TDA9106A View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA9106A' PDF : 30 Pages View PDF
OPERATING DESCRIPTION (continued)
Figure 12 : LOCK/UNLOCK Block Diagram
TDA9106A
5V
From
Phase
Comparator
A
NOR1
20kΩ H-Lock CAP
B
13
220nF
6.5V
6V
37 HLOCKOUT
function is described in Figure 12.
The NOR1 gate is receiving the phase comparator
output pulses (which also drive the charge pump).
When PLL1 is locked, on point A there is a very
small negative pulse (about 100ns) at each hori-
zontal cycle, so after RC filter, there is a high level
on Pin 13 which forces Hlockout to low level. Hys-
terisis comparator detects locking when Pin 13 is
reaching 6.5V and unlocking when Pin 13 is de-
creasing to 6.0V.
When PLL1 is unlocked, the 100ns negative pulse
on A becomes much larger and consequently the
average level on Pin 13 decreases. It forces Hlock-
out to go high.
The Pin 13 status is approximately the following :
- near 0V when there is no H-Sync
- between 0 and 4V with H-Sync frequency differ-
ent from VCO
- between 4 to 8 V when VCO frequency reaches
H-Sync one (but not already in phase)
- near 8V when PLL1 is locked.
Figure 13 : PLL2 Timing Diagram
H Osc
Sawtooth 7/8TH
1/8TH
6.4V
4.0V
1.6V
Flyback
Internally
Shaped Flyback
H Drive
Ts
Duty Cycle 48%
It is important to notice that Pin 13 is not an
output pin but is only used for filtering purpose
(see Figure 12).
The lock/unlock information is also available throw
I2C read.
II.3 - PLL2
Figure 14 : Flyback Input Electrical Diagram
HFLY 6
400Ω
Q1
20kΩ
GND 0V
The PLL2 ensures a constant position of the
shaped flyback signal in comparion with the saw-
tooth of the VCO (Figure 13).
The phase comparator of PLL2 (phase type com-
parator) is followed by a charge pump with ± 0.5mA
(typ.) output current.
The flyback input is composed of an NPN transis-
tor. This input must be current driven. The maxi-
mum recommanded input current is 2mA
(see Figure 14).
The duty cycle is fixed and equal to 48% of hori-
zontal-period.
Maximum storage time is about 43.75% - (Tfly/2.TH).
Typically, Tfly/TH is around20% thatmeansTs max is
around 33.75%.
II.4 - Output Section
The H-drive signal is transmitted to the output
througha shapingblock ensuringTs and dutycycle.
In order to secure scanning power part operation,
the output is inhibited in the following circum-
stances :
21/30
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