tda9112a STMicroelectronics, tda9112a Datasheet - Page 36

• Manufacturer Part Number: tda9112a
• Description: High-end I2c Controlled Deflection Processor For Multisync Monitor
• Manufacturer: STMicroelectronics

TDA9112A
Figure 5. Horizontal PLL1 block diagram
Figure 6. Horizontal oscillator (VCO) schematic diagram
9.3.3
The VCO makes part of both PLL1 and PLL2
loops, being an “output” to PLL1 and “input” to
PLL2. It delivers a linear sawtooth.
plains its principle of operation. The linears are ob-
tained by charging and discharging an external ca-
pacitor on pin
current forced through an external resistor on pin
RO
age
and falling linears are limited by
VHOThrHi
36/60
H/HVSyn
, which itself depends on the input tuning volt-
VHO
(PLL1 filter)
1
HPLL1F
Voltage controlled oscillator
(filtered charge pump output). The rising
thresholds filtered through
from charge pump
INTERFACE
CO
Extracted
9
Polarity
V-sync
INPUT
Sync
, with currents proportional to the
VHO
+
-
PLL1
RO
REF1
DETECTOR
COMP
LOCK
VHOThrLo
8
HOscF
Figure 6
Blank
I
0
pin.
HLckVBk
4 I
I
2
0
and
High
0
Low
ex-
3
PLL1Pump
CHARGE
VHOThrHi
At no signal condition, the
clamped to its minimum (see section 6.4 - page
10), which corresponds to the free-running VCO
frequency
mula to calculate this frequency using external
components values. The ratio between the fre-
quency corresponding to maximum
one corresponding to minimum
frequency) is about 4.5. This range can easily be
increased in the application. The PLL1 can only
lock to input frequencies falling inside these two
limits.
HLock
PUMP
(I²C)
(I²C)
6
VHOThrLo
CO
PLL1InhEn
4
fHO(0)
(I²C)
HOscF
VHOThrHi
VHOThrL
INHIBITION
+
+
-
-
SHAPER
HPosF
PLL
10
. Refer to
V-sync (extracted)
Flip-Flop
HPLL1F RO CO HOscF
RS
subsection 9.3.1
9
HPOS
VHO
(I²C)
VCO discharge
control
VHO
8
tuning voltage is
VCO
HOSC
VHO
(free-running
6
and the
4
for for-