Author Topic: Tc7660s charge pump noise filtered down to 5mv pkpk  (Read 257 times)

Asktoro

Tc7660s charge pump noise filtered down to 5mv pkpk
« on: January 24, 2021, 07:05:35 PM »
Trying to make an ABY splitter, wanted wicked headroom so i ended up designing this, not sure if i wanna use it. Almost no noise, if any gets carried into the op amp, but this is only my second pedal ever so im not sure how much noise is acceptable, what kind of current i should be expecting through it. I have no music gear, been testing it with a function generator, also with iphone, and some 8 ohm speakers. I usually do high voltage experiments, or other random stuff so not exactly a newbie to electronics, but definitely total scrub to music stuff. Earlier i tried splitting a rail with an op amp and biasing it. Was a lot cleaner, bit virtual ground was goofing on me too much.






danfrank

Re: Tc7660s charge pump noise filtered down to 5mv pkpk
« Reply #1 on: January 25, 2021, 01:56:40 PM »
Hi,
5mv is nothing in the world of guitar effects. I don't know if you're using the charge pump as a voltage doubler or to get a negative voltage from a positive voltage, but if you're using it as a voltage doubler a regulator usually follows which will clean up the noise even further.
Make sure you read the data sheet on whichever charge pump you're using as some of them have the internal oscillator work at audio frequencies. You don't want to use those... The "SCPA" suffix on the charge pumps denote that the internal oscillator works at higher than 20kHz which one s wanted.

anotherjim

Re: Tc7660s charge pump noise filtered down to 5mv pkpk
« Reply #2 on: January 25, 2021, 02:28:56 PM »
You won't know how much the ripple noise will be until you load it with a circuit. More load current = higher ripple.
Op-amp based circuits are very good at rejecting supply noise.
All good circuits should have sufficient supply bypass capacitors close to the active devices.
Even so, anything oscillating produces noise that can find its way into the audio via common ground loop connection or radiation, so as Danfrank points out, you want a pump chip running above audio frequencies.


Croeso i Diystompboxes.

antonis

Re: Tc7660s charge pump noise filtered down to 5mv pkpk
« Reply #3 on: January 25, 2021, 03:11:45 PM »
I apologize on behalf of non-welcoming forum members.. :icon_redface:
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

anotherjim

Re: Tc7660s charge pump noise filtered down to 5mv pkpk
« Reply #4 on: January 25, 2021, 04:30:25 PM »
I never do welcome. I believe a reply is better, and I hit reply before reading their details and you can't see those in thread summary below the reply form.

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