January 2007 157
Intel
®
855GME Chipset and Intel
®
6300ESB ICH Embedded Platform Design Guide
Integrated Graphics Display Port
The recommended routing of the termination resistors is shown in Figure 77.
6.1.5 DAC Power Requirements
The DAC requires a 1.5 V supply through its two VCCADAC balls. The two may share a set of
capacitors, 0.1 µF and 0.01 µF, but this connection shall have low inductance. Separate analog
power or ground planes are not required for the DAC.
However, because the DAC is an analog circuit, it is particularly sensitive to AC noise seen on its
power rail. Designs shall provide as clean and quiet a supply as possible to the VCCA_DAC.
Additional filtering and/or separate voltage rail may be needed to do so.
• Video DAC Power Supply DC Specification: 1.50 V ± 5 percent
• Video DAC Power Supply AC Specification:
— ± 0.3 percent from 0.10 Hz to 10 MHz
— ± 0.95 percent from 10 MHz to maximum pixel clock frequency
• Absolute minimum voltage at the VCCA package ball = 1.40 V
Refer to the latest
Intel
®
855GM/855GME Chipset (GMCH) Datasheet for latest AC/DC
specification.
Figure 77. DAC R, G, B Routing and Resistor Layout Example
Complement Output
(e.g. BLUE#)
DAC Output
(e.g. BLUE)
Via to
ground
plane
37.5Ω Trace Impedance
20 mil Space between channels
855GME
20 mil Space between channels
Large via or
multiple vias
straight down to
ground plane
No toggling
signals should be
routed near these
video outputs
75.0Ω, 1%,
1/16W, SMT metal
film resistor
75.0
VGA
Π-Filter
75Ω Trace Impe
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