MAX9595 Maxim Integrated Products, MAX9595 Datasheet - Page 13

• Manufacturer Part Number: MAX9595
• Description: Audio/Video Switch
• Manufacturer: Maxim Integrated Products

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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,
150Ω, back-terminated coax load with respect to
ground. Since some televisions and VCRs use the hori-
zontal sync height for automatic gain control, the
MAX9595 accurately reproduces the sync height to
within ±2%.
The MAX9595 supports the IEC 933-1, Amendment 1,
tri-level slow switching that selects the aspect ratio for
the display (TV). Under I
MAX9595 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 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. When enabled, INTER-
RUPT_OUT becomes high impedance if the voltage
level changes on TV_SS or VCR_SS.
Table 1. Slow-Switching Modes
SLOW-SWITCHING
SIGNAL VOLTAGE
Audio/Video Switch for Dual SCART Connector
9.5 to 12.6
4.5 to 7.0
0 to 2
(V)
______________________________________________________________________________________
Display device uses an internal source
such as a built-in tuner to provide a
video signal
Display device uses a video signal from
the SCART connector and sets the
display to 16:9 aspect ratio
Display device uses a signal from the
SCART connector and sets the display
to 4:3 aspect ratio
2
C-compatible control, the
MODE
Slow Switching
Video Outputs
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
I
through writing to register 07h.
The MAX9595 includes an on-chip mixer to produce
composite video (CVBS) when S-video (Y and C) is pre-
sent. 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.
The encoder DAC outputs need to be lowpass-filtered
to reject the out-of-band noise. The MAX9595 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 100kΩ resis-
tor from SET to ground.
The audio block has three stereo audio inputs from the
TV, the VCR, and the MPEG decoder SCART. Each input
has a 100kΩ resistor connected to an internally generat-
ed voltage equal to 0.23 x V
2
C interface. The fast-switching output can be set
Video Reconstruction Filter
SCART Audio Switching
12
, and is AC-coupled.
Fast Switching
Audio Inputs
Y/C Mixer
13