Vga; Vga Signals Definition; Reference Schematic; Layout Consideration - Emerson COM Express Carrier Design Manual

9 VGA

9.1 VGA Signals Definition

Pins for an analog VGA interface are defined in the COM Express Specification for all module types. The
interface consists of three analog color signals (red, green, blue), digital horizontal and vertical sync
signals as well as a dedicated I
capability identification. The corresponding signals can be found on the COM Express module
connector row B.

9.2 Reference Schematic

Figure 16 VGA Reference Schematic
To prevent leakage, level shift CRT DDC from 3.3 V to 5 V and enable with CB_RESET#.
Connection between logic GND and chassis depends on the grounding architecture. Connect GND
with the chassis on a single point. This connection is drawn on all schematic examples
throughout this document.

9.3 Layout Consideration

The three analog VGA signals (VGA_RED, VGA_GRN, VGA_BLU) and the two sync signals (VGA_HSYNC
and VGA_VSYNC) should be routed as single-ended signals with a trace impedance of 75 ohms. The
COM Express Carrier Type 2
Design Guide
2 C bus for display data control (DDC) implementation for monitor
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