© 2006 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FMS6145 • Rev. 2.0.6

8

The same method can be used for biased signals, with the

addition of a pull-up resistor to make sure the clamp never

operates. The internal pull-down resistance is 800kΩ

±20%, so the external resistance should be 7.5MΩ to set

the DC level to 500mV; as shown in Figure 12.

LCVF

Bias

Input

0.1μ

External video

source must

be AC coupled

500mV +/-350mV

75Ω

7.5MΩ

75Ω

Figure 12. Biased SCART with

DC-Coupled Outputs

The same circuits can be used with AC-coupled outputs if

desired.

DVD or

STB

SoC

DAC

Output

LCVF

Clamp

Active

0.1μ

0V - 1.4V

75Ω

220μ

Figure 13. DC-Coupled Inputs,

AC-Coupled Outputs

DVD or

STB

SoC

DAC

Output

75Ω

LCVF

Clamp

Active

0.1μ

0V - 1.4V

220μ

Figure 14. AC-Coupled Inputs and Outputs

Figure 15. Biased SCART with

AC-Coupled Outputs

Note:

The video tilt or line time distortion is dominated by

the AC-coupling capacitor. The value may need to be incre-

ased beyond 220μF to obtain satisfactory operation in

some applications.

Power Dissipation

The FMS6145 output drive configuration must be considered

when calculating overall power dissipation. Care must be

taken not to exceed the maximum die junction temperature.

The following example can be used to calculate the

FMS6146’s power dissipation and internal temperature rise.

EQ. 1

EQ. 2

EQ. 3

EQ. 4

EQ. 5

Board layout can also affect thermal characteristics. Refer

to the Layout Considerations section for details.

The FMS6145 is specified to operate with output currents

typically less than 50mA, more than sufficient for a dual

(75Ω) video load. Internal amplifiers are current limited to a

maximum of 100mA and should withstand brief-duration

short-circuit conditions; this capability is not guaranteed.

LCVF

Clamp

Active

0.1μ

External video

source must

be AC coupled

0V - 1.4V

220μ

75Ω

75Ω