MAX7474EAE+T Maxim Integrated Products, MAX7474EAE+T Datasheet - Page 7

• Manufacturer Part Number: MAX7474EAE+T
• Description: IC ADAPTV EQ VID OVER UTP 16SSOP
• Manufacturer: Maxim Integrated Products
• Type: Equalizerr

Specifications of MAX7474EAE+T

• Applications: Security Systems
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 1. Fixed Equalization Level Settings
The chroma gain for the MAX7474 is automatically
adjusted between 0dB and +12dB, while the low-fre-
quency gain is automatically adjusted between -6dB
and +3.6dB, providing full equalization for cable losses
that can occur when using up to 300m of UTP cable to
transmit CVBS signal with color burst.
The automatic gain control circuit corrects low-frequen-
cy signal losses such that the output signal obtains a
nominal sync level (V
input sync pulse amplitude in the 210mV
600mV
nal output sync level (V
If the sync is lost for 32 consecutive horizontal lines, the
LOS output goes high and OUT is set to a high-imped-
ance state.
The automatic equalization control circuit corrects the
chroma signal attenuation such that the output-signal
burst amplitude is 293mV (subcarrier frequency, f
3.58MHz or 4.43MHz). Differential input color-burst
amplitude in the 76mV
matically adjusted to the nominal output color-burst
level (V
The AGC and AEQ equalization take approximately 1s
(16,384 lines) to change from the lowest gain to the
highest gain. During this time, the chroma amplitude is
gradually increased from minimum to maximum.
If the color-burst amplitude at the output of the
MAX7474 (OUT) is less than 80mV
gain set to maximum for 32 consecutive horizontal
lines, the loss-of-burst output (LOB) goes high. LOB
returns low when color bursts with amplitude greater
than 80mV
horizontal lines.
For applications where the input signal has no color
burst, or the input burst amplitude is lower than the LOB
threshold voltage (V
automatically applies a user-defined fixed equalization
set by logic inputs FEQ1 and FEQ0 (see Table 1).
X = V
MAX7474
PART
CC
Fixed Equalization Mode (LOB Is High)
P-P
Automatic Equalization Control (AEQ)
BURST_OUT
or GND.
range is automatically adjusted to the nomi-
P-P
FEQ1
GND
GND
V
CC
are present at OUT for 32 consecutive
Automatic Gain Control (AGC)
_______________________________________________________________________________________
).
LOB
SYNC_OUT
FEQ0
GND
V
P-P
SYNC_OUT
), the MAX7474 asserts LOB and
CC
X
and 300mV
T YP ( d B )
) of 293mV. Differential
10.5
4.5
).
0
P-P
P-P
with the equalizer
CABLE LENGTH
range is auto-
RANGE (m)
75 to 225
0 to 75
≥ 225
P-P
SC
and
=
Video Over Twisted Pair
When using cable lengths greater than 75m, set the
fixed equalization level according to Table 1, or higher,
to ensure the device comes out of the fixed equaliza-
tion mode. If the fixed equalization is set to a lower gain
setting than specified in Table 1, the amplitude of the
color-burst signal at the output may remain smaller than
the LOB threshold (V
device in LOB mode (see the Automatic Equalization
Control (AEQ) section). If the conditions in Table 1 are
not met, set FEQ1 to high to ensure the device always
comes out of LOB mode for longer cable lengths.
The MAX7474 features a single-ended video output dri-
ver with 0dB gain. The typical output voltage swing of
the output driver is 1.2V
ble of driving two AC-coupled or DC-coupled 150Ω
video loads. The output back-porch DC level is set by
an internal back-porch clamp circuit (see the Back-
Porch Clamp section). OUT enters a high-impedance
state when sync is lost for 32 consecutive horizontal
lines, asserting LOS.
The MAX7474 features a back-porch clamp to set the
output blanking level. This clamp shifts the DC level of
the video signal so that the back-porch level is approxi-
mately equal to the voltage level on the BPLVL input. The
voltage range allowed at the BPLVL input is 1V to 1.6V.
Applications with differential input interface require
proper input voltage levels, termination, and AC-cou-
pling (Figure 1). The maximum differential input voltage
swing allowed is 2.4V. Use active drivers to drive the
cable as shown in Figure 1. For Category 5e cables,
the proper termination resistance is 50Ω to ground at
INN and INP inputs. Apply a 0.022µF coupling capaci-
tor at each input.
The video output is capable of driving an AC-coupled
or DC-coupled load. Use a 220µF or larger coupling
capacitor for AC-coupling. Figure 1 shows applications
with AC- and DC-coupled output interface.
Security systems typically consist of many cameras that
are viewed and recorded on a relatively smaller number
Adaptive Equalizer for
Differential UTP Input Interface
Applications Information
Security Systems Application
LOB
P-P
) of 80mV
. The output driver is capa-
Output Video Driver
Back-Porch Clamp
Output Interface
P-P
, keeping the
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