Am experimenting with a project that is powered with a 9V battery, but I'd like to have 18V available to the opamp. That is, +9V and -9V. It's for a guitar pedal, so sound quality is important, but not as critical as for, say, a line driver, preamp or amplifier.
The MAX1044 seems to be a good choice for this. With 3 small tantalum caps it can take a +9V input and produce a regulated -9V output. I think its just what the doctor ordered.
I'm wondering what the alternatives might be, and if anybody else has used something similar to this part.. If so, I'd like to hear what you think.
The MAX1044 seems to be a good choice for this. With 3 small tantalum caps it can take a +9V input and produce a regulated -9V output. I think its just what the doctor ordered.
I'm wondering what the alternatives might be, and if anybody else has used something similar to this part.. If so, I'd like to hear what you think.
For a line level output (1VRMS) you probably don't have need for +/-9V but MAX1044 will do it if that's your thing. A good choice as against an inductor boost converter as there's no stray magnetic field to speak of. Note that the output isn't regulated and comes from a relatively high (65ohm) source impedance.
I've used plenty of LM2662 which is similar though not such a high voltage capability.
P.S. nowadays ceramics are potentially a better choice than tants vis-a-vis conflict minerals.
I've used plenty of LM2662 which is similar though not such a high voltage capability.
P.S. nowadays ceramics are potentially a better choice than tants vis-a-vis conflict minerals.
I use a TC7660. It faithfully produces the exact same negative output voltage as the input positive voltage.
https://www.mouser.com/datasheet/2/268/21465C-1180085.pdf
See fig 5.1
Only two extra components required and no inductors.
https://www.mouser.com/datasheet/2/268/21465C-1180085.pdf
See fig 5.1
Only two extra components required and no inductors.
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The MAX1044/TCL7660 are basically the same and oscillate in the audio band, so bad bad choice. Get one that's at least ultrasonic, preferably a modern fast one (I've used the MAX1681 (which only goes to 5V though, and it switches at around 1MHz, so only small caps are needed, small SMT ceramic will do.) MAXIMs website has a selection tool to help with such chips.
Although the MAX1044 is old, there is good news: it has a "BOOST" pin (pin 1) which will increase the switching frequency above the audio band.
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Maybe, as the saying goes, a bird in hand...
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Maybe, as the saying goes, a bird in hand...
I designed a USB scope and used a 7660 to generate -ve voltage.
For some reason I passed scope input signal through middle of 7660.
The result was large 10KHz signal on top of my scope signal !
I had to cut the track at both ends and link direct with a wire.
Quickly learned from that one !
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