Max1044 Substitute

[jimmy54]

Hi fellas,

I want to get -9v and +9v from a 9v battery as in this circuit from Geofex:

http://www.geofex.com/circuits/voltpmp2.gif

Will a ICL7660SCPA be an OK substitite to a Max1044?  Would it be wired in the same way as the Max1044 in this circuit from Geofex?

This is apparently the layout of the ICL7660SCPA.

http://www.rapidonline.com/netalogue/photos/82078801.jpg

Cheers

[MetalGuy]

Yes, you can use an ICL7660S /make sure it has the S/ as direct replacement for MAX1044. As a bonus it's cheaper and provides more current. I have couple of them working in some of my pedals.

[jimmy54]

Thanks Metal, the chip is listed as ICL7660SCPA so I guess it's OK then.

Cheers

[Peter Snowberg]

The MAX1044 is an upscale ICL7660, but it contains the extra feature of a selectable switching frequency to raise the oscillator to well above audio frequencies. This is why the 1044 is preferred in audio.

[e178453]

Jimmy, So happens that just last night I ordered from Mouser TC1044SCPA (Mouser part # 579-TC1044SCPA).  The spec sheet indicates to me a direct replacement, with faster oscillator option some similar chips don't have.  $1.25 each so I ordered two, going to use one to give me 18V for PT-80 delay I built a while back.  If you buy this part make sure you get the DIP package, not the SOIC suface mount (different part #), unless you want that.
Scott

[Cliff Schecht]

I wonder if NTE has a direct replacement for either the MAX1044 or the 7660... I haven't seen anything yet, but I'm going to call around town to see if I can't find a charge pump.

[jimmy54]

Yeah, I ordered the DIP package.  I've read about the whine that can be audible when using a Max1044.  The Geofex site mentions that you tie pin 1 of the Max1044 to 9v to remove this whine.  Geofex mentions that for other chips such as TLC7660CPA, pin 1 should not be connected to 9v (or if it is, the whine will not be removed).  If I get this whine with a TLC7660S, how would I go about getting rid of it (or is it not possible)?

[hank reynolds 3rd]

I think the LT1054 works pretty much the same,IIRC,Nelson opted for this chip instead of the max1044 in some of his desings/layouts....the LT1054 uses an external cap to help tune out any noise.....

http://www.elixant.com/~stompbox/smfforum/index.php?topic=41005.msg295330#msg295330

[zjokka]

Jimmy, So happens that just last night I ordered from Mouser TC1044SCPA (Mouser part # 579-TC1044SCPA).  The spec sheet indicates to me a direct replacement, with faster oscillator option some similar chips don't have.  $1.25 each so I ordered two, going to use one to give me 18V for PT-80 delay I built a while back.  If you buy this part make sure you get the DIP package, not the SOIC suface mount (different part #), unless you want that.
Scott

yeah, I was thinking, I have mulitiple 9V outlets on my board, but no 18V or higher for the PT-80. Was going for 24V but will settle for 18V if I  can feed it 9V externally. Really don't understand why this wasn't integrated in the initial pt-80 design (cf the ibanez delay which does have the  charge pump)

zj

[e178453]

According to geofex, you can get 25V or 33V out of the charge pump by adding diodes and caps.  BTW, I really like my PT-80, but don't have anything to compare it to.
scott 

[MetalGuy]

If I get this whine with a TLC7660S, how would I go about getting rid of it (or is it not possible)?

You're not going to get whine because the ICL7660S  is a direct substitute for MAX1044 and has the same frequency boost pin /pin #1/ as MAX1044. In addition to that it's cheaper, works up to 12V and supplies more current that MAX1044. For more details check out the data sheet:

http://www.intersil.com/cda/deviceinfo/0,1477,ICL7660S,0.html

According to geofex, you can get 25V or 33V out of the charge pump by adding diodes and caps.  BTW, I really like my PT-80, but don't have anything to compare it to.
scott

Yes, it works.

[jimmy54]

The ICL7660S arrived today and works great in the geofex -9v/+9v geofex circuit.  Thanks for the advice fellas and have a great Christmas.