VDP3104B Ver la hoja de datos (PDF) - Micronas

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VDP3104B

Video Processor Family

Micronas 

PRELIMINARY DATA SHEET

VDP 31xxB

2.9. Analog Back End

The digital RGB signals are converted to analog RGBs

using three video digital to analog converters (DAC) with

10-bit resolution. An analog brightness value is provided

by three additional DACs. The adjustment range is 40%

of the full RGB range.

Controlling the whitedrive/analog brightness and also

the external contrast and brightness adjustments is

done via the Fast Processor, located in the front-end.

Control of the cutoff DACs is via I2C-bus registers.

Finally cutoff and blanking values are added to the RGB

signals. Cutoff (dark current) is provided by three 9-bit

DACs. The adjustment range is 60% of full scale RGB

range.

The analog RGB-outputs are current outputs with cur-

rent-sink characteristics. The maximum current drawn

by the output stage is obtained with peak white RGB. An

external half contrast signal can be used to reduce the

output current of the RGB outputs to 50%.

2.9.1. CRT Measurement and Control

The display processor is equipped with an 8-bit PDM-

ADC for all measuring purposes. The ADC is connected

to the sense input pin, the input range is 0 to 1.5V. The

bandwidth of the PDM filter can be selected; it is

40/80 kHz for small/large bandwidth setting. The input

impedance is more than 1 MΩ.

Cutoff and white drive current measurement are carried

out during the vertical blanking interval. They always use

the small bandwidth setting. The current range for the

cutoff measurement is set by connecting a sense resis-

tor to the MADC input. For the whitedrive measurement,

the range is set by using another sense resistor and the

range select switch 2 output pin (RSW2). During the ac-

tive picture, the minimum and maximum beam current

is measured. The measurement range can be set by us-

ing the range select switch 1 pin (RSW1) as shown in

Fig. 2–21 and Fig. 2–22. The timing window of this mea-

surement is programmable. The intention is to automati-

cally detect letterbox transmission or to measure the ac-

tual beam current. All control loops are closed via the

external control microprocessor.

beam current

A

D

MADC

SENSE

RSW1 R2

RSW2 R3

R1

Fig. 2–21: MADC Range Switches

black

ultra black

CR + IBRM + WDRV·WDR

CR + IBRM

cutoff

R

white

drive

R

CG + IBRM

cutoff

G

CB + IBRM

cutoff

B

active

measurement

resistor

R1øR2øR3

RSW1=on, RSW2=on

PICTURE MEAS.

Lines

PMSO

Fig. 2–22: MADC Measurement Timing

R1

R1øR3

RSW2

=on

TUBE MEASUREMENT

TML

Micronas

R

G

B

R1øR2øR3

RSW1=on, RSW2=on

PICTURE MEAS.

PMST

21

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