la7688b Sanyo Semiconductor Corporation, la7688b Datasheet - Page 14

• Manufacturer Part Number: la7688b
• Description: Pal/ntsc Color Television-use Single-chip Lsi
• Manufacturer: Sanyo Semiconductor Corporation

Continued from preceding page.
[Chroma block NTSC]
Demodulator
output ratio
Demodulation
angle
ACC amplitude
characteristics 1/2
ACC phase
characteristics 1/2
Killer operating
point
Killer hysteresis
RGB output level
Parameter
B/RP
G/RP
G/BP
∠RBP
ACC1n
ACC2n
PCC1n
PCC2n
EKILn
DEKILn
EBn
Symbol
O-33
O-35
O-34
O-35
O-33
O-34
O-33
O-35
O-33
O-33
O-33
O-33
O-33
O-33
O-33
point
Test
(4)
(4)
(4)
(4)
(1)
0dB/6dB
(1)
-20dB
(1)
0dB/6dB
(1)
-20dB
(1) : Level
variable
(1) : Level
variable
(1)
Y-OFF
chroma
50%
signal
Input
Calculate the ratio between output
amplitude BM corresponding to 0
degrees and 180 degrees of the chroma
input in the B output and output amplitude
RM corresponding to 90 dgrees and 270
degrees of the chroma input in the R
output.
Measure the output amplitude
corresponding to 90 degrees and 270
degrees of the chroma input in the G
output and calculate the ratio to the above
RM.
Measure the output amplitude
corresponding to 0 dgrees and 180
degrees of the chroma input in the G
output and calculate the ratio to the above
BM.
Take Ba and Bb as the output amplitudes
corresponding to the first and the third of
the chroma 8-division signal inputs in the
B output respectively and calculate by
using the following formula. For the R
output also, calculate with Ra and Rb.
Adjust the relative phase of the SG's
chroma and burst so that the B output
assumes a horizntal waveform. And then
measure the B output's Vp-p value.
After changing the input signal level from
0dB to 6dB, adjust the relative phase of
the SG's chroma and burst again when
the B-Y output assumes a horizontal
waveform ; that adjusted phase amount is
PCC1n. Measure the B output's Vp-p at
that moment and calculate the ratio in dB
to the B output's Vp-p when the input
signal level is 0dB ; that ratio is ACC1n.
In the same manner as above, measure
the variations of the amplitude and phase
when the input signal level is changed
from 0dB to -20dB.
Same as for ACC1.
Same as for ACC2.
Attenuate the input signal level from 0dB
until there comes a point where the B
output ceases ; that point is the killer
operating point.
Measure the difference between killer-on
level and killer-off level.
Adjust the SG so that the B output
assumes a horizontal waveform and
measure the Vp-p value of the B output's
signal component.
BRIGHT : 5V
Tan
Tan
LA7688B
−
−
1
1
(
(
Rb
Bb
Test method
/
/
Ra
Ba
)
)
+
COLOR VR
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
2.5V
Continued on next page.
CONTRAST
4V
4V
4V
4V
4V
4V
4V
4V
4V
4V
4V
No.0077-14/20
TINT VR
0V
0V
0V
0V
3V
3V
3V
3V
3V
3V
3V