Hi Team,
I got the following question regarding the ULPI interface to the OMAP
Hi Amit,
Following our conversation:
I will refer to two configurations:
a. OMAP3530 paired with TPS65920
b. OMAP3530 paired with TPS65921
In option a, we learn from the TPS65920 datasheet that the ULPI pads have an impedance of 90 Ohm. We conclude this from the following clip taken from the TPS65920 layout guide: (see first bullet attached).
From the fact that ULPI traces reach the OMAP3530 pin pads, we conclude that OMAP's ULPI pin pads have an impedance of 90 Ohm as well (On Mistral's EVM no termination exists on those line, only jumper resistors).
On the other hand, in option b we learn from the document SWCU066 that TPS65921's ULPI pins have been modified to have an impedance of 50 Ohm instead of the 90 Ohm its predecessor had. Still, the TPS65921 connects to the same OMAP3530. So now it appears as if the ULPI pin pads on OMAP3530 have an impedance of 50 Ohm instead of 90.
My questions:
1. Which one is it for the OMAP? 50 or 90?
2. How is it possible that OMAP can be connected to two different components with different impedances, and not require any termination?
3. Bottom line - As I see it, some termination is required this way or the other, though on Mistral's EVM none exists. I need to know what TI's recommendation is regarding the way OMAP and TPS65920 are connected, since this is the PMIC we are currently using. What kind of termination is required?
Regards,
Matan Medalion
