"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message news:p0usmu$hos$1@dont-email.me...> I was using it to make an isolated supply, so I need it to keep on PWMing > under all circumstances. (It was a 'flybuck' design.) The main output > didn't need much current.Ah, kind of thought so. I've done that before, put in a SimpleSwitcher when I meant to use a synchronous one -- I just put a dummy load on the main rail, since efficiency wasn't a problem there. I recall playing with TPS54233 in a coupled buck/neg flyback circuit and seeing it work just fine at most combinations of loads. Load on the negative output (and insufficient load on the positive buck output) draws negative current through the sync rect, which it seems to handle just fine. Or I'm misreporting this because I tested it years ago. I can dig up the proto board if needed. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
Buck regulator chips
Started by ●December 14, 2017
Reply by ●December 14, 20172017-12-14
Reply by ●December 14, 20172017-12-14
"Tim Williams" <tiwill@seventransistorlabs.com> wrote in message news:p0uta5$lsl$1@dont-email.me...> Or I'm misreporting this because I tested it years ago. I can dig up the > proto board if needed....I'm greatly misreporting that, as it's not even a synchronous regulator. :^) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
Reply by ●December 14, 20172017-12-14
On Thu, 14 Dec 2017 09:17:25 -0800, John Larkin <jjlarkin@highlandtechnology.com> wrote:>On Thu, 14 Dec 2017 09:45:17 -0500, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>Modern buck regulators seem to have way too many features that I can't >>turn off or customize. >> >>The otherwise very nice AOZ1282-1 snookered me by having a 600-us fixed >>short-circuit protection interval--it wouldn't start up into a 220 uF >>capacitor, even with a very light load. Fortunately, switching to 22 uF >>fixed it, and I had some with the right footprint. >> >>And then many go into stutter mode at light loads, e.g. the MCP16311. >>Its brother, the MCP16312, is claimed to stay in vanilla PWM mode >>throughout the load range, but the data sheet lies. That bit me once >>when I was trying to make an isolated +24 -> +-5V converter for an >>industrial control system, using two coupled inductors. Simulated >>great, but the undocumented stutter mode of the MCP16312 screwed it up. >> >>Chips these days. >> >>Cheers >> >>Phil Hobbs > >My latest fave is the TPS54302. It's a 6-pin SOT23, nice and dumb, and >behaves very well. > >There is no usable model (Web-bench never works for me) so I had to >breadboard the various compensations, but that's done now.Huh? There's a TINA model AND a PSpice model. The PSpice model should run just fine in LTspice. Oooops! It's encrypted. Sorry about that... I can run it, you can't. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | It's what you learn, after you know it all, that counts.
Reply by ●December 14, 20172017-12-14
On Thu, 14 Dec 2017 15:52:01 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Thu, 14 Dec 2017 09:17:25 -0800, John Larkin ><jjlarkin@highlandtechnology.com> wrote: >[snip]>> >>My latest fave is the TPS54302. It's a 6-pin SOT23, nice and dumb, and >>behaves very well. >> >>There is no usable model (Web-bench never works for me) so I had to >>breadboard the various compensations, but that's done now. > >Huh? There's a TINA model AND a PSpice model. The PSpice model >should run just fine in LTspice. > >Oooops! It's encrypted. Sorry about that... I can run it, you can't. > > ...Jim ThompsonThose of you who build systems with parts from multiple sources should opine, "No _generic_ Spice model, no appearance on the BOM." For me... models are no big deal. When one of my customers wants a custom chip to work along-side an OTS device, but no generic Spice models exists for the OTS device, I simply make creating a Spice model a part of my quote... with the proviso that it can't be published/used elsewhere. My customer gets a system-development advantage... and I get another "One more nose rubbed in the dirt" notch added to my ammo-belt >:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | It's what you learn, after you know it all, that counts.
Reply by ●December 14, 20172017-12-14
>> I was using it to make an isolated supply, so I need it to keep on PWMing >> under all circumstances. (It was a 'flybuck' design.) The main output >> didn't need much current.>Ah, kind of thought so. I've done that before, put in a SimpleSwitcher when >I meant to use a synchronous one -- I just put a dummy load on the main >rail, since efficiency wasn't a problem there.Well, you kind of thought wrong then. ;) The Microchip part is a sync buck, and so would have worked fine if it had really been as the datasheet described. Cheers Phil Hobbs
Reply by ●December 14, 20172017-12-14
On Thu, 14 Dec 2017 17:02:41 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 12/14/2017 04:42 PM, John Larkin wrote: >> On Thu, 14 Dec 2017 14:40:49 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 12/14/2017 12:17 PM, John Larkin wrote: >>>> On Thu, 14 Dec 2017 09:45:17 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> Modern buck regulators seem to have way too many features that I can't >>>>> turn off or customize. >>>>> >>>>> The otherwise very nice AOZ1282-1 snookered me by having a 600-us fixed >>>>> short-circuit protection interval--it wouldn't start up into a 220 uF >>>>> capacitor, even with a very light load. Fortunately, switching to 22 uF >>>>> fixed it, and I had some with the right footprint. >>>>> >>>>> And then many go into stutter mode at light loads, e.g. the MCP16311. >>>>> Its brother, the MCP16312, is claimed to stay in vanilla PWM mode >>>>> throughout the load range, but the data sheet lies. That bit me once >>>>> when I was trying to make an isolated +24 -> +-5V converter for an >>>>> industrial control system, using two coupled inductors. Simulated >>>>> great, but the undocumented stutter mode of the MCP16312 screwed it up. >>>>> >>>>> Chips these days. >>>>> >>>> >>>> My latest fave is the TPS54302. It's a 6-pin SOT23, nice and dumb, and >>>> behaves very well. >>>> >>>> There is no usable model (Web-bench never works for me) so I had to >>>> breadboard the various compensations, but that's done now. >>>> >>>> >>> Looks like a nice part, but distributor stock appears to be very thin. >>> >>> Cheers >>> >>> Phil Hobbs >> >> I'd better check on that. It's very similar to the AOZ part but, of >> course, different pinout. >> >> >Yeah, there's a big run on quite a few chips at the moment, it seems. >The AOZ1282-1 is in "full production" but nobody has any more till at >least January. It's the 400 mA, 1-MHz version of the vanilla 1282, >which is a 1A, 500 kHz part. Faster is nice when you're coming off a >24V rail. > >Cheers > >Phil HobbsWe just nabbed 500 of the TI parts from Arrow. The 54302 works fine making 24 into 5 or 3.3. It gets inefficient making +1 (FPGA core voltage) from 24. For that, I went from 24 to 5, then 5 to 1. The TI claims to run up to 3 amps, and it does, but it gets pretty warm. 2.5 seems more prudent. Not bad for a SOT-23. It's not entirely clear how the heat gets out of this chip, so we hung some copper on everything. https://www.dropbox.com/s/mxjunh0ykivkjys/P5_Regs_1.JPG?raw=1 -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 14, 20172017-12-14
On Thu, 14 Dec 2017 15:52:01 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Thu, 14 Dec 2017 09:17:25 -0800, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >>On Thu, 14 Dec 2017 09:45:17 -0500, Phil Hobbs >><pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>>Modern buck regulators seem to have way too many features that I can't >>>turn off or customize. >>> >>>The otherwise very nice AOZ1282-1 snookered me by having a 600-us fixed >>>short-circuit protection interval--it wouldn't start up into a 220 uF >>>capacitor, even with a very light load. Fortunately, switching to 22 uF >>>fixed it, and I had some with the right footprint. >>> >>>And then many go into stutter mode at light loads, e.g. the MCP16311. >>>Its brother, the MCP16312, is claimed to stay in vanilla PWM mode >>>throughout the load range, but the data sheet lies. That bit me once >>>when I was trying to make an isolated +24 -> +-5V converter for an >>>industrial control system, using two coupled inductors. Simulated >>>great, but the undocumented stutter mode of the MCP16312 screwed it up. >>> >>>Chips these days. >>> >>>Cheers >>> >>>Phil Hobbs >> >>My latest fave is the TPS54302. It's a 6-pin SOT23, nice and dumb, and >>behaves very well. >> >>There is no usable model (Web-bench never works for me) so I had to >>breadboard the various compensations, but that's done now. > >Huh? There's a TINA model AND a PSpice model. The PSpice model >should run just fine in LTspice. > >Oooops! It's encrypted. Sorry about that... I can run it, you can't. > > ...Jim ThompsonThe breadboard worked fine. I hacked an eval board and used the actual caps that we'll use in production. Load current stepping gave me the transient response to tweak the loop compensation. The suggested TI values weren't very close, possibly because of cap ESR issues. The breadboard gave me thermal information that a sim wouldn't. And I enjoy soldering and scoping stuff now and then. I wouldn't really trust the sim anyhow. I wonder if the sim includes the spread-spectrum stuff. I was concerned if the spread-spectrum would show up as noise on the final DC output. Now I know. The SS is pretty radical: https://www.dropbox.com/s/s9aqx1z3glab423/TPS54302_PWM.JPG?raw=1 -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 14, 20172017-12-14
>Those of you who build systems with parts from multiple sources should >opine, "No _generic_ Spice model, no appearance on the BOM."But then you live in a very sheltered world, where foundries live and die by the quality of their libraries, so that a sufficiently skilled and careful worker can be pretty sure that the silicon will adequately match the model. The board-level and (especially) the mixed-technology worlds aren't like that at all. Cheers Phil Hobbs
Reply by ●December 14, 20172017-12-14
On 12/14/2017 07:19 PM, John Larkin wrote:> On Thu, 14 Dec 2017 17:02:41 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 12/14/2017 04:42 PM, John Larkin wrote: >>> On Thu, 14 Dec 2017 14:40:49 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 12/14/2017 12:17 PM, John Larkin wrote: >>>>> On Thu, 14 Dec 2017 09:45:17 -0500, Phil Hobbs >>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>> >>>>>> Modern buck regulators seem to have way too many features that I can't >>>>>> turn off or customize. >>>>>> >>>>>> The otherwise very nice AOZ1282-1 snookered me by having a 600-us fixed >>>>>> short-circuit protection interval--it wouldn't start up into a 220 uF >>>>>> capacitor, even with a very light load. Fortunately, switching to 22 uF >>>>>> fixed it, and I had some with the right footprint. >>>>>> >>>>>> And then many go into stutter mode at light loads, e.g. the MCP16311. >>>>>> Its brother, the MCP16312, is claimed to stay in vanilla PWM mode >>>>>> throughout the load range, but the data sheet lies. That bit me once >>>>>> when I was trying to make an isolated +24 -> +-5V converter for an >>>>>> industrial control system, using two coupled inductors. Simulated >>>>>> great, but the undocumented stutter mode of the MCP16312 screwed it up. >>>>>> >>>>>> Chips these days. >>>>>> >>>>> >>>>> My latest fave is the TPS54302. It's a 6-pin SOT23, nice and dumb, and >>>>> behaves very well. >>>>> >>>>> There is no usable model (Web-bench never works for me) so I had to >>>>> breadboard the various compensations, but that's done now. >>>>> >>>>> >>>> Looks like a nice part, but distributor stock appears to be very thin. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> I'd better check on that. It's very similar to the AOZ part but, of >>> course, different pinout. >>> >>> >> Yeah, there's a big run on quite a few chips at the moment, it seems. >> The AOZ1282-1 is in "full production" but nobody has any more till at >> least January. It's the 400 mA, 1-MHz version of the vanilla 1282, >> which is a 1A, 500 kHz part. Faster is nice when you're coming off a >> 24V rail.> > We just nabbed 500 of the TI parts from Arrow.Which was about 40% of the total world supply at that point. Weird--you don't look at all like Bunker Hunt. ;)> > The 54302 works fine making 24 into 5 or 3.3. It gets inefficient > making +1 (FPGA core voltage) from 24. For that, I went from 24 to 5, > then 5 to 1. > > The TI claims to run up to 3 amps, and it does, but it gets pretty > warm. 2.5 seems more prudent. Not bad for a SOT-23. > > It's not entirely clear how the heat gets out of this chip, so we hung > some copper on everything. > > https://www.dropbox.com/s/mxjunh0ykivkjys/P5_Regs_1.JPG?raw=1Yup, vias are free, pours are cheap, but field fails are _expensive_. BTW we took your advice and standardized on the highest commonly-available wall wart voltage (+24). We use a pretty strict UVLO setting (19V) so that if somebody connects the wrong supply, nothing happens. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●December 14, 20172017-12-14
On Thu, 14 Dec 2017 19:59:23 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 12/14/2017 07:19 PM, John Larkin wrote: >> On Thu, 14 Dec 2017 17:02:41 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 12/14/2017 04:42 PM, John Larkin wrote: >>>> On Thu, 14 Dec 2017 14:40:49 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 12/14/2017 12:17 PM, John Larkin wrote: >>>>>> On Thu, 14 Dec 2017 09:45:17 -0500, Phil Hobbs >>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>> >>>>>>> Modern buck regulators seem to have way too many features that I can't >>>>>>> turn off or customize. >>>>>>> >>>>>>> The otherwise very nice AOZ1282-1 snookered me by having a 600-us fixed >>>>>>> short-circuit protection interval--it wouldn't start up into a 220 uF >>>>>>> capacitor, even with a very light load. Fortunately, switching to 22 uF >>>>>>> fixed it, and I had some with the right footprint. >>>>>>> >>>>>>> And then many go into stutter mode at light loads, e.g. the MCP16311. >>>>>>> Its brother, the MCP16312, is claimed to stay in vanilla PWM mode >>>>>>> throughout the load range, but the data sheet lies. That bit me once >>>>>>> when I was trying to make an isolated +24 -> +-5V converter for an >>>>>>> industrial control system, using two coupled inductors. Simulated >>>>>>> great, but the undocumented stutter mode of the MCP16312 screwed it up. >>>>>>> >>>>>>> Chips these days. >>>>>>> >>>>>> >>>>>> My latest fave is the TPS54302. It's a 6-pin SOT23, nice and dumb, and >>>>>> behaves very well. >>>>>> >>>>>> There is no usable model (Web-bench never works for me) so I had to >>>>>> breadboard the various compensations, but that's done now. >>>>>> >>>>>> >>>>> Looks like a nice part, but distributor stock appears to be very thin. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> >>>> I'd better check on that. It's very similar to the AOZ part but, of >>>> course, different pinout. >>>> >>>> >>> Yeah, there's a big run on quite a few chips at the moment, it seems. >>> The AOZ1282-1 is in "full production" but nobody has any more till at >>> least January. It's the 400 mA, 1-MHz version of the vanilla 1282, >>> which is a 1A, 500 kHz part. Faster is nice when you're coming off a >>> 24V rail. > >> >> We just nabbed 500 of the TI parts from Arrow. > >Which was about 40% of the total world supply at that point. Weird--you >don't look at all like Bunker Hunt. ;)Maybe they will be the next bitcoin.>> >> The 54302 works fine making 24 into 5 or 3.3. It gets inefficient >> making +1 (FPGA core voltage) from 24. For that, I went from 24 to 5, >> then 5 to 1. >> >> The TI claims to run up to 3 amps, and it does, but it gets pretty >> warm. 2.5 seems more prudent. Not bad for a SOT-23. >> >> It's not entirely clear how the heat gets out of this chip, so we hung >> some copper on everything. >> >> https://www.dropbox.com/s/mxjunh0ykivkjys/P5_Regs_1.JPG?raw=1 > >Yup, vias are free, pours are cheap, but field fails are _expensive_. > >BTW we took your advice and standardized on the highest >commonly-available wall wart voltage (+24). We use a pretty strict UVLO >setting (19V) so that if somebody connects the wrong supply, nothing >happens.Yeah, somebody might accidentally plug a 12v wart into a 6v box, but it's unlikely anyone will have anything above 24, so no transzorbs needed. Maybe reverse protection, though. This one is nice, rated 36 watts with good margin. https://www.digikey.com/product-detail/en/cui-inc/SMI36-24-V-P6/102-3833-ND/5417799 Comes with all the international adapters. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
