Valour of capacitors and diodes in circuit with 7660s

[Gabi Smith]

Hello guys,

In my present project (a little amp in a pedalbox), I need a voltage rail of +/-18v from a voltage of 9v. To pump the charge(*), I will use two 7660S and realise the figures 7 and 8 of this data sheet : http://pdf1.alldatasheet.com/datasheet-pdf/view/110720/MICROCHIP/TC7660HCOA.html . What are the valours needed for the capacitors and the diodes? What diodes can I use? Or, how to calculate them?

Thank you  


(*Wow, It was to cool to write this)

[Travis]

I think you might run into some issues with the two charge pumps heterodyning. Also depending on the amp circuit you are using, a charge pump may not output enough current

That data sheet says the caps can be “inexpensive non-polarized 1uf” which would probably be a multilayer ceramic

The diodes are usually chosen for a low voltage drop, you see 1N5817 in the main page charge pumps

[Gabi Smith]

Thank you for the response. I think it will be enough (Only a TDA2040 and a j201 to supply).

The1uf is given for the inversion (positive to negative). Nothing is said about the capacitors needed to doubling the voltage. I've seen on the internet that the common valours given in this case is 10UF for the one coming from the second pin of the chip and 100uf for those who are going to the ground.

On the breadboard, i've got the figure 8 (+/-9v for the tda2040 power amp and 18v for the j201 pramp), but i'm meeting a bug : a tremolo effect coming I think from an oscillation of the invertor. The multimetter is alternating -2, -3. and -6v and never show -9v. The 18V seems ok (17.6V for the supplied 9.5V). There-s a high treble hiss too. Soooo, a little debubugging is waiting me tomorow.

[Travis]

Actually the charge pump would not be remotely close to being capable of putting out the current required for the TDA2040. Check out the documentation for the tiny giant amp which is a pretty popular build that recommends a laptop power supply as an inexpensive alternative