Page 2 of the datasheet specifies Differential Output Voltage (VOUT-DIFF) under two conditions: OAMP_ = 1 for low output amplitude or OAMP_ = 0 for high output amplitude.
Does the output amplitude setting have anything to do with the standard for SAS/SATA or SATA3G/SATA6G, or is it application specific?
Answer:
While SAS and SATA do have different input and output threshold limits, depending on the application, the MODE_ and OAMP_ pins should be adjusted based on the channel losses and compliance points.
For example, if the signal at the input of the re-driver must first go through a lossy channel, it would be better to use the lower input threshold (50mVpp vs 120mVpp). The output drive level (OAMP_ control) and pre-emphasis level settings depend on how close these parts are placed to a connector and if the connector must meet compliance point requirements. For example, if this part is placed near a SATA connector on a motherboard the customer may want this port to meet compliance requirements which means that the output amplitude drive cannot be more than 700mVpp for 3Gbps data rates when measured at the SATA connector (which is where SATA compliance would be measured) so the lower swing option (OAMP = high or 1) would be used. However, if the part sits on a backplane with long trace at both the input and output of the re-driver the customer may be more concerned with end-to-end communication. In this case, pre-emphasis or higher output swing may be used.
Usually, the customer will take an eye diagram measurement at the end of the channel and adjust the part’s input EQ, output PE, and OAMP levels to get the best results.