TSH346 Ver la hoja de datos (PDF) - STMicroelectronics

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TSH346

Triple video buffer/filter for HD video applications

STMicroelectronics 

TSH346

Using the TSH346 to drive YC, CVBS, YUV, YPbPr and RGB video components

Figure 25. Shapes of HD video signals coming from DACs including the synchronization tip

(Y signal)

27 ns

(2t)

54 ns 27 ns

(4t) (2t)

590 ns

(44 t)

White (100IRE)

Image content

300 mV

Black (30IRE)

300 mV

GN D

590 ns

(44 t)

14.8 us (110 0t): 1920/1080i

24.3 us (180 0t): 1280/720i

s yn c.t ip

•Fclock=74.25 MHz

•t=1/Fclock=13.5 ns

AM00827

The TSH346 is used to drive high definition video signals up to 30 MHz. It can drive

components such as YPbPr and RGB where the bottom of the signal is close to zero volts.

An internal input DC value is added to the video signal in order to shift the bottom from GND.

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. This provides a

real advantage in terms of cost and board space.

Under these conditions, it is possible to drive the signal in single supply with no saturation of

the driver against the lower rail.

Because half of the signal is lost through output impedance matching, in order to correctly

drive the video line the shifted signal is multiplied by a gain of +2 or +6 dB.

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