MC34063 with small inductors
in [Design]
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From: Joerg on 8 Apr 2010 15:41 Jim Thompson wrote: > On Thu, 08 Apr 2010 10:46:22 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Thu, 08 Apr 2010 10:08:49 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> dagmargoodboat(a)yahoo.com wrote: >>>>> On Apr 7, 9:48 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>>> dagmargoodb...(a)yahoo.com wrote: >>>>>>> On Apr 7, 7:06 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>>>>> There's actually three more models around but they essentially behave >>>>>>>> similar. Thing is, the chip is not supposed to turn off the switch >>>>>>>> during the positive ramp because the comparator does not tie into the >>>>>>>> reset input of the register, only the set input. >>>>>>>> <scratching_ head> >>>>>>> Yeah. I read TI's app note. So it can start an ON cycle any time >>>>>>> during ramp up, but can't ever stop until ramp-down. Crude. Burp, >>>>>>> sputter, and cough, in this application. >>>>>> Well, if it did that I'd be happy. But it does cut during ramp-down and >>>>>> according to the internal wire-up it's not supposed to. Helmut >>>>>> Sennewald, one of the LTSpice gurus, could not reproduce the error I >>>>>> saw. Sent him my file, so we'll see. >>>>> It's s'posed to cut off during ramp-down--that's when the flop gets >>>>> reset, unconditionally. So says TI, anyhow. >>>>> >>>>> http://focus.ti.com/lit/an/slva252b/slva252b.pdf >>>>> >>>>> the operative paragraph being the last one pg. 5. And, the last >>>>> comment in Table 1 confirms: >>>>> >>>>> "Output switch conduction is always >>>>> terminated when Ct is ramping down." >>>>> >>>> I know but as shown in my sim plot if is terminated before Ct is ramping >>>> down. That not s'posed to happen. But does, at least according to SPICE. >>> What does it do in the lab? >>> >> I don't know yet. The package just arrived but I have a much more >> pressing problem from an other client to deal with right now. Also a >> chip that seems to not exactly do what I think it should. For that one >> we have lab bench scope plots and the manufacturer is investigating. >> This one simulates alright but chokes in real life. > > Is it happening simultaneous with _on-set_ of ramp-down? > On the 34063? I have simulated the dickens out of that and the comparator never shuts off the switch at onset, just occasionally in the middle of a ramp-up which it ain't supposed to be able to do. And in Hammy's case doesn't do. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 8 Apr 2010 15:51 On Thu, 08 Apr 2010 12:41:49 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Thu, 08 Apr 2010 10:46:22 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Jim Thompson wrote: >>>> On Thu, 08 Apr 2010 10:08:49 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> dagmargoodboat(a)yahoo.com wrote: >>>>>> On Apr 7, 9:48 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>>>> dagmargoodb...(a)yahoo.com wrote: >>>>>>>> On Apr 7, 7:06 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>>>>>> There's actually three more models around but they essentially behave >>>>>>>>> similar. Thing is, the chip is not supposed to turn off the switch >>>>>>>>> during the positive ramp because the comparator does not tie into the >>>>>>>>> reset input of the register, only the set input. >>>>>>>>> <scratching_ head> >>>>>>>> Yeah. I read TI's app note. So it can start an ON cycle any time >>>>>>>> during ramp up, but can't ever stop until ramp-down. Crude. Burp, >>>>>>>> sputter, and cough, in this application. >>>>>>> Well, if it did that I'd be happy. But it does cut during ramp-down and >>>>>>> according to the internal wire-up it's not supposed to. Helmut >>>>>>> Sennewald, one of the LTSpice gurus, could not reproduce the error I >>>>>>> saw. Sent him my file, so we'll see. >>>>>> It's s'posed to cut off during ramp-down--that's when the flop gets >>>>>> reset, unconditionally. So says TI, anyhow. >>>>>> >>>>>> http://focus.ti.com/lit/an/slva252b/slva252b.pdf >>>>>> >>>>>> the operative paragraph being the last one pg. 5. And, the last >>>>>> comment in Table 1 confirms: >>>>>> >>>>>> "Output switch conduction is always >>>>>> terminated when Ct is ramping down." >>>>>> >>>>> I know but as shown in my sim plot if is terminated before Ct is ramping >>>>> down. That not s'posed to happen. But does, at least according to SPICE. >>>> What does it do in the lab? >>>> >>> I don't know yet. The package just arrived but I have a much more >>> pressing problem from an other client to deal with right now. Also a >>> chip that seems to not exactly do what I think it should. For that one >>> we have lab bench scope plots and the manufacturer is investigating. >>> This one simulates alright but chokes in real life. >> >> Is it happening simultaneous with _on-set_ of ramp-down? >> > >On the 34063? I have simulated the dickens out of that and the >comparator never shuts off the switch at onset, just occasionally in the >middle of a ramp-up which it ain't supposed to be able to do. And in >Hammy's case doesn't do. But I can't convince any of these companies to hire me to do high quality modeling... they want me to submit a quote for about the equivalent of one day's work, when it would generally take a week to do a real quality job :-( I guess they really don't care. Have you tried other models for the 34063? So far I've seen two, but haven't had time to try either one yet.... I Usenet while running sims that might pay off :-) ...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 | The only thing bipartisan in this country is hypocrisy
From: Joerg on 8 Apr 2010 15:56 Jim Thompson wrote: > On Thu, 08 Apr 2010 12:41:49 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Thu, 08 Apr 2010 10:46:22 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Jim Thompson wrote: >>>>> On Thu, 08 Apr 2010 10:08:49 -0700, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> dagmargoodboat(a)yahoo.com wrote: >>>>>>> On Apr 7, 9:48 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>>>>> dagmargoodb...(a)yahoo.com wrote: >>>>>>>>> On Apr 7, 7:06 pm, Joerg <inva...(a)invalid.invalid> wrote: >>>>>>>>>> There's actually three more models around but they essentially behave >>>>>>>>>> similar. Thing is, the chip is not supposed to turn off the switch >>>>>>>>>> during the positive ramp because the comparator does not tie into the >>>>>>>>>> reset input of the register, only the set input. >>>>>>>>>> <scratching_ head> >>>>>>>>> Yeah. I read TI's app note. So it can start an ON cycle any time >>>>>>>>> during ramp up, but can't ever stop until ramp-down. Crude. Burp, >>>>>>>>> sputter, and cough, in this application. >>>>>>>> Well, if it did that I'd be happy. But it does cut during ramp-down and >>>>>>>> according to the internal wire-up it's not supposed to. Helmut >>>>>>>> Sennewald, one of the LTSpice gurus, could not reproduce the error I >>>>>>>> saw. Sent him my file, so we'll see. >>>>>>> It's s'posed to cut off during ramp-down--that's when the flop gets >>>>>>> reset, unconditionally. So says TI, anyhow. >>>>>>> >>>>>>> http://focus.ti.com/lit/an/slva252b/slva252b.pdf >>>>>>> >>>>>>> the operative paragraph being the last one pg. 5. And, the last >>>>>>> comment in Table 1 confirms: >>>>>>> >>>>>>> "Output switch conduction is always >>>>>>> terminated when Ct is ramping down." >>>>>>> >>>>>> I know but as shown in my sim plot if is terminated before Ct is ramping >>>>>> down. That not s'posed to happen. But does, at least according to SPICE. >>>>> What does it do in the lab? >>>>> >>>> I don't know yet. The package just arrived but I have a much more >>>> pressing problem from an other client to deal with right now. Also a >>>> chip that seems to not exactly do what I think it should. For that one >>>> we have lab bench scope plots and the manufacturer is investigating. >>>> This one simulates alright but chokes in real life. >>> Is it happening simultaneous with _on-set_ of ramp-down? >>> >> On the 34063? I have simulated the dickens out of that and the >> comparator never shuts off the switch at onset, just occasionally in the >> middle of a ramp-up which it ain't supposed to be able to do. And in >> Hammy's case doesn't do. > > But I can't convince any of these companies to hire me to do high > quality modeling... they want me to submit a quote for about the > equivalent of one day's work, when it would generally take a week to > do a real quality job :-( > Sometimes I have those request as well but never from exisiting clients. If the conversation starts with "We've got something that should be rather trivial for you ..." I can smell it, and usually must decline. > I guess they really don't care. > > Have you tried other models for the 34063? ... Grand total of four, same problem. > ... So far I've seen two, but > haven't had time to try either one yet.... I Usenet while running sims > that might pay off :-) > Same here. But now I've got a li'l RF project for dessert, solder iron time :-) And the last Weller ETS tip just bit the dust, have to see if I can revive that with some sandpaper for now so it'll hang on until Saturday. Did I already say that I hate RoHS solder? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Spehro Pefhany on 8 Apr 2010 16:05 On Thu, 08 Apr 2010 12:56:44 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Did I already say that I hate RoHS solder? You use it even for test circuits?
From: Joerg on 8 Apr 2010 16:31
Spehro Pefhany wrote: > On Thu, 08 Apr 2010 12:56:44 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Did I already say that I hate RoHS solder? > > You use it even for test circuits? > Oh no, never. But I do have clients who market internationally so there's the occasional RoHS board crossing my lab bench. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |