Such a horrible design from Lenovo - Page 1
Forum section: electronics / general

author: terrance
author_rank: Contributor
timestamp: April 29, 2024, 08:22:45 pm
content: I took apart my Thinkpad 40AS USB-C dock, and shocked by the bad power design.They used TI TPS51285B1 for 5V and 3V3. The 5V part, is using 1uH 6x6x3 inductor. Then I measured buck switch waveform, on time is 600-650ns. So the ripple current is 9A! Current rating of inductors that size is at most 5A. with 2 220uF Cout, output ripple will be 280mV even at 0 ESR.

author: wraper
author_rank: Unknown
timestamp: April 29, 2024, 08:46:47 pm
content: QuoteI wonder how you came to this conclusion?QuoteSo did you actually measure it?

author: terrance
author_rank: Contributor
timestamp: April 29, 2024, 09:14:46 pm
content: (20V-5V) * 600ns / 1uH(20-5) * 600e-9 / 1e-6 = 9any questions?9A / 2 * 600ns / (2 * 220uF) + 9A * ESR9. / 2 * 600e-9 / (2 * 220e-6) + 9 ESR0.006 + 9*ESRok this one is miscalculatedStill a horrible design

author: jonpaul
author_rank: Super Contributor
timestamp: April 30, 2024, 05:42:29 am
content: Lenovo Thinkpad Carbon X1 running for many years in continuous use.No issus on PSU or cooling.Just my experiencej

author: nctnico
author_rank: Super Contributor
timestamp: April 30, 2024, 07:19:20 am
content: Quote from: terrance on April 29, 2024, 09:14:46 pmI suggest to run this through a simulator... But first think where the energy is going when your estimated 9A would actually flow through the inductor.

author: wraper
author_rank: Unknown
timestamp: April 30, 2024, 09:22:44 am
content: 6x6x3mm size claim is BS because MOSFET next to it is 5x6mm, inductor size is 8x8mm, and here is an inductor of this size with 30A saturation currenthttps://eu.mouser.com/datasheet/2/54/bourns_06062019_SRP7030CA_datasheet-1601312.pdf

author: brucehoult
author_rank: Super Contributor
timestamp: April 30, 2024, 11:22:53 am
content: Quote from: jonpaul on April 30, 2024, 05:42:29 amMany machines have worn that title over the years.QuoteThe i7-8650U Carbon X1 I was issued with by my employer in 2019 had HUGE cooling issues. It took ~30 minutes to build the riscv-gnu-toolchain compared to 20 minutes for the exact same CPU in a NUC that I already owned. The CPU didn't throttle much at all in the NUC (IIRC from 4.2 GHz to 3.4 GHz) while in the X1 it throttled back to about 2 GHz.

author: terrance
author_rank: Contributor
timestamp: May 08, 2024, 09:03:56 pm
content: Do you know what is a wide angle lens? look at the bottom of that inductor.Also I measured with a caliper.Also why would any one use a 30A rated inductor with 9 A ripple current for 6 usb ports?

author: terrance
author_rank: Contributor
timestamp: May 08, 2024, 09:08:14 pm
content: can't you even do any basic elementary school level calculations?you don't need to run simulation on this kind of simple circuit to find out it is crappy.

author: terrance
author_rank: Contributor
timestamp: May 08, 2024, 09:11:14 pm
content: That's exactly why we have so many crappy products, just like the macbook, a tiny fan blowing somewhere else rather than the heatsink. So many engineers don't even know any basics.

author: wraper
author_rank: Unknown
timestamp: May 08, 2024, 09:20:02 pm
content: Quote from: terrance on May 08, 2024, 09:03:56 pmDunno how you measured or what lens but it's very obvious MOSFET and inductor are not of the same dimensions. Lens argument absolutely falls apart if you look on their size on PCB level, so equal distance from the lens.

author: Whales
author_rank: Super Contributor
timestamp: May 09, 2024, 05:17:21 am
content: Faringdon?

author: mikerj
author_rank: Super Contributor
timestamp: May 09, 2024, 07:29:58 am
content: Quote from: Whales on May 09, 2024, 05:17:21 amMaybe, but seems a little aggressive for Faringdon.

author: mikerj
author_rank: Super Contributor
timestamp: May 09, 2024, 07:34:32 am
content: Quote from: brucehoult on April 30, 2024, 11:22:53 amHigher end x86 CPUs throttling down under sustained heavy load on slim, compact laptops is not "HUGE cooling issues", it's pretty much par for the course.

author: Gyro
author_rank: Super Contributor
timestamp: May 09, 2024, 08:38:43 am
content: Quote from: mikerj on May 09, 2024, 07:29:58 amNo, teenager at a guess. As you say too aggressive for Faringdon/treez and the telltale thanking of every post is missing.This thread rather reinforces the view, it reads like somebody who's just read their first datasheet and doesn't quite 'get it'. [Edit: Oops...https://www.eevblog.com/forum/chat/how-many-ees-know-this-basic-thing/]Nothing wrong with being a teenager, as long as you don't try to make out that you know more than you do.

author: MK14
author_rank: Super Contributor
timestamp: May 09, 2024, 09:39:06 am
content: Quote from: Whales on May 09, 2024, 05:17:21 amNo but, previously banned member eti, is another possibility. But it perhaps is too early to be sure.Here is an example, where they create a similar thread, to say horrible things about an amazon device:https://www.eevblog.com/forum/chat/amazon-fire-tv-remotes-designed-to-be-thrown-away!/msg3921323/#msg3921323

author: terrance
author_rank: Contributor
timestamp: May 09, 2024, 09:32:32 pm
content: Nice job!your 5mm is 400pxand 8mm is 508pxalso, nice math

author: terrance
author_rank: Contributor
timestamp: May 09, 2024, 09:55:43 pm
content: Yeah, saying something just true, is "too aggressive".

author: terrance
author_rank: Contributor
timestamp: May 09, 2024, 10:06:02 pm
content: yes, it's a cheapo plastic made in china caliper, but it will not mess up 6mm/250mil and 8mm

author: wraper
author_rank: Unknown
timestamp: May 09, 2024, 11:44:02 pm
content: Quote from: terrance on May 09, 2024, 10:06:02 pmExcept it's a different part and still closer to 7x7mm anyway. EDIT: I see it's a different inductor from the same board.

author: wraper
author_rank: Unknown
timestamp: May 09, 2024, 11:57:43 pm
content: Quote from: terrance on May 09, 2024, 09:32:32 pmYou don't consider inductor has rounded corners when counting the pixels. However yes it's not right and closer to 7mm, not 8.

author: wraper
author_rank: Unknown
timestamp: May 10, 2024, 12:20:51 am
content: Similar size to NPIM74P1R0MTRF 11A Irms, 22A Isat

author: Jim from Chicago
author_rank: Regular Contributor
timestamp: May 10, 2024, 02:57:31 am
content: "Current rating of inductors that size is at most 5A"This statement seems wrong. For example, Wurth 74439346010 is in the ballpark of the dimensions you stated, and it's rated for 13A. I just randomly found this part doing a cursory search, so there are likely even higher rated parts out there with similar dimensions.I wouldn't judge the quality of the design without knowing the exact component specs, requirements, background info, etc, that the engineers were dealing with.https://www.we-online.com/components/products/datasheet/74439346010.pdf

author: brucehoult
author_rank: Super Contributor
timestamp: May 10, 2024, 04:49:05 am
content: Quote from: terrance on May 08, 2024, 09:11:14 pmThinking you're a better engineer than Apple's engineers is pretty strong hubris!If they make compromises from time to time, it is not because they don't know the basics! It is very deliberately and knowingly.

author: brucehoult
author_rank: Super Contributor
timestamp: May 10, 2024, 04:59:33 am
content: Quote from: mikerj on May 09, 2024, 07:34:32 amIt certainly IS a huge cooling issue for a developer. There are other kinds of users who only need burst performance, but developers working on larger systems need sustained performance.The Lenovo Legion Pro 5i (2023) I currently have (with 24 core i9-13900HX) has pretty decent cooling, managing around 3.95 GHz on all cores indefinitely (or 10 minutes, anyway, which is a long time with 24 cores).Sure, it weighs 2.5kg vs 2.5lb for the X1, but the extra 1.4kg is WELL worth it if you're using your laptop for serious development of large systems -- a lot more cores, running at a lot more sustained MHz.

author: terrance
author_rank: Contributor
timestamp: May 10, 2024, 08:26:37 pm
content: I replaced it with IHLP2525CZER8R2M11What I meant is, they should not design the operating point at 9A ripple current. It is unreasonable even if the best part can handle 13A. For buck converters, very high ripple current also puts lot of stress on input capacitors. The low inductance also drive the switching frequency so low, that it was buzzing.

author: terrance
author_rank: Contributor
timestamp: May 10, 2024, 08:28:36 pm
content: it is not about if the inductor can handle that ripple current, it's about the unreasonably high ripple current.

author: wraper
author_rank: Unknown
timestamp: May 10, 2024, 08:32:26 pm
content: Quote from: terrance on May 10, 2024, 08:26:37 pmAnd then you'll find out it cannot handle the full load.

author: terrance
author_rank: Contributor
timestamp: May 10, 2024, 08:39:56 pm
content: so the real problem is user uses too much performance for too long time.

author: terrance
author_rank: Contributor
timestamp: May 10, 2024, 08:42:12 pm
content: a compromise against heat dispassion performance for a hot cpu IS an awful design.or it's the user's fault using too much performance.

author: wraper
author_rank: Unknown
timestamp: May 10, 2024, 09:16:34 pm
content: Quote from: terrance on May 10, 2024, 08:42:12 pmAny laptop is a compromise of size/thermals and (especially sustained) performance, no way around it. Increasing inductance 8x with no consideration of how much current that rail may pull is absolutely dumb. In the end you may find out that nearly everything connected to that voltage rail is dead if TPS51285B fails short due to inductor saturation/failure.

author: thm_w
author_rank: Super Contributor
timestamp: May 10, 2024, 10:13:56 pm
content: For anyone wondering:https://www.digikey.com/en/products/detail/vishay-dale/IHLP2525CZER8R2M11/12206848.2uH 4AFeel free to post some waveforms.Was the 600ns measured at full load or partial load? Is that a 24% duty cycle then?

author: mtwieg
author_rank: Frequent Contributor
timestamp: May 11, 2024, 12:33:57 pm
content: If you increased the inductance that much I would be concerned about operation at max load. Do you know what the max load current will be?Also I'm assuming you verified the stability margins..?

author: f4eru
author_rank: Super Contributor
timestamp: May 12, 2024, 08:49:16 am
content: perhaps the frequency increases at high loads ?

author: thm_w
author_rank: Super Contributor
timestamp: May 13, 2024, 10:45:13 pm
content: Quote from: f4eru on May 12, 2024, 08:49:16 amDatasheet implies fixed frequency 400 or 500kHz.Though pulse skipping at low loads.

author: terrance
author_rank: Contributor
timestamp: May 13, 2024, 10:49:06 pm
content: mow much load does 6 usb ports with current limiters take? 30A?

author: wraper
author_rank: Unknown
timestamp: May 13, 2024, 10:58:30 pm
content: Up to 1.5A per port if port supports rapid charging. Not to say some phones will try to pull such current from any port and this converter may power more things than just USB. Using a 5A inductor for powering 6 USB ports is nuts.