Dac Power Requirements - Intel 855GME Design Manual

®
Intel 855GME Chipset and Intel
The recommended routing of the termination resistors is shown in
Figure 77. DAC R, G, B Routing and Resistor Layout Example
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
specification.
®
6300ESB ICH Embedded Platform Design Guide
Complement Output
(e.g. BLUE#)
Via to
ground
plane
20 mil Space between channels
Large via or
multiple vias
straight down to
ground plane
®
855GM/855GME Chipset (GMCH) Datasheet for latest AC/DC
January 2007
Integrated Graphics Display Port
Figure
DAC Output
855GME
(e.g. BLUE)
20 mil Space between channels
37.5Ω Trace Impedance
75Ω Trace Impedance
VGA
Π-Filter
75.0
75.0Ω, 1%,
1/16W, SMT metal
film resistor
No toggling
signals should be
routed near these
video outputs
77.
157