Looking for a PWM chip number.

[Jamie]

I need to locate a basic 8 PDIP (testing) and
later on maybe a smt version of it.
This needs to be a PWM output driver normally
found in switch mode powers supplies.

I need it to output 0..100 % duty cycle via
the current regulation input or a reference feed
back.
Selectable CW frequency via RC components is fine.

The supply voltage will vary from 8 up to 15 volts.

Now, I found a perfect chip from a switching supply how
ever, it requires a minimum of 30 volts to operate.
PLus, it seems that it's not a common stock item..
Also, this unit maybe in a highly static environment
where cmos/bimos maybe sensitive to.

I already have a working circuit using a PIC how ever,
I'm looking to reduce part count and price down to a minimum
due to the nature of the overall unit. ( through away device).

This isn't a precision device..

Does any one have part numbers that are cheap and reliable in maybe
lots of 2000 or more ?
If I can get a few for testing a prototype then i'll
have my employer buy some so that we can have the
fab house assemble the boards for us.

The final unit will be a potted device.

Thanks.

 

[John Popelish]

I need to locate a basic 8 PDIP (testing) and
later on maybe a smt version of it.
This needs to be a PWM output driver normally
found in switch mode powers supplies.

I need it to output 0..100 % duty cycle via
the current regulation input or a reference feed
back.
Selectable CW frequency via RC components is fine.

The supply voltage will vary from 8 up to 15 volts.

Now, I found a perfect chip from a switching supply how
ever, it requires a minimum of 30 volts to operate.
PLus, it seems that it's not a common stock item..
Also, this unit maybe in a highly static environment
where cmos/bimos maybe sensitive to.

I already have a working circuit using a PIC how ever,
I'm looking to reduce part count and price down to a minimum
due to the nature of the overall unit. ( through away device).

This isn't a precision device..

Does any one have part numbers that are cheap and reliable in maybe
lots of 2000 or more ?
If I can get a few for testing a prototype then i'll
have my employer buy some so that we can have the
fab house assemble the boards for us.

You don't mention frequency, but I would look into a dual
comparator, one half set up to make a triangle wave
generator and the the other to compare that triangle with
the signal being converted to a PWM output. For modest
frequencies, you might get by with an LM393.

 

[Jamie]

You don't mention frequency, but I would look into a dual comparator,
one half set up to make a triangle wave generator and the the other to
compare that triangle with the signal being converted to a PWM output.
For modest frequencies, you might get by with an LM393.

Ok, I'll look into that, I think i've done something like the before
where I used a single reference driving both inputs as common mode
and then offsetting one side.

Thanks for the heads up. Most likely will do just fine. We have lots
393's kicking around in our tubes.

 

[Tim Williams]

UC384x series.

Tim

 

[Jamie]

UC384x series.

Tim

Ok, had a look. to much over head. I currently
have an 8 PDIP that works but starts at 30 volts
and does not seem to be a common stock item.

LM393 was suggested to do what I need. something
that I over looked which i've done in the past for
some other project..
I just need a simple 0..100 % duty cycle pulse with
minimum over head. This is not going to be a smps.. I
just needed the function of an integral IC used in smps
to keep the part count down and space limited.
The Cw frequency is going to be nothing more than 10khz
on the average.
Thanks for the suggestions.

I originally used a PIC chip how ever, I've had experience with
those getting corrupted programs if you don't exercise all the
protection precautions. In the end, the part count and cost out
weights a simple linear circuit.