TEA2028B 데이터 시트보기 (PDF) - STMicroelectronics
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TEA2028B Datasheet PDF : 9 Pages
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TEA2028B
Frame Saw-tooth Generator
The current to charge the capacitor is automatically
switched to 60Hz operation to maintain constant
amplitude.
Switch Mode Power Supply (S.M.P.S) Sec-
ondary to Primary Regulation
This power supply uses a differential error amplifier
with an internal reference voltage of 1.26V and a
phase modulator operating at the line frequency.
The power transistor is turned off bythe falling edge
of the horizontal saw-tooth.
The ”soft start” device imposes a very small con-
duction angle on starting up, this angle progres-
sively increases to its nominal regulation value.
The maximum conduction angle may be monitored
by forcing a voltage on pin 15. This pin may also
be used for current limitation.
The output pulse is sent to the primary I.C.
TEA2261 via a low cost synchro transformer.
Security Circuit And Start-up Processor
When the security input (pin 28) is at a voltage
below 1.26V the two outputs are simultaneously cut
off until this voltage reaches the 1.26V threshold
again. In this case the switch mode power supply
is restarted by the ”soft start” system.
If this cycle is repeated three times, the two outputs
are cut off definitively. To reset the safety logic
circuits, VCC must be lower than 3.5V.
This circuit eliminates the risk to switch off the TV
receiver in the event of a flash affecting the tube.
On starting up the horizontal scanning function
comes into operation at VCC = 6V. The power
supply then comes into operation progressively.
On shutting down, the two functionsare interrupted
simultaneously after the first line fly back.
Frame Blanking Safety (Pin 2)
The frame blanking safety checks the normal of
frame scanning.
In case of any problem pin 4 and pin 11 is at a high
level (frame blanking) in order to protect the tube.
ABSOLUTE MAXIMUM RATINGS (limiting values) (Tamb = 25oC unless otherwise noted)
Symbol
VCC
I24
V1 2
I12
I10
I3
I4
I7
I28
V2 8
Parameter
Supply Voltage (pin 8)
Operating Supply Voltage (pin 8)
Video Identification Current (pin 24)
Positive voltage (pin 12)
Line retrace current (pin 12)
Line Output Current (pin 10)
Frame Saw-tooth Generator (pin 3)
Frame Blanking Input Current (pin 4)
SMPS Output Current (pin 7)
Safety Input Current (pin 28)
Safety Input Voltage (pin 28)
Min.
Max.
Unit
14
V
Starting threshold
13.2
V
10
mA
–5
V
+ 10
mA
– 10
40
mA
20
mA
100
mA
– 40
mA
5
mA
VCC
THERMAL DATA
Symbol
Rth (j-a)
Parameter
Junction-ambient Thermal Resistance
Value
55
Unit
°C/W
ELECTRICAL OPERATING CHARACTERISTICS
Tamb = 25oC, VCC = 12V (unless otherwise noted) Pulse duration at 50% of the ampifier
Symbol
Parameter
ICC Supply Current (pin 8) (frame, line and SMPS output without load)
SYNC SEPARATOR (Pins 26-27)
Min. Typ. Max. Unit
50 80 mA
Positive Video Input AC Coupled (output impedance of signal source < 200Ω)
– I27 Negative Clamping Current (during sync pulse)
I27 Clamping Current
Pin for slicing level 0.2V < V27pp < 2V (50% of sync amplitude)
– I26 Negative Current
I26 Positive Current
0.2 1.8 3 VPP
-25 -40 -55 µA
3
6
9 µA
0 -750 -1000 µA
17 25 36 µA
4/9
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