LA7696 查看數據表（PDF） - SANYO -> Panasonic
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LA7696 Datasheet PDF : 6 Pages
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LA7696
Example 1
Control voltage on pin 12
0V
12V
R-Y=–0.212V
G-Y=+0.100V
B-Y=–0.167V min
Changed
equivalently
R-Y=–0.212V
G-Y=+0.100V
B-Y=–0.358V max
If the G-Y component is +0.1V when a color on the G-Y demodulation axis comes, the B output voltage changes with the
control voltage on pin 12 as shown in Fig. 2. The maximum change is –0.19V.
Fig. 2. Auto Green Characteristic
Function of the Service Switch
(screen grid voltage adjustment function during white balance adjustment)
The LA7679 output can be switched between the three modes a , b and c described below by the state of pin 13.
a) Service switch function (for adjustment by a serviceman in the field)
This function is provided to allow the screen grid voltage to be adjusted easily during white balance adjustment.
As shown in Figure 3, when pin 13 is connected to VCC through the resistor R13, the pin 15, 17 and 19 output transistors
will be off. At the same time, a current equivalent to the current (I13) flowing in resistor R13 flows into each of the pins
15, 17 and 19. As a result, the CRT cathode potential can be fixed at an arbitrary value by changing R13. Thus the screen
grid voltage can be adjusted easily.
The current flowing into pins 15, 17 and 19 is determined by the following formula.
I15=I17=I19=I13=
VCC
2×R13
Since pin 13 is connected to VCC through a 2.2kΩ resistor, a current of about 2.7mA flows into each pin 15, 17 and 19.
If + High B is set to 200V, the CRT cathode is fixed at 160V. The purpose of Tr1 is to protect the IC.
b) Service switch function (for adjustment at the factory)
The pin 15, 17 and 19 currents can be set to 0 (I15=I17=I19=0) by applying 5V (when VCC=12V) to pin 13. In this state
the pin 15, 17 and 19 output transistors will be off. Fix the CRT cathode potential by connecting a constant current
cource to the points (a total of 3 points) indicated with stars in Figure 3, and then adjust the screen grid voltage.
The mode is appropriate for use in the manufacturing process where the TV set is assembled.
C) Normal operation
When pin 13 is left open, the video signal will be output from pins 15, 17 and 19.
No.2921–4/6
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