USB Hub Design

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madhub

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Hi,
I am using an USB Hub in my PCB design. The Hub requires 3.3V & 1.2V power supplies, a reset & a 24MHz clock. I have given powers & reset to the IC. I am using an external crystal as the Hub has an internal crystal driver circuit. The powers & reset are proper but I am not getting the clock. Is the clock expected now or any other configurations needs to be done? The IC also has a PLLFILT (Phase Locked Loop filter capacitor) pin where an output voltage of 1.8V will come if the internal PLL circuit is configured. I am not getting this output also. Waiting for any kind of help...

With Regards,
Madhusoodana Bairy
 
Are you building this on breadboard or a proper PCB ? If its on breadboard they often have quite a high capacitance so worth looking at that as well.
 
picbits said:
Are you building this on breadboard or a proper PCB ? If its on breadboard they often have quite a high capacitance so worth looking at that as well.
Click to expand...

On a PCB, I have tried by mounting 33pF (greater than previous 18pF) as well. But did not get the clock...
 
Do you have a PPL regulater filter cap hooked up?
Do you have a 1meg load across the XTAL leads?
Are you supplying power to all the VDD leads?
 
So after you pull the reset high, the 1.8V regulator does not turn on?
I think you should check your soldering for cold joints or shorts. What current does the IC draw from the 3.3V and 1.2V rails?
 
kubeek said:
So after you pull the reset high, the 1.8V regulator does not turn on?
I think you should check your soldering for cold joints or shorts. What current does the IC draw from the 3.3V and 1.2V rails?
Click to expand...

Yes, the internal 1.8V regulator is not turning on.
The IC draws such a less current of around 220mA.
 
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