DS92LV2421 Datasheet, PDF (24/50 Pages) National Semiconductor (TI) – 10 to 75 MHz, 24-bit Channel Link II Serializer and Deserializer

DS92LV2421, DS92LV2422
SNLS321B – MAY 2010 – REVISED APRIL 2013
www.ti.com
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
Ser 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.
Table 4. De-Emphasis Resistor Value
Resistor Value (kΩ)
Open
0.6
1.0
2.0
5.0
De-Emphasis Setting
Disabled
- 12 dB
- 9 dB
- 6 dB
- 3 dB
0.00
-2.00
VDD = 1.8V,
T_A = 25^oC
-4.00
-6.00
-8.00
-10.00
-12.00
-14.00
1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06
R VALUE - LOG SCALE (:)
Figure 21. De-Emph vs. R value
Power Saving Features
Ser — Power Down Feature (PDB)
The Ser has a PDB input pin to ENABLE or POWER DOWN the device. This pin is controlled by the host and is
used to save power, disabling the link when the it is not needed. In the POWER DOWN mode, the high-speed
driver outputs are both pulled to VDD and present a 0V VOD state. Note – in POWER DOWN, the optional Serial
Bus Control Registers are RESET.
Ser — Stop Clock Feature
The Ser will enter a low power SLEEP state when the CLKIN is stopped. A STOP condition is detected when the
input clock frequency is less than 3 MHz. The clock should be held at a static Low or high state. When the
CLKIN starts again, the Ser will then lock to the valid input clock and then transmits the serial data to the Des.
Note – in STOP CLOCK SLEEP, the optional Serial Bus Control Registers values are RETAINED.
1.8V or 3.3V VDDIO Operation
The Ser parallel bus and Serial Bus Interface can operate with 1.8 V or 3.3 V levels (V_DDIO) for host compatibility.
The 1.8 V levels will offer lower noise (EMI) and also a system power savings.
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