Detailed Description

In the typical application circuit for a portable DVD

player (Figure 1), the current DACs on a DVD decoder

chip generate video signals. When the internal signal

sources are selected, the MAX9508 filters those signals

and then drives the video connectors through a 75Ω

back termination resistor. When external video sources

are selected, the MAX9508 selects the external com-

posite video signal (EXTCVBSIN), filters, and amplifies

it. The output stages of the amplifiers connected to

COUT, YOUT, and CVBSOUT1 become high imped-

ance. The n-channel switch at CVBSOUT1 turns on,

thereby converting the back termination resistor into an

input termination resistor.

SmartSleep Feature

The SmartSleep feature is activated when the SMARTSLEEP

input is connected to logic high. The SmartSleep feature

provides intelligent power management by selectively

disabling the filters and output amplifiers based on

the presence of video signals or loads attached to the

Video Filter Amplifier with SmartSleep and

Bidirectional Video Support

10

______________________________________________________________________________________

75Ω

CURRENT

DAC

CURRENT

DAC

CURRENT

DAC

DVD CHIP

SVIDEO CHROMA

SVIDEO LUMA

TO Y/C SEPARATION

CVBS

CIN

YIN

EXTCVBSIN

COUT

YOUT

CVBSOUT1

INT/EXT

ACTIVE VIDEO

DETECT

CVBSIN

CVBSOUT2

LPF

CONTROL

LOGIC

MICROCONTROLLER

TO TFT LCD

TO TFT LCD

GND

+3.3V

0.1µF

CLAMP

BUFFER

LOAD SENSE

6dB

75Ω

75Ω

75Ω

LPF

BUFFER

LOAD SENSE

BUFFER

6dB

LOAD SENSE

6dB

75Ω

LOAD SENSE

6dB

75Ω

LPF

MAX9508

0.1µF

SHDN

SMARTSLEEP

+3.3V

Figure 1. Typical Application Circuit for Portable DVD Player