TUSB8041: reset: active high or active low?

Hi Hans:

    Did you use  oscillator  or crystal? Is upstream port connected? Did you ocntrol GRST with external signal?

Regards

Brian

Hi Brian,

please find the answers below …

1. We are using a crystal:

24MHZ CRY 30PPM 18PF KX-7 12.88496

2. In our test setup upstream port three is open, port one and two are connected.

3. Signal GRST is controlled by an external signal.

Best Regards,

Hans

Hi Hans:

    from schematic: Is SMBus floating?

                             for pin 40/42, external PU is needed  for  not using power switching.

                            Since power switching is not used , how  do you supply 5v Vbus for downstream  ports?

       Did Crystal oscillating later when upstream port is connected to host?

Regards

Brian

Hi Brian,

Mr. Kremser asked me to answer your questions.

1) Is SMBus floating?

--> Yes the SMBus is floating. We just want to use this device for USB2.0 links and do not need SMBus.

2) For pin 40/42, external PU is needed  for  not using power switching. Since power switching is not used , how  do you supply 5v Vbus for downstream  ports?

--> Do you think that a PU is needed? In the data sheet I can find the following description ... (please see the phrase in bold).

--> We do not need power management. The downstream devices do not use a switched power supply and do not need +5V.

---- Data Sheet, page 7 / Description for pin 40 ----------------------

Full power management enable/SMBus address bit 1/SuperSpeed USB Connection Status
Upstream port.
The value of the pin is sampled at the de-assertion of reset to set the power switch control
follows:
0 = Power switching and over current inputs supported
1 = Power switching and over current inputs not supported
Full power management is the ability to control power to the downstream ports of the
TUSB8041 using PWRCTL[4:1]/BATEN[4:1].
When SMBus mode is enabled using SMBUSz, this pin sets the value of the SMBus slave
address bit 1.

Can be left unconnected if full power management and SMBus are not implemented.

After reset, this signal indicates the SuperSpeed USB connection status of the upstream port
if enabled through the Additional Feature Configuration register. When enabled a value of 1
indicates the upstream port is connected to a SuperSpeed USB capable port.
Note: Power switching must be supported for battery charging applications.

--------------------------------------------------------

We can mount the PUs for pins 40/42 if necessary. That´s no problem.

3) Did Crystal oscillating later when upstream port is connected to host?

I have to check this.

Can you please tell me the correct level for asserting the GRST input (high or low)?

Thank you and best regards,

Tobias

Hi Brian

regarding question 3) Did Crystal oscillating later when upstream port is connected to host?

--> With GRST input = high (+3.3V) the crystal is not oscillating when upstream port is connected to host.

Best regards,

Tobias

HI Tobias:

    If power on sequence is correct and meet timing requirement mentioned in datasheet, Crystal should oscillate when upstream port is connected to host.

Are there any soldering issue for the part?

Regadrs

Brian

Hi Brian,

we solved the problem. Unfortunately we twisted the USB P/N signals at the upstream port (and the downstream ports). After fixing this mistake the Hub works properly.

Thank you and best regards,

Tobias