Implementation in the application

TSH120

8/13

3

Implementation in the application

This section explains how the TSH120 video buffer operates in a typical application.

On the input, a DC level shifter optimizes the position of the video signal with no clamping

on the output rails. The filter is a reconstruction filter. It is used to attenuate the DAC’s

sampling frequency which causes a parasitic signal in the video spectrum (typically at

27MHz in the case of standard video). This function must be achieved while keeping a low

group delay.

(see Figure 18). Nevertheless, the output can be directly connected to the line without any

capacitor. In this case, both OUT and SAG pins are connected together and the equivalent

gain of the buffer remains 6dB (see Figure 19).

Figure 18.

Schematic diagram with output capacitor

Figure 19.

Schematic diagram without output capacitor

75

75

cable

75

+

-

+2.2V to +5.5V

33µF

Rail-to-rail

DC shifter

LPF

1

TV

Video

DAC

SAG

6

2

4

3

5 Shutdown

22µF

75

75

cable

75

+

-

+2.2V to +5.5V

33µF

Rail-to-rail

DC shifter

LPF

1

TV

Video

DAC

SAG

6

2

4

3

5 Shutdown

22µF

75

75

cable

75

+

-

Rail-to-rail

DC shifter

LPF

1

TV

Video

DAC

SAG

6

2

4

3

5 Shutdown

+2.2V to +5.5V

75

75

cable

75

+

-

Rail-to-rail

DC shifter

LPF

1

TV

Video

DAC

SAG

6

2

4

3

5 Shutdown

+2.2V to +5.5V