TSH343I(2006) View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
TSH343I Datasheet PDF : 14 Pages
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TSH343
Using the TSH343 to Drive Y-Pb-Pr Video Components
Figure 28 shows a schematic diagram of the use of the TSH343 to drive video output from
DACs.
The TSH343 is used to drive high definition video signals up to 30MHz on 75-ohm video
lines. It is dedicated to driving YPbPr signals where the synchronization tip—close to zero
volts—is included in Y signal, as seen in (1). An internal input DC value of 600mV is added
to the video signal in order to shift the bottom from 0V to 600mV as seen in (2).
The shift is not based on the average of the signal, but is an analog summation of a DC
component to the video signal. Therefore, no input capacitors are required which provides a
real advantage in terms of cost and board space.
Under these conditions, 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
600mV
+ +6dB
75Ω
75Ω Cable
V1
75Ω
Vin
75Ω
600mV
+ +6dB
75Ω
75Ω Cable
V2
75Ω
600mV
+ +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 TSH343 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
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