DS92LV0411_14 Datasheet, PDF (28/53 Pages) Texas Instruments – 5 - 50 MHz Channel Link II Serializer/Deserializer with LVDS Parallel Interface

DS92LV0411, DS92LV0412
SNLS331B – MAY 2010 – REVISED APRIL 2013
EMI REDUCTION FEATURES
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Data Randomization & Scrambling
Channel Link II Ser / Des feature a 3 step encoding process which enables the use of AC coupled interconnects
and also helps to manage EMI. The serializer first passes the parallel data through a scrambler which
randomizes the data. The randomized data is then DC balanced. The DC balanced and randomized data then
goes through a bit shuffling circuit and is transmitted out on the serial line. This encoding process helps to
prevent static data patterns on the serial stream. The resulting frequency content of the serial stream ranges
from the parallel clock frequency to the nyquist rate. For example, if the Ser / Des chip set is operating at a
parallel clock frequency of 50 MHz, the resulting frequency content of serial stream ranges from 50 MHz to 700
MHz ( 50 MHz *28 bits = 1.4 Gbps / 2 = 700 MHz ).
Ser — Spread Spectrum Compatibility
The RxCLKIN of the Channel Link input is capable of tracking spread spectrum clocking (SSC) from a host
source. The RxCLKIN will accept spread spectrum tracking up to 35kHz modulation and ±0.5, ±1 or ±2%
deviations (center spread). The maximum conditions for the RxCLKIN input are: a modulation frequency of
35kHz and amplitude deviations of ±2% (4% total).
SER — INTEGRATED SIGNAL CONDITIONING FEATURES
Ser — VOD Select (VODSEL)
The DS92LV0411 differential output voltage may be increased by setting the VODSEL pin High. When VODSEL
is Low, the DC VOD is at the standard (default) level. When VODSEL is High, the DC VOD is increased in level.
The increased VOD is useful in extremely high noise environments and also on extra long cable length
applications. When using de-emphasis it is recommended to set VODSEL = H to avoid excessive signal
attenuation especially with the larger de-emphasis settings. This feature may be controlled by the external pin or
by register.
Input
VODSEL
H
L
Table 4. Ser — Differential Output Voltage
VOD
mV
±450
±300
Effect
VOD
mVp-p
900
600
Ser — De-Emphasis (De-Emph)
The De-Emph pin controls the amount of de-emphasis beginning one full bit time after a logic transition that the
device drives. This is useful to counteract loading effects of long or lossy cables. This pin should be left open for
standard switching currents (no de-emphasis) or if controlled by register. De-emphasis is selected by connecting
a resistor on this pin to ground, with R value between 0.5 kΩ to 1 MΩ, or by register setting. When using De-
Emphasis it is recommended to set VODSEL = H.
Resistor Value (kΩ)
Open
0.6
1.0
2.0
5.0
Table 5. De-Emphasis Resistor Value
De-Emphasis Setting
Disabled
- 12 dB
- 9 dB
- 6 dB
- 3 dB
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