TDA9105 ST Microelectronics, TDA9105 Datasheet - Page 18

• Manufacturer Part Number: TDA9105
• Description: DEFLECTION PROCESSOR FOR MULTISYNC MONITORS
• Manufacturer: ST Microelectronics

TDA9105
OPERATING DESCRIPTION (continued)
Output Section
The H-drive signal is transmitted to the output
through a shaping block ensuring a duty cycle
adjustable from 30% to 50%. In order to ensure a
reliable operation of the scanning power part, the
output is inhibited in the following circumstances :
- V
- Xray protection activated,
- During the horizontal flyback,
- Output voluntarily inhibited through Pin 4.
The output stage is composed of a Darlington NPN
bipolar transistor. Both the collector and the emitter
are accessible (see Figure 16).
The output Darlington is in off-state when the power
scanning transistor is also in off-state.
The maximum output current is 20mA, and the
correspondingvoltage drop of the output darlington
is 1.1V typically.
It is evident that the power scanning transistor
cannot be directly driven by the integrated circuit.
An interface has to be designed between the circuit
and the power transistor which can be of bipolar or
MOS type.
Outputs inhibition
The application of a voltage lower than 1V (typ.) on
Pin 4 (duty cycle adjust) inhibits the horizontal and
vertical outputs. This is not memorised.
Figure 17 : Safety Functions Block Diagram
18/32
CC
too low,
retrace time
H-Duty cycle
V sawtooth
Flyback
Vsync
XRAY
H-fly
V
V-fly
CC off
REF
0.7V
V
1V
CC
XRAY Protection
V
CC
Inhibition
Checking
S
R
BLOCK
LOGIC
Q
to 2ND PLL
X-RAY PROTECTION : the activation of the X-ray
protection is obtained by application of a high level
on the X-ray input (>8V). Consequences of X-ray
protection are :
- Inhibition of H drive output,
- Activation of composite blanking output.
The reset of this protection is obtained by V
switch off (see Figure 17).
Figure 16 : Output stage simplified diagram,
H OUTPUT
INHIBITION
V OUTPUT
INHIBITION
showing the two possibilities of
connection
V
COMPOSITE
BLANKING
CC
21
21
V
20
20
CC
H-DRIVE
H-DRIVE
CC