Datasheet

0
1023
0
700
512 400
50
800
64
960
300 mV
800 mV
700 mV
300 mV
Illegal Color
Difference Outputs
Input
Codes
V
O
mV
0
0
64
940
1023
400
350
1100
1167
100
Input
Codes
V
O
mV
300 mV
300 mV
817 mV
700 mV
Super-Black/Super-White
Excursions (Reduced-Scale
Input Code Range)
THS8135
SLAS343B –MAY 2001–REVISED APRIL 2013 www.ti.com
NOTE: Choose RFS for 700 mV from input codes 64−940 on Y.
Figure 3. YRGB Outputs, Reduced-Scale Input Code Range
Figure 4. CbCr Outputs, Reduced-Scale Input Code Range
Output Amplitude Control
The current drive on all three output channels (including sync) is controlled by a resistor R
FS
that must be
connected between FSADJ and AVSS. In all operation modes the relative amplitudes of these current drivers are
maintained irrespective of the R
FS
value, as long as a maximum current drive capability is not exceeded.
Therefore, a 7:3 video to sync ratio is preserved when adjusting R
FS.
The sync generator is composed of different current sources that are internally routed to a corresponding DAC
output. Because they are additional to the video DACs, full 10-bit DAC resolution is preserved for video.
Depending on the setting of INS3_INT during SYNC low, the sync current drive is added to either only the green
channel output (sync-on-G/Y) if INS3_INT = L or all three channel outputs (sync-on-all) if INS3_INT = H. Sync
insertion is only available in video DAC mode.
Figure 5 shows the relationship between R
FS
and the current drive level on each channel for full-range DAC
input. When using reduced-scale range, the codes on the G/Y channel are not internally scaled (only BCb and
RCr channels are scaled). Therefore, the user should increase the DAC full-scale current by decreasing R
FS
by a
factor of 1023/(940-64) to map the reduced-scale Y input code range to the same output current drive level.
Because these are the current drive levels for the video DACs, they do not take into account the additional dc
bias for sync insertion when using video DAC mode. The voltage compliance outputs in Figure 5 assume
termination with a 37.5-Ω resistor.
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