TUSB2036: TUSB2036 HUB IC

Do you have the hub connected to the host when you check the clock?

Is the reset pulled directly to 3.3V with no capacitor?  This will not provide adequate power on reset timing, a capacitor needs to be added.

Regards,

JMMN

Yeah sir, a cap is been already been added in reset part.

I have tried pulling up reset pin directly to power, still  experiencing the same issue.

Yellow mark shows reset pin connection.

Earlier the crystal (6MHz) was working , have checked using scope. It stopped After 2-5 min

sir,

As you told ,I connected capacitor directly to reset pin respected to ground without connecting it to power rail (3.3V).while powering on , i got the frequency for some 2 seconds and it stopped after that. It was 50mA when the crystal showed signal ,then when it reduced to 40mA i only got voltage around 1.5V at XTAL1 pin and in 30mA no response was there in tat pin.

I repeated three time after that .I got only 1.5V ( 40mA ) and no response that's crystal off (30mA).

Hello Dinesh,

You mentioned that the yellow mark shows the reset pin connection, but in that case RESET is connected to a pullup and the capacitor is connected to the 3.3V rail, not the RESET pin.  If the capacitor is connected directly to the pin, the reset timing is ok.

Are there any downstream devices connected?  It sounds like the hub is entering suspend mode since no devices are connected.

Regards,

JMMN

Hi,

Yeah ,i had done the said modification by you in the hardware part and checked the clock frequency for 6MHz,
faced the same issue(above mentioned amps details) as i mentioned before. I have connected three downstream devices with the IC.
Three connection form TUSB2036 connected to three MCP2200 IC ( USB to UART converter ) and then to the device.MCP2200 also has crystal (12MHz) working perfectly.

Can you check the line states on DP0 and DM0.  DP0 should be pulled high when the hub is attached to the host and then there should be some signaling from the host, does that occur?  What operating system is running on the host?

Regards,

JMMN

Its partially working now and i getting 6MHz in pin29(XTAL2).Now the issue is i am not getting 6MHz constantly in pin30(XTAL1).While placing a DSO probe in XTAL1,i am getting 6MHz for 2 second and it reduces suddenly. Again if i place probe i get it and will go after 2 second ,then taking the probe out and place again will get 6MHz for 2 second, its not constant as i m getting in pin29(XTAL2) 

Can you share the part number of the crystal, have you tried adding a trim resistor?

No, I haven't used used trim resistor.

6MHz.pdf

Attached crystal data

Ok, the load capacitance looks correct.  Can you confirm that both caps are grounded, I see a ground symbol on both caps but only one has a DGND signal connection?  Are you seeing the same issue across multiple boards?

Yeah,two caps are grounded. I have checked it.

Now have taken new board and populated all components same as i did in the previous board . Now i facing same issue in the crystal past. Power everything in check ,everything is ok ,but only the crystal portion i m not getting anything. 

Does it behave the same where it works for several seconds when a probe is attached?  

Does DP get driven low by the host?

Yeah, that was in my previous board. Now I am using new board and facing same issue of not getting crystal frequency (6MHz) in TUSB2036 pin29,30.

I am getting 2.2V in DP pin.

Are the VCC and DP0PUR set to 3.3V?  DP should be either low or greater than 3V.

Yeah ,VCC - 3.4 and DP0PUR to 3.44

DP - 2.23V

Hi Dinesh,

The 2.23V voltage is not a valid USB voltage.  Is R20 populated with a 1.5K resistor, what are the upstream DP/DM lines connected to?

Regards,

JMMN

Yes R20 populated with1.5k.

Upstream DP and DM connected to main USB port.

Can you measure the resistance on the board?  The schematic is correct, but I want to confirm the resistor installed is correct.