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MAX7474 の電気的特性と機能

MAX7474のメーカーはMaxim Integratedです、この部品の機能は「Adaptive Equalizer」です。


製品の詳細 ( Datasheet PDF )

部品番号 MAX7474
部品説明 Adaptive Equalizer
メーカ Maxim Integrated
ロゴ Maxim Integrated ロゴ 




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MAX7474 Datasheet, MAX7474 PDF,ピン配置, 機能
19-3216; Rev 0; 1/08
EVAALVUAAILTAIOBNLEKIT
Adaptive Equalizer for
Video Over Twisted Pair
General Description
The MAX7474 adaptive equalizer recovers losses
incurred in the transmission of a composite video
(CVBS) signal over unshielded twisted-pair (UTP)
cable. The device fully recovers losses for cable
lengths of up to 300m and greatly improves signal qual-
ity for cable lengths of up to 600m. The device automat-
ically adapts to all cable lengths for CVBS signals with
color burst and allows fixed-equalization settings for
video signals without burst. The MAX7474 is optimized
to provide compensation for losses that occur when
transmitting composite video signals over UTP cables
such as Category 5e. The device compensates for low
frequency and chroma band losses. The MAX7474 is
compatible with NTSC and PAL standards.
The MAX7474 accepts differential input and provides a
single-ended output. The output is capable of driving
two AC- or DC-coupled standard 150video loads.
The output back-porch DC level is adjustable with an
externally applied DC voltage at the BPLVL input. The
device also features loss-of-sync (LOS) and loss-of-burst
(LOB) logic outputs.
The MAX7474 is available in a 16-pin SSOP package
and is fully specified over the extended (-40°C to
+85°C) temperature range.
Applications
Security Video Systems
Video Switching Systems
Home Automation
Features
Automatically Equalizes Up to 600m
(Fully Recovers Losses Up to 300m) of UTP Cable
Carrying CVBS
Automatic Switchover to Fixed Equalization for
CVBS Without Color Burst
Integrated Video Driver with Adjustable
Back-Porch Clamp Level
LOS and LOB Output
NTSC and PAL Compatible
16-Pin SSOP Package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
PKG
CODE
MAX7474EAE+
-40°C to +85°C
16 SSOP
(5.3mm x 6.2mm)
+Denotes a lead-free package.
A16+2
Pin Configuration and Typical Application Circuit appear at
end of data sheet.
Functional Diagram
+5V +5V
CAMERA
UNSHIELDED TWISTED PAIR
(0 TO 300m)
50
0.022µF
INP
INN
0.022µF
50
FEQ0
FEQ1
0.1µF
VCC
0.1µF
VCC
CLAMP
ADAPTIVE
EQUALIZER
MAX7474
AGC AND AEQ
CONTROL
BACK-PORCH
CLAMP
GND
OUT ADC
BPLVL (1.0V TO 1.6V)
LOB
LOS
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

1 Page





MAX7474 pdf, ピン配列
Adaptive Equalizer for
Video Over Twisted Pair
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +4.75V to +5.25V, RL = 150(AC-coupled), FEQ1 = GND, FEQ0 = GND, VBPLVL = 1.4V, TA = -40°C to +85°C, unless otherwise
noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
DIGITAL INPUTS (FEQ0, FEQ1)
CONDITIONS
MIN TYP MAX UNITS
Input High Voltage
VIH
0.7 x
VCC
V
Input Low Voltage
VIL
0.3 x
VCC
V
Input Leakage Current
Digital inputs = 0 or VCC
±0.01 ±10
µA
Input Capacitance
CIN
DIGITAL OUTPUTS (LOS, LOB)
Output Low Voltage
VOL
ISINK = 500µA
15
0.4
pF
V
Output High Voltage
VOH
ISOURCE = 500µA
VCC
- 0.4
V
POWER SUPPLY
Supply Voltage Range
Supply Current
VCC
ICC No load
Normal mode
LOS mode
4.75 5.0 5.25
47 59
24
V
mA
DC Power-Supply
Rejection Ratio
PSRR
20log(VCC/VOUT-BlackLevel), black video input with no
color burst
65
dB
Note 1: VIN-DIFF = VINP - VINN.
Note 2: VOUT-BL = VBPLVL + VOUT-BL.
Note 3: LOS is high when the input video sync amplitude goes below VLOS for 32 consecutive horizontal lines. LOS goes low when
the input video sync amplitude exceeds VLOS for 32 consecutive horizontal lines.
Note 4: LOB is high when the output color burst amplitude goes below VLOB for 32 consecutive horizontal lines when at maximum
equalizer gain. LOB goes low when the output color burst amplitude exceeds VLOB for 32 consecutive horizontal lines.
_______________________________________________________________________________________ 3


3Pages


MAX7474 電子部品, 半導体
Adaptive Equalizer for
Video Over Twisted Pair
PIN
1, 2, 3,
5, 10, 13
4, 9
6
7
8
11
12
14
15
16
NAME
GND
VCC
LOB
BPLVL
OUT
FEQ0
FEQ1
INP
INN
LOS
FUNCTION
Pin Description
Ground. Connect all GND terminals together.
Power-Supply Input. Connect a +4.75V to +5.25V supply to VCC. Connect both VCC inputs together.
Bypass each VCC input with a 0.1µF capacitor to GND as close as possible to the device.
Loss-of-Burst Logic Output. LOB goes high when the output color burst goes below the LOB threshold
(VLOB) for 32 consecutive horizontal lines when the equalizer is at its maximum gain. LOB goes low
when the output color burst exceeds VLOB for 32 consecutive horizontal lines. When LOB is active, the
device enters the fixed equalization mode. LOB is valid only when LOS is low.
Back-Porch Level Input. The voltage applied to BPLVL sets the output back-porch voltage level.
Composite Video Output
Fixed-Cable Equalization inputs. FEQ0 and FEQ1 set the fixed equalization level. See Table 1.
Noninverted Video Input. AC-couple video signal with a 0.022µF capacitor.
Inverted Video Input. AC-couple video signal with a 0.022µF capacitor.
Loss-of-Sync Logic Output. LOS goes high when the input sync amplitude goes below the loss-of-sync
threshold (VLOS) for 32 consecutive horizontal lines. LOS is pulled low when the input sync amplitude
exceeds VLOS for 32 consecutive horizontal lines. When LOS is active, the output enters a high-
impedance state.
Detailed Description
The MAX7474 compensates for cable losses that
occur when transmitting a composite video signal over
unshielded twisted-pair cable (see the Typical
Application Circuit). The device automatically adapts
to cable length by monitoring the sync and color-burst
amplitudes of the color video signal at the output
(OUT) and adjusting the gains accordingly. Video sig-
nals without burst are automatically detected and a
user-selectable fixed equalization is applied to the sig-
nal. The MAX7474 provides full equalization up to
300m of Category 5e cable and greatly improves per-
formance up to 600m.
The MAX7474 accepts differential video input signals in
NTSC or PAL standards. The MAX7474 includes an
output unity-gain video driver and adjustable back-
porch DC level. The device also features LOS and LOB
logic outputs.
Video Input
The MAX7474 accepts a differential video input with a
maximum 2.4VP-P voltage swing. A twisted-pair cable
carries the differential video signal to the positive (INP)
and negative (INN) inputs, which are AC-coupled with
0.022µF capacitors. Each input is internally clamped to
a DC level (see the Input Clamp section).
Input Clamp
The MAX7474 clamps the sync tip of the input signal to
internally set DC levels effectively correcting, on a line-
by-line basis, any shift in the sync-tip level of the input
video signal. The sync-tip of the positive video input
signal (VINP) is clamped to typically 2.0V and the nega-
tive video input signal (VINN) is clamped to typically
3.2V. The input clamp enables capacitive coupling of
the input, permitting a large common-mode DC differ-
ence between the line driver (camera) and the device.
Adaptive Equalizer
The adaptive equalizer in the MAX7474 provides the
appropriate inverse frequency response needed to
compensate for UTP cable loss. The equalizer adjusts
the low-frequency amplitude and chroma amplitude of
the input CVBS signal. The low-frequency component
of the CVBS is adjusted according to the feedback
information obtained from the internal automatic gain-
control (AGC) circuit, which monitors the sync pulse
amplitude of the output signal (see the Automatic Gain
Control (AGC) section). The chroma gain of the video
signal is adjusted according to the feedback informa-
tion obtained from the internal automatic equalization
control circuit, which monitors the color-burst amplitude
of the output signal (see the Automatic Equalization
Control (AEQ) section).
6 _______________________________________________________________________________________

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