TDA9109N View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA9109N' PDF : 32 Pages View PDF
TDA9109/N
OPERATING DESCRIPTION (continued)
II.2 - PLL1
The PLL1 consists of a phase comparator, an
external filter and a voltage-controlled oscillator
(VCO). The phase comparator is a ”phase fre-
quency” type designed in CMOS technology. This
kind of phase detector avoids locking on wrong
frequencies. It is followed by a ”charge pump”,
composed of two current sources : sunk and sour-
ced (typically I = 1mA when locked and I = 140µA
whenunlocked).This differencebetweenlock/unlock
allows smooth catching of the horizontal frequency
by PLL1. This effect is reinforced by an internal
original slow down system when PLL1 is locked,
avoiding the horizontal frequency changing too
quickly. The dynamic behaviour of PLL1 is fixed by
an external filter which integrates the current of the
charge pump. A ”CRC” filter is generally used
(see Figure 7).
The PLL1 is internally inhibited during extracted
vertical sync (if any) to avoid taking in account
missing pulses or wrong pulses on phase compa-
rator.The inhibition is done by a switch located
between the charge pump and the filter (see Fig-
Figure 8 : Block Diagram
H/HVIN 1
INPUT
INTERFACE
Tramext
LOCKDET
COMP1
E2
High
Low
ure 8). The VCO uses an external RC network. It
delivers a linear sawtooth obtained by the charge
and the discharge of the capacitor, with a current
proportional to the current in the resistor. The typi-
cal thresholds of the sawtooth are 1.6V and 6.4V.
The control voltage of the VCO is between 1.33V
and 6V (see Figure 9). The theorical frequency
range of this VCO is in the ratio of 1 to 4.5.
The effective frequency range has to be smaller
(1 to 4.2) due to clamp intervention on the filter
lowest value.
Figure 7
PLL1F
7
1.8kΩ
1µF
4.7µF
Lock/Unlock
PLL1F R0 C0
Status
Tramext
I2C
7
Forced
65
Frequency
CHARGE
PUMP
PLL
INHIBITION
HPOSITION
8
PHASE
ADJUST
VCO
I2C
HPOS
Adj.
OSC
Figure 9 : Details of VCO
18/32
Loop
Filter
7
(1.3V < V7 < 6V)
I0
2
I0
4 I0
6
R0
6.4V
1.6V
RS
FLIP FLOP
5 6.4V
C0
1.6V
0 0.875TH TH
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