gs2988 Gennum Corporation, gs2988 Datasheet - Page 14

• Manufacturer Part Number: gs2988
• Description: Gs2988 Dual-slew-rate, Cable Driver With 3gb/s Capability
• Manufacturer: Gennum Corporation

5. Application Information
5.1 PCB Layout
Special attention must be paid to component layout when designing serial digital
interfaces for HDTV.
An FR-4 dielectric can be used, however, controlled impedance transmission lines are
required for PCB traces longer than approximately 1cm. Note the following PCB artwork
features used to optimize performance:
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NOTE: For more recommendations on Trace Lengths, ORL Inductor Values and other
PCB Layout Considerations, please refer to Gennum’s GS2989 Design Guide
(Doc ID 52070).
5.2 Typical Application Circuit
Figure 5-1: Typical Application Circuit
GS2988 Dual-Slew-Rate, Cable Driver with 3Gb/s
Capability
Data Sheet
52131 - 1
GND
GND
SMA
SMA
The PCB trace width for HD rate signals is closely matched to SMT component
width to minimize reflections due to changes in trace impedance
The PCB ground plane is removed under the GS2988 output components to
minimize parasitic capacitance (NOTE: care should be taken, as removing too much
of the plane will make the system susceptible to EMI)
The PCB ground plane is removed under the GS2988 RSET pin and resistor to
minimize parasitic capacitance. The RSET resistor should be directly connected to
the VCC plane
Input and output BNC connectors are surface mounted in-line to eliminate a
transmission line stub caused by a BNC mounting via high-speed traces
High-speed traces are curved to minimize impedance variations due to change of
PCB trace width
NOTE: All resistors in Ohms, capacitors in Farads,
and inductors in Henrys, unless otherwise stated.
4u7
4u7
February 2010
GND
VCC
*Customer to choose resistor value.
10n
10n
GND
R*
10n
1
2
4
DDI
DDI
RSET
14
VCC
9
GS2988
GND
3
16
10
6
SDO
SDO
12
11
75R
75R
VCC_Term
VCC_Term
10n
10n
* Typical value: varies with layout, and represents a trade-off
between good eye shape and output return loss.
5n6 is the optimum value for an 800mV output swing.
6n8 is the optimum value for an 1800mV output swing.
GND
GND
5n6*
75R
75R
5n6*
4u7
4u7
BNC
BNC
GND
GND
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