TUSB2046B not detected

John Williams1

hello,

I am having difficulties with a circuit i am trying to develop.

it is powered externally with 3.3V as VCC.

the Reset time is 0.02s

The clock only works if the reset is set low (as seen in the schematic) rather than high.

Nothing is attached to its downstream ports at the moment.

Also I would like to know if it is possible to combine two of these hubs together to create a 7way port?

Regards

0 Elias Villegas M. over 12 years ago

Hello,

There is an error on the RESET# implementation, you have to switch the position of the 2.2uF capacitor with the 4K7.

Regards.

0 John Williams1 over 12 years ago in reply to Elias Villegas M.

I have tried that, but i get no clock signal and the device still isn't recognized by the PC.

I have also tried this with the recommended 2Kohm pullup and 0.1uF pull down

0 Elias Villegas M. over 12 years ago in reply to John Williams1

The switch I am telling you (between 2.2uF and 4K7) has to be done, otherwise the hub will never work.

The series resistors on DP/DM are labeled as 27K, if this is not a typo then they must be changed to 27 ohm.

You schematic looks correct, check the power rails, Is the SUSPEND output active?

Regards.

0 John Williams1 over 12 years ago in reply to Elias Villegas M.

They are switched over to the correct way, but the hub will not run. (pullup resistor and pull down capacitor)

The 27K is a typo, 27ohm resistors were used.

I have a very clean 3V3 power rail and also a clean GND

Suspend is high

0 Elias Villegas M. over 12 years ago in reply to John Williams1

Hello,

SUSPEND should be low, can you take a scope capture of the power-up sequence showing 3.3V, RESET# and XI.

Make sure the OVRCUR# terminals are high.

Regards.

0 John Williams1 over 12 years ago in reply to Elias Villegas M.

after a full days work i found the fault was a short on the output of the cyrstal, shorting it to ground.

Thanks for the help

Interface forum