DS99R101_13 Datasheet, PDF (19/29 Pages) Texas Instruments – DS99R101/DS99R102 3-40MHz DC-Balanced 24-Bit LVDS Serializer and Deserializer

DS99R101, DS99R102
www.ti.com
SNLS240D – MARCH 2007 – REVISED APRIL 2013
APPLICATIONS INFORMATION
USING THE DS99R101 AND DS99R102
The DS99R101/DS99R102 Serializer/Deserializer (SERDES) pair sends 24 bits of parallel LVCMOS data over a
serial LVDS link up to 960 Mbps. Serialization of the input data is accomplished using an on-board PLL at the
Serializer which embeds clock with the data. The Deserializer extracts the clock/control information from the
incoming data stream and deserializes the data. The Deserializer monitors the incoming clockl information to
determine lock status and will indicate lock by asserting the LOCK output high.
POWER CONSIDERATIONS
An all CMOS design of the Serializer and Deserializer makes them inherently low power devices. Additionally,
the constant current source nature of the LVDS outputs minimize the slope of the speed vs. I_DD curve of CMOS
designs.
NOISE MARGIN
The Deserializer noise margin is the amount of input jitter (phase noise) that the Deserializer can tolerate and still
reliably recover data. Various environmental and systematic factors include:
Serializer: TCLK jitter, V_DD noise (noise bandwidth and out-of-band noise)
Media: ISI, V_CM noise
Deserializer: V_DD noise
For a graphical representation of noise margin, please see Figure 16.
TRANSMISSION MEDIA
The Serializer and Deserializer can be used in point-to-point configuration, through a PCB trace, or through
twisted pair cable. In a point-to-point configuration, the transmission media needs be terminated at both ends of
the transmitter and receiver pair. Interconnect for LVDS typically has a differential impedance of 100 Ohms. Use
cables and connectors that have matched differential impedance to minimize impedance discontinuities. In most
applications that involve cables, the transmission distance will be determined on data rates involved, acceptable
bit error rate and transmission medium.
LIVE LINK INSERTION
The Serializer and Deserializer devices support live pluggable applications. The “Hot Inserted” operation on the
serial interface does not disrupt communication data on the active data lines. The automatic receiver lock to
random data “plug & go” live insertion capability allows the DS99R102 to attain lock to the active data stream
during a live insertion event.
PCB LAYOUT AND POWER SYSTEM CONSIDERATIONS
Circuit board layout and stack-up for the LVDS SERDES devices should be designed to provide low-noise power
feed to the device. Good layout practice will also separate high frequency or high-level inputs and outputs to
minimize unwanted stray noise pickup, feedback and interference. Power system performance may be greatly
improved by using thin dielectrics (2 to 4 mils) for power / ground sandwiches. This arrangement provides plane
capacitance for the PCB power system with low-inductance parasitics, which has proven especially effective at
high frequencies, and makes the value and placement of external bypass capacitors less critical. External bypass
capacitors should include both RF ceramic and tantalum electrolytic types. RF capacitors may use values in the
range of 0.01 uF to 0.1 uF. Tantalum capacitors may be in the 2.2 uF to 10 uF range. Voltage rating of the
tantalum capacitors should be at least 5X the power supply voltage being used.
Surface mount capacitors are recommended due to their smaller parasitics. When using multiple capacitors per
supply pin, locate the smaller value closer to the pin. A large bulk capacitor is recommend at the point of power
entry. This is typically in the 50uF to 100uF range and will smooth low frequency switching noise. It is
recommended to connect power and ground pins directly to the power and ground planes with bypass capacitors
connected to the plane with via on both ends of the capacitor. Connecting power or ground pins to an external
bypass capacitor will increase the inductance of the path.
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: DS99R101 DS99R102
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