MC34063 with small inductors
in [Design]
|
From: krw on 6 Apr 2010 21:33 On Tue, 6 Apr 2010 18:12:49 -0700 (PDT), brent <bulegoge(a)columbus.rr.com> wrote: >On Apr 6, 9:10�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- >Web-Site.com> wrote: >> On Tue, 06 Apr 2010 18:00:41 -0700, Joerg <inva...(a)invalid.invalid> >> wrote: >> >> >Hello Folks, >> >> >Have to correct a design with a 34063 in there. Buck, VIN 16-30V, VOUT >> >slightly under 12V, 400mA max output. And no, I don't like it much :-) >> >> >One of the issues is a saturating inductor. Can't change the layout and >> >to be able to cram one in there I probably have to drop down to 47uH, >> >maybe 68uH if lucky. >> >> >SPICE says it's ok but none of the datasheets or app notes recommends >> >going that low. Any reason why not? >> >> Just stick a CD4060 in there. �That oughta fix it ;-) >> >> � � � � � � � � � � � � � � � � � � � � ...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 athttp://www.analog-innovations.com| � �1962 � � | >> >> � � � The only thing bipartisan in this country is hypocrisy > >Won't a 555 do the trick? Hell no. You need a PIC!
From: Tim Williams on 6 Apr 2010 21:51 <krw(a)att.bizzzzzzzzzzzz> wrote in message news:l5onr5toifqtk29575n2hvvq47il966av9(a)4ax.com... >>Won't a 555 do the trick? > > Hell no. You need a PIC! Jan can do it! He's the PIC master! 8-p Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: brent on 6 Apr 2010 22:01 On Apr 6, 9:23 pm, "tm" <no...(a)msc.com> wrote: > "brent" <buleg...(a)columbus.rr.com> wrote in message > > news:91110477-cc99-4dc0-844c-e4322b214131(a)n13g2000vbn.googlegroups.com... > On Apr 6, 9:10 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- > > > > Web-Site.com> wrote: > > On Tue, 06 Apr 2010 18:00:41 -0700, Joerg <inva...(a)invalid.invalid> > > wrote: > > > >Hello Folks, > > > >Have to correct a design with a 34063 in there. Buck, VIN 16-30V, VOUT > > >slightly under 12V, 400mA max output. And no, I don't like it much :-) > > > >One of the issues is a saturating inductor. Can't change the layout and > > >to be able to cram one in there I probably have to drop down to 47uH, > > >maybe 68uH if lucky. > > > >SPICE says it's ok but none of the datasheets or app notes recommends > > >going that low. Any reason why not? > > > Just stick a CD4060 in there. That oughta fix it ;-) > > > ...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 athttp://www.analog-innovations.com|1962 | > > > The only thing bipartisan in this country is hypocrisy > > Won't a 555 do the trick? > > I think it needs an ideal diode. :) and a few 1K pots
From: John Larkin on 6 Apr 2010 22:02 On Tue, 06 Apr 2010 18:00:41 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Hello Folks, > >Have to correct a design with a 34063 in there. Buck, VIN 16-30V, VOUT >slightly under 12V, 400mA max output. And no, I don't like it much :-) > >One of the issues is a saturating inductor. Can't change the layout and >to be able to cram one in there I probably have to drop down to 47uH, >maybe 68uH if lucky. > >SPICE says it's ok but none of the datasheets or app notes recommends >going that low. Any reason why not? What's the frequency? It's spec'd for 100K max. Those old things are slow. With 24 in, 12 out, on time is ~5 usec at 100 KHz. Ripple current into 47 uH is 1.25 A p-p. Not good. It will go seriously discontinuous. Does Spice really approve? If you can't change the layout, push the frequency above spec and go with 68 uH maybe. Best of luck. Or kluge in one of the new National packaged switchers, the dpak ones with inductors and all. John
From: Spehro Pefhany on 6 Apr 2010 22:20
On Tue, 06 Apr 2010 18:00:41 -0700, the renowned Joerg <invalid(a)invalid.invalid> wrote: >Hello Folks, > >Have to correct a design with a 34063 in there. Buck, VIN 16-30V, VOUT >slightly under 12V, 400mA max output. And no, I don't like it much :-) > >One of the issues is a saturating inductor. Can't change the layout and >to be able to cram one in there I probably have to drop down to 47uH, >maybe 68uH if lucky. > >SPICE says it's ok but none of the datasheets or app notes recommends >going that low. Any reason why not? Too slow. IIRC there's somewhat faster (and more expensive) parts that might be pin-compatible at OnSemi. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |