MC13081X データシートの表示（PDF） - Motorola => Freescale

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MC13081X

Multimode Color Monitor Horizontal, Vertical, and Video Combination Processor

Motorola => Freescale 

MC13081X

means, the overall adjustment is about 70% to 130%, which

provides additional ±10% margin.

During normal operation, the frequency switch will switch

“off” when the pin voltage falls 60 mV below the 5.0 V

reference voltage (≈ 4.94 V), and will switch “on” when the pin

voltage rises to 40 mV above the 5.0 V reference (≈ 5.04 V).

An Example: Require Trip Point @ 35 kHz

+ I12

35 x 103

122

µA

+ Trip Point Reference Current

I12

2

+ 35 k

122 x 2

µA

) + Ra

Rb

5.0 V

35 k

122 x 2

µA

+ 34857 Ω

+ Hysteresis @ 35 kHz

5.04 – 4.94

34857 Ω

V

x

122 Hz

µA

[ 350 Hz

From above, Ra + Rb = 34857 Ω

Select Ra = 24 k, and Rb = 20 k Trim Pot

The Temperature Coefficient of the potentiometer can also

be considered. If the value of the potentiometer and Ra vary

NJ Nj by 1% (for example) over temperature, the error would be:

5x

1

34857 x

0.99

–

1

34857 x

1.01

x

122 Hz

µA

[ 350 Hz

6. Horizontal Position Compensation for Selected Scan

Frequency in Using FHA Switch

Refering to Figure1 (block diagram), there is an output

from the FHA switch to the horizontal drive output. When the

FHA switch is switched on, at a specified horizontal

frequency, there is a 1/8th horizontal line shift of H–Ramp1.

Referring to Figures 5 and 9, a shift of H–Ramp1 will result in

a shift of the H–Drive output timing with respect to flyback

input.

The exact H–Drive output shift will be determined by the

PD2 voltage (Pin 45), which is generated by the flyback input

and the internal Comp1 output. That is related to the H–Drive

output transistor storage time.

This function is particularly useful for high frequency scan

rates. The higher the frequency, the more significant the

storage time becomes, compared to the horizontal scan time.

Figure 5.

H–Sync

H–Drive

Without

Shift

X

To Be Determined

By Application

H–Drive

With FHA

On

7. Proper Horizontal Phase Control

The horizontal adjustment range depends on the phase

angle between the H–Sync signal and the horizontal flyback

input. In reality, the actual adjustment range is a

combination of horizontal frequency, front porch/back porch

timing, flyback pulse width, and horizontal output transistor

storage time. The following paragraph conveys the concept

for normal operation.

There are two clamping situations for video signals. In

case 1, separate VTTL and HTTL sync are provided, the

video signal is clamped at sync tip, and the dc voltage built up

is used for black level reference. In this instance, the clamp

pulse has the same pulse width as H–Sync, and nearly the

same position. This clamp pulse is blanked out internally. In

order to allow the video output to complete the blanking

action during horizontal retrace, the horizontal phase should

not be over–adjusted. See Figure 6 for a pictorial perception.

Accordingly, the total horizontal position adjustment range is

calculated as the sum of ∆t1 and ∆t2.

Should the phase of horizontal flyback/H–Sync move

further left or right from the normal adjustment range, the black

level reference voltage will be restored, and consequently a

slightly brighter than screen dark region will be observed

on–screen. See Figure 7 for pictorial explanation.

+ ) Horizontal Blanking Time FPtime Sync Width

+ BPtime = THB

Criterion for Normal Operation:

t |Dt1|

THB

2

t |Dt2|

THB

2

In other words, the left/right 0.7 V threshold flyback

reference should be within the H–Sync pulse (shaded area

of Figure 6).

MOTOROLA ANALOG IC DEVICE DATA

13

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