CXA2061 Sony Corporation, CXA2061 Datasheet - Page 36

• Manufacturer Part Number: CXA2061
• Description: Y/C/RGB/D for NTSC Color TVs
• Manufacturer: Sony Corporation

5) C signal processing
The TV, CVBS or chroma signal (specified input level: burst level of 300mVp-p) selected by the video switch
passes through the ACC, chroma band-pass filter, chroma amplifier and demodulation circuits, becomes the R-Y
and B-Y signals, and input to the RGB signal processing circuit.
Like the Y output, the signals (R-Y, B-Y signals) output from this C signal processing circuit can be monitored
at Pins 30 (B2 IN) and 31 (G2 IN) by setting C DECOD register to 1. B-Y is outputted from Pin 30 (B2 IN) and
R-Y is output from Pin 31 (G2 IN). (In this case, connect Pins 30 and 31 to Vcc via a 10kΩ Ioad resister.)
If the burst level goes to –36dB or less with respect to the specified input level, the color killer operates.
6) RGB signal processing
The Y and color difference signals obtained from the Y and C signal processing circuits are first inputted to
YUV SW, and then selected and switched with the external Y and color difference signals. The selected Y and
color difference signals become the RGB signals after synthesizing the G-Y signal at the next axis circuit
(including color control). After that, the RGB signals pass through the YS1 SW switch circuit for the external
RGB signals, YM SW (half-tone switch), YS2 SW switch circuit for the external RGB signals, dynamic color,
picture control, gamma compensation, clamp, brightness control, drive control and cut-off control circuits, and
are outputted from Pins 22, 23 and 24 (R, G, B OUT).
The external RGB signals (100 IRE, 100% white 0.7Vp-p) are input to Pins 26, 27 and 28, and Pins 30, 31 and
32 in accordance with the standard for normal video signals.
The voltage applied to Pin 3 (ABL IN) is compared with the internal reference voltage, integrated by the
capacitor which is connected to Pin 42 (ABL FIL), and becomes the control signal which performs picture
control and brightness control. This ABL mode can be switched to a mode where only picture control is
performed and a mode where both picture control and brightness control are performed by ABL MODE
register. Picture control only mode also has a function to guarantee that brightness control operates when an
excessive beam current flows.
In order to adjust the white and black balance, this IC has a drive control function which adjusts the gain
between the RGB outputs and a cut-off control function which adjusts the DC Ievel between the RGB outputs.
These functions can be adjusted with three independent channels by the I
(AKB) which forms a loop between the IC and CRT and performs adjustment automatically has also been
added. This function can compensate for changes in the CRT with time.
Auto cut-off operation is as follows.
The reference voltage in the IC can be adjusted independently for R, G and B through cut-off control by the I
bus. The cathode signal current flowing during the reference pulse interval is about 13µA when the cathode
current signal is set to cut-off control center. In addition, the cathode leak current flowing during blanking can
be supported up to 100µA. Large currents flowing during the video interval may damage the areas around IK
IN, so be sure to connect a Zener diode of about 4V to the IK IN pin.
1. R, G and B reference pulses for auto cut-off, shifted 1H each in the order mentioned, appear at the top of
2. The RGB cathode current (lK) is input to Pin 21 (lK IN).
3. The cathode current input to Pin 21 (lK IN) is converted to a voltage within the IC. The reference pulse
4. The loop functions to change the DC Ievel of the R, G and B outputs in accordance with the capacitor
the picture (actually, in the overscan portion). The reference pulse uses 1H in the V blanking interval, and
is output from each R, G and B output pin.
interval of this voltage is compared with the reference voltage in the IC, and the current generated by the
resulting error voltage charges the capacitors in the IC. The charge is held during all intervals other than
the reference pulse interval.
genenated voltage so that the voltage obtained by converting the current input to Pin 21 (IK IN) matches
the reference voltage in the IC.
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2
C bus. An auto cut-off function
CXA2061S
2
C