MAX4397 datasheet(13/30 Pages) MAXIM

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Video Outputs

The DC level at the video outputs is controlled so that

coupling capacitors are not required, and all of the

video outputs are capable of driving a DC-coupled,

150

Ω, back-terminated coax load with respect to

ground. Since some televisions and VCRs use the hori-

zontal sync height for automatic gain control, the

MAX4397 accurately reproduces the sync height to

within ±2%.

Slow Switching

The MAX4397 supports the IEC 933-1, Amendment 1,

tri-level slow switching that selects the aspect ratio for

the display (TV). Under I2C-compatible control, the

MAX4397 sets the slow-switching output voltage level.

Table 1 shows the valid input levels of the slow-switch-

ing signal and the corresponding operating modes of

the display device.

Two bidirectional ports are available for slow-switching

signals for the TV and VCR. The slow-switching input

status is continuously read and stored in the register

0Eh. The slow-switching outputs can be set to a logic

level or high impedance by writing to registers 07h and

09h. See Tables 8 and 10 for details.

Fast Switching

The VCR or MPEG decoder outputs a fast-switching

signal to the display device or TV to insert on-screen

display (OSD). The fast-switching signal can also be

set to a constant high or low output signal through the

I2C interface. The fast-switching output can be set

through writing to register 07h.

Y/C Mixer

The MAX4397 includes an on-chip mixer to produce

Composite video (CVBS) when S-video (Y and C) is

present.

The

Composite

video

drives

the

RF_CVBS_OUT output pin. The circuit sums Y and C

signals to obtain the CVBS component. A +6dB output

buffer drives RF_CVBS_OUT.

Video Reconstruction Filter

The encoder DAC outputs need to be lowpass-filtered

to reject the out-of-band noise. The MAX4397 inte-

grates the reconstruction filter. The filter is fourth order,

which is composed of two Sallen-Key biquad in cas-

cade, implementing a Butterworth-type transfer func-

tion. The internal reconstruction filters feature a 6MHz

cutoff frequency, and -35dB minimum attenuation at

27MHz. Note that the SET pin is used to set the accura-

cy of the filter cutoff frequency. Connect a 100k

Ω resis-

tor from SET to ground.

SCART Audio Switching

Audio Inputs

All audio inputs for the MAX4397S are single-ended

and are AC-coupled. The MAX4397D audio inputs are

singled-ended and AC-coupled except for the audio

encoder input, which is differential DC-coupled.

The audio block has three stereo audio inputs from the

TV, the VCR, and the MPEG decoder SCART. Each

input has a 100k

Ω resistor connected to an internally

generated voltage equal to 0.23 x V12, except for the

encoder input of the MAX4397D, where the DC bias is

fixed externally.

Audio/Video Switch for Dual SCART Connectors

______________________________________________________________________________________

Table 1. Slow-Switching Modes

SLOW-SWITCHING

SIGNAL VOLTAGE

(V)

MODE

0 to 2

Display device uses an internal source

such as a built-in tuner to provide a

video signal

4.5 to 7.0

Display device uses a video signal from

the SCART connector and sets the

display to 16:9 aspect ratio

9.5 to 12.6

Display device uses a signal from the

SCART connector and sets the display

to 4:3 aspect ratio

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