Getting Hysterical over the Hysteretic Buck Controller

[D from BC]

I've taken an interest in Hysteretic controllers..

An old 1994 article:
http://www.edn.com/archives/1994/042894/09df3.htm#ref

Which lead me to the old Cherry Semiconductor CS-322 hysteretic
current mode controller.
Datasheet on:
http://www.datasheetcatalog.com/datasheets_pdf/C/S/3/2/CS322.sht
ml

What similiar/better hysteretic chips are now in production?
I looked a bit on the NatSemi site, ON semi, Vishay and Maxim
sites.
Maybe I missed it...

I'm looking for the following chip contents:
2 internal comparators configured for hysteretic control
1 FF
1 internal bandgap ref
1 N channel MOSFET driver
1 op amp for current sensing

Can't help but think that if I can't find it...I'm looking for
the wrong thing.

This is for my idea for controlling a 130W 100V Cuk convertor.

Any hints?
Ridicule welcome..but it has to be funny...

 

[Paul Mathews]

I've taken an interest in Hysteretic controllers..

An old 1994 article:http://www.edn.com/archives/1994/042894/09df3.htm#ref

Which lead me to the old Cherry Semiconductor CS-322 hysteretic
current mode controller.
Datasheet on:http://www.datasheetcatalog.com/datasheets_pdf/C/S/3/2/CS322.sht
ml

What similiar/better hysteretic chips are now in production?
I looked a bit on the NatSemi site, ON semi, Vishay and Maxim
sites.
Maybe I missed it...

I'm looking for the following chip contents:
2 internal comparators configured for hysteretic control
1 FF
1 internal bandgap ref
1 N channel MOSFET driver
1 op amp for current sensing

Can't help but think that if I can't find it...I'm looking for
the wrong thing.

This is for my idea for controlling a 130W 100V Cuk convertor.

Any hints?
Ridicule welcome..but it has to be funny...

National and TI both offer hysteretic control ICs, which have the very
rapid response times required for modern CPU loads and have thus had a
revival in popularity. However, the non-constant switching frequency
and sensitivity to output capacitor characteristics are aggravating,
and National seems to be pushing what they're calling 'emulated current
mode' more now. For one example, see LM3475, LM3489, LM3485 for
examples of hysteretic controllers.
Paul Mathews

 

[D from BC]

I've taken an interest in Hysteretic controllers..

An old 1994 article:http://www.edn.com/archives/1994/042894/09df3.htm#ref

Which lead me to the old Cherry Semiconductor CS-322 hysteretic
current mode controller.
Datasheet on:http://www.datasheetcatalog.com/datasheets_pdf/C/S/3/2/CS322.
sht
ml

What similiar/better hysteretic chips are now in production?
I looked a bit on the NatSemi site, ON semi, Vishay and Maxim
sites.
Maybe I missed it...

I'm looking for the following chip contents:
2 internal comparators configured for hysteretic control
1 FF
1 internal bandgap ref
1 N channel MOSFET driver
1 op amp for current sensing

Can't help but think that if I can't find it...I'm looking for
the wrong thing.

This is for my idea for controlling a 130W 100V Cuk convertor.

Any hints?
Ridicule welcome..but it has to be funny...

National and TI both offer hysteretic control ICs, which have
the very
rapid response times required for modern CPU loads and have thus
had a
revival in popularity. However, the non-constant switching
frequency
and sensitivity to output capacitor characteristics are
aggravating,
and National seems to be pushing what they're calling 'emulated
current
mode' more now. For one example, see LM3475, LM3489, LM3485 for
examples of hysteretic controllers.
Paul Mathews

..
-------------
I came across the NatSemi numbers above.. Those IC's drive P
FETS..Prefer N FET drive.

Checked out TI's hysteretic controllers and found the TI
"monster" 28 pin TPS5210 hysteretic controller for powering
microprocessors. Wayy to many goodies for my app.

I'll keep hammering on the TI and NatSemi sites.

Thanks..

 

[Paul Mathews]

On Jan 2, 12:24 am, [email protected] (D from BC) wrote:> I've taken an interest in Hysteretic controllers..






the very
rapid response times required for modern CPU loads and have thus
had a
revival in popularity. However, the non-constant switching
frequency
and sensitivity to output capacitor characteristics are
aggravating,
and National seems to be pushing what they're calling 'emulated
current
mode' more now. For one example, see LM3475, LM3489, LM3485 for
examples of hysteretic controllers.
Paul Mathews

.
-------------
I came across the NatSemi numbers above.. Those IC's drive P
FETS..Prefer N FET drive.

Checked out TI's hysteretic controllers and found the TI
"monster" 28 pin TPS5210 hysteretic controller for powering
microprocessors. Wayy to many goodies for my app.

I'll keep hammering on the TI and NatSemi sites.

Of course, power supply controllers intended for CPUs are complex these
days, so have high pin-count. The low-end types from National target
low-cost and small size, so they drive P-FETs. There's usually no good
reason to avoid P-FETs for low voltage applications these days. Tiny
and inexpensive PFETs are avaiable from IR, Fairchild, Infineon, etc.
The NFET alternative, for buck controllers, usually requires a charge
pump to derive gate drive bias, which has its own costs. Again, if you
do go the hysteretic route, take care to observe cautions about output
cap characteristics. This may include your bypass caps, unless you
isolate the load with an additional inductor.
Paul Mathews

 

[D from BC]

-------------

I came across the NatSemi numbers above.. Those IC's drive P
FETS..Prefer N FET drive.

Checked out TI's hysteretic controllers and found the TI
"monster" 28 pin TPS5210 hysteretic controller for powering
microprocessors. Wayy to many goodies for my app.

I'll keep hammering on the TI and NatSemi sites.

Of course, power supply controllers intended for CPUs are
complex these
days, so have high pin-count. The low-end types from National
target
low-cost and small size, so they drive P-FETs. There's usually
no good
reason to avoid P-FETs for low voltage applications these days.
Tiny
and inexpensive PFETs are avaiable from IR, Fairchild, Infineon,
etc.
The NFET alternative, for buck controllers, usually requires a
charge
pump to derive gate drive bias, which has its own costs. Again,
if you
do go the hysteretic route, take care to observe cautions about
output
cap characteristics. This may include your bypass caps, unless
you
isolate the load with an additional inductor.
Paul Mathews

Thanks..- Hide quoted text -- Show quoted text -

--------------
"Hide and show" text??? Ooops...don't know if I'm breaking some
netiquette..

The N fet drive is preferred because the buck hysteretic
controller is going to be forced into use as a Cuk controller..
(It's like looking for a Cuk in a hay stack of Bucks. )

The Vd in my app is about 300Vpeak. Id is about 2A.
I'm no pro so...I do pad that and use an overated 500V Nmos just
to be sure.
If I recall P MOSFET gets pricy in this performance area.

Unfortunately, I'm starting to lean toward glueing a bunch a
chips together to get the functions I need.
Might be better than searching and forcing a chip into something
it's not designed to do.

D