DS100DF410 Datasheet, PDF (11/43 Pages) Texas Instruments – Low Power 10GbE Quad Channel Retimer

DS100DF410
www.ti.com
SNLS399A – JANUARY 2012 – REVISED FEBRUARY 2013
Output Driver
Once the input data has been retimed by the DS100DF410 to the recovered, cleaned, clock, it is output to the
next device in the signal path using the output driver. The DS100DF410 is commonly used in applications where
lossy transmission media exist both at the input and the output of the DS100DF410. The CTLE and the DFE
compensate for lossy transmission media at the input to the DS100DF410. The output de-emphasis
compensates for the lossy transmission media at the output of the DS100DF410.
When there is a transition in the output data stream, the output differential voltage reaches its configured
maximum value within the configured rise/fall time of the output driver. Following this, the differential voltage
rapidly falls off until it reaches the configured VOD level minus the configured de-emphasis level. This “pre-
distortion” of the output signal accentuates the high-frequency components of the output signal at the expense of
the low-frequency components. The pre-distorted signal, with its high-frequency components emphasized relative
to its low-frequency components, travels down the dispersive transmission media at the output of the
DS100DF410 with less inter-symbol interference than an undistorted signal would exhibit.
The output driver is capable of driving variable output voltages with variable amounts of analog de-emphasis.
The output voltage and de-emphasis level can be configured by writing registers over the SMBus. The
DS100DF410 cannot determine independently the appropriate output voltage or de-emphasis setting, so the user
is responsible for configuring these parameters. They can be set for each channel independently.
An idealized transmit waveform with analog de-emphasis applied is shown in Figure 2.
1.0
0.5
0.0
-0.5
-1.0
0 1 2 3 4 5 6 7 8 9 10
TIME (UI)
Figure 2. Idealized De-Emphasis Waveform
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