I am working on some projects where a variable frequency variable duty cycle PWM could be really useful. I know how to make various 555 circuits to do this. But it can be annoying to have to troubleshoot and modify the design so much. And there are often a lot of components. Being honest, I often do not have the time for this.

So I am looking for an IC that can create a variable duty cycle and variable frequency from two analog voltages (potentiometers). I want 50Hz-1MHz, and 1 to 99%, with at least 1 percent accuracy. It should run on 5V. It should be able to supply at least 100mA on the output. I am OK with using regulators and other external components to get ideal performance. I am willing to spend up to $3-4 for each. It would be great if it was from mouser. So suggestions? Thanks,
live wire

 

I am working on some projects where a variable frequency variable duty cycle PWM could be really useful. I know how to make various 555 circuits to do this. But it can be annoying to have to troubleshoot and modify the design so much. And there are often a lot of components. Being honest, I often do not have the time for this.

So I am looking for an IC that can create a variable duty cycle and variable frequency from two analog voltages (potentiometers). I want 50Hz-1MHz, and 1 to 99%, with at least 1 percent accuracy. It should run on 5V. It should be able to supply at least 100mA on the output. I am OK with using regulators and other external components to get ideal performance. I am willing to spend up to $3-4 for each. It would be great if it was from mouser. So suggestions? Thanks,
live wire

Your best bet is a low pin count microcontroller. You need two A/D inputs to read the pots, a PWM output pin, power and ground. You might even find a suitable 8-pin part. Terrific little project.

 

Ok. I try to avoid microcontrollers when there is likely a faster and more precise analog/logic way to do something. But So could you suggest some microcontrollers that have a very fast clock, the two analogs, and the digital pin? It would also be great if it is arduino/C compatible or easy to program but with something else. And thanks for the quick reply.

 

Ok. I try to avoid microcontrollers when there is likely a faster and more precise analog/logic way to do something. But So could you suggest some microcontrollers that have a very fast clock, the two analogs, and the digital pin? It would also be great if it is arduino/C compatible or easy to program but with something else. And thanks for the quick reply.

Sure you go to www.microchip.com and you root around until you find the Master Selection Guide. Now you probably have over 10,000 choices to start with and you have to narrow it down by selecting the things you want:

1. 2 Analog Inputs
2. 1 Compare Capture Output
3. Internal oscillator
4. Anything else that comes to mind

That should narrow thing down a bit. The software tools are free and the programming hardware might cost $25.00 or so. The parts should be about $1.00 each in quantities of 10-25.

 

Sure you go to www.microchip.com and you root around until you find the Master Selection Guide. Now you probably have over 10,000 choices to start with and you have to narrow it down by selecting the things you want:

1. 2 Analog Inputs
2. 1 Compare Capture Output
3. Internal oscillator
4. Anything else that comes to mind

That should narrow thing down a bit. The software tools are free and the programming hardware might cost $25.00 or so. The parts should be about $1.00 each in quantities of 10-25.

OR
You don't like microcontrollers, so try the PSOC from Cypress Semiconductor which has been mentioned in other threads on this board.
https://forum.allaboutcircuits.com/threads/ultra-low-power-timer.145519/#post-1252906
http://www.cypress.com/products/psoc-creator-integrated-design-environment-ide

 

12F1822 32Mhz 8pin Picmicro.
PWM, 3 analog.
Max.

 

Here are some suggestions:
TPIC2101
https://media.digikey.com/pdf/Data Sheets/Texas Instruments PDFs/tpic2101.pdf
Intersil (now something else)
CDP68HC68W1
http://www.customsiliconsolutions.com/downloads/Revised Standard products/CSS68HC68W1_Spec.pdf
LM3524/SG3524
http://www.ti.com/lit/ds/symlink/lm3524d.pdf
http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.CD00000117.pdf

I have used the TPIC2101 and SG3524 for PWM motor control. I have not used the CDP68HC68W1. I thought it was interesting at the time (almost 20 years ago) and put it in my files. As time goes by, such hardware solutions are getting harder to find. You may find more current devices by searching on PWM motor control or buck/boost converters.

 

Texas Instruments MSP430G2230ID

Another cheap and cheerful microcontroller. 8 pin package, four ADC channels and one Timer with all the usual capture/compare registers by the looks of things. It is a 3.3V device but if you're using it to provide control inputs to a gate drive or suchlike I would think that 3.3V would be fine.

 

Microcontroller solutions will likely need an added transistor at the output to handle 100mA.

 

How about this chip? http://www.analog.com/en/design-cen...s/1mhz-pulse-width-modulator.html#cc-overview

 

Thanks. I'll take a look at what people suggested. I know it is hard to find stuff like that with 100mA+ outputs. It would be convenient not to have to have another transistor stage because most of the things I am thinking of involve powerful stuff where the main transistor might need a little bit of power.

 

Thanks. I'll take a look at what people suggested. I know it is hard to find stuff like that with 100mA+ outputs.

2n7000 Fet, doesn't take much room!
Max.

 

It is still another thing to buy, solder and wire up, and it still takes up a little bit of space. But I guess it's not too big a deal.

 

A 32MHz PIC is not going to give you 1% resolution PWM at 1 MHz. In fact, it will get you only 8 different duty cycles.

Bob

 

It is still another thing to buy, solder and wire up, and it still takes up a little bit of space. But I guess it's not too big a deal.

No no no! Use one of the online PCB websites. For not much in the way of money you can get 3 boards of a particular size. Schematic capture and layout tools are free.

https://www.expresspcb.com/
http://www.sunstone.com/?gclid=EAIaIQobChMI7emxquuA2wIV3IWzCh2GbglFEAAYASAAEgKYe_D_BwE
https://www.pcb123.com/pcb123-and-s...MI3bilu-uA2wIViY-zCh2ZJQ4xEAAYASAAEgIZbfD_BwE

 

A 32MHz PIC is not going to give you 1% resolution PWM at 1 MHz. In fact, it will get you only 8 different duty cycles.

Bob

The 12F1822 can give 32Khz to 32Mhz selectable.
Max.

 

A PSOC 4 would do this with very little code. Board is $ 4, IDE and Compiler free.

Has Multiple PWMs, and clocks. Scanning 12 bit SAR with Vref. Lots of other resources
available as well.

Example attached.

http://www.cypress.com/documentation/development-kitsboards/psoc-4-cy8ckit-049-4xxx-prototyping-kits

 

A 32MHz PIC is not going to give you 1% resolution PWM at 1 MHz. In fact, it will get you only 8 different duty cycles.
Bob

Wouldn't you get 16 different resolutions? But I do not need a ton of resolution at higher frequencies anyways.

A PSOC 4 would do this with very little code. Board is $ 4, IDE and Compiler free.

Has Multiple PWMs, and clocks. Scanning 12 bit SAR with Vref. Lots of other resources
available as well.

Example attached.

http://www.cypress.com/documentation/development-kitsboards/psoc-4-cy8ckit-049-4xxx-prototyping-kits

I will take a look at it. But what exactly are PSoCs? And what external stuff do I need to program that board?

And would it be possible to operate a 16MHz ATMega328p chip, from an arduino uno, at a higher frequency with an external clock? How would this affect it? Would it completely not work? I assume you'd have to have it in the arduino with the 16MHz clock for programming.

 

A PIC that has 10-bit control (e.g, enhanced mid-range ones)should give 5-bit resolution at 1 MHz with a 32 MHz clock. You can extrapolate from the charts in the datasheet (e.g., 250 KHz =7 bit), calculate manually, or cheat here (http://www.micro-examples.com/public/microex-navig/doc/097-pwm-calculator.html).

 

I will take a look at it. But what exactly are PSoCs? And what external stuff do I need to program that board?

Programming and debugging that board just a usb cable to your PC. The
board has two PSOCs on it, a low end target PSOC 4, and a high end to
run a bootloader/debugger/programmer. High end PSOCs have multiple
A/Ds, digital filters, a lot more logic fabric. When you are done with the low
end design you can snap off the programmer and use the high PSOC,
but only coupled with its bootloader. And you cant debug it. However a
full proto board for high end is $ 10, thats a -

http://www.cypress.com/documentatio...oc-5lp-prototyping-kit-onboard-programmer-and

PSOC is a UP with analog + digital + rout-ability + logic fabric + 32 bit arm core

https://www.element14.com/community/thread/26434/l/psoc-101-what-is-psoc?displayFullThread=true

Regards, Dana.