TUSB2036: Hub not enumerating..

Mir M

Prodigy 30 points

Part Number: TUSB2036
Other Parts Discussed in Thread: TLV740P

Tool/software:

Greetings!

Trying to build a 3-port hub with TUSB2036 with the following pin config:

BUSPWR: low; bus power mode
OCPROT: low; OC protection not used
NP3: low; 3 ports
NPINT0, NPINT1: low; all ports removable
EXTMEM: high; eeprom not used
MODE: low; 6mhz xtal used

Attached is the schematic of hub portion.

Behavior:
On Windows 11, when upstream cable is plugged in:

Most times the suspend goes low soon after plugging in (turning the LED on)
Occasionally, the suspend pin goes high and turns off LED soon after plugging in (unable to reproduce consistently)

In both cases, the device does not enumerate and does not show up in device manager.

USB protocol analyzer (Totalphase Beagle) does not show any bus activity in both of the scenarios above.

Crystal is operational - shows waveform but have not measured frequency

Downstream part of the board is not populated - would this be an issue?
Reset circuit - tried (1uf, 1.5k), (1uf, 2.7k) - no success

22pf caps for data lines in both up/downstream path are not used since datasheet says they are for EMI - is this an issue for enumeration?

Crystal being used is ecsxtal.com/.../ whose load cap is 20pf, but the circuit uses 33pf since that is commonly recommended - would this be an issue?

I would really appreciate your insights on getting the circuit enumerate. Thanks in advance!

7 months ago

0 Brian Zhou 7 months ago

TI__Guru*** 145215 points

Hi Sir:

Did DP0PUR goes high? Downstream port connection should not affect upstream port status.

Can you take waveform for 3.3v/1.1v/Reset as well as XI clock?

Best

Brian

0 Mir M 7 months ago in reply to Brian Zhou

Prodigy 30 points

Hi Brian, Thanks for the quick response. DP0PUR remains low, and suspend is low as well.

sure, I can take 3.3v/Reset/Xtal1 waveform and update the post. Where do i capture 1.1v waveform?

Best Regards..

+1 Brian Zhou 7 months ago in reply to Mir M

TI__Guru*** 145215 points

It seems something is wrong , DP0PUR should go high.

Sorry, there is no 1.1v supply for this device.

Best

Brian

0 Mir M 7 months ago in reply to Brian Zhou

Prodigy 30 points

Ok, will build another board to test things out. Just so I've insight into what is expected, could you please clarify the following: If upstream VBUS/GND is used to feed 3v3, after Reset TUSB2036 will set DP0PUR high even if DP0+ and DP0- are open -- correct? Thank you.

0 Brian Zhou 7 months ago in reply to Mir M

TI__Guru*** 145215 points

correct, after reset, DP0PUR should pull up to 3.3v.

Best

Brian

0 Mir M 7 months ago in reply to Brian Zhou

Prodigy 30 points

Hi Brian,

With a new board assembled here is an update:

Hub still does not enumerate, and suspend pin remains low, so the LED from the schematics is on and steady
DP0PUR is measured to be 3.4V
Attached are the XTAL1, Reset, and VCC/Pin3 waveforms.
VRM/LDO is TLV740P with 4.7uF output capacitor; its output waveform looks similar to that of VCC/Pin3

I would appreciate your input on how to proceed. Thanks in advance.

0 Brian Zhou 6 months ago in reply to Mir M

TI__Guru*** 145215 points

XTAL1 signal should be around 3.3v, but it's only 2.1v in your waveform.

from power supply waveform, it seems it switching at certain frequency, you may need to adding more caps or filter it with bead.

Best

Brian

0 Mir M 6 months ago in reply to Brian Zhou

Prodigy 30 points

Thanks Brian.

1. Regd, power supply waveform -- sure will use bead filter.

2. Regd. XTAL1, as I mentioned in the intro above, the crystal part mentioned in the TUSB2036 datasheet is no longer available, I'm using ECS part https://ecsxtal.com/products/crystals/surface-mount-crystals/ecs-60-20-5px-tr/ whose load capacitance is 20pF, however, I ended up using 33pF since that is the recommended value in all of TUSB documentation, and lacking any insight into how TUSB works. Could this be an issue? I'll have 20pF part soon, and I'll try with that. Will the value of feedback resistor remain 1.5K or will it have to change as well?

Best regards.

0 Brian Zhou 6 months ago in reply to Mir M

TI__Guru*** 145215 points

it could be, just keep 1.5k for feedback resistor.

we use X49SS2-6.000-F20LJDT as replacement.

Best

Brian

0 Mir M 6 months ago in reply to Brian Zhou

Prodigy 30 points

An update: The hub enumerates and all 3 downstream ports work. There was a drysolder on DP pin of the TVS diode that was causing issues. Thank you for the help!

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TUSB2036: Hub not enumerating..