Datasheet

Intel
®
82845G/82845GL/82845GV GMCH Datasheet 153
Electrical Characteristics
6.6 DAC Characteristics
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
Ω 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)
Figure 6-1. System Bus HCLKP/N VCROSS Range
VHigh Average (mV) (Measured)
Vcross(rel) Max = 0.5 (Vhavg - 0.710) + .550
Vcross(rel) Min = 0.5 (Vhavg - 0.710) + .250
550
500
450
400
350
300
250
625 650 675 700 725 750 775 800
200
825 850
Allowable
Crossing Point (mV)
Vcross(rel) Max
Vcross(rel) Min
Vcross Range
For VHigh < 0.71V
Vcross Range
For VHigh > 0.71V
Table 6-7. DAC DC Characteristics: Functional Operating Range (VCCDAC = 1.5 V ±5%)
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
µA 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