TUSB8040A on custom board, no functionality. Any probe points for signs of life?

Hello Nick,

It looks like a problem of connections or configuration, you can check the properly configuration of the GRST, oscillator inputs, and SUSPEND terminals. Also you should confirm (if it is possible) the voltages directly on the power terminals of the devices. Or if you want it, you can send me the schematics for a brief review.

Regards,
Diego.

Hello,

I will see if I can send you schematics.

As for configuration, these are brand new out of the package, never programmed/configured parts. They are default, which from the datasheet I understood should be functional. No?

The GRST is minimally above ground 0.2mV above ground.

I have the both of the SUSPEND terminals connected to an LED then through a 330ohm resistor to ground.

I have not probed the oscillator inputs yet, but will do so.

I am also seeing 0.5v on the VBUS identification pin which is spot on with the 1:10 resistor divider. I used 0.1% resistors for that.

Looking at the oscillator circuit, I did not have the 1Mohm resistor between XI and XO. I have added it, but no change. I will bring out the oscilloscope tomorrow.

Hi Nick,

Please let me know if you need more help.

Regards,

Diego.

Hi,

Is this the GRSTz value during reset? 

"The GRST is minimally above ground 0.2mV above ground."

If this is during normal operation, the device is being held in reset since the reset input is active low.  If that isn't the issue, check that you don't have SMBUSz pulled low, the device will wait for the SMBUS master before connecting to USB.

Regards,

Julie

Yes that is during reset. Both on power up, and I have a push button so I can press it and test.

I do not have pin A17 connected (full power management). I also do not have A19/B17/B18 connected (SDA/SCL/SMBUSz). All 4 signals are floating as per the datasheet.

Those pin settings are ok.  Can you tell if the thermal pad is making a good connection?  That is the ground of the device, if it isn't connected the device would be dead.

I can't really tell since I don't know of a probe point for the other side of the ground.

I did however use a computer controlled IR reflow machine that showed the board and device heating up to specs, the solder reflowed nicely and no movement. So I think it should be good. But I have not x-rayed it.

I also have all 4 of the OVERCURnz ports pulled to 3.3v through individual 10K resistors as well as the 4 PWRONnz pulled to 3.3v through 10K resistors.

I am in the process of posting a schematic.

Schematic as an Image: http://www.image-host.us/images/uberusbhubrev001cmasterschematicjpg___RTHAw2bYuS.jpg

Schematic as a PDF: http://www.googlywebs.com/Nick/TI_USB_Schematic_Master_Page/UberUSBHubRev001C_Master_Schematic.pdf

All the bypass caps are really close to the chip and right next to their respective pin. I have since added some jumpers over the reset button so I can jump to keep it low and measure (currently open, just jumped for testing). I also added a 1Mohm resistor between A49 and A48 piggy backing off of the crystal's pins. The crystal has a max ESR of 50 which is within the specified limit, although high.

Well I ordered some ECS-240-20-30B-DU-TR crystals from Mouser on Friday, got them today, installed, and no change. I chose that crystal because it is the part used in the evaluation kit schematic.

I still have no signs of life on the board. Not sure where to probe...

Can you send an email to USB3_support@ti.com so we can support this off-line?

Thanks,

Julie

Email sent.

Thankyou