TC1044 theory questions

8 years 1 month ago #446 by RedLlama
First off, Hi, and thank you for making such a cool pedal. I am using this project
as my electronics lab project. Since I have full use of oscilloscopes, function generators, and various testing equipment, i thought it would be fun to poke around at various smaller components of your design and see if there is any room for improvement. As i am brand new to this, i was hoping you could help me out a bit. The first component i built was the power supply. I noticed you decided on the TC1044 chip, which was a very interesting little chip to use.
So looking at this datasheet,
ww1.microchip.com/downloads/en/DeviceDoc/21348a.pdf

I find..
"Theoretical Power Efficiency
Considerations
In theory, a capacitive charge pump can approach
100% efficiency if certain conditions are met:
(1) The drive circuitry consumes minimal power.
(2) The output switches have extremely low ON
resistance and virtually no offset.
(3) The impedances of the pump and reservoir
capacitors are negligible at the pump frequency.
The TC1044S approaches these conditions for negative
voltage multiplication if large values of C1 and C2 are
used. Energy is lost only in the transfer of charge
between capacitors if a change in voltage occurs. "

Basically, it says if you use 100uF caps, you can obtain 100% efficiency. So my question is, would using 100uF caps in this design have any negative effect on the pedal?

Further on down the page, i also came across this section,

"Paralleling Devices
Any number of TC1044S voltage converters may be
paralleled to reduce output resistance (Figure 4). The reservoir
capacitor, C2, serves all devices, while each device
requires its own pump capacitor, C1. The resultant output
resistance would be approximately:
R out= R out(of TC1044s)/n(number of devices)"

So running these chips in parallel will lower the output impedance. This, of course is mostly for academic curiosity, and i realize that a serious modification to the final pc board would be the result if it worked, but is this actually going to affect my overall sound when completed?
I have a few more questions, but since they are not related to the TC1044 chip, I think i will just email you instead.
BTW, the troubleshooting guide is a great focus on helping me test this project as i go, THANK YOU!!!
Anyways, happy :guitarsg: :guitargibso and whatnot,
Red Llama

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8 years 4 weeks ago #448 by Ray
Replied by Ray on topic TC1044 theory questions
Hi,

Basically, it says if you use 100uF caps, you can obtain 100% efficiency. So my question is, would using 100uF caps in this design have any negative effect on the pedal?

The most important factor for the efficiency is the load, so taking as little current as possible its important. In the datasheet I did not see any graph showing this caps vs efficiency. I used 10uF because are the ones recommended in the datasheet. You can try increasing the values or putting some in parallel and check if the efficiency improves.

So running these chips in parallel will lower the output impedance. This, of course is mostly for academic curiosity, and i realize that a serious modification to the final pc board would be the result if it worked, but is this actually going to affect my overall sound when completed?

Yes, using chips in parallel will improve the efficiency a lot because also the load would be shared and that is the most important factor in efficiency. However the efficiency by "default" is over 70% which is pretty good. And no, I dont think that the sound would be affected in any negative way.


Its nice to see that you like the project and you are looking ways to improve it! ;)

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