THS8134 Datasheet, PDF (21/24 Pages) Texas Instruments – TRIPLE 8-BIT, 80 MSPS VIDEO D/A CONVERTER WITH TRI-LEVEL SYNC GENERATION

THS8134, THS8134A, THS8134B
TRIPLE 8-BIT, 80 MSPS VIDEO D/A CONVERTER
WITH TRI-LEVEL SYNC GENERATION
SLVS205D – MAY 1999 – REVISED MARCH 2000
APPLICATION INFORMATION
comparison to EIA RS-343/RS-170 levels
Traditionally, video amplitude levels are specified according to the EIA RS-343 or RS-170 standards. RS-343
uses a bi-level negative going sync. Also, there is a difference between the reference blanking and black video
level. Figure 15 shows the relative amplitudes and the current drives that would be needed to generate
compliant relative amplitudes with a double-terminated 75-Ω load, as is specified for RS-343. RS-170 compliant
levels can be reached using the same current sources but a different 150-Ω source termination resistor, which
brings the load to 150 || 75 Ω = 50 Ω. In this case a blank-to-white level of approximately 1 V is reached
(0.714 V × 50 ÷ 37.5) as required by RS-170.
With Sync Insertion Without Sync Insertion
mA
V
mA
V
26.67 1.000
19.05 0.714
92.5 IRE
9.05 0.340
7.62 0.286
0
0
1.44 0.340
0
0
7.5 IRE
40 IRE
BLACK Level
BLANK Level
SYNC Level
Figure 15. RS-343 Video Definition
The video signal contains 140 IRE, equal to 1 Vpp. This is split into 40 IRE for the composite sync, 7.5 IRE for
blanking-to-black and 92.5 IRE for the active video portion.
designing with PowerPAD™
The THS8134 is housed in a high-performance, thermally enhanced, 48-pin PowerPAD package (TI package
designator: 48-PHP). Use of the PowerPAD package does not require any special considerations except to note
that the PowerPAD, which is an exposed die pad on the bottom of the device, is a metallic thermal and electrical
conductor. Therefore, if not implementing the PowerPAD PCB features, solder masks (or other assembly
techniques) may be required to prevent any inadvertent shorting by the exposed PowerPAD of connection
etches or vias under the package. The recommended option, however, is not to run any etches or signal vias
under the device, but to have only a grounded thermal land as explained below. Although the actual size of the
exposed die pad may vary, the minimum size required for the keep-out area for the 48-pin PHP PowerPAD
package is 7 mm × 7 mm.
It is recommended that there be a thermal land, which is an area of solder-tinned-copper, underneath the
PowerPAD package. The thermal land will vary in size, depending on the PowerPAD package being used, the
PCB construction, and the amount of heat that needs to be removed. In addition, the thermal land may or may
not contain numerous thermal vias, depending on PCB construction.
More information on this package and other requirements for using thermal lands and thermal vias are detailed
in the TI application note PowerPAD™ Thermally Enhanced Package Application Report, TI literature number
SLMA002, available via the TI Web pages beginning at URL: http://www.ti.com.
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