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19-0553; Rev 0; 5/06
Loss-of-Sync Alarm
General Description
The MAX7461 single-channel loss-of-sync alarm (LOS) provides composite video sync detection in NTSC, PAL, and SECAM standard-definition television (SDTV) systems. The MAX7461's advanced detection circuitry delivers robust performance by preventing false lossof-sync alarms due to noise. The device accepts an AC-coupled composite (CVBS), luma (Y), or any other video signal with sync, and outputs a logic-level signal. The open-drain LOS output is low when no sync is detected and high impedance when sync is detected. The device operates from a single +5V supply. The MAX7461 is available in a 5-pin SOT23 package and is specified for operation over the -40C to +85C temperature range. Loss-of-Sync Alarm Output Robust Performance in Noisy Environments Wire-OR Alarm Output NTSC, PAL, and SECAM Small 5-Pin SOT23 Package
Features
Accepts CVBS, Y, or Any Other Video with Sync
MAX7461
Ordering Information
PART MAX7461EUK TEMP RANGE -40C to +85C PINPACKAGE 5 SOT23-5 PACKAGE CODE U5-2
Applications
Security Systems Automotive Rear Seat Entertainment (RSE) Systems Consumer Electronics
IN 1
Pin Configuration
TOP VIEW
5 VCC
GND 2
MAX7461
GND 3
4
LOS
SOT23-5
Functional Diagram
+5V 0.1F VCC
5 VCC SYNC SLICE LEVEL
MAX7461
RO 1k SYNC DETECTOR SYNC LOS FILTER LOS 4
CIN 0.1F 75
IN 1
CLAMP
LPF
GND 3
________________________________________________________________ Maxim Integrated Products
1
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Loss-of-Sync Alarm MAX7461
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V LOS to GND..............................................................-0.3V to +6V IN to GND.................-0.3V to the lower of +6V and (VCC + 0.3V) Continuous Power Dissipation (TA = +70C) 5-Pin SOT23-5 (derate 7.1mW/C above +70C) ......571.0mW Maximum Current Into Any Pin .........................................50mA Operating Temperature Range MAX7461EUK ...................................................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Junction Temperature ......................................................+150C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +4.5V to +5.5V, GND = 0, CIN = 0.1F, RO = 500, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER AC CHARACTERISTICS Minimum Input Sync Height Maximum Input Voltage LOS Release Time LOS Detect Time DIGITAL CHARACTERISTICS Output Low Voltage Logic High Leakage Current POWER REQUIREMENTS Supply Voltage Supply Current Power-Supply Noise Immunity VCC ICC VPSNI 0 to 5MHz sinusoid on VCC (Note 4) 4.5 5.0 1.7 200 5.5 2.2 V mA mVP-P VOL IOLEAK ISINK = 10mA 0.4 1 V A VIN-MIN VIN-MAX tRT tDT AC-coupled (Note 1) AC-coupled (Note 2) (Note 3) 2.4 1.7 1.9 2.2 3.4 2.7 4.9 105 130 mVP-P VP-P ms SYMBOL CONDITIONS MIN TYP MAX UNITS
Note 1: Minimum input sync height is the voltage above which LOS is guaranteed to be in high-impedance mode after the maximum LOS time-constant time. Note 2: LOS release time is the time that the video input must be continuously present before LOS goes high (inactive state). Note 3: The LOS detect time is the time that the video input must be continuously absent before LOS goes low (active state). Note 4: The MAX7461 LOS output is accurate with a power-supply noise level below VPSNI.
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Loss-of-Sync Alarm MAX7461
Typical Operating Characteristics
(VCC = 5V, GND = 0, CIN = 0.1F, RO = 10k, TA = +25C, unless otherwise noted.)
CVSB LOS ALERT TRANSIENT
MAX7461 toc01
LOS DETECT TIME vs. SUPPLY VOLTAGE
MAX7461 toc02
LOS RELEASE TIME vs. SUPPLY VOLTAGE
MAX7461 toc03
3.0
4.0
2.5 TIME (ms) TIME (ms) 4.5 4.7 4.9 5.1 5.3 5.5 IN 500mV/div
3.5
2.0
3.0
LOS 5V/div
1.5
2.5
1.0 t = 10ms/div SUPPLY VOLTAGE (V)
2.0 4.5 4.7 4.9 5.1 5.3 5.5 SUPPLY VOLTAGE (V)
SYNC HEIGHT LOS ALERT THRESHOLD vs. SUPPLY VOLTAGE
MAX7461 toc04
SUPPLY CURRENT vs. TEMPERATURE (CVBS INPUT)
MAX7461 toc05
0.20
2.0
0.15 SYNC HEIGHT (V) ICC (mA) 4.5 4.7 4.9 5.1 5.3 5.5
1.9
0.10
1.8
0.05
1.7
0 SUPPLY VOLTAGE (V)
1.6 -40 -20 0 20 40 60 80 TEMPERATURE (C)
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Loss-of-Sync Alarm MAX7461
Pin Description
PIN 1 2, 3 NAME IN GND FUNCTION Video Input. Accepts CVBS, luma (Y), or any video input with sync. AC-couple IN with a series 0.1F capacitor. Ground Loss-Of-Sync Output (Open Drain). LOS is in high impedance when sync pulses are detected, and is pulled low when no horizontal sync signal is detected for more than the LOS detect time. LOS returns high when sync pulses are detected for more than the LOS release time. Connect a 1k pullup resistor from LOS to VCC. Power-Supply Input. Bypass to GND with a 0.1F capacitor.
4
LOS
5
VCC
General Description
The MAX7461 single-channel LOS alarm is ideal for any video system needing to verify the presence of a video source. The device accepts an AC-coupled CVBS, Y, or any video signal with sync, and pulls LOS low when no composite sync signal is detected for more than the LOS detect time (3.4ms, typ) at the input (IN).
Applications Information
Input Considerations
Use 0.1F ceramic capacitors to AC-couple the input. The input cannot be DC-coupled. The input capacitor stores a DC level so that the video signal is clamped to an appropriate DC voltage for proper sync detection.
Clamp
The MAX7461 features an input clamp that corrects any DC shift, on a line-by-line basis. The external AC-coupling capacitor provides DC isolation for the input.
Power-Supply Bypassing
Careful PC board layout is important for optimal system performance. Do not use wire-wrapped boards or breadboards. When possible, use a multilayer board with a dedicated low-inductance ground plane and supply plane. Connect all GND inputs to a single ground plane and V CC to a single-supply plane. Bypass VCC to GND with a 0.1F capacitor.
Lowpass Filter
The MAX7461 integrates a lowpass filter for enhanced sync detection. The lowpass filter prevents false sync detection by reducing color burst, chroma, and noise.
Wired-OR Application
The LOS open-drain output allows the MAX7461 to be used in wired-OR applications as shown in the automotive RSE typical application diagram of Figure 1.
Sync Detector/LOS Filter
The sync detector looks for sync pulses greater than the minimum sync voltage (0.13VP-P). If the detector does not detect any sync pulses for 3.4ms (typ), the LOS filter pulls LOS low. After detecting sync for at least 2.2ms (typ), the LOS filter returns LOS to a highimpedance state. LOS is an open-drain output. Connect a 1k pullup resistor between LOS and VCC.
Chip Information
PROCESS: BiCMOS
Power-On Reset (POR)
At power-up, LOS is pulled low and the MAX7461 checks for 2.2ms (typ) of valid sync pulses before releasing LOS. LOS remains high impedance while a valid sync signal is detected at the input.
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Loss-of-Sync Alarm MAX7461
VCC 1k
C
MAX7461
0.1F TV TUNER 75
MONITOR 1
MAX7461
0.1F RGB VIDEO SOURCE SWITCH MATRIX AND PROCESSING 75
MONITOR N
MAX7461
0.1F CAMERA 75
Figure 1. Automotive RSE System
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5
Loss-of-Sync Alarm MAX7461
VCC 1k 1 C N
MAX7461
0.1F CAM 1 75 1k VCC MONITOR 1
MAX7461
0.1F CAM 2 VCC 75 1k MONITOR N SWITCH MATRIX AND PROCESSING
MAX7461
0.1F CAM N 75
Figure 2. Video Security System
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Loss-of-Sync Alarm
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SOT-23 5L .EPS
MAX7461
PACKAGE OUTLINE, SOT-23, 5L
21-0057
E
1
1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ______________________7 (c) 2006 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
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