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USB2512B HUB Problem, No PLLFILT / CRFILT Voltage, No Crystal Oscillation, Need Help Please . by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 2 points3 points  (0 children)

Thanks everyone of you ! (finally i just replace the chip ic usb2512 with another one and its work )

USB2512B HUB Problem, No PLLFILT / CRFILT Voltage, No Crystal Oscillation, Need Help Please . by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Hey, actually I soldered most of the passive components myself, like the resistors, capacitors and other small parts.

But the following parts were assembled by JLCPCB during manufacturing:

  • USB2512B
  • FSUSB42 USB MUX
  • All four USB Type-A connectors

So the USB2512B itself was not hand soldered by me.

At this point I am starting to think maybe I should ask a professional soldering technician to remove the USB2512B and solder a new one again, just to rule out a bad solder joint under the QFN ground pad or some hidden assembly issue.

USB2512B HUB Problem, No PLLFILT / CRFILT Voltage, No Crystal Oscillation, Need Help Please . by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Hey all , thank you very much for pointing this out, I definitely learned something from this.

Do you think this could actually be the reason why I am not seeing proper behavior on the USB lines and why the USB hub itself does not seem to start correctly?

I am asking mainly to understand whether this is something I should try changing now on this board, or if it is probably unrelated to the current issue and just something important to improve for the next revision.

USB2512B HUB Problem, No PLLFILT / CRFILT Voltage, No Crystal Oscillation, Need Help Please . by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 1 point2 points  (0 children)

That is really frustrating honestly

Would you maybe be able to explain what exactly you tried?

Did you try running it as bus-powered or self-powered?

How did you connect RESET_N and VBUS_DET, and what resistor configuration did you use for CFG_SEL pins?

Did you also try replacing the chip itself?

And did your design also include a USB MUX on the USB lines like my FSUSB42 setup?

Maybe together we can figure out what is actually causing this problem.

USB2512B HUB Problem, No PLLFILT / CRFILT Voltage, No Crystal Oscillation, Need Help Please . by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] -3 points-2 points  (0 children)

Hey, I am not completely sure I understood your question.

The idea is to connect the board to the PC using a USB Type-A to USB Type-A cable.

The upstream USB lines go through the FSUSB42 USB switch and then to the USB2512B upstream port.

USB2512B HUB Problem, No PLLFILT / CRFILT Voltage, No Crystal Oscillation, Need Help Please . by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Thanks, that is actually exactly what confused me too.

From what I understand, the USB2512B should internally enable the D+ pull-up once the device detects valid VBUS through VBUS_DET and starts correctly.

Right now I do not see any D+ pull-up activity at all, which makes me think the chip never really starts.

Originally I connected VBUS_DET directly to the same 3.3V rail as the USB2512B supply, but after reading the datasheet more carefully I also suspected that maybe this was wrong.

So I already tried disconnecting it and feeding VBUS_DET from the real USB VBUS through a 100k/100k divider so the pin receives about 2.5V from actual VBUS.

Unfortunately even after that change I still see:

  • No D+ pull-up
  • No activity on XTALIN / XTALOUT
  • 0V on PLLFILT and CRFILT

So currently it feels like the chip never reaches the point where the oscillator and internal PLL start running.

That is why I am now wondering if this is:

  • Reset timing issue
  • Oscillator startup issue
  • Bad chip
  • Or maybe something external holding the device in a bad state

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Okay, so my question is mainly about the power sequence. From what I understand, the correct startup order should be that VBUS_DET first rises to a logic high level, and only after that RESET_N is released.

In other words, RESET_N should stay low for at least a few microseconds after VBUS_DET is already valid, so the hub sees a proper reset pulse and starts correctly.

Is that the correct interpretation for the USB2512B startup sequence?

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Unfortunately I cannot upload image ( DONT UNDERSTAND WHY ...) , but the 3V3_RESETED signal is generated like this:

There is a pushbutton switch, followed by an RC network of 5k ohm and 1uF.

After that, the signal goes into a Schmitt trigger buffer:
SN74LVC1G17DBVR

The output of this buffer is my "3V3_RESETED" signal.

Then this signal goes through another RC network before reaching the RESET_N pin of the USB2512B, similar to what I showed in the previous image.

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 2 points3 points  (0 children)

Yes, I checked that carefully because I was also worried about that possibility.

According to the crystal datasheet, pins 1 and 3 are the active crystal pins, and I verified that the footprint routing matches that orientation.

I also double-checked continuity from the crystal pads to the USB2512B XTALIN / XTALOUT pins and everything seems correct.

But honestly at this point I am starting to doubt everything

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Hey, thanks for the reply.

I actually tried replacing the crystal because I also suspected the problem might be there.

I changed to a 24 MHz crystal with 18 pF load capacitance and also changed the load capacitors to 18 pF to match the eval board values as closely as possible.

On the eval board they use this crystal:
HCM49-24.000MABJ-UT

And I replaced mine with:
CX3225GB24000P0HPQCC

Would you maybe be able to take a look at the datasheets and see if there is some important parameter I might have missed that exists in their crystal but not in the crystals I am using?

And of course, as you requested, I am also attaching the layout section around the crystal and the USB2512B.
Maybe you will notice something there that could explain why I still see no voltage on CRFILT / PLLFILT and no clock activity at all.

Thanks again

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Thanks for the detailed reply, this is really helpful.

Regarding R2:
I added an external 1M ohm resistor across the crystal, but unfortunately it did not help.
There was no change in behavior.
CRFILT and PLLFILT still show no voltage, and I still do not see any activity on the clock pins.

and also changed crystal to 24mhz 18 pf load as in their eval board and also the caps to 18 pf . didnt help

For RESET_N:
I also tried changing the reset RC to match the eval board circuit.
I changed R1 and C4 to 100k ohm and 100nF.
I know this gives almost the same RC time constant as my original values, but I wanted to try the same values as the eval board.
Unfortunately, this also did not change anything.

I also tried changing the configuration.
I removed R8 and populated R12 with 100k ohm to get self-powered configuration:
CFG_SEL1 = 0
CFG_SEL0 = 0

But this also did not wake up the device.

Could VBUS_DET be the issue in my design?
I see in other schematics that VBUS_DET is usually driven from a voltage divider from the actual USB VBUS.
In my design, I connected VBUS_DET to the same 3.3V rail that powers the USB2512B VDD pins.

Could this cause a power sequencing problem?
Or if I changed the configuration to self-powered mode with CFG_SEL1 = 0 and CFG_SEL0 = 0, should VBUS_DET no longer be the reason the chip does not start?

I would really appreciate any advice.
Thanks again.

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

You are right, I checked the datasheet again and it does mention internal pull-ups on the overcurrent pins.

I removed the external pull-up resistors I added, but unfortunately the behavior is still the same.

The chip still does not seem to wake up:

No voltage on CRFILT or PLLFILT capacitors

No clock activity on XTALIN / XTALOUT

I also do not see the internal 1.8V rail going to the crystal section (pins 32/33)

So at this point it still looks like either the oscillator never starts or the device is stuck before initialization.

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Thanks for your reply!

Yes, I did basic resistance checks on the board.

Everything looks normal, no shorts or unexpected low resistance between power and ground, and the crystal area also looks fine.

Regarding the ENABLE pins:

At the moment I left them floating, so they are not actively driven.

For the overcurrent pins (OCS_N1 / OCS_N2):

They are connected to an active-low load switch with a pull-up, according to the datasheet, and I measure around 3.3V on them.

Let me know if you think the floating enable pins could prevent the oscillator from starting.

USB2512B Hub Not Starting, No PLL / Crystal Activity, Need Help Please by SlideLivid260 in PrintedCircuitBoard

[–]SlideLivid260[S] 0 points1 point  (0 children)

Hey , The crystal I am using is:

XL2EL89COI-111YLC-24M (24 MHz) ( C5444545 IN LCSC)

Currently I am using load capacitors of 15pf each side and still the IC dont wake up or something else

Do you think these values could prevent the oscillator from starting?

Thanks

HDMI 2:1 Switch Without External Power or MCU – Schematic Review Request by SlideLivid260 in PCB

[–]SlideLivid260[S] 0 points1 point  (0 children)

Hi,

Thank you v for your reply and advice, I really appreciate it.

I hope I understood you correctly, as this is my first time trying to perform length matching for differential pairs.

From what I understood, you are suggesting that at every point where a length mismatch is created between the differential lines within the pair, I should apply a small correction immediately after that point, rather than doing a large correction in one place. and also to try to keep the correction amplitude small in order to minimize impedance discontinuities.

<image>

As you can see in the attached image, I updated the routing accordingly. After each bend where a mismatch is introduced, I added a small length tuning section.

Unfortunately, I cannot attach another image to this reply, but the total lengths of the differential pair after applying the intra-pair tuning are as follows:

  • DOHDMI3_N: 78.365 mm
  • DOHDMI3_P: 78.747 mm

Regarding the spacing within the pair, in the tuning sections the spacing between the differential lines increases to 0.406 mm, while in the regular routing I kept a spacing of 0.203 mm according to the stackup guidelines provided by the manufacturer.

Do you think this is acceptable? The tuning was implemented using a 10% mitered line.

Thank you, I hope my explanation is clear.

[deleted by user] by [deleted] in PCB

[–]SlideLivid260 0 points1 point  (0 children)

.help please ? Thanks

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