Original question:
Hi,
I'd like to confirm the value of AC coupling cap for SATA only application.
Ii is clear to have the ferrite bead along with 49.9 ohm resistor at between C(TX2) and SATA connector.
For AC coupling capacitor, there are 10nF nearby intel chipset SATA TX and RX already.
- Does it still need all TX1, TX2, RX1, and RX2 A/C coupling capacitors?
- If so, the value is as below, right?
TX1, TX2, and RX2 A/C coupling capacitor : 220nF
RX1 A/C coupling capacitor : 330nF
Thanks
Mark
Hi Mark,
To answer your questions
Does it still need all TX1, TX2, RX1, and RX2 A/C coupling capacitors?
Yes
If so, the value is as below, right?
TX1, TX2, and RX2 A/C coupling capacitor : 220nF
RX1 A/C coupling capacitor : 330nF
Yes
For SATA you need AC coupling capacitors on TX1 (220nF), RX1 (330nF), TX2 (220nF), and RX2 (220nF) of the 1002A re-driver. The SATA device should also have AC capacitors (12nF max).
Best,
Shane
Hi Shane,
Thanks for your feedback.
I have another question about L/R terminator.
Please refer to above figure.
Since there are 10nF on both TX and RX of intel chipset SATA.
Should I add FB+49.9 on RX path between chipset and TUSB1002A?
Thanks
Mark
Hi Mark,
The image you show is correct, let me explain.
The 1002A will perform RX detect on its transmitters before passing signals. This only happens on the TX pins of the re-driver and is the reason FB + 49.9ohm resistors are needed. The 10nF capacitors will stop RX detect from happening so if you have a TX line with these capacitors you need FB + 49.9ohm on that line.
This is not the case for RX lines. You do not need FB + 49.9ohm resistors on the RX lines because the RX detect happens only on TX lines of the 1002A.
Best,
Shane
