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LED driver chips, TLC5923

J

Joerg

Jan 1, 1970
0
Hello Folks,

Need to drive up to 16 LEDs from a serial data. To avoid as many
resistors as LEDs there are some nice chips such as the TLC5923, for
under $1.50. This one current-controls all 16 LED individually and AFAIK
allows brightness control from a port in addition to the usual resistor.
Which is exactly what I'd need and the price is right. Of course, a chip
like this does get hot.

Since EEs always want one more thing: Is there such a chip that does
some kind of PWM instead of burning off the excess voltage in a linear
stage? An inductor wouldn't be a problem either, as long as it's only one.

What I could imagine is something that runs a buck converter and then
each LED is fed via an LDO that controls the current. The buck converter
would operate just at the point that none of the 16 LDOs runs out of
steam. Technically this can certainly be done but is there already such
a chip?

Regards, Joerg
 
J

Joerg

Jan 1, 1970
0
Hello Martin,
Maybe The philips variants (I2C) ? PCA9532 1kpc @ $1.4

Thanks. I like the fact that it even has two PWM. One for dimming and
another for visible blinking. Smart. The only concern is that Avnet has
no stock and Arrow carries very little stock. Don't know if that could
be a bad sign or not. Then again Digikey has some which usually means
it's popular.

Regards, Joerg
 
T

Terry Smith

Jan 1, 1970
0
Joerg said:
Hello Folks,

Need to drive up to 16 LEDs from a serial data. To avoid as many resistors
as LEDs there are some nice chips such as the TLC5923, for under $1.50.
This one current-controls all 16 LED individually and AFAIK allows
brightness control from a port in addition to the usual resistor. Which is
exactly what I'd need and the price is right. Of course, a chip like this
does get hot.

Since EEs always want one more thing: Is there such a chip that does some
kind of PWM instead of burning off the excess voltage in a linear stage?
An inductor wouldn't be a problem either, as long as it's only one.

What I could imagine is something that runs a buck converter and then each
LED is fed via an LDO that controls the current. The buck converter would
operate just at the point that none of the 16 LDOs runs out of steam.
Technically this can certainly be done but is there already such a chip?

Regards, Joerg

Joerg,

A bit of house tidy required here
http://www.analogconsultants.com/situations.htm
 
T

Terry Smith

Jan 1, 1970
0
Joerg said:
Hello Terry,


Thanks for the hint. I did find one typo and polished it some more. Could
you tell me what's wrong with it?

copied .....

Where can Analog Consultants help?

home

by Joerg Schulze-Clewing

<!--[if !supportEmptyParas]--> <!--[endif]-->

<!--[if !supportEmptyParas]--> <!--[endif]-->

Difficult Analog Designs

<!--[if !supportEmptyParas]--> <!--[endif]-->

It isn't possible to furnish all expertise in house at all times. Sometimes
it doesn't even make sense to have a full time analog engineer on staff.
Whatever the scenario, there often comes a point when a design becomes
difficult. Going it alone at that point might lead to huge problems later,
be that in production, in the field, or simply a large cost overrun. I have
seen boards that unnecessarily contained numerous precision chips totaling
over $1000 just in parts and they still would not work reliably. This will
often require a redesign from scratch, meaning that all the engineering
hours that had gone into it were basically wasted.

<!--[if !supportEmptyParas]--> <!--[endif]-->

Other designs are just partially difficult. This could be an RF section,
something that needs to provide incredible precision or maybe a disposable
portion that must be realized at rock bottom cost. In that case the
consultant can handle the "nasty" parts while the other engineers develop
the rest. That has worked very well in the past. It also provides an
opportunity for the client's engineers to learn how to handle this type of
challenge next time.

<!--[if !supportEmptyParas]--> <!--[endif]-->

<!--[if !supportEmptyParas]--> <!--[endif]-->

Digital Designs

<!--[if !supportEmptyParas]--> <!--[endif]-->

Analog consultants are not FPGA designers, so what should they be doing
here? A lot. As soon as clock frequencies exceed 100 MHz or rise and fall
times reach picosecond levels things become analog rather quickly. A minor
oversight on the clock distribution, phase jitter, cross talk, unwanted
transmission line behavior, all this can have effects that can drive the
digital designer up the wall. The simulations show that everything should
work fine but the design behaves outright weird. That can cost many work
hours and throw the time schedule a real curve.

<!--[if !supportEmptyParas]--> <!--[endif]-->

Analog consultants use tools such as oscilloscopes, analyzers and meters in
different ways. They look for those subtle yet revealing signs of trouble.
Bus contentions, transient pulses, runt pulses, brief bits of data

....... was that your intention



Cheers.
 
J

Joerg

Jan 1, 1970
0
Hello Terry,
Thanks for the hint. I did find one typo and polished it some more. Could
you tell me what's wrong with it?

copied .....

Where can Analog Consultants help?

home

by Joerg Schulze-Clewing

<!--[if !supportEmptyParas]--> <!--[endif]-->

<!--[if !supportEmptyParas]--> <!--[endif]-->

Oh drat. Thanks for the hint. It reads just fine with Mozilla, Netscape
and an older IE. But not with a newer version IE that came with a PC and
which I never used. There I got the same results that you saw. So I
guess I fell victim to another one of those dreaded (intentional?)
incompatibilities. Maybe I am being punished for defecting from an MS
product.

I am using Mozilla Composer. Guess I'll have to look around for another
option now to fix this.

Regards, Joerg
 
J

Joerg

Jan 1, 1970
0
Hello Terry,

Just as a side note, I snooped around and found that IE butchers the
display of other web sites in a similar fashion. Even government sites
like this:
http://www.govdocs.com/service/docs/CACORON/CACORON_8/CACORON_8_20010710_en.htm

Maybe IE has a major problem. Anyway, since it's still used by many
(don't know why...) I'll have to make my web site compatible. I had a
hunch when I was at a client w/o my laptop and used one of their PCs to
find some vendor info. They only had IE on it and several sites that I
had accessed ok before with Mozilla were nearly unintelligible. Error
messages, text columns mashed into each other and so on.

Regards, Joerg
 
J

Joerg

Jan 1, 1970
0
Hello Terry,

Ok, tried it. Loaded that page into MS-Word which, after all, is a
Microsoft product. MS-Word displayed it correctly (!). Hmm...

Anyway, I saved it again from MS-Word which miraculously increased the
file size by a few hundred bytes. Oh well. Then I uploaded it to the web
server and tried it. Fine with Netscape and Mozilla. IE still mangles it.

If it was me I would ditch IE.

Regards, Joerg
 
M

Martin Riddle

Jan 1, 1970
0
MSWORD, Tools->Options->Compatibility->Dont use HTML paragraph auto spacing.

Your welcome,
 
T

Terry Smith

Jan 1, 1970
0
Joerg said:
Hello Terry,

Ok, tried it. Loaded that page into MS-Word which, after all, is a
Microsoft product. MS-Word displayed it correctly (!). Hmm...

Anyway, I saved it again from MS-Word which miraculously increased the
file size by a few hundred bytes. Oh well. Then I uploaded it to the web
server and tried it. Fine with Netscape and Mozilla. IE still mangles it.

If it was me I would ditch IE.

No, I can't do that - least problems with using it as it is the dominate
browser. Also I use FrontPage Express to compile my own web site - it's
fairly straight forward. I can see from my stats that over 90% of my
visitors are using IE and a lot of sites are set up predominately for IE for
that reason. Yeah, I know it stinks but I just go with the flow.

PS. I would think it would be easy just to use > View > Source to edit your
page anyway.


Good luck.
 
J

Joerg

Jan 1, 1970
0
Hello Martin,
MSWORD, Tools->Options->Compatibility->Dont use HTML paragraph auto spacing.

Thanks! That did it. Still puzzled why two products, both from MS,
aren't compatible.

Regards, Joerg
 
J

Joerg

Jan 1, 1970
0
Hello Terry,
No, I can't do that - least problems with using it as it is the dominate
browser. Also I use FrontPage Express to compile my own web site - it's
fairly straight forward. I can see from my stats that over 90% of my
visitors are using IE and a lot of sites are set up predominately for IE for
that reason. Yeah, I know it stinks but I just go with the flow.

PS. I would think it would be easy just to use > View > Source to edit your
page anyway.


Martin had the solution right there. Tried it and now it works. It seems
that the MS-Word defaults and IE are incompatible but I can't say that
this surprises me much.

I also see in the stats that IE is still higher than others. Sometimes I
have the impression that it is declining though. As for browsing I find
that Mozilla is much more efficient. No pop-ups, way faster and it
hardly ever hangs. A site that is IE-centric usually means that it's a
vendor that I probably won't want to do business with anyway. If they
can't design an efficient web site I don't expect their customer support
to be much better.

Now I'll have to fix the German part of the site. Oh well. Thanks for
pointing out this IE problem to me.

Regards, Joerg
 
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