# Hysteretic buck converters

J

#### Joerg

Jan 1, 1970
0
Hello Newsgroup,

Just got the regular TI analog update and there was an article about
hysteretic buck converter chips (page 10, the real page 10, or Acrobat's
page 14):

http://focus.ti.com/lit/an/slyt010b/slyt010b.pdf

Nice concept but the TPS5211 didn't show up anymore at all at TI's site
and the TPS5210 seems to be above $4 on the market. IMHO that's about an order of magnitude too high, way above where I'd even consider it. Is this a case of where something has been kept up there in the "boutique price range"? Regards, Joerg J #### Jim Thompson Jan 1, 1970 0 Hello Newsgroup, Just got the regular TI analog update and there was an article about hysteretic buck converter chips (page 10, the real page 10, or Acrobat's page 14): http://focus.ti.com/lit/an/slyt010b/slyt010b.pdf Nice concept but the TPS5211 didn't show up anymore at all at TI's site and the TPS5210 seems to be above$4 on the market. IMHO that's about an
order of magnitude too high, way above where I'd even consider it.

Is this a case of where something has been kept up there in the
"boutique price range"?

Regards, Joerg

Duh! You can make that type of converter from an LM339. Did it all

...Jim Thompson

S

#### Spehro Pefhany

Jan 1, 1970
0
Hello Newsgroup,

Just got the regular TI analog update and there was an article about
hysteretic buck converter chips (page 10, the real page 10, or Acrobat's
page 14):

http://focus.ti.com/lit/an/slyt010b/slyt010b.pdf

Nice concept but the TPS5211 didn't show up anymore at all at TI's site
and the TPS5210 seems to be above $4 on the market. IMHO that's about an order of magnitude too high, way above where I'd even consider it. Is this a case of where something has been kept up there in the "boutique price range"? I notice that Natsemi has jacked up the prices of their LM500x hysteretic converters by over 60% (1K price in USD). What's with those guys, they want to abandon the low end analog to others? Best regards, Spehro Pefhany J #### Joerg Jan 1, 1970 0 Hello Spehro, I notice that Natsemi has jacked up the prices of their LM500x hysteretic converters by over 60% (1K price in USD). That's are sure-fire way to kill a technology. It is what has brought down switched capacitor filters, IMHO. The chips were too expensive. I used them in exactly one design. What's with those guys, they want to abandon the low end analog to others? I don't understand the marketing logic behind that either. Abandoning the low end would be like Toyota abandoning their Corolla (which is a nice car). It's hard to come up with even a brief list of companies that has survived such strategy over for long. Regards, Joerg J #### Joerg Jan 1, 1970 0 Hello Jim, Duh! You can make that type of converter from an LM339. Did it all the time at GenRad, 1977-1987. So did I and still do, although I prefer logic chips. Looking back at all my switcher designs I'd bet that >50% did not contain any PWM chip. But it's a bit more involved than a lone LM339. For a sufficiently high frequency and small magnetics you need brawny drivers (hence logic chips) and some dead-time control for a synchronous scheme. BTW, was that the switcher where a guy convinced you that the design wasn't fool-proof by rocking the power switch up and down until the guts blew out? Regards, Joerg J #### John Larkin Jan 1, 1970 0 Hello Newsgroup, Just got the regular TI analog update and there was an article about hysteretic buck converter chips (page 10, the real page 10, or Acrobat's page 14): http://focus.ti.com/lit/an/slyt010b/slyt010b.pdf Nice concept but the TPS5211 didn't show up anymore at all at TI's site and the TPS5210 seems to be above$4 on the market. IMHO that's about an
order of magnitude too high, way above where I'd even consider it.

Is this a case of where something has been kept up there in the
"boutique price range"?

Regards, Joerg

Hysteretic buck is probably the oldest and simplest switcher topology
of all. I did these in the early 70's, using an uncompensated LM709 as
the comparator and a PNP-NPN pair (2N2905 PNP driving a nonsaturating
2N3055.) I can't imagine why this would be any more expensive than any
other topology.

John

J

#### Jim Thompson

Jan 1, 1970
0
Hello Jim,

So did I and still do, although I prefer logic chips. Looking back at
all my switcher designs I'd bet that >50% did not contain any PWM chip.

But it's a bit more involved than a lone LM339. For a sufficiently high
frequency and small magnetics you need brawny drivers (hence logic
chips) and some dead-time control for a synchronous scheme.

I'm of the "iron" school ;-) (At least for simple-minded buck
designs.)
BTW, was that the switcher where a guy convinced you that the design
wasn't fool-proof by rocking the power switch up and down until the guts
blew out?

Regards, Joerg

No. The one that blew was an off-line switcher... straight from
110VAC rectified into a bridge inverter.

...Jim Thompson

J

#### Joerg

Jan 1, 1970
0
Hello Jim,
I'm of the "iron" school ;-) (At least for simple-minded buck
designs.)

I never quite warmed up to laminate cores. So I guess I am a "ferrite"
guy. Unless you count iron powder into the iron class but I've never
used much of that in designs either. Always tried to keep things at
least above the audible range of dogs and cats.

Back at the university there was an unspoken rule not to run heavy stuff
below 80kHz. That's because there is a time signal transmission at
77.5kHz (similar to our 60kHz WWVB) and some places use that for
calibration and sync purposes.

Regards, Joerg

J

#### Joerg

Jan 1, 1970
0
Hello John,
Hysteretic buck is probably the oldest and simplest switcher topology
of all. I did these in the early 70's, using an uncompensated LM709 as
the comparator and a PNP-NPN pair (2N2905 PNP driving a nonsaturating
2N3055.) I can't imagine why this would be any more expensive than any
other topology.

That's another reason why I don't understand how they could possibly ask
so much money for these chips. One of their chips gets around the ESR
issue with hysteretic converters to keep the frequency in check but
AFAICT it vanished.

Regards, Joerg

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