"1) In section 2.2 of the TUSB9261 implementation guide, it discusses both an “analog 1.1V (VDDA11)” and “analog 3.3V (VDDA33)” supplies.
……………..In the datasheet, there is no analog 1.1V supply listed. Which document is correct?
2) Section 2.2 also states that bypass caps for the analog 1.1 and 3.3 supplies should return to the VSSA Pin.
………………In the datasheet, there is no VSSA pin listed. Is pin 44 or pin 58 the VSSA pin perhaps?
Reference copied below
2.2 1.1-V and 3.3-V Analog Supplies
A Pi filter is recommended on all analog power terminals to minimize circuit noise. These filters can be
combined on a per-rail basis for a total of two (VDDA11/VDDA11_USB2) + (VDDA33).
Analog power terminals must have a 1-μF and a 10-μF bypass capacitor connected to VSSA (ground) to
ensure proper operation. Place the capacitor as close as possible to the associated terminal to minimize
trace length. Smaller value capacitors such as 0.1-μF and 0.01-μF are also recommended on the analog
supply terminals.
3) In the schematics on page 13 of the implementation guide, there is a filtered version of 1.1V created, called USB2_1P1V. I do not see it connected anywhere. What is that used for?
4) In the schematics on page 13 of the implementation guide, there is a filtered version of 1.8V created, called VDDA_1P8V. The oscillator appears to run off the board_1P8V supply. What is that used for VDDA_1P8V used for?
5) On page 12 of the schematics in the implementation guide, it shows pins 44 and 58 as NC2 and NC3. In the spec, these are ground. I assume those are ground pins and just tie to the ground plane of the board?
6) Also, does TI recommend any of the choices of 20, 25, 30, or 40MHz clock input options as having better performance than any other frequency? (PPL range, temperature performance….etc)
7) In the TUSB9261 datasheet for the part it states:
“XI should be tied to the 1.8-V clock source and XO should be left floating.”
With Vih = 1.05 and Vil = 0.7, I would assume this to be a 1.8V CMOS type oscillator.
In the TUSB9261 Implementation guide for the part on page 10 (figure 4), the clock is shown driven from a 3.3V oscillator. Considering that TI went to the trouble to get rid of the 1.8V supply in making the 9261 from the 9260, I can see why a 3.3V oscillator would be nice to use.
So, which is correct? Does it need a 1.8v or 3.3v oscillator, and with what drive type (CMOS, TTL….)?"
Thanks,
Tim Starr on behalf of MS.B
