]

LT1054 can supply 100ma on the negative rail, it's pretty nice. I use one to power the negative rail on four tl074's and a v2164 on a current project and it doesn't even get warm.

[Mark Hammer]

Thanks.  I'll order a bunch of those.  Sounds good for a variety of circuit needs.