FEDEVEL
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elessargr , 08-30-2025, 01:26 PM

Hello to all,
hope everyone goes well.

I would like to ask a quick question if anyone is aware.
I am working with the TUSB8020B (TUSB8020BIPHPRQ1) which I am using it as a 2x port HUB. From the moment I am connecting it to the USB port the IC in less than 1sec gets extremely hot.
With a thermal camera the IC shows 60C. Yes the IC is designed to be okay at that temperature but I am not sure if it should be reaching this without any load on it and especially in 1sec from the moment its energized.

Is this normal?

On the PCB yes I have some vias for thermal relief (4) but something seems off.

To clarify I am still learning when it comes to electronic schematic design and PCBs.

Any recommendations, ideas are welcome in order to figure out what causes this if its not expected.

Thanks again!

Sniper2 , 08-30-2025, 05:00 PM

pcb picture?

elessargr , 08-30-2025, 06:15 PM

I assume you mean those?

elessargr , 08-30-2025, 06:16 PM

the two middle layers are ground and power. So nothing much to show

FuzzyOtter , 08-31-2025, 02:10 AM

Any reason you didn't follow the recommended footprint shown in the datasheet? It shows a significantly larger area of copper placed under the thermal pad of the IC, with more vias. You also have vias running under the chip where TI recommends the thermal pad should be. Are your vias tented? Is the "thermal pad" solder shorting against any of those vias?

Robert Feranec , 08-31-2025, 02:42 AM

if it gets hot in less than 1s that looks like something is wrong. measure currents and voltages going into the chip

elessargr , 08-31-2025, 09:45 AM

good morning!
Thank you both for those details/suggestions!!

elessargr , 08-31-2025, 09:46 AM

FuzzyOtter tbh I didnt see that picture all those months now in the datasheet until you mentioned it. I was always going until page 37/38 where I thought the datasheet ended. I was wrong 🙁
Definitely the vias are not tented.
On my new design (attached) I placed more vias and now I think I would place even more. Not sure if there is a way to remove vias and make it a solid piece through all layers as copper or something like that. Need to check.
I dont believe there is a short somewhere since I had 4x PCB made and all of those have the same issue.

elessargr , 08-31-2025, 09:50 AM

Robert This is what I was thinking also! Getting that hot soo quickly I dont think is normal.
I have some basic tools which I believe can do what I need.
I will check each input for the IC.
Thanks!

elessargr , 08-31-2025, 06:53 PM

okay so managed to check the voltage on power pins.
I marked them with orange the values that my multimeter gave me. 🙂
The only ones that looks weird to me are the pin5,8 since on the one side of the resistor we have 3.33v and on the other 3.3v.

For the current still checking how to do this on a PCB

Robert Feranec , 09-01-2025, 02:46 AM

if there would be problem you would probably see a high drop on the voltage rails, but depends on how strong your power supplies are. did you try to check the whole board power consumption? It still could be the thermal connection (not enough vias on the copper under the exposed pad), but if the hub is only connected to power and nothing else is connected I would expect the chip to stay cold or maybe only a little bit worm .. I would not expect it to get hot within 1s. BTW, does the board work?

tomas.kaplan , 09-02-2025, 02:49 PM

Sometimes, power sequencing is important. There could be some internal latch-up in the chip if you dont meet the following power-up timing requirements. Check your power supply rails on the oscilloscope during turn-on phase.

tomas.kaplan , 09-02-2025, 02:51 PM

The picture right below this table on page 7 shows power rails turning ON after each other.

elessargr , 09-02-2025, 06:29 PM

sorry for the delay here,
thank you both for the insights!

elessargr , 09-02-2025, 06:29 PM

Hi Robert,
> did you try to check the whole board power consumption?
Not yet. I am just plugging this to my PC or Laptop 🙂
There are two more items connected to the downstream ports. I did a test on a test board that I was previous to this one which doesnt have anything downstream connected and after I plug something to the port then its getting hot.

Yes the board works! 🥳

I got myself today a smartphone thermal camera and start playing with it. Very helpful.

elessargr , 09-02-2025, 06:32 PM

Hi Tomas,
tbh I didnt know this was a key factor for those kind of ICs since its my first time and still learning!
I do not have an oscilloscope (yet*) 🙁
I will see how this can be implemented in my PCB.
Thanks!!

tomas.kaplan , 09-03-2025, 05:12 AM

No worries, good job and keep it going. I am pretty sure that if you improve the ground layer under your chip with plenty of vias + you make sure your power rails turn on correctly, with reset release after everything is stabilized, you will have working piece of electronic device. 🙂

You can implement the turn-on sequence by using Power good signals and Enable signals of your supply regulators for the chip (if they offer this functionality). Maybe if you share your power supply section, we can look at it.

Maybe you could work it out without oscilloscope, just from the datasheets, but i think you cannot avoid buying one in a near future.

elessargr , 09-03-2025, 04:32 PM

Hi Tomas!
thanks for the encouraging words! Trying my best 🙂

Yes on my new design I placed already quite few vias. So this is one part done.

The power sequensing is what I am checking now.
https://www2.mouser.com/datasheet/2/1458/DS8075_04-3104774.pdf
This is the power converter I use.
You can see it on the Back copper layer (blue) top right corner.

tomas.kaplan , 09-04-2025, 05:40 AM

Hi there, ok. As I am looking at it more closely, it seems that VDD and VDD33 can be turned on at the same time. From table I posted, Td1 timing requirement is 0 ms at minimum, so its fine. The only missing part is the reset signal GRSTz.

From the TUSB datasheet I would say that you need to hold reset LOW during the power-up sequence and release it after 3ms (minimum) when power rails are within operating range.

tomas.kaplan , 09-04-2025, 05:40 AM

Do you have control over this reset signal?

elessargr , 09-04-2025, 04:43 PM

Hi Tomas,
No idea tbh.

Chef Jeff , 09-04-2025, 10:25 PM

I think the point of that diagram is to show you 3V3 must come up before 5V0 (or at the same time like you said). Gonna need an oscilloscope to confirm that. looks like to me your 5V is plugged in charges all the caps then enables your 3V3 to turn on and charge its caps so 5V is stable before 3V3 is stable which causes the ic to be in a weird state. (also using this ic on a new board I’m working on so I’m interested in your findings)

elessargr , 09-05-2025, 07:04 PM

Hi Chef,
how can the 5v come after the 3.3v if the 5v are coming from the USB-C (host)?

elessargr , 09-05-2025, 07:38 PM

I remember seeing somewhere this
https://www.ti.com/tool/TIDA-00287
being sold and now I cant find it anywhere. I was thinking maybe to purchase this and check if indeed the temperature gets that high that quickly 🙁

elessargr , 09-05-2025, 07:39 PM

The weird thing is that yes it does have more vias for the IC but I see them only around the pad not in the center.

corlas , 09-05-2025, 07:46 PM

you can buy this if you want eval board but it's quite expensive https://www.ti.com/tool/TUSB8020BEVM#order-start-development

elessargr , 09-05-2025, 08:59 PM

Hi Corlas!
Yes I saw this also but indeed its expensive 🙂

Robert Feranec , 09-06-2025, 10:40 PM

yes, you may want to order it, it can be helpful

elessargr , 09-07-2025, 11:39 AM

https://www.krypton-solutions.com/products/ks2ph-2-port-usb-3-0-hub-reference-product/

Finally found it!
but looks like they dont sell it anymore :S
I reached out to them to see.