TDA9112 datasheet(29/51 Pages) STMICROELECTRONICS

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TDA9112

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depends on current value provided by the charge

pump. While not locked, the current is very low, to

slow down the changes of VCO frequency and

thus protect the external power components at

sync. signal change. In locked state, the currents

are much higher, two different values being se-

lectable via PLL1Pump I2C bus bit to provide a

means to control the PLL1 speed by S/W. Lower

value make the PLL1 slower, but more stable.

Higher values make it faster and less stable. In

general, the PLL1 speed should be higher for high

deflection frequencies. The response speed and

stability (jitter level) depend on the choice of exter-

nal components making up the loop filter. A “CRC”

filter is generally used (see Figure 4 on page 29).

Figure 4. H-PLL1 filter configuration

The PLL1 is internally inhibited during extracted

vertical sync. pulse (if any) to avoid taking into ac-

count missing or wrong pulses on the phase com-

parator. Inhibition is obtained by forcing the charge

pump output to high impedance state. The inhibi-

tion

mechanism

can

disabled

through

PLL1InhEn I2C bus bit.

The Figure 7, in its upper part, shows the position

of the VCO ramp signal in relation to input sync.

pulse for three different positions of adjustment of

horizontal position control

HPOS.

Figure 5. Horizontal PLL1 block diagram

HPLL1F

Lock

Status

PLL

INHIBITION

HPosF

SHAPER

Low

High

LOCK

COMP

CHARGE

PUMP

HPLL1F R0

VCO

HOSC

(I2C)

HPOS

INPUT

INTERFACE

H/HVSyn

Sync

PLL1Pump

V-sync (extracted)

PLL1InhEn

(I2C)

HOscF

DETECTOR

Polarity

V-sync

Extracted

REF1

(pin & I2C)

(I2C)

PLL1

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