Such a horrible design from Lenovo

[terrance]

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. 

[wraper]

Then I measured  buck switch waveform, on time is 600-650ns. So the ripple current is 9A!

I wonder how you came to this conclusion?

with 2 220uF Cout, output ripple will be 280mV even at 0 ESR.

So did you actually measure it?

[terrance]

(20V-5V) * 600ns / 1uH
(20-5) * 600e-9 / 1e-6 = 9

any questions?

9A / 2 * 600ns / (2 * 220uF) + 9A * ESR
9. / 2 * 600e-9 / (2 * 220e-6) + 9 ESR
0.006 + 9*ESR

ok this one is miscalculated

Still a horrible design

[jonpaul]

Lenovo Thinkpad Carbon X1 running for many years in continuous use.

No issus on PSU or cooling.

Just my experience

j

[nctnico]

(20V-5V) * 600ns / 1uH
(20-5) * 600e-9 / 1e-6 = 9

any questions?

I 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.

[wraper]

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 current https://eu.mouser.com/datasheet/2/54/bourns_06062019_SRP7030CA_datasheet-1601312.pdf

[brucehoult]

Lenovo Thinkpad Carbon X1 running for many years in continuous use.

Many machines have worn that title over the years.

No issus on PSU or cooling.

The 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.

[terrance]

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?

[terrance]

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.

[terrance]

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.

[wraper]

Do you know what is a wide angle lens? look at the bottom of that inductor.
Also I measured with a caliper.

Dunno 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.

[Whales]

Faringdon?

[mikerj]

Faringdon?

Maybe, but seems a little aggressive for Faringdon.

[mikerj]

The 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.

Higher 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.

[Gyro]

Faringdon?

Maybe, but seems a little aggressive for Faringdon.

No, 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.

[MK14]

Faringdon?

No 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

[terrance]

Nice job!

your 5mm is 400px
and 8mm is 508px

also, nice math

[terrance]

Yeah, saying something just true, is "too aggressive".

[terrance]

yes, it's a cheapo plastic made in china caliper, but it will not mess up 6mm/250mil and 8mm

[wraper]

yes, it's a cheapo plastic made in china caliper, but it will not mess up 6mm/250mil and 8mm

Except it's a different part and still closer to 7x7mm anyway. EDIT: I see it's a different inductor from the same board.

[wraper]

Nice job!

your 5mm is 400px
and 8mm is 508px

also, nice math

You don't consider inductor has rounded corners when counting the pixels. However yes it's not right and closer to 7mm, not 8.

[wraper]

Similar size to NPIM74P1R0MTRF 11A Irms, 22A Isat

[Jim from Chicago]

"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

[brucehoult]

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.

Thinking 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.

[brucehoult]

The 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.

Higher 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.

It 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.