SGM9116

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Applications Information

Functional Description

SGM9116 operates from a single +2.5V to +5V supply. In

application, SGM9116 is a fully integrated solution for filtering

and buffering HDTV signals in front of video decoder or behind

video encoder. For example, SGM9116 can replace three

passive LC filters and three amplifier drivers at R\G\B and

Y\Pb\Pr output side in set-top box and DVD player, this

solution can help you save PCB size and production cost, it

also improves video signal performance comparing with

traditional design using discrete components. SGM9116

features a DC-coupled input buffer, 3-pole low-pass filter to

eliminate out-of-band noise of video encoder, and a gain of

+6dB in the output amplifier to drive 75Ω load. The AC or

DC-coupled input buffer eliminates sync crush, droop, and field

tilt. The output of SGM9116 also can be DC-coupled or

AC-coupled.

Input Considerations

Besides AC coupling, the SGM9116 inputs also can be

DC-coupled. In DC coupling application, No input coupling

capacitors are needed because the amplitude of input video

signal from DAC includes ground and extends up to 1.4V, then

SGM9116 can be directly connected to the output of a

single-supply, current-output DAC without any external bias

network. Some time, if DAC’s output level exceeds the range of

0V to 1.4V, or SGM9116 is driven by an unknown external

source or a SCART switch which has its own clamping circuit,

AC coupling is needed in such application.

Output Considerations

The SGM9116 outputs can be DC-coupled or AC-coupled.

While 0V is input, the SGM9116 output voltage is 260mV

typically. In DC coupling design, one 75Ω resistor is used to

Connect SGM9116’s output pin with external load directly, this

serial back-termination resistor is used to match the

impedance of the transmission line between SGM9116 and

external load to cancel the signal reflection. The SGM9116

outputs can sink and source current allowing the device to be

capacitor will be used in order to cancel field tilt.

Power-Supply Bypassing and Layout

Correct power supply bypassing is very important for

optimizing video performance in design. One 0.1µF and one

SGM9116, please place these two capacitors as close to the

SGM9116 output pin as possible, a large ground plane is also

needed to ensure optimum performance. The input and output

termination resistors should be placed as close to the related

pin of SGM9116 as possible to avoid performance degradation.

The PCB traces at the output side should have 75Ω

characteristic impedance in order to match the 75Ω

characteristic impedance cable connecting external load. In

design, please keep the board trace at the inputs and outputs

of the SGM9116 as short as possible to minimize the parasitic

stray capacitance and noise pickup.

Typical Application Diagram

The following schematic in Figure 2 is normally used for AC

coupled output and DC-coupled input with DAC which has an

output voltage range of 0V to 1.4V. AC coupled output offer

slightly lower power dissipation and high ESD protection ability.

The schematics in Figure 1 is are also popular in design.

Figure 3 is a kind of special application in STB.

4

5

6

7

8

IN1

IN2

IN3

GND

OUT1

OUT2

OUT3

75Ω

75Ω

75Ω

SGM9116

0.1µF

or 0.01µF

10µF

+5V

75Ω

1

2

3

75Ω

75Ω

R/Pr

G/Y

B/Pb

R/Pr

G/Y

B/Pb

Figure 1. DC Coupling Application Schematic

4

5

6

7

8

IN1

IN2

IN3

GND

OUT1

OUT2

OUT3

75Ω

75Ω

75Ω

SGM9116

0.1µF

or 0.01µF

10µF

+5V

220µF

220µF

220µF

75Ω

1

2

3

75Ω

75Ω

R/Pr

G/Y

B/Pb

R/Pr

G/Y

B/Pb

Figure 2. Input DC Coupling and Output AC

Coupling Application Schematic