
Intel
82845GE/82845PE Datasheet
149
Electrical Characteristics
6.6
DAC Characteristics (Intel
82845GE only)
The GMCH DAC (digital-to-analog converter) consists of three identical 8-bit DACs to provide
red, green, and blue color components. Each DAC can output a current from 0 to 255 units of
current, where one unit of current (LSB) is defined based on the VESA video signal standard.
6.6.1
DAC DC Characteristics
NOTES:
1. Measured at each R,G,B termination according to the VESA Test Procedure – Evaluation of Analog Display
Graphics Subsystems Proposal (Version 1, Draft 4, December 1, 2000)
2. Max steady-state amplitude
3. Min steady-state amplitude
4. Defined for a double 75
termination
5. Set by external reference resistor value
6. INL and DNL measured & calculated according to VESA Video Signal Standards
7. Max full-scale voltage difference among R,G,B outputs (percentage of steady-state full-scale voltage)
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 R,G,B outputs)
Table 6-7. DAC DC Characteristics: Functional Operating Range (VCCDAC = 1.5 V
±
5%)
(Intel
82845GE only)
Parameter
Min
Typical
Max
Units
Notes
DAC Resolution
8
Bits
Note 1
Max Luminance (full-scale)
0.665
0.700
0.770
V
Notes 1, 2, 4, white video level
voltage
Min Luminance
0.000
V
Notes 1, 3, 4, black video level
voltage
LSB Current
73.2
μ
A
Notes 4, 5
Integral Linearity (INL)
–1.0
+1.0
LSB
Notes 1, 6
Differential Linearity (DNL)
–1.0
+1.0
LSB
Notes 1, 6
Video channel-channel voltage
amplitude mismatch
6
%
Notes 7
Monotonicity
Guaranteed
Table 6-8. DAC Reference and Output Specifications (Intel
82845GE only)
Parameter
Min
Typical
Max
Units
Notes
Reference resistor
137
1% tolerance, 1/16 W
R,G,B termination resistor
75
Note 1, 1% tolerance, 1/16 W
R#,G#,B# termination resistor
37.5
Note 2, 1% tolerance, 1/16 W
(applies to differential routing)
Video Filter Ferrite Bead
75
Note 3, @ 100 MHz, (each R,G,B
output)
Video Filter Capacitors
3.3
pF
Note 3, two capacitors per R,G,B
output