DDP3310B datasheet(13/60 Pages) MICRONAS

13 / 60 page

ADVANCE INFORMATION

DDP 3310B

Micronas

2.2.3. Fast-Blank Monitor

The presence of external analog RGB sources can be

detected by means of a Fast-Blank monitor. The status

of the selected Fast-Blank input can be monitored via

an I2C register. There is a 2-bit information, giving

static and dynamic indication of a Fast-Blank signal.

The static bit is directly reading the Fast-Blank input

line, whereas the dynamic bit is reading the status of a

flip flop triggered by the negative edge of the Fast-

Blank signal.

With this monitor logic it is possible to detect if there is

an external RGB source active and if it is a full-screen

insertion or only a box. The monitor logic is connected

directly to the FBLIN1 or FBLIN2 pin. Selection is done

via I2C register.

Fig. 2–9: Fast-Blank selection logic

2.2.4. CRT Measurement and Control

The display processor is equipped with an 8/12-bit

PDM-ADC for all picture tube measuring purposes.

This MADC is connected to the SENSE input pin, the

input range is 0 to 1.6V.

Cutoff and white-drive current measurement are car-

ried out with 8-bit resolution during the vertical blank-

ing interval. The current range for cutoff measurement

is set by connecting the resistor R1 to the SENSE

input. Due to the fact of a 1:10 relation between cutoff

and white-drive current, the range select 2 output

(RSW2) becomes active for the white-drive measure-

ment and connects R3 in parallel to R1, thus determin-

ing the correct current range. During the active picture,

the MADC is used for the average beam current limiter

with a 12-bit resolution. Again, a different measure-

ment range is selected with active range select 1&2

outputs (RSW1&RSW2) connecting R2 in parallel to

R3 and R1. See Fig. 2–10 and Fig. 2–11 for the corre-

sponding timing. These measurements are typically

done at the summation point of the picture tube cath-

ode currents.

Another method uses two different current measure-

ments. The range switch 1 pin (RSW1) can be used as

a second Sense input, selectable by software. In this

case, the cutoff and white-drive currents are measured

as before at the SENSE input. The active picture mea-

surement can be done with the second Sense input

(RSW1). The signal may come (via a proper interface)

from the low end of the EHT coil (CRT anode current).

In this case, the resistor R2 in Fig. 2–10 has to be

removed.

Fig. 2–10: MADC range switch

FBLIN1

FBLIN2

Fast-

Blank

Monitor

FBPOL

FBFOH1

FBPRIO

Fast-

Blank

int

Fast-

Blank

Selection

FBFOH2

FBMON

FBFOL1

FBFOL2

SENSE

RSW1

RSW2

Beam Current 1

MADC

Beam Current 2

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