PSA: do not use the TPS61099 boost reg in your designs - Page 1
Forum section: electronics / projects

author: jeremy
author_rank: Super Contributor
timestamp: January 22, 2019, 02:36:36 am
content: Hi all,Just reporting a rather poor experience I have had with a new boost regulator on the market. It works like a normal adjustable boost regulator in that there is a resistor divider to set the output voltage (you can also get fixed devices that have it internally). However, if the rise time on the power supply is too slow or there are glitches, it ignores the feedback loop and goes to maximum duty cycle mode and locks up. For example, using the TPS610995 (which is the only one in a DFN package), instead of boosting my 2.8V supply to 3.6V, it occasionally boosts it to a constant 5.7V on startup. The worst part is that I am using the exact supporting components from the datasheet, with the exact same layout as per the datasheet (well, as close as possible; they don't specify dimensions).Although this part is designed to be connected directly to a battery (they even have a reference design for it!), I have reproduced this problem using the contact bounce of just putting a battery in a holder. I assume that the same thing would happen with a particularly bouncy mechanical switch.I wouldn't be so bothered if it would at least fail safe, rather than failing to max duty cycle and boosting to a high enough voltage to kill everything...More info on the TI forum here:https://e2e.ti.com/support/power-management/f/196/t/756614if you search the forum, it seems I am not the only one who has discovered this problem. But no satisfactory solution seems to exist.I have tried to work around it with a voltage supervisor on the EN pin, but there seems to be a related issue I have found today wherein if the output voltage is higher than the input voltage on startup (for example, output capacitors still charged) the same thing can happen.If anyone has any ideas about how I could work around something like this, I'm all earsThanks,Jeremy

author: Siwastaja
author_rank: Super Contributor
timestamp: January 22, 2019, 06:19:58 am
content: Thanks for warning.Sounds like typical TI engineering. I use their power conversion/management ICs less and less - they are overcomplicated and have excess state space, and therefore tend to hit unwanted states - and a typical "wrong state" tends to mean: blow up everything.In this case, looking at the TI E2E forum posts, it seems like an UVLO event is running some kind of special startup sequence, which blows everything up if happening more than once inside a small time window. The problem is, it's completely normal and unavoidable that UVLO events happen frequently, and it shouldn't cause erratic behavior.These things are IC design equivalents of spaghetti code from a total beginner. If this was a software, a fix would be another overcomplicated "UVLO filter unit" which would reduce the number of issues, but increase complexity again. But ICs can't be updated.

author: Gibson486
author_rank: Frequent Contributor
timestamp: January 22, 2019, 06:29:54 pm
content: That sucks...I have always had good experiences with TI's power chips (not a boost though). That said, I had a horrible experience with their high power op amps...and it was related to the enable pin as well. I have always relied on Linear Tech for boost converter stuff. It can be pricey, but it usually always works.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 22, 2019, 08:32:06 pm
content: Damn, that's good to know. This IC looked interesting on paper.Reading the datasheet, we can see it's got quite a few different modes of operation. Between the soft-start feature, the "down mode", "pass-through", bust mode and synchronous mode... eek, there's probably a lot of cases, depending on how Vin and Vout relate, to make it go bonkers. In your case, I'm guessing it's probably stuck cycling between two of those modes (or more) in an unexpected way. This IC looks like a bunch of good ideas gone bad.Not sure what you can do to get something reliable, short of switching to another boost converter altogether. Maybe select one of the Linear boost converters that have a burst mode and very low quiescent current (although this one will be hard to beat). Never had any problem with them.A zener diode at the output is probably a bit pointless. It may protect your circuit but with the common Zener voltages of 3.6V and 3.9V (off the top of my head), you are likely to be in the diode knee most of the time, wasting unnecessary current... and even if that protects your circuit, I'm not even sure this would get the IC out of this weird mode when it happens, so either way, your device would probably not work properly. Maybe adding a second voltage supervisor at the output with a threshold of say 4V (if 4V is still safe for your circuit), that would disable the boost converter when getting higher than this. But that may just get it into an infinite loop of starting and disabling... and it starts getting a bit much for just one converter. Sucks.

author: PartialDischarge
author_rank: Super Contributor
timestamp: January 22, 2019, 10:16:19 pm
content: Not saying the IC is perfect but I see some fault on your part for not assuring a stable Vin before enabling the converter. You mention connecting directly the battery, or that the same would happen with a switch, but that is not how you are suppose to turn on the converter, that is what the enable pin is for. This chip has true disconnect so the battery is supposed to be connected at all times and use the enable pin to discoonect.First connect the Vin source, of course if the impendance is high an input capacitor helps, then enable the converter. I personally would use a resistive divider in the E pin.I have designed circuits with chained switched converters, and needed to control the enable of each one, assuring that the output of the previous converter was stable.

author: jeremy
author_rank: Super Contributor
timestamp: January 22, 2019, 10:29:48 pm
content: Fair enough mastertech, but the datasheet and reference design doesn’t have anything connected to the EN pin. Seehttp://www.ti.com/lit/ug/tiduee2/tiduee2.pdfYou make a good point about the resistor divider, I’ll need to think about that more.In the “test setup” section, it even says to specifically connect the EN pin to Vin *before* applying power (I’ve also tested what happens when the EN pin is floating; it ain’t pretty)I don’t think it would be too much of a stretch to see this happening upon connecting a battery using a connector, or when using a depleted cell with a bursty load like a cellular radio. You can only increase input capacitance so much, and given the primary package of this device is a CSBGA I can’t imagine they expect you to use a bunch of bulky electrolytic caps.

author: PartialDischarge
author_rank: Super Contributor
timestamp: January 22, 2019, 10:37:36 pm
content: Caps are only needed if you are using a weak battery with lowish mAh. That helps at the startup.The EN pin can be connected directly to Vin only for a source that has enough low impendance to turn on the converter, and that doesnt seem to be your case.In summary, your problem lies in the low energy of your battery, so you will have to use input caps + control the EN pin.

author: jeremy
author_rank: Super Contributor
timestamp: January 22, 2019, 10:48:57 pm
content: Although I agree on the overall cause, we will have to agree to disagree on the scenario it occurs in. In particular, the chemistry of the cells used in the reference design are intended to be extremely long life and as such are installed in difficult to reach places. My experience is that due to this, they are used until they are completely and utterly dead, so at the end of this cycle you will almost certainly have a cell with very poor impedance which no reasonable amount of capacitance will save you from. In this case, a low mAh cell is the same as a depleted one.

author: PartialDischarge
author_rank: Super Contributor
timestamp: January 22, 2019, 10:56:13 pm
content: But the reference design, unless I read wrongly, only starts up once. It is a very low Iq design designed to be on forever. The problem lies at the startup in these converters, always, not in steady state.If you can’t change the requirement that your system be turned on by connecting a battery repeatedly, then you have 2 choices, come up with a way of controlling the EN pin in an effective manner, or choose a boost converter with a programmable soft-start, that allows very looooong startup time.

author: iMo
author_rank: Super Contributor
timestamp: January 22, 2019, 11:00:07 pm
content: The DS Fig23 shows a nice sharp Vin leading edgeBtw - I was using the similarhttps://datasheets.maximintegrated.com/en/ds/MAX1722-MAX1724.pdf- except lower Iout and almost 20y old.Also it was not so easy to get what it claimed - the efficiency achieved with some special L and C types/materials only. But it worked from 0.5V up, as I can remember, and the package was easy to solder..

author: jeremy
author_rank: Super Contributor
timestamp: January 22, 2019, 11:01:34 pm
content: Quote from: MasterTech on January 22, 2019, 10:56:13 pmYes, the reference design is sort of only intended to startup until the battery is depleted, but the contact bounce of connecting the battery initially could cause the issue. Also, “forever” is relative, a typical cellular modem in this configuration will draw 100mA for many seconds (I’ve measured it). Forever could be years, yes, but not literally forever.

author: Bud
author_rank: Super Contributor
timestamp: January 22, 2019, 11:16:29 pm
content: I am suggesting we start from where you sourced the parts. If out of eBay or Aliexpress, the conversation should end right there.

author: tszaboo
author_rank: Super Contributor
timestamp: January 22, 2019, 11:26:27 pm
content: These converters sometimes go through a silicon revision. If there is a TPS61099A arriving, that is basically TI improving on it's silicon to avoid this. It wouldnt be the first time, and wont be the last.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 22, 2019, 11:28:37 pm
content: Quote from: Siwastaja on January 22, 2019, 06:19:58 amThis, this and ALL OF THIS!!!It's a bloody switcher, what does it need all that logic for? Do they start with an MCU and strip out unused bits? Just look:https://zeptobars.com/en/read/Ti-TPS62321-3-MHz-Step-Down-Chip-Scale-CSPThey're great when they work, but it's all too easy to trip over this bullshit. It's not a new thing, I've got a question on E2E (that shall remain unanswered, it seems) regarding the apparently old TPS40210, which seems to have an analog discrepancy. Also relating to startup conditions, oddly enough.I wish they'd put the transistor count on the datasheet, just so I can avoid these stinkers. But who knows. Transistor count doesn't really mean anything, it's the shitty design that makes it shitty.Tim

author: jeremy
author_rank: Super Contributor
timestamp: January 22, 2019, 11:32:33 pm
content: Quote from: Bud on January 22, 2019, 11:16:29 pmDigi-KeyBut good point nonetheless.

author: amyk
author_rank: Super Contributor
timestamp: January 23, 2019, 01:41:33 am
content: Quote from: T3sl4co1l on January 22, 2019, 11:28:37 pmIt's more like "start with an MCU and add power transistors"... I wouldn't be surprised if there was some sort of primitive microcode and CPU-ish logic in them.I'd be interested in a die photo of a simpler switching regulator, for comparison.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 23, 2019, 01:56:39 am
content: I mean, this might be a littletoosimple, but it illustrates the point:https://zeptobars.com/en/read/MC34063I've synthesized similar functionality to the UC3842 with a mereseven transistors, lacking some functions like low-current startup and UVLO, which would hardly take a dozen more. It's not hard to do, they just don't care about analog design anymore.Tim

author: DaJMasta
author_rank: Super Contributor
timestamp: January 23, 2019, 02:21:45 am
content: Even if there are some ways to reduce the likelihood of a faulty start to near zero, they should probably be described in the reference circuit in the datasheet and much more importantly: this kind of over-boosting failure mode shoudln't ever be acceptable in such a chip. If you have a faulty start and need extra stuff to clean up power, fine, it may not be a treat to use in your design but it will work well enough.... if a potential failure mode for a boost converter is to overdrive the target voltage by like 50%.... that's a design failure.Maybe they can update their datasheet to include clamping circuitry, but they really should be looking into respinning it and considering recalling the parts - it's not going to be a converter of choice if the BoM inflates with larger clamping diodes.

author: radioactive
author_rank: Regular Contributor
timestamp: January 23, 2019, 03:41:07 am
content: What values did you use for R1/R2 feedback? Did you see this in the datasheet?QuoteAlso, another thing that would be worth trying is switching to the fixed 3.6V (TPS610995)?Another last ditch type effort would be to have an external voltage ref / comparator monitor for over voltage and the drive enable pin low. Probably not worth the cost unless you really need to use this part.

author: jeremy
author_rank: Super Contributor
timestamp: January 23, 2019, 03:55:36 am
content: I am using theQuote from: radioactive on January 23, 2019, 03:41:07 amI am using the fixed 3.6V option partially because I didn't want to be bothered with problems like this. I have been playing with various voltage supervisors, etc and I just can't seem to get the circuit right. It's fairly easy to delay the startup of the converter with one, but the overvoltage condition is what is stumping me. Really, you need a circuit which de-asserts the enable pin if it goes too high *and* discharges the capacitors on the output stage. A comparator with wide hysteresis and a voltage ref is probably what is needed, but cost and complexity starts to be a problem there. Also it has to be crazy low Iq. Right now my circuit uses 4 times the sleep current of the entire rest of the system.Quote from: DaJMasta on January 23, 2019, 02:21:45 amI suspect this is a marketing problem perhaps (though I suppose Hanlon's razor says that its a case of nobody who can do anything about it knows about it). This is clearly designed for a tiny board area (otherwise who would bother to use the CSBGA), and clamping would make that a lot worse. You can also kiss the ~1uA Iq goodbye as well. At that point, this converter basically has no market; who wants a low Iq boost converter that isn't really that low Iq, takes up a bunch of board space but still requires you to solder and inspect a CSBGA, and still might get into a glitch loop where it draws too much current.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 23, 2019, 03:57:32 am
content: Quote from: T3sl4co1l on January 22, 2019, 11:28:37 pmOddly, this reminded me of the C vs. C++ thread raging in the CPU/MCU forum.Here it is expressed in hardware... excessive complexity that often ends up being more of a hindrance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 23, 2019, 04:08:38 am
content: Quote from: IDEngineer on January 23, 2019, 03:57:32 amSort of. Notwithstanding style issues ("blargh blargh don't use C++ because I don't like its syntax and when I use it it's always so bloated!", etc.), most of that is semantics and syntax -- complexity used to generate code, but not complexity in the code itself. The resultcanbe quite lean and orderly. You just have to make sure you aren't telling it to compile with more code features than you need.So too, HDL can be quite complex at the design level, but the synthesis doesn't need to be complex.It seems we have the worst of both worlds here. One should not blame the tools (necessarily), but the commitment to quality is what's lacking.Tim

author: IDEngineer
author_rank: Super Contributor
timestamp: January 23, 2019, 04:13:22 am
content: Quote from: T3sl4co1l on January 23, 2019, 04:08:38 amAgreed, but I was thinking more in line with your comment:Quote from: T3sl4co1l on January 23, 2019, 04:08:38 am...and how that syncs up with the original intent of C, to be a portable Assembly language - not a "high level" language. Just as a "simple" switcher doesn't need "all that logic", so too does a "mid-level" language not need all of the baggage of a true high level language. There are plenty of complex IC's, and complex high level languages, to choose from. Why corrupt the intentionally simpler IC's/languages?Sorry for the hijack, back to our regularly scheduled programming....

author: BrianHG
author_rank: Super Contributor
timestamp: January 23, 2019, 04:29:17 am
content: With TI, it's not just their power management ICs. Their new norm on documentation SUCKS shit. On their clocking ICs, I tried to get information as their formulae in the data sheet made no sense and had non-standard characters. I was told from TI support, just use their PC configuration app to get the IC2 configuration settings. NO... The IC said I can program any frequency I wanted, both setting the reference and feedback dividers and their config software didn't always make the most stable oscillator configuration unless I manually tweaked it. Their own engineers couldn't decipher their own documentation... It took 5 days and a few friends who specialized in math and physics to reverse engineer the notation in their .pdf data sheet and to get the IC to dynamically be programmed to do exactly what I want.I also found bugs in a few of their other ICs. If you stray anywhere from the documented examples with any TI part above opamps, be warned... They do not proof their complex devices or test for extraneous bugs at all.

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 23, 2019, 04:48:12 am
content: Subscribing to this thread.Hope that I can find some documents to share, related to some Intersil multi-phase buck converters, that were an unmitigated disaster.

author: fireworks
author_rank: Contributor
timestamp: January 23, 2019, 09:34:22 am
content: Quote from: BrianHG on January 23, 2019, 04:29:17 amHi Brian,Which TI datasheet was that ? I want to take a look at the weird formulas ☺

author: TheDane
author_rank: Regular Contributor
timestamp: January 23, 2019, 09:49:22 am
content: Quote from: jeremy on January 22, 2019, 02:36:36 amNot much of a TI device work around; more a protection in general: ESD Suppressors / TVS Diodes UNIDIRECTIONAL 3.3V + a polyfuse on the input.Getting the correct part for your device can be tricky, as operating voltage vs. clamping voltage is quite close so not to blow up everything.What is your device supply absolute max rating, and the device current draw?https://www.mouser.com/datasheet/2/80/CPDH3V3UP-HF_RevB034941-1481125.pdfClamping voltage - 5V5, I_PP = 1 APunch-through voltage - 3V5, I_PT = 2uASnap-back voltage - 2V8, I_SB = 50mAFig.3 - Clamping voltage vs. peak pulse current - 8V@5A down and stops at 1A@5V5, extrapolating it down could result in a working protection solution for you?

author: JPortici
author_rank: Super Contributor
timestamp: January 23, 2019, 10:02:06 am
content: Quote from: Siwastaja on January 22, 2019, 06:19:58 amAnd yet newer TI chips ARE updated. I've used some of their newer LDOs in a design and between batches (like 6 to 12 months later) the exact partnumber didn't even exist anymore, but a partnumber followed with "A1" was available. then "A2" and so on...

author: forrestc
author_rank: Unknown
timestamp: January 23, 2019, 10:50:25 am
content: Quote from: Siwastaja on January 22, 2019, 06:19:58 amI miss National Semiconductor. Back before TI gobbled them, I found the national power conversion IC's to be top notch and just work. I never had the same luck with TI.Right now I'm sort of looking for a replacement for a buck converter which was an original National design. It's old enough that it's got a way high I(q) but it sure makes me nervous to try something else especially when you hear stories like this on a fairly regular basis.

author: jeremy
author_rank: Super Contributor
timestamp: January 23, 2019, 11:24:44 am
content: Quote from: TheDane on January 23, 2019, 09:49:22 amThanks for the pointers. I’ve been measuring some zener diodes I have around but as I suspected even a good 5.1V zener had around 100uA of leakage at 3.6V. Unfortunately my entire power budget during sleep is 100uA @ ~3V at Vin (incl regulator efficiency loss and Iq), but of course I’m trying to beat that. I’ll have to do some reading on these esd devices, I didn’t realise the reverse leakage was so good.System can withstand up to 4.2V, and needs about 250mA peak at 3.6V when radio activity is heavy, but it normally stays around 20-30mA otherwise.My other concern with clamping is that it doesn’t actually reset the converter and in my experience with this problem it needs a reset to be fixed. I’ve managed to get my double voltage supervisor down to 10uA, which I think I can live with. But testing it with this intermittent problem is tricky...Edit: sorry, I see you mentioned polyfuse as well. That could cause a UVLO reset perhaps

author: Siwastaja
author_rank: Super Contributor
timestamp: January 23, 2019, 12:36:16 pm
content: Quote from: MasterTech on January 22, 2019, 10:16:19 pmSorry to use such strong word, but: bullshit.Ramping and intermittent voltages are completely normal on any system. This is the exact task for an UVLO circuit, this is why it exists, and because the need is so common, this is why it'sintegrated.If they claim they have UVLO, it must accommodate exactly the ramping and bouncing Vin case, of course within maximum ratings.It's ridiculous to ask the user (only after sales, of course!) to provide an external UVLO on the enable pin when they claim to have one internally.Outputting too high of an output voltage due to input brown out cannot be justifiedeven withoutan UVLO, let alone with one, unless the input bounces outside the allowed range, which probably isn't the case here.

author: OwO
author_rank: Super Contributor
timestamp: January 23, 2019, 01:19:53 pm
content: Is there a reason for using the TPS610995 in the first place? If the requirements are just <1V startup voltage and low shutdown current there are many cheap boost converter ICs that can do the job, for example the SGM6603.

author: splin
author_rank: Frequent Contributor
timestamp: January 23, 2019, 01:25:05 pm
content: Quote from: SiliconWizard on January 22, 2019, 08:32:06 pmAh, that must be the one the OP was using.

author: jeremy
author_rank: Super Contributor
timestamp: January 23, 2019, 01:35:24 pm
content: Quote from: OwO on January 23, 2019, 01:19:53 pmNot low shutdown, low Iq and high efficiency at light load. Also relatively high current at 250mA (peak inductor pulse is up to 0.8A)

author: OwO
author_rank: Super Contributor
timestamp: January 23, 2019, 02:09:21 pm
content: Quote from: jeremy on January 23, 2019, 01:35:24 pmsome more parts to investigate:PT1301ME2108XC6367

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 23, 2019, 04:35:12 pm
content: Quote from: splin on January 23, 2019, 01:25:05 pmAhah, this typo was unintentional but that's a good one.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 23, 2019, 04:44:19 pm
content: I suggest the LTC3528 as an alternative. Linear has never failed me.

author: Bassman59
author_rank: Super Contributor
timestamp: January 23, 2019, 08:38:36 pm
content: Quote from: BrianHG on January 23, 2019, 04:29:17 amI've been using the Silicon Labs clock ICs (synthesizers, etc etc) and while you have to use the Clock Builder software, the parts behave and the support has been responsive (don't use the forum, just send email to their support staff).QuoteI have an issue with their not-new-anymore audio SRC chip, its receiver simply won't lock on S/PDIF signals whose sample rate is a multiple of 44.1 kHz. The 48 kHz family works fine. At least the support guy is honest: "none of the people on the design team work here any more." Still, there's no help and no support. This is why I haven't considered their microcontrollers for anything, even now that they've made the development tools free.

author: BrianHG
author_rank: Super Contributor
timestamp: January 23, 2019, 08:47:13 pm
content: Quote from: fireworks on January 23, 2019, 09:34:22 amI've attached the original cdce925_2007.pdf I had to work with at the time. See page 21, part 2 and the line after.I wish I had my notes, this ended up being simplified down to easy.

author: BrianHG
author_rank: Super Contributor
timestamp: January 23, 2019, 08:49:00 pm
content: Quote from: Bassman59 on January 23, 2019, 08:38:36 pmI'm sorry but TI's forum didn't yet exist in 2007, or didn't have anyone useful there when I was working on the stuff.

author: Daixiwen
author_rank: Frequent Contributor
timestamp: January 24, 2019, 08:41:38 am
content: I can relate to that. I had some problems several times with some components from Benchmarq and was told by TI that after their merger with Benchmarq the engineers that worked on the BQ components weren't there any more and TI couldn't offer any support on them.So I can't say I've had a good experience with TI's support either

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 24, 2019, 02:46:27 pm
content: I would say something similar happened to Unitrode when it was absorbed by TI.Unitrode had *many* outstanding and legendary Engineers. Their app notes were superlative. The products performed, and any pitfalls were clearly spelled outBack in the 90s I went to a power seminar. The speaker was Laslo Balogh (sorry if the spelling is incorrect) and he was pure genius.

author: kony
author_rank: Regular Contributor
timestamp: January 24, 2019, 03:18:22 pm
content: I wouldn't speak so highly about Unitrode. Literally the only switcher chip I had problem with from TI portfolio was inherited acient unitrode universal switchmode controller (don't remember exact PN anymore). Noise sensitive as hell.

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 24, 2019, 03:51:11 pm
content: No one is perfect............As I mentioned in my earlier post, Unitrode parts had their shortcomings clearly spelled out. Which were several, because of the "ancient" technology.Their seminars were full of design tips, based on an excellent analysis, to circumvent those pitfalls.That was one of their greatest strengths, which unfortunately TI has not followed through

author: Hydron
author_rank: Super Contributor
timestamp: January 24, 2019, 06:07:32 pm
content: When we started having large numbers of TI DSPs go bad in service (having used them in 10s of thousands quantities for years, so we knew when something was up) they refused to do anything useful to help track down the issue.Got someone to analyse them and sure enough, very poor wirebond quality compared to earlier samples, bad enough to cause reliability issues - the parts should have never made it out of TI's door. Now in the process of designing them out of everything...

author: IDEngineer
author_rank: Super Contributor
timestamp: January 24, 2019, 07:02:32 pm
content: Quote from: Hydron on January 24, 2019, 06:07:32 pmSheesh, what happened to TI? Used to be they were like Linear... pricey but you could rely on them for great products with great support. Sounds like someone is now optimizing for short term profits instead of long term design wins to maximize the area (profit) under the curve.If I had to guess, maybe their semiconductor division used to be run by IC people but is now run by MBA's?

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 24, 2019, 08:02:46 pm
content: Your guess may be accurate.Also, they have grown to be very large through acquisitions. When that happens, the culture shock in the acquired companies cause the best talent to migrate somewhere else.

author: jeremy
author_rank: Super Contributor
timestamp: January 25, 2019, 12:44:57 am
content: A neat little tidbit from the LTC3528 datasheet which might give a clue to what the issue could be with the TI converter:Quote

author: amyk
author_rank: Super Contributor
timestamp: January 25, 2019, 02:29:48 am
content: That's better than nothing, but I think the best way to design something like that is either fully document what the test mode does and how to exit it, or fuse it off permanently so it would never be entered again. Weird undocumented functionality in an IC is overall bad for a variety of reasons.

author: LukeW
author_rank: Frequent Contributor
timestamp: January 25, 2019, 02:45:40 am
content: Who makes decent affordable DC-DC silicon other than TI?Don’t say high-price LT.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 25, 2019, 02:57:46 am
content: AoS isn't obscure.Diodes Inc makes a bunch of regulators, and controllers maybe, I forget. ST, On Semi, Rohm, Infineon, Intersil.There's a ton of Taiwanese sources, even in the western market now. The documentation is usually terrible, so you may want to evaluate a kit before designing them in. I haven't seen any that are obviously embarrassingly worse than some of TI's stupider designs.Tim

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 25, 2019, 02:58:22 am
content: Quote from: LukeW on January 25, 2019, 02:45:40 amAnalog Devices.MPS makes decent stuff at significantly lower prices.https://www.monolithicpower.com/en/products/dc-dc-power-conversion/switching-regulators.html

author: KE5FX
author_rank: Super Contributor
timestamp: January 25, 2019, 03:00:12 am
content: Quote from: LukeW on January 25, 2019, 02:45:40 amThere's an obscure company called "Alpha and Omega Semiconductor" that seems to be doingsome decent work. E.g.,AOZ1050(although that particular one is NRND). Their parts seem to have a decent compromise between simplicity, performance, EMI, and overall efficiency.They are present on some FPGA integration boards that I've used and I haven't seen any of them melt down yet. That particular board also uses a part fromRichtekthat seems to work well.One concern I have with LT lately is that they don't seem to be able to deliver certain new parts in volume. The LT8650 is a nice part that I'm using in a design now, but either they can't build them for some reason, don't care to provide them via normal distribution channels, or somebody is buying all of them they can make. This has been true for the better part of a year now. I don't remember this happening with Linear before.Quote from: T3sl4co1l on January 25, 2019, 02:57:46 am(Shrug) I'd never heard of them before I encountered their parts on the ZTex boards. Never seen them used anywhere else.Goofy name, that's for sure. Makes me think I'm buying from the Branch Davidians or something.

author: amyk
author_rank: Super Contributor
timestamp: January 25, 2019, 03:44:11 am
content: Quote from: KE5FX on January 25, 2019, 03:00:12 amA&O MOSFETs areverycommon, especially on PC (in particular laptop) motherboards. In general, looking at schematics for mass-produced consumer products can be a very educational experience for seeing who "the big guns" turn to for their designs, and what parts they use (some of TI's switching regulators are common in PCs too.)

author: OwO
author_rank: Super Contributor
timestamp: January 25, 2019, 04:57:41 am
content: Quote from: LukeW on January 25, 2019, 02:45:40 amThere are many Ching Chong brands that are ok. You can find them on LCSC or by just searching "buck converter ic" on aliexpress and googling the part numbers.

author: JPortici
author_rank: Super Contributor
timestamp: January 25, 2019, 06:43:46 am
content: Quote from: LukeW on January 25, 2019, 02:45:40 amI like to use microchip power parts. cheap and works as intended. I was always able to get near the advertised efficiency (around 1% less) without much effortI however tend to use TI parts because there's always this or that feature that they seem to be the only one to have (pick a number of requirements, TI will usually have the converter with the ENABLE/SHUTDOWN polarity i need not to complicate the circuit too much)