SAA7120 Просмотр технического описания (PDF) - Philips Electronics
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SAA7120 Datasheet PDF : 32 Pages
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Philips Semiconductors
Digital Video Encoder (ConDENC)
Preliminary specification
SAA7120; SAA7121
handbook, full pagewidth
CVBS/Y
TTX
TTXRQ
tTTX
tTTXWin
textbit #: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
tPD
tFD
Fig.7 Teletext timing.
MBH788
Analog output voltages
The analog output voltages are dependent on the
open-loop voltage of the operational amplifiers for
full-scale conversion (typical value 1.35 V), the internal
series resistor (typical value 2 Ω), the external series
resistor and the external load impedance.
The digital output signals in front of the DACs under
nominal conditions occupy different conversion ranges, as
indicated in Table 1 for a 100⁄100 colour bar signal.
Values for the external series resistors result in a 75 Ω
load.
Input levels and formats
The ConDENC expects digital Y, Cb, Cr data with levels
(digital codes) in accordance with “CCIR 601” (see
Tables 2 and 3).
For C and CVBS outputs, deviating amplitudes of the
colour difference signals can be compensated by
independent gain control setting, while gain for luminance
is set to predefined values, distinguishable for 7.5 IRE
set-up or without set-up.
Reference levels are measured with a colour bar,
100% white, 100% amplitude and 100% saturation.
Table 1 Digital output signals conversion range
CONVERSION RANGE (peak-to-peak) (digits)
CVBS, SYNC
TIP-TO-PEAK CARRIER
1 016
Y (VBS) SYNC
TIP-TO-WHITE
881
Table 2 “CCIR 601” signal component levels
COLOUR
White
Yellow
Cyan
Green
Magenta
Red
Blue
Black
SIGNALS
Y
Cb
Cr
235
128
128
210
16
146
170
166
16
145
54
34
106
202
222
81
90
240
41
240
110
16
128
128
1997 Jan 06
10
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