Lvds Routing Guidelines - Intel 855GME Design Manual

®
Intel 855GME Chipset and Intel
Integrated Graphics Display Port
6.2.2

LVDS Routing Guidelines

Table 46. LVDS Signal Group Routing Guidelines
Signal Group
Topology
Reference Plane
Differential Mode Impedance (Zdiff)
Nominal Trace Width
Nominal Pair Spacing (edge to edge)
Minimum Pair to Pair Spacing
(See exceptions for breakout region below.)
Minimum Serpentine Spacing
Minimum Spacing to Other LVDS Signals
(See exceptions for breakout region below.)
Minimum Isolation Spacing to non-LVDS
Signals
Maximum Via Count
Package Length Range – P1
Total Length –
Clock Length Matching
Clock to Clock Length Matching (Total Length)
Breakout Exceptions
(Reduced geometries for GMCH breakout
region)
The traces associated with the LVDS Transmitter timing domain signals are differential traces
terminated across 100 Ω ± 15 Ω and shall be routed as:
•
Strip-line only.
•
Isolate all other signals from the LVDS signals to prevent coupling from other sources onto the
LVDS lines.
•
Use controlled impedance traces that match the differential impedance of your transmission
medium (i.e., cable) and termination resistor (Note: the transmission medium's Zdiff shall be
maintained to 100 Ω ± 15 percent).
•
Run the differential pair trace lines as close together as possible as soon as they leave the IC,
not greater than 10 mils. This helps eliminate reflections and ensure noise is coupled as
common mode. Plus, noise induced on the differential lines is much more likely to appear as
common mode, which is rejected by the receiver.
•
The LVDS transmitter timing domain signals have a maximum trace length of 10.0 inches.
This maximum applies to all of the LVDS transmitter signals.
•
Traces must be ground referenced and must not switch layers between the GMCH and
connector.
160
®
6300ESB ICH Embedded Platform Design Guide
Parameter Definition
LVDS
Differential Pair Point to Point
Ground Referenced
100 Ω
±
15%
4 mils
7 mils
20 mils
20 mils
20 mils
20 mils
2 (per line)
±
550 mils 150mils
(Refer to Table 47 for exact lengths.)
Max 10"
Match all segments to ± 20 mils (Refer to
more information.)
±
Match clocks to X0 20 mils
Breakout section shall be as shorter as possible. Try to
maintain trace width as 4 mils, spacing 7 mils, while the
spacing between pairs may be 10-20 mils.
Section 6.2.1 for