Single Chip PWM solution?

[Analog]

Looking for advice on a single chip PWM generator.

Ideal solution would be 0-5V in, 0 - 100% Duty out, settable frequency (like a VCO). I'm looking in the range of 25KHz -100KHz range for the frequency. Single supply operation.

I know that I could do this with a small outline microcontroller, using the A/D input and PWM output - but I'm sure someone has used something like this that is off the shelf. I appreciate any input. Thanks.

 

[peufeu]

You could probably do that with a 556 or a dual opamp, and lots of passives, but if you want linearity in the amplitude response, then you got to generate your ramp with a current source charging a capacitor, not just a simple RC. You probably cannot beat a SOT23-6 PIC.

 

[ericgibbs]

Looking for advice on a single chip PWM generator.

Ideal solution would be 0-5V in, 0 - 100% Duty out, settable frequency (like a VCO). I'm looking in the range of 25KHz -100KHz range for the frequency. Single supply operation.

I know that I could do this with a small outline microcontroller, using the A/D input and PWM output - but I'm sure someone has used something like this that is off the shelf. I appreciate any input. Thanks.

hi,
Look thru these links.
555 pwm generator - Google Search

 

[Sceadwian]

A 555 will not give 0-100% duty cycle.
You may be able to find a single IC solution that meets your needs but I doubt it those are pretty specific requirements.

Atmel's Tiny25 would be one I would suggest it'll do what you want and quiet a bit more if you want it to and will only set you back about 2 dollars. I would have said the tiny15 but Atmel is phasing it out so you'll have a hard time finding a place to get them. Personally I wish they still made the tiny11's didn't have the features you need but it had a basic instruction set and fast I/O, best of all they only cost 25 cents and had an internal oscilator so they could replace hordes of other IC's, but I digress =)

 

[Analog]

A 555 will not give 0-100% duty cycle.
You may be able to find a single IC solution that meets your needs but I doubt it those are pretty specific requirements.

Atmel's Tiny25 would be one I would suggest it'll do what you want and quiet a bit more if you want it to and will only set you back about 2 dollars. I would have said the tiny15 but Atmel is phasing it out so you'll have a hard time finding a place to get them. Personally I wish they still made the tiny11's didn't have the features you need but it had a basic instruction set and fast I/O, best of all they only cost 25 cents and had an internal oscilator so they could replace hordes of other IC's, but I digress =)

Thanks, but I wanted to stay away from the programmable route. Was hoping someone used an analog single chip solution.

 

[Nigel Goodwin]

What are you actually trying to do? - is it speed control?.

 

[3v0]

There used to be a company that had a set of programs for the little PICs that did useful stuff. I think a PWM generator was one of them.

They gave up selling them and put the code on the net but I do can not find the URL.

If we can find that code I would gladly send you a programmed PIC for cost (about $1) and postage.

If we can not find the code it we could write it and a few other of these useful dittys, use them to start our code repository. Joint coding efforts has been fun in the past.

One of the other projects was a 555 like program.

 

[Sceadwian]

Analog, your requirements are too specific you won't find one. If you can do witthout some of the specifications you listed you need to fully define what is absolutly required to get the results you need, or you have nothing to base a device choice from.

 

[Analog]

The application is a regulated buck converter. Looks like the TI TL494 may be suitable. About $1.73/ea. That seems to be the closest thing I've found, unless someone has another that is better. Thanks.

 

[Nigel Goodwin]

The application is a regulated buck converter.

There are huge numbers of suitable chips, and the application bears little ressemblance to your original question.

 

[DerStrom8]

Must it be a single chip? The circuit on the link below from RMCybernetics.com uses a 555 and a 393 (both 8-pin DIPs) that I have always had luck with. Because they each have only 8 pins, they take up the same amount of space as a single 16-pin DIP. If you're not worried about space, but complexity instead, the PWM circuit on this site is actually quite simple:

RMCybernetics - DIY Homemade Power Pulse Controller

I'm not sure this is what you wanted (I haven't done much with buck converters), so please let me know. Thanks.
-Der Strom

 

[Ubergeek63]

Thanks, but I wanted to stay away from the programmable route. Was hoping someone used an analog single chip solution.

SG3524 ... add connection from pin 7 to pin 1, 0-5V on pin 2, and extra feedback resistor from output to pin 7 should improve linearity.

pins 11 & 14 to GND, pins 12 & 14 are the outputs pulled up with a 1K or less resistor

 

[Analog]

Must it be a single chip? The circuit on the link below from RMCybernetics.com uses a 555 and a 393 (both 8-pin DIPs) that I have always had luck with. Because they each have only 8 pins, they take up the same amount of space as a single 16-pin DIP. If you're not worried about space, but complexity instead, the PWM circuit on this site is actually quite simple:

RMCybernetics - DIY Homemade Power Pulse Controller

I'm not sure this is what you wanted (I haven't done much with buck converters), so please let me know. Thanks.
-Der Strom

Thanks - what frequency does it operate at?

 

[Analog]

SG3524 ... add connection from pin 7 to pin 1, 0-5V on pin 2, and extra feedback resistor from output to pin 7 should improve linearity.

pins 11 & 14 to GND, pins 12 & 14 are the outputs pulled up with a 1K or less resistor

Thanks, this is what I was thinking of!

 

[Ubergeek63]

Thanks, this is what I was thinking of!

i suspected it might be... i did not iron out the details, but it seems you have it together enough to figure them out

 

[DerStrom8]

The frequency is adjustable by VR1 and C1. Change the values of these to get the frequency you want.

 

[DerStrom8]

The frequency is adjustable by VR1 and C1. Change the values of these to get the frequency you want.

That is, with the circuit from RMCybernetics.