THS8134 Datasheet, PDF (9/24 Pages) Texas Instruments – TRIPLE 8-BIT, 80 MSPS VIDEO D/A CONVERTER WITH TRI-LEVEL SYNC GENERATION

blanking generation (continued)
THS8134, THS8134A, THS8134B
TRIPLE 8-BIT, 80 MSPS VIDEO D/A CONVERTER
WITH TRI-LEVEL SYNC GENERATION
SLVS205D – MAY 1999 – REVISED MARCH 2000
CLK
SYNC
ts
th
td(D)
td(D)
td(D)
td(D)
BRSGPBPYYbLrN[[[A777CN–––_000^{ÎÎÎÎÎKT]]] ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎD(ÎÎ0) ÎÎÎÎ}
Value
Corresponds
to D(0)
Figure 6. Sync and Blanking Generation
DAC operation
The analog output drivers generate a current of which the drive level can be user-modified by choice of an
appropriate resistor value R_FS, connected to the FSADJ terminal. Refer to the paragraph on output amplitude
control for details on how the output drive is affected by the operation mode of the device.
All current sources derive their amplitudes from an internal generator that produces a 1.35 V reference level.
All current source amplitudes (video, blanking, sync) also come from this reference so that the relative
amplitudes of sync/blank/video are always equal to their nominal relationships. For increased stability on the
absolute levels, the user can overdrive the reference by directly driving the V_REF input terminal.
output amplitude control
The current drive on all three output channels and on the internal sync generator is controlled by a resistor R_FS
that must be connected between FSADJ and AV_SS. In all operation modes the relative amplitudes of the current
drivers are maintained irrespective of the R_FS value, as long as a maximum current drive capability is not
exceeded.
The sync generator is composed of different current sources that are internally routed to a corresponding DAC
output. 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-green) if INS3_INT = L or all three channel outputs INS3_INT = H. In either
case the relative current levels, as defined below, are maintained.
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