Author Topic: I modified the "Road Rage" charge pump circuit, thoughts?  (Read 9 times)

Boner

I need to make a "bullet proof" charge pump circuit that I could drop in to any circuit I throw at it. I know that's dangerous thinking since power is a finicky old lady. I also need these to be compatible with boss style supplies and daisy chain power supplies. I know I'm asking for the moon, but I want something that 90% of the time, the power circuit is over overkill, but for that other 10% the circuit is robust enough that there won't be any problems. This is what I've come up with so far. I'm still waiting on some LT1054s to arrive but I'm 99% sure this will work. Wanted to of course run it by all of you to take a look or possibly take something of value from it.


This is a mishmash of "road rage" and things I've learned from here, btw R.G. is a national treasure.....

I imagine the whole idea originates from the klon centaur, electrosmash has an amazing writeup on the pedal if you haven't seen it already.
https://www.electrosmash.com/klon-centaur-analysis



Its LT1054 based for higher current demands than with a MAX1044 used previously. I included (I believe) RGs trick on switching/reverse polarity protection) power switching circuit with a 2n2907. From my understanding the 2n2907 is capable of providing 300mA and the LT1054 can't take more than 200mA so that should not be a problem.

1n4742A is for overvoltage protection (12v input max).

This entire thing needs a "true ground" and thats the grounding pin on the DC jack. Everything eventually hooks back up here via star ground.

Effect is powered on with the TS/TRS switching trick on the output jack. Inserting a jack shorts Vss on the ring to "true ground" on the sleeve thereby turning on the BJT and turning on the LT1054. Each Vss from any and all audio circuits (transistor boost stages or OP amps for example) connect to Vss on the audio jack ring forming a "star audio ground" to the ring. A single wire on the sleeve hooks up to true ground, so this "star audio ground" on the ring is shorted to true ground.

Each Vss pertaining to power (power conditioning caps for example) is connected to LT1054s Vss pin first (pin 3), and then THIS pin is connected to true ground via wire or thick 20mil trace.

Any and all LEDs in the audio circuit connect to true ground via star grounding.

A grounding spring (my personal perference) connects the metal enclosure to true ground (DC ground) vi thick 20mil trace or wire.

You may be wondering why I'm spending so much time on grounding. After reading so many of RGs posts on "sewer ground, I've learned proper grounding SEEMS simple enough, but it REALLY requires great attention to detail, maybe the most attention out of everything pertaining to guitar pedals. Google "site:diystompboxes.com "sewer ground" and just read everything you find.


The 15pF cap connecting pin 6 (Vref) to pin 7 (OSC ref) raises the internal clock outside the audio range to help mitigate "whining". All of this is from the datasheet (They recommend 5pF-25pF I think). In my research here, this whining is apparently a huge problem that is difficult to fix and trace/wire placement of ground with signal traces is critical. Cross talk is a problem with audio ins being next to audio outs and I'm guessing form some weird cross-talk loop. So keeping signal ins as far from possible from signal outs. Remember all this nonsense is just loops. Signal in forms a loop, signal out forms a loop and power is another loop.


1n5817 diodes are low forward voltage types thereby lowering the voltage drop at 18V output. Using 1n4004s or whathaveyou will cause 18v output to be lower, than with low forward voltage diodes.


LT1054s datasheet calls for tantalum caps for C29/C28. I normally go with a fat ass aluminum electrolytic cap and a smaller alumina electrolytic cap, "large" MLCC and a "small" MLCC all in parallel for power filtering like everyone else, however with the datasheet calling for low ESR tantalum caps, I'm not sure if you would then leave out or include the MLCC caps.

C8 in parallel with C33 and C6 in parallel with C34 are cost saving measures. Normally (per datasheet) these would just be large valued, low ESR tarantula caps, however they are balls expensive. So you can go with a fat electrolytic (C8 and C6) each in parallel with a low ESR, lower valued tantalum to save some moolah. All this is from the datasheet btw.

All the remaining 100uF aluminum electrolytic caps in parallel with 100nF MLCCs are decoupling caps for each power point, 18v, 9v, 4.5v and -9v.
« Last Edit: Today at 04:32:19 PM by Boner »