TSH344
Using the TSH344 to Drive RGB Video Components
Figure 28 shows a schematic diagram of the use of the TSH344 to drive video output from
DACs.
The TSH344 is used to drive high definition video signals up to 30MHz on 75-ohm video
lines. It is dedicated to driving RGB signals typically between 300mV and 1V, as seen in (1).
With a very low output rail (VOL) guaranteed in test of production at 60mV maximum, it is
possible to drive the signal in single supply without any saturation of the driver against the
lower rail.
Assuming that we lose half of the signal by output impedance-matching in order to properly
drive the video line, the shifted signal is multiplied by a gain of 2 or +6dB (3).
4.1
Delay between channels
Figure 29. Measurement of the delay between each channel
5V
+6dB
75Ω
75Ω Cable
V1
75Ω
Vin
75Ω
+6dB
75Ω
75Ω Cable
V2
75Ω
+6dB
75Ω
75Ω Cable
V3
75Ω
Delay between each video component is an important aspect in high definition video
systems. To drive porperly the three video components without any relative delay, the dice of
the TSH344 is layouted out with a very symetrical geometry. The effect is direct on the
synchronization of each channel, as shown in Figure 30. No delay appears between each
channel when the same Vin signal is applied on the three inputs. Note that the delay from
the inputs the outputs equals 4ns.
Rev. 2
11/14