Favorite Buck Regulators

On 18 Nov., 00:56, Joerg <inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:

On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott <t...@seemywebsite.com
wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.

So -- who do you think is best, and why?  I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas".  If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them.  Simulation is a big factor.  I've had good
luck with TI, too.

LT certainly is nice.  I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").

Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--
Click to expand...
I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...

Regards

Klaus
 
On Fri, 18 Nov 2011 08:11:56 -0500, Rich Webb
<bbew.ar@mapson.nozirev.ten> wrote:

On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even pretends
to sell analog circuit parts sells these, with a wide variety of price
ranges, features, etc.

So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly bad
about supply hiccups -- mention that, too.

It depends on what the meaning of 24V is. For operating on a shipboard
24V DC bus (Unclean! Unclean!) we generally go with a string of fuses,
transorbs, & filters into a potted module from, e.g., GAIA (MGDSI-04)
down to 5V, and then a linear to bring that down to a quiet Vdd for the
processor. The 5V bus also goes to the less demanding components.
Click to expand...
Yup. In that kind of situation, you really want some significant
margin on whatever circuit you use to allow for the Transzorbs etc.
some room to do their clamping. There are a couple of chips that can
take 80-100V input, and they would be easy to protect, but it's also
possible to just add a regulator and use an external switch as in the
off-line (and many telecom 48V input) switchers.
 
On Nov 17, 4:35 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott <t...@seemywebsite.com
wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.

So -- who do you think is best, and why?  I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas".  If anyone has been particularly
bad about supply hiccups -- mention that, too.

LTC, if you can afford them.  Simulation is a big factor.  I've had good
luck with TI, too.

LT certainly is nice.  I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").

--www.wescottdesign.com- Hide quoted text -

- Show quoted text -
Click to expand...
Okay, what is it this time that's not "exactly in line with what the
regulator was designed for" ?
 
On Fri, 18 Nov 2011 08:36:58 -0800, Fred Bloggs wrote:

On Nov 17, 4:35 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott
t...@seemywebsite.com> wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide
variety of price ranges, features, etc.

So -- who do you think is best, and why?  I'm mostly looking for
parts that actually work the way that the data sheet says they will,
and that don't have any really bad "gotchas".  If anyone has been
particularly bad about supply hiccups -- mention that, too.

LTC, if you can afford them.  Simulation is a big factor.  I've had
good luck with TI, too.

LT certainly is nice.  I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been
doing something exactly in line with what the regulator was designed
for I may have had a different answer -- but I still didn't like the
attitude of "oh just use our design tools, you don't actually have to
understand what our products do").

--www.wescottdesign.com- Hide quoted text -

- Show quoted text -

Okay, what is it this time that's not "exactly in line with what the
regulator was designed for" ?
Click to expand...
This time, nothing. That time, I wanted to be able to adjust the
regulator output from a DAC, and I wanted to verify that it didn't have
any nasty transients.

--
www.wescottdesign.com
 
On Fri, 18 Nov 2011 00:12:37 -0600, Vladimir Vassilevsky wrote:

Tim Wescott wrote:

24V --> 3.3V, around 250mA, good enough for digital.

MAXIM is good
except for that is from MAXIM
Click to expand...
:)

--
www.wescottdesign.com
 
On Fri, 18 Nov 2011 08:11:56 -0500, Rich Webb wrote:

On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott <tim@seemywebsite.com
wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.

So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.

It depends on what the meaning of 24V is. For operating on a shipboard
24V DC bus (Unclean! Unclean!) we generally go with a string of fuses,
transorbs, & filters into a potted module from, e.g., GAIA (MGDSI-04)
down to 5V, and then a linear to bring that down to a quiet Vdd for the
processor. The 5V bus also goes to the less demanding components.
Click to expand...
The 24V is coming from a switching regulator about two inches away from
the board, in a quiet environment. So I would expect that it's pretty
clean.

--
www.wescottdesign.com
 
On Nov 18, 1:53 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Fri, 18 Nov 2011 08:36:58 -0800, Fred Bloggs wrote:
On Nov 17, 4:35 pm, Tim Wescott <t...@seemywebsite.com> wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott
t...@seemywebsite.com> wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide
variety of price ranges, features, etc.

So -- who do you think is best, and why?  I'm mostly looking for
parts that actually work the way that the data sheet says they will,
and that don't have any really bad "gotchas".  If anyone has been
particularly bad about supply hiccups -- mention that, too.

LTC, if you can afford them.  Simulation is a big factor.  I've had
good luck with TI, too.

LT certainly is nice.  I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been
doing something exactly in line with what the regulator was designed
for I may have had a different answer -- but I still didn't like the
attitude of "oh just use our design tools, you don't actually have to
understand what our products do").

--www.wescottdesign.com-Hide quoted text -

- Show quoted text -

Okay, what is it this time that's not "exactly in line with what the
regulator was designed for" ?

This time, nothing.  That time, I wanted to be able to adjust the
regulator output from a DAC, and I wanted to verify that it didn't have
any nasty transients.

--www.wescottdesign.com- Hide quoted text -

- Show quoted text -
Click to expand...
Seems straightforward with something like http://www.national.com/ds/LM/LMR24210.pdf
which is stable over a wide range of both line and output voltages.
Can't really use a DAC, but certainly a digital pot for the feedback
resistors gets you to the same place.
 
Klaus Kragelund wrote:
On 18 Nov., 00:56, Joerg <inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott <t...@seemywebsite.com
wrote:
24V --> 3.3V, around 250mA, good enough for digital.
There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.
So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them. Simulation is a big factor. I've had good
luck with TI, too.
LT certainly is nice. I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").
Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--

I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...
Click to expand...
Be happy that it only went "blurp". I had a LDO from them, client
insisted on using it against my advice. Long story short it had an
undocumented flaw. I gradually raised the source impedance during
testing ... *KABLAM* ... a capacitor vaporized. Turns out it burst into
oscillation when you got above a certain limit. The datasheet was
completely silent about this.

--
Regards, Joerg

http://www.analogconsultants.com/
 
On Nov 18, 1:30 am, Gerhard Hoffmann <dk...@arcor.de> wrote:
On 11/18/2011 12:31 AM, John Miles, KE5FX wrote:

On Nov 17, 11:47 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
NS is #1 in performance in every product line they produce.

That's an interesting assertion, to say the least.

If you are after low phase noise (and methinks you are),
then some of their CLC-family CFB Opamps are hard to beat.

And they have really nice _fast_ ADCs.

73, Gerhard
Click to expand...
Mostly I'm thinking of how they allowed their LMX23xx line of PLL
chips to be steamrolled by Analog Devices. There may be some other
categories where NatSemi doesn't hold the #1 position in chip
performance, but that's the one that came to mind first.

They do have some great RF ADCs but it's not easy to point at one ADC
and say it's uniformly "better" than another. There are too many
different parameters and too many different applications... and
sometimes the most important attributes aren't mentioned on the data
sheet.

-- john
 
On 11/18/2011 3:10 PM, Joerg wrote:
Klaus Kragelund wrote:
On 18 Nov., 00:56, Joerg<inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott<t...@seemywebsite.com
wrote:
24V --> 3.3V, around 250mA, good enough for digital.
There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.
So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them. Simulation is a big factor. I've had good
luck with TI, too.
LT certainly is nice. I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").
Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--

I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...


Be happy that it only went "blurp". I had a LDO from them, client
insisted on using it against my advice. Long story short it had an
undocumented flaw. I gradually raised the source impedance during
testing ... *KABLAM* ... a capacitor vaporized. Turns out it burst into
oscillation when you got above a certain limit. The datasheet was
completely silent about this.
Click to expand...
And they haven't fixed it in roughly 10 years. We had an undocumented
problem as well. Not exactly the same as yours, but caused us to
eliminate the Simple Switcher as a contender. We never looked back.
 
John Miles, KE5FX wrote:
On Nov 18, 1:30 am, Gerhard Hoffmann <dk...@arcor.de> wrote:
On 11/18/2011 12:31 AM, John Miles, KE5FX wrote:

On Nov 17, 11:47 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
NS is #1 in performance in every product line they produce.
That's an interesting assertion, to say the least.
If you are after low phase noise (and methinks you are),
then some of their CLC-family CFB Opamps are hard to beat.

And they have really nice _fast_ ADCs.

73, Gerhard

Mostly I'm thinking of how they allowed their LMX23xx line of PLL
chips to be steamrolled by Analog Devices. ...
Click to expand...

Somebody quoted a saying, maybe in this group. It went something like
this: When you are about to get hit by a steamroller you can either
become part of the steamroller or become part of the road :)

--
Regards, Joerg

http://www.analogconsultants.com/
 
On 11/18/2011 10:09 PM, John Miles, KE5FX wrote:

Mostly I'm thinking of how they allowed their LMX23xx line of PLL
chips to be steamrolled by Analog Devices. There may be some other
categories where NatSemi doesn't hold the #1 position in chip
performance, but that's the one that came to mind first.
Click to expand...
If you want low phase noise PLLs, you don't go to NS or AD.
You go to Peregrine and Hittite.


They do have some great RF ADCs but it's not easy to point at one ADC
and say it's uniformly "better" than another. There are too many
different parameters and too many different applications... and
sometimes the most important attributes aren't mentioned on the data
sheet.
Click to expand...
Come on. You have your sampling frequency, RF or IF frequency
and the available SFDR. That pretty much sorts it out. It's fun
enough to team drivers of company A with ADCs from B. And if your
sample clock generator is not good enough, you won't see the
difference at all.


regards, Gerhard
 
On Nov 18, 7:41 am, Klaus Kragelund <klausk...@hotmail.com> wrote:
On 18 Nov., 00:56, Joerg <inva...@invalid.invalid> wrote:





Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:

On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott <t...@seemywebsite.com
wrote:

24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.

So -- who do you think is best, and why?  I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas".  If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them.  Simulation is a big factor.  I've had good
luck with TI, too.

LT certainly is nice.  I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").

Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--

I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...

Regards

Klaus- Hide quoted text -

- Show quoted text -
Click to expand...
That one is a voltage mode control which is always risky. I still find
your story hard to believe. Now if you experienced it with the
evaluation board, I'd say NS had a problem, but if not, it was most
likely something you overlooked.
 
On Nov 18, 4:39 pm, Gerhard Hoffmann <dk...@arcor.de> wrote:
On 11/18/2011 10:09 PM, John Miles, KE5FX wrote:

Mostly I'm thinking of how they allowed their LMX23xx line of PLL
chips to be steamrolled by Analog Devices.  There may be some other
categories where NatSemi doesn't hold the #1 position in chip
performance, but that's the one that came to mind first.

If you want low phase noise PLLs, you don't go to NS or AD.
You go to Peregrine and Hittite.
Click to expand...
Hittite's HBT parts are great in certain respects but they bring a
different set of compromises, compared to the CMOS parts from AD and
NS. They have historically needed much more power, for instance.

Either way, the availability of "better" chips from Hittite and
Peregrine would move National down the leader board to #3 or #4 in the
PLL performance category, knocking them out of the second-place slot
beneath the ADF4xxx parts.

Come on. You have your sampling frequency, RF or IF frequency
and the available SFDR. That pretty much sorts it out. It's fun
enough to team drivers of company A with ADCs from B. And if your
sample clock generator is not good enough, you won't see the
difference at all.
Click to expand...
True enough for a lot of applications. Others, like phase
comparators, are affected by some of the more obscure specs. Thermal
stability is important, as are certain under-documented properties of
the sample/hold front end. Even the effect of clock noise on jitter
performance is one of those things that isn't quite as simple as the
data sheets make it look.

-- john
 
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:cqydnak6KboiS1jTnZ2dnUVZ_jOdnZ2d@supernews.com...
(I still have a dozen or so LH0063 "Damn fast buffer amplifiers" in my
drawer. Best data sheet
_ever_.)
Click to expand...
That *was* a good datasheet. I wonder if the writers went off to work at
LT?

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
 
On Nov 17, 5:18 pm, Tim Wescott <t...@seemywebsite.com> wrote:
24V --> 3.3V, around 250mA, good enough for digital.

There are a bazillion out there -- it seems like anyone who even pretends
to sell analog circuit parts sells these, with a wide variety of price
ranges, features, etc.

So -- who do you think is best, and why?  I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas".  If anyone has been particularly bad
about supply hiccups -- mention that, too.

--www.wescottdesign.com
Click to expand...
I am finishing a desing with LM2574 wich is a 40 V in, 3.3 V
(LM2574-3.3) x 0.5 A out, SMD and DIP-8 packages are available. I have
seen it in other commercial designs as well. Hope it helps!
 
On Fri, 18 Nov 2011 17:01:22 -0600, John S <sophi.2@invalid.org>
wrote:

On 11/18/2011 3:10 PM, Joerg wrote:
Klaus Kragelund wrote:
On 18 Nov., 00:56, Joerg<inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott<t...@seemywebsite.com
wrote:
24V --> 3.3V, around 250mA, good enough for digital.
There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.
So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them. Simulation is a big factor. I've had good
luck with TI, too.
LT certainly is nice. I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").
Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--

I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...


Be happy that it only went "blurp". I had a LDO from them, client
insisted on using it against my advice. Long story short it had an
undocumented flaw. I gradually raised the source impedance during
testing ... *KABLAM* ... a capacitor vaporized. Turns out it burst into
oscillation when you got above a certain limit. The datasheet was
completely silent about this.


And they haven't fixed it in roughly 10 years. We had an undocumented
problem as well. Not exactly the same as yours, but caused us to
eliminate the Simple Switcher as a contender. We never looked back.
Click to expand...
Gentlemen. Could we please have some part numbers? They are printed on
the bodies of the parts in question.

I dispise gossip, but dislike buggy parts a lot worse.

RL
 
On 11/19/2011 12:42 PM, legg wrote:
On Fri, 18 Nov 2011 17:01:22 -0600, John S<sophi.2@invalid.org
wrote:

On 11/18/2011 3:10 PM, Joerg wrote:
Klaus Kragelund wrote:
On 18 Nov., 00:56, Joerg<inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott<t...@seemywebsite.com
wrote:
24V --> 3.3V, around 250mA, good enough for digital.
There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.
So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them. Simulation is a big factor. I've had good
luck with TI, too.
LT certainly is nice. I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").
Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--

I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...


Be happy that it only went "blurp". I had a LDO from them, client
insisted on using it against my advice. Long story short it had an
undocumented flaw. I gradually raised the source impedance during
testing ... *KABLAM* ... a capacitor vaporized. Turns out it burst into
oscillation when you got above a certain limit. The datasheet was
completely silent about this.


And they haven't fixed it in roughly 10 years. We had an undocumented
problem as well. Not exactly the same as yours, but caused us to
eliminate the Simple Switcher as a contender. We never looked back.

Gentlemen. Could we please have some part numbers? They are printed on
the bodies of the parts in question.

I dispise gossip, but dislike buggy parts a lot worse.

RL
Click to expand...
Sorry I don't have a part number. As I said, that was 10 years ago. I
just remember that it was a three-terminal plastic package similar to a
to-220 and was called Simple Switcher.
 
legg wrote:
On Fri, 18 Nov 2011 17:01:22 -0600, John S <sophi.2@invalid.org
wrote:

On 11/18/2011 3:10 PM, Joerg wrote:
Klaus Kragelund wrote:
On 18 Nov., 00:56, Joerg<inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott<t...@seemywebsite.com
wrote:
24V --> 3.3V, around 250mA, good enough for digital.
There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.
So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them. Simulation is a big factor. I've had good
luck with TI, too.
LT certainly is nice. I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").
Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--
I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...

Be happy that it only went "blurp". I had a LDO from them, client
insisted on using it against my advice. Long story short it had an
undocumented flaw. I gradually raised the source impedance during
testing ... *KABLAM* ... a capacitor vaporized. Turns out it burst into
oscillation when you got above a certain limit. The datasheet was
completely silent about this.

And they haven't fixed it in roughly 10 years. We had an undocumented
problem as well. Not exactly the same as yours, but caused us to
eliminate the Simple Switcher as a contender. We never looked back.

Gentlemen. Could we please have some part numbers? They are printed on
the bodies of the parts in question.

I dispise gossip, but dislike buggy parts a lot worse.
Click to expand...
It's been very long ago but IIRC mine was the LM2931. Another part where
I have experienced unexpected pathologies not so long ago (in 2006) was
the TPS71550, also related to input impedance issues. Considering that
this thing is advertized for ultra low power that is a rather sad state
of affairs.

Long story short I despise LDOs and advise clients not to use LDOs.
Occasionally I am overruled but then at least I've told them :)

--
Regards, Joerg

http://www.analogconsultants.com/
 
On Sat, 19 Nov 2011 12:06:02 -0800, Joerg <invalid@invalid.invalid>
wrote:

legg wrote:
On Fri, 18 Nov 2011 17:01:22 -0600, John S <sophi.2@invalid.org
wrote:

On 11/18/2011 3:10 PM, Joerg wrote:
Klaus Kragelund wrote:
On 18 Nov., 00:56, Joerg<inva...@invalid.invalid> wrote:
Tim Wescott wrote:
On Thu, 17 Nov 2011 13:51:35 -0600, k...@att.bizzzzzzzzzzzz wrote:
On Thu, 17 Nov 2011 13:18:21 -0600, Tim Wescott<t...@seemywebsite.com
wrote:
24V --> 3.3V, around 250mA, good enough for digital.
There are a bazillion out there -- it seems like anyone who even
pretends to sell analog circuit parts sells these, with a wide variety
of price ranges, features, etc.
So -- who do you think is best, and why? I'm mostly looking for parts
that actually work the way that the data sheet says they will, and that
don't have any really bad "gotchas". If anyone has been particularly
bad about supply hiccups -- mention that, too.
LTC, if you can afford them. Simulation is a big factor. I've had good
luck with TI, too.
LT certainly is nice. I had a National apps engineer tell me flat out
that they didn't have behavioral SPICE models of their switching
controllers, and that I should just use their web tool -- which lead me
to tell him flat out that National had just lost a sale (had I been doing
something exactly in line with what the regulator was designed for I may
have had a different answer -- but I still didn't like the attitude of
"oh just use our design tools, you don't actually have to understand what
our products do").
Just for kicks I had used Webbench on a few of my projects. Every single
one of them came back as impossible to build. Yet oodles of them have
come out of various production facilities over the years :)

--
I second that.

On a project that needed to finish quickly it was the easy path.

We used the National LM2267x and KM267x simple switchers. They should
be called trouble switchers. Designed it according to the
recommendations, and they would overshoot at startup, overshoot at
shutdown too. At a certain input voltage the controller just lost
control of the FET and a big blurp.

I am never going to use national switcher parts again...

Be happy that it only went "blurp". I had a LDO from them, client
insisted on using it against my advice. Long story short it had an
undocumented flaw. I gradually raised the source impedance during
testing ... *KABLAM* ... a capacitor vaporized. Turns out it burst into
oscillation when you got above a certain limit. The datasheet was
completely silent about this.

And they haven't fixed it in roughly 10 years. We had an undocumented
problem as well. Not exactly the same as yours, but caused us to
eliminate the Simple Switcher as a contender. We never looked back.

Gentlemen. Could we please have some part numbers? They are printed on
the bodies of the parts in question.

I dispise gossip, but dislike buggy parts a lot worse.


It's been very long ago but IIRC mine was the LM2931. Another part where
I have experienced unexpected pathologies not so long ago (in 2006) was
the TPS71550,
Click to expand...
"Leakage Null Control Circuit" ?? Bwahahahahahaha!

also related to input impedance issues. Considering that
this thing is advertized for ultra low power that is a rather sad state
of affairs.

Long story short I despise LDOs and advise clients not to use LDOs.
Occasionally I am overruled but then at least I've told them :)
Click to expand...
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
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