Searching \ for '[EE] selecting capacitors for Max232, and in g' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=selecting+capacitors
Search entire site for: 'selecting capacitors for Max232, and in g'.

No exact or substring matches. trying for part
PICList Thread
'[EE] selecting capacitors for Max232, and in gener'
2005\12\16@142202 by Danny Sauer

flavicon
face
My immediate need is to figure out what to use with my Max232, so I'll
start there.  On the data sheet, the Max232 says it needs five 1uF
capacitors.  Ok, that's easy enough.  However, the caps are all drawn
as being polarized.  Should I then presume that means I need to use
polarized caps, or is that just for the benefit of someone who woudl
use a polarized cap?  It doesn't say in the data sheet, but I've seen
several example circuits with that chip, and most of them seem to use
tantalum or unspecified caps.  Now, I *know* what a capacitor does,
but I'm not really sure when one would use a polarized (presumably
electrolytic) v/s a ceramic disk, dipped tantalum, polyester film,
etc.  I figure that people up here might know. :)

So, for my immediate need: can I use the tantalum caps I have laying
around, or do I need to find polarized caps for the max232?  I thought
that the polarized caps were just more efficient one way than another,
but otherwise were pretty much the same as any other cap (accuracy and
expense nonwithstanding), but like I said - I don't know for sure.

For my future reference - is there a good document somewhere I can
read, or does someone with some time to kill wanna help me understand
the difference and why one would choose one kind over another?

Thanks much.
--Danny

2005\12\16@143238 by Dave Wheeler

flavicon
face
Danny,

The type of capacitor for this application is not that critical.
I tend to use polarised Tants because I have loads in stock, others use
mini electrolytic and I think Olin uses Surface Mount Ceramic.

It's not that many years ago that a 1uF ceramic was a pipe dream (if
they were around I didn't see them !!) which may be why the example
circuit shows polarised devices.

Cheers,

Dave


Danny Sauer wrote:

{Quote hidden}

2005\12\16@145830 by Byron A Jeff

face picon face
On Fri, Dec 16, 2005 at 01:22:01PM -0600, Danny Sauer wrote:
> My immediate need is to figure out what to use with my Max232, so I'll
> start there.  On the data sheet, the Max232 says it needs five 1uF
> capacitors.  Ok, that's easy enough.  However, the caps are all drawn
> as being polarized.  Should I then presume that means I need to use
> polarized caps, or is that just for the benefit of someone who woudl
> use a polarized cap?

The former. Use a polarized cap.

>  It doesn't say in the data sheet, but I've seen
> several example circuits with that chip, and most of them seem to use
> tantalum or unspecified caps.

tantalums are polarized.

[snip]

> So, for my immediate need: can I use the tantalum caps I have laying
> around, or do I need to find polarized caps for the max232?

tantalums are polarized. You can use them for your MAX232.

BAJ

2005\12\16@150807 by Danny Sauer

flavicon
face
Byron wrote regarding 'Re: [EE] selecting capacitors for Max232, and in general' on Fri, Dec 16 at 14:02:
> On Fri, Dec 16, 2005 at 01:22:01PM -0600, Danny Sauer wrote:
> > So, for my immediate need: can I use the tantalum caps I have laying
> > around, or do I need to find polarized caps for the max232?
>
> tantalums are polarized. You can use them for your MAX232.

Oh, huh, I've never looked at them that closely.  I'll be darned if
there's not a little plus sign on them.  Huh. :)  That does explain
things... :)

--Danny, randomly ordering parts that he clearly doesn't know how to
use, 'cause learnin's fun

2005\12\16@152608 by David Van Horn
picon face
> Oh, huh, I've never looked at them that closely.  I'll be darned if
> there's not a little plus sign on them.  Huh. :)  That does explain
> things... :)

They have a habit of exploding if connected backwards, across anything
that can deliver much current..  Or forwards for that matter, if the
risetime on the voltage is too quick.





2005\12\16@162945 by ike, K8LH (sent by Nabble.com)

flavicon
face

Danny,

I tend to use MAX202, MAX232A, or ST202 devices which can use 0.1-uf values...  Example (below); five Kemet ceramic 0.1-uf monolythic caps' installed in the open space of a machined pin socket...

Happy Holidays...  Regards, Mike


--
Sent from the MicroControllers - PIC forum at Nabble.com:
www.nabble.com/-EE-selecting-capacitors-for-Max232%2C-and-in-general-t757512.html#a1981210

2005\12\16@163012 by Mark Chauvin

picon face
Ceramic caps work just fine.  That's what I use.
They're non-polarized & cheap, don't explode, and I've
recently noticed ceramic caps and a max232 chip on
some tank gauging hardware that we use out here in the
chemical plant, that's been in service for years.  If
it's the wrong cap for the job, then I'm not the only
one making that mistake.

-Mark


--- David Van Horn <spam_OUTdvanhornTakeThisOuTspammicrobrix.com> wrote:

{Quote hidden}

> --

2005\12\16@163809 by David Van Horn

picon face


> -----Original Message-----
> From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu] On
Behalf
> Of Mark Chauvin
> Sent: Friday, December 16, 2005 4:46 PM
> To: Microcontroller discussion list - Public.
> Subject: RE: [EE] selecting capacitors for Max232, and in general
>
> Ceramic caps work just fine.

Yeah, me too.


I was surprised recently on a search at digi-key.

10uF ceramic caps as small as 0402!

I have some 0603s in a project now.




2005\12\16@164623 by Andre Abelian

flavicon
face
Danny,

I have been using  .1uf caps in years with MAX232ACPE didn't
have any problem with it only very old max requires electrolytic
no body uses electrolytic  takes too much space and more expensive.
By the way you can also use tantalum caps it is even more expensive
then standard electrolytics sure why not.

Andre Abelian


Danny Sauer wrote:

{Quote hidden}

2005\12\16@165841 by olin piclist

face picon face
Danny Sauer wrote:
> Should I then presume that means I need to use
> polarized caps,

No.  It's showing you the polarization in case you use polarized caps.
Nowadays, there is no point using polarized caps at 1uF and 10V.  Ceramic
caps are better, cheaper, and more reliable.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\16@165925 by Spehro Pefhany

picon face
At 04:48 PM 12/16/2005 -0500, you wrote:


> > -----Original Message-----
> > From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu] On
>Behalf
> > Of Mark Chauvin
> > Sent: Friday, December 16, 2005 4:46 PM
> > To: Microcontroller discussion list - Public.
> > Subject: RE: [EE] selecting capacitors for Max232, and in general
> >
> > Ceramic caps work just fine.
>
>Yeah, me too.
>
>
>I was surprised recently on a search at digi-key.
>
>10uF ceramic caps as small as 0402!
>
>I have some 0603s in a project now.

I like ceramics for many applications, however I tend to avoid anything
crappier than X7R dielectric.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\12\16@170154 by olin piclist

face picon face
Danny Sauer wrote:
> can I use the tantalum caps I have laying
> around, or do I need to find polarized caps for the max232?

Tantalum caps *are* polarized.

******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\16@170735 by M Graff

flavicon
face
Mike, K8LH (sent by Nabble.com) wrote:

> Sent from the MicroControllers - PIC forum at Nabble.com:
> http://www.nabble.com/-EE-selecting-capacitors-for-Max232%2C-and-in-general-t757512.html#a1981210

One must wonder, do the list admin know this list is being "sponsored"
by nabble.com?

--Michael

2005\12\16@195315 by David Van Horn

picon face
> >I have some 0603s in a project now.
>
> I like ceramics for many applications, however I tend to avoid
anything
> crappier than X7R dielectric.

In my case, I just needed some low impedance joules. :)



2005\12\16@200008 by Xiaofan Chen

face picon face
On 12/17/05, Spehro Pefhany <@spam@speffKILLspamspaminterlog.com> wrote:
> >I have some 0603s in a project now.
>
> I like ceramics for many applications, however I tend to avoid anything
> crappier than X7R dielectric.
>

We are using mostly ceramics capacitors (0402/0603/0805/1206/1210).
X7R is recommenced. Y5U is not as good. COG is better than X7R in terms of
temperature stability but not so common with bigger values and generally bigger.

Regards,
Xiaofan

2005\12\16@200440 by Todd Bailey

picon face

All right, a cap question!
Finally something I can offer an opinion on!

 To answer some of your questions:

 1.) -- There's never a need to explicitly use a polarized cap as far as I
know.  Polarization is part of the chemical process involved in making some
caps (especially electrolytic and tantalum -- traditional wet-chemistry
devices) which involves coating one of the foil layers of the cap... Blah
blah.  Anyway, it's an evil assoicated with a specific kind of chemistry,
and not something anybody does to make a cap more efficient.  In general, if
you can only stock a given capacitance at a given voltage, you're safer
getting a non-polar cap since it is useful in more applications.

2.)  That having been said, polar caps (by which I mean electrolytics and
tantalums) generally have poorer electrical characteristics (ESR,
inductance, leakage, aging, temperature and voltage variations)
than their non-polar counterparts like ceramic and film caps.  People use
electrolytics and tantalums anyway because they have a TON of capacitance
for a given size.  Anytime you need a 10,000uF filter cap, you can pretty
much bet on the fact that it'll be electrolytic.  That's  why Dave was so
excited when he saw a ceramic cap at 10uF and 0402 size.  That didn't used
to be the case.
 All this  having been said, E and T caps are fine for most low-frequency
blocking and bypassing applications.  Tantalum caps generally have a better
rep electrically, except for the "blowing up when reverse biased" part.

3.)  Ceramic caps have different grades, but the really good ones (C0G /
NP0) are really good.  Even the worse grades are better than electrolytics
ESR wise, which is why people use them for bypassing high-speed applications
like microcontroller stuff -- they respond to transients faster.  A common
technique in bypassing a fast chip is to use a small (like .01 or .1uF)
ceramic in parallel with a slower, bigger tantalum (like a 4.7uF).  I think
this rule of thumb begins to change at high frequencies (like above 50MHz or
so) however.
 Ceramic caps, until now, were really big, however, and the good ones are
expensive.  The not-so-good grades (while they have a ton of capacitance)
exhibit someweird behavior including piezoelectric effect (ie, they act like
a little piezo transducer, meaning they create a voltage under mechanical
stresses) and drift with temperature and voltage.

4.)  Film caps are great in many respects (except size, again) but are
really expensive.  They're mostly used for analog applications and audio
nerds love them.  Again, they aren't all the same.

 If you care to read more about caps, my favorite website about them is:

http://my.execpc.com/~endlr/index.html

 This guy is a real head.
 Horowitz and Hill's section on capacitors is pretty good, too.

Hope this helps!

-Todd




From: "David Van Horn" <KILLspamdvanhornKILLspamspammicrobrix.com>
Reply-To: "Microcontroller discussion list - Public." <RemoveMEpiclistTakeThisOuTspammit.edu>
To: "Microcontroller discussion list - Public." <spamBeGonepiclistspamBeGonespammit.edu>
Subject: RE: [EE] selecting capacitors for Max232, and in general
Date: Fri, 16 Dec 2005 16:48:09 -0500



> -----Original Message-----
> From: TakeThisOuTpiclist-bouncesEraseMEspamspam_OUTmit.edu [RemoveMEpiclist-bouncesspamTakeThisOuTmit.edu] On
Behalf
> Of Mark Chauvin
> Sent: Friday, December 16, 2005 4:46 PM
> To: Microcontroller discussion list - Public.
> Subject: RE: [EE] selecting capacitors for Max232, and in general
>
> Ceramic caps work just fine.

Yeah, me too.


I was surprised recently on a search at digi-key.

10uF ceramic caps as small as 0402!

I have some 0603s in a project now.




2005\12\16@202606 by olin piclist

face picon face
Xiaofan Chen wrote:
> We are using mostly ceramics capacitors (0402/0603/0805/1206/1210).
> X7R is recommenced. Y5U is not as good. COG is better than X7R in terms
> of temperature stability but not so common with bigger values and
> generally bigger.

These can all be considerations, but remember the OP just wanted capacitors
for a charge pump.  Whatever ceramic type he can get cheapest will work just
fine.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\16@203223 by Spehro Pefhany

picon face
At 08:03 PM 12/16/2005 -0500, you wrote:
> > >I have some 0603s in a project now.
> >
> > I like ceramics for many applications, however I tend to avoid
>anything
> > crappier than X7R dielectric.
>
>In my case, I just needed some low impedance joules. :)

Yes, I know where you're coming from, but something like Z5U can lose 20%
to 80% of the capacitance based on the applied voltage (voltage coefficient)
and will lose 60% of capacitance at both the high and low temperature
extremes.
Plus they age at double the rate of X7R.

That's enough of a change to cause stuff to stop working or LDOs to *start*
working (as an oscillator)-- probably in the field under conditions that
are unusual and hard to pin down. I like stuff that is conservatively designed
to work right off and that keeps working anywhere it's reasonably applied for
a very long time. Only if it's something that never sees other than room
temperature,
and has a short life (throw-away consumer goods maybe)  could I see using
them. Of course if it's a one off in the lab, it doesn't matter.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffEraseMEspam.....interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\12\16@210208 by Spehro Pefhany

picon face
At 08:25 PM 12/16/2005 -0500, you wrote:
>Xiaofan Chen wrote:
>>We are using mostly ceramics capacitors (0402/0603/0805/1206/1210).
>>X7R is recommenced. Y5U is not as good. COG is better than X7R in terms
>>of temperature stability but not so common with bigger values and
>>generally bigger.
>
>These can all be considerations, but remember the OP just wanted capacitors
>for a charge pump.  Whatever ceramic type he can get cheapest will work just
>fine.

Or they might just quit or get flaky when a long cable is attached, the
baud rate is set high, and they get warm.

I always specify the dielectric on the BOM to (help) prevent unauthorized
substitutions by purchasing folks who know just enough to be dangerous. It's
certainly possible to design for the crappier dielectrics, but you might
have to go to 0.22uF from 0.1uF and/or place limits on the range of operation.
After-the-fact substitutions are going to require new calculations, and
preferably regression testing.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeffspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\12\17@104515 by olin piclist

face picon face
Spehro Pefhany wrote:
> Only if it's something that
> never sees other than room temperature,
> and has a short life (throw-away consumer goods maybe)  could I see
> using them.

Or in situations where the required capacitance value can vary a great deal
without any ill effects.  A good example is bypass caps.  We used to use
10nF many years ago, then 100nF for quite a while once those became readily
available and cheap.  Now I sometimes use 1uF surface mount ceramic
especially when bypassing something that takes more than a few mA or runs at
high frequency or switches a lot of outputs at once, etc.  I don't really
care if these 1uF caps become 500nF or even 200nF over temperature or time.
Just due to the multi-layer construction and suface mount alone they will
have better characteristics than the 100nF thru hole caps I was happy with
in the same application just a few years ago (and would probably work fine
electrically in this application too).

I'm working on a design now where I'm using 1uF 10V 0805 ceramic as the
generic cap.  There are places it's overkill, but they are very cheap in
quantity and save money by cutting down on the number of different values
that have to be bought and stocked.  For a small volume producer like me,
the number of different parts in a design is an issue to be considered.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\17@152110 by Peter

picon face

>> tantalums are polarized. You can use them for your MAX232.
>
> Oh, huh, I've never looked at them that closely.  I'll be darned if
> there's not a little plus sign on them.  Huh. :)  That does explain
> things... :)

The tantalums have built-in reverse polarity indication. If you see a
red flame ball about 20 cm diameter scorching everything around then it
means you put it in backwards. The overvoltage indication is similar but
has a shorter delay.

Peter

2005\12\17@155454 by David Van Horn

picon face
> The tantalums have built-in reverse polarity indication. If you see a
> red flame ball about 20 cm diameter scorching everything around then
it
> means you put it in backwards. The overvoltage indication is similar
but
> has a shorter delay.

And it automatically removes itself from the circuit!




2005\12\17@170203 by Peter Todd

picon face
On Sat, Dec 17, 2005 at 10:21:04PM +0200, Peter wrote:
> The tantalums have built-in reverse polarity indication. If you see a
> red flame ball about 20 cm diameter scorching everything around then it
> means you put it in backwards. The overvoltage indication is similar but
> has a shorter delay.

So... How can I reliable get a tantalum to do this anyway? How high a
reverse polarity voltage, compared to rated voltage, do I need? Sounds
like a fun thing to try... and I've got snow covered driveway and proper
faceshields to keep me from killing anything!

--
RemoveMEpeteEraseMEspamEraseMEpetertodd.ca http://www.petertodd.ca

2005\12\17@174052 by michael brown

picon face

> Mike, K8LH (sent by Nabble.com) wrote:
>
> > Sent from the MicroControllers - PIC forum at Nabble.com:
> >
http://www.nabble.com/-EE-selecting-capacitors-for-Max232%2C-and-in-general-t757512.html#a1981210
>
> One must wonder, do the list admin know this list is being "sponsored"
> by nabble.com?

No comments from the list admins concerning http://www.nabble.com and more
specifically,
http://www.nabble.com/MicroControllers-f2055.html?

2005\12\17@215623 by Josh Koffman

face picon face
On 12/17/05, michael brown <RemoveMEspam-mespam_OUTspamKILLspamhouston.rr.com> wrote:
> No comments from the list admins concerning http://www.nabble.com and more
> specifically,
> http://www.nabble.com/MicroControllers-f2055.html?

Our position in the past has been that as long as they obfuscate the
email addresses, there isn't a whole lot of time we're willing to
waste shutting them down. At the moment I don't really see a huge
reason to change that policy unless anyone can offer a really
convincing reason.

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

2005\12\18@045714 by Jake Anderson

flavicon
face


> -----Original Message-----
> From: RemoveMEpiclist-bouncesTakeThisOuTspamspammit.edu [EraseMEpiclist-bouncesspamspamspamBeGonemit.edu]On Behalf
> Of David Van Horn
> Sent: Saturday, December 17, 2005 07:36
> To: Microcontroller discussion list - Public.
> Subject: RE: [EE] selecting capacitors for Max232, and in general
>
>
> > Oh, huh, I've never looked at them that closely.  I'll be darned if
> > there's not a little plus sign on them.  Huh. :)  That does explain
> > things... :)
>
> They have a habit of exploding if connected backwards, across anything
> that can deliver much current..  Or forwards for that matter, if the
> risetime on the voltage is too quick.
>

yeah they explode reeeal good like ;->
I was hunting for a short once on a stripboard.
Couldn't find it, gave it to another guy he couldn't find it.
it was putting a 7805 into thermal shutdown straight off the mark.
well the board needed to be used tomorrow, so...
remove all easily removable components
person I was with said "uhh you might want to point that away from your
face"
connect 12V SLA after the 7805.
tantalum cap "explodes" sending glowing red things across the desk which
burn themselves little holes about 3mm deep
also killed the 7805 but everything else survived.
12V was in spec for the cap too

2005\12\19@080852 by Alan B. Pearce

face picon face
>> The tantalums have built-in reverse polarity indication.
>> If you see a red flame ball about 20 cm diameter scorching
>> everything around then it means you put it in backwards.
>> The overvoltage indication is similar but has a shorter delay.
>
>And it automatically removes itself from the circuit!

<VBG> but on a serious note, a colleague of mine very nearly lost an eye
when a tear drop tantalum in a piece of new equipment that was DOA, flew up
just as he leaned over it to look for the trouble while the power was still
on. Luckily it flew past his ear, and the equipment was suddenly not DOA
anymore.

2005\12\19@082548 by Alan B. Pearce

face picon face
>Ceramic caps, until now, were really big, however, and the
>good ones are expensive.  The not-so-good grades (while
>they have a ton of capacitance) exhibit someweird behavior
>including piezoelectric effect (ie, they act like a little
>piezo transducer, meaning they create a voltage under
>mechanical stresses) and drift with temperature and voltage.

Another nasty trick that some will do is play battery. There were some nasty
ones made in Australia about 30-40 years ago which were good at this. The
higher capacitance and lower voltage ones were the best at it.

I do not know what the chemistry was behind this happening - it may have
been that they had a particularly bad processing facility that did not clean
up after some of the stages, or something like that. I do not know if
current SMD ones have ever been known to do things like this.

2005\12\19@091331 by olin piclist

face picon face
Alan B. Pearce wrote:
> <VBG> but on a serious note, a colleague of mine very nearly lost an eye
> when a tear drop tantalum in a piece of new equipment that was DOA,
> flew up just as he leaned over it to look for the trouble while the
> power was still on. Luckily it flew past his ear, and the equipment was
> suddenly not DOA anymore.

A few years back I accidentally put an electrolytic in backwards on a
protoboard.  The circuit was working as the power supply was beefy enough to
overcome the extra current, so I had no idea anything was wrong.  I happened
to be leaning over the circuit, and boom!  Luckily I was wearing glasses as
there was a big splat of noxious liquid on the middle of the right lens.
There was also a welt on my forehead that took a few days to go away.

I thought I was being careful with these things before, but now I'm *really*
careful when turning anything on for the first time.  I make it a point not
to put my head over any circuit that hasn't been well time-tested and wear
glasses on initial power up.


******************************************************************
Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
consultant in 2004 program year.  http://www.embedinc.com/products

2005\12\19@174713 by Jinx

face picon face
How to select caps for a circuit

http://www.piclist.com/techref/power/decouple.htm

and its link

http://www.piclist.com/techref/caps.htm#reliability

More... (looser matching)
- Last day of these posts
- In 2005 , 2006 only
- Today
- New search...