Datasheet
Electrical Characteristics
154 Intel
®
82845G/82845GL/82845GV GMCH Datasheet
6.6.2 DAC Reference and Output Specifications
NOTES:
1. VESA Video Signal Standard
2. Complement DAC channel output termination resistors are only required for differential video routing to the
VGA connector.
3. Video filter capacitors and ferrite bead arranged in a PI configuration (one PI filter for RED, GREEN, BLUE
outputs)
6.6.3 DAC AC Characteristics
NOTES:
1. Measured at each RED, GREEN, BLUE termination according to the VESA Test Procedure – Evaluation of
Analog Display Graphics Subsystems Proposal (Version 1, Draft 4, December 1, 2000)
2. R,G,B Max Video Rise/Fall Time: 50% of minimum pixel clock period
3. R,G,B Min Video Rise/Fall Time: 20% of minimum pixel clock period
4. Max settling time: 30% of minimum pixel clock period
5. Video channel-channel output skew: 25% of minimum pixel clock period
6. Overshoot/undershoot: ± 12% of black-white video level (full-scale) step function
7. Noise injection ratio: 0.5% of maximum luminance voltage (dc to max. pixel frequency)
Table 6-8. DAC Reference and Output Specifications
Parameter Min Typical Max Units Notes
Reference resistor 137 Ω 1% tolerance, 1/16 W
RED, GREEN, BLUE
termination resistor
75
Ω Note 1, 1% tolerance, 1/16 W
RED#,GREEN#,BLUE#
termination resistor
37.5
Ω
Note 2, 1% tolerance, 1/16 W
(applies to differential routing)
Video Filter Ferrite Bead 75
Ω
Note 3, @ 100 MHz, (each RED,
GREEN, BLUE output)
Video Filter Capacitors 3.3 pF
Note 3, two capacitors per RED,
GREEN, BLUE output
Table 6-9. DAC AC Characteristics
Parameter Min Typical Max Units Notes
Pixel Clock Frequency 350 MHz
RED, GREEN, BLUE Video
Rise Time
0.57 1.43 ns
Notes 1, 2, (10–90% of black-to-
white transition, at 350 MHz pixel
clock)
RED, GREEN, BLUE Video
Fall Time
0.57 1.43 ns
Notes 1, 3, (90–10% of white-to-
black transition, at 350 MHz pixel
clock)
Settling Time 0.86 ns Notes 1, 4, at 350 MHz pixel clock
Video channel-to-channel
output skew
0.714 ns Notes 1, 5, at 350 MHz pixel clock
Overshoot/ Undershoot -0.084 +0.084 V
Notes 1, 6, Full-scale voltage step
of 0.7 V
Noise Injection Ratio 0.5 % Notes 1, 7