TUSB2046BI 48 Mhz Jitter Spec

Roland Prager

Expert 4110 points

Other Parts Discussed in Thread: TUSB2046B

What is the jitter requirement for the 48 Mhz signal (pin 27) for the TUSB2046BI.

To we have a spec or a estimation for this. in the d/s nothing mention there.

thanks Roland

over 16 years ago

0 Sandeep Dattaprasad over 16 years ago

TI__Prodigy 225 points

Roland,

An ESR of around 100-200ohms would be good.

Regards,
Sandeep.

0 Roland Prager over 16 years ago in reply to Sandeep Dattaprasad

TI__Expert 4110 points

Sandeep,

What do you mean with an ESR?

I was asking for a jitter spec ..?

Roland

0 Sandeep Dattaprasad over 16 years ago in reply to Roland Prager

TI__Prodigy 225 points

Roland,

Sorry, I thought you were going to use a crystal, didn't realize that there is an option to use 48MHz clock instead of a crystal for TUSB2046B. This is an old design, I'll have to digup specs to find out what the tolerance is on the internal PLL. Will get back to you soon on this.

0 Sandeep Dattaprasad over 16 years ago in reply to Roland Prager

TI__Prodigy 225 points

Roland,

I checked with our internal PLL design for TUSb2046B and the clock must meet the USB 2.0 full speed jitter spec as outlined in Table 7-9 of the full speed spec (available at http://www.usb.org/developers/docs/). The source jitter tolerance TDJ1 has to be between -3.5 (min) to 3.5 (max) ns. TDJ2 has to be between -4 to 4 ns.

Note that there are many sources of jitter, much of which is from different delay on the driver between differential 0 to 1 and 1 to 0 transitions.

Since this hub uses a clock input pin that is separate from the oscillator input, it is more straightforward to use the clock. Tie TSTMODE high as defined in the data sheet.

0 Roland Prager over 16 years ago in reply to Sandeep Dattaprasad

TI__Expert 4110 points

Sounds good, thanks ..

Roland

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TUSB2046BI 48 Mhz Jitter Spec