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19-3267; Rev 2; 11/04
Video-Signal Conditioners with AGC and Back-Porch Clamp
General Description
The MAX7450/MAX7451/MAX7452 complete front-end video-signal conditioners are designed to improve the quality of standard-definition video signals. The devices restore the DC level of the video input, correct for amplitude errors up to 6dB, detect fault conditions, and filter out-of-band noise. The MAX7450/MAX7451/ MAX7452 optimize the signal quality for further video processing through a crosspoint switch or video decoder (ADC). Each device integrates an input video clamp, automatic gain control (AGC), loss-of-sync (LOS) detector, and an out-of-band noise/lowpass filter. These devices also incorporate a user-selectable buffer gain (0 or +6dB) and an AGC-disable function. The MAX7450 and MAX7451 operate from dual power supplies of 5V or 3.3V respectively, and they restore the video blanking level to GND. The MAX7452 operates from a single +5V supply and features a user-adjustable clamp level. The devices are available in an 8-pin SO package with an exposed pad and are specified for operation over the extended (-40C to +85C) temperature range.
Features
Back-Porch Clamp to GND (MAX7450/MAX7451) Adjustable Back-Porch Clamp (MAX7452) Automatic Gain Control (6dB Range) Normalizes Signals to Standard Video Level Input Fault Detection with LOS Output Inherent 50Hz/60Hz Input Rejection of 60dB Single-Supply Operation: MAX7452 (+5V) Out-of-Band Noise Filter Output Buffer Drives Standard 150 Video Load with 0dB or +6dB Gain Dual-Supply Operation MAX7450 (5V) MAX7451 (3.3V) Tiny 8-Pin SO Package
MAX7450/MAX7451/MAX7452
Ordering Information
PART MAX7450ESA MAX7451ESA MAX7452ESA TEMP RANGE PINSUPPLY PACKAGE VOLTAGE (V)
5 3.3
Applications
Signal Conditioner for Standard-Definition Video Inputs Security Video Systems Video-Switching Systems
-40C to +85C 8 SO-EP* -40C to +85C 8 SO-EP* -40C to +85C 8 SO-EP*
+5
*EP = Exposed pad. Package code = S8E-12.
Functional Diagram
VCC GAIN SET (0dB OR +6dB)
VIDEO INPUT
IN
NOISE FILTER
6dB
0 OR +6dB
OUT
75
75 SYNC SEPARATOR AND AMPLITUDE DETECTOR
LOS AGCD
MAX7450 MAX7451
VSS GND
________________________________________________________________ Maxim Integrated Products
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Video-Signal Conditioners with AGC and Back-Porch Clamp MAX7450/MAX7451/MAX7452
ABSOLUTE MAXIMUM RATINGS
VCC to GND MAX7450/MAX7452...........................................................+6V MAX7451 ...........................................................................+4V VSS to GND MAX7450.............................................................................-6V MAX7451.............................................................................-4V OUT MAX7450/MAX7451 ..........................................-2.5V to +3.5V MAX7452 ................................................-0.3V to (VCC + 0.3V) GSET, AGCD, LOS .....................................-0.3V to (VCC + 0.3V) All Other Pins MAX7450/MAX7451...................(-0.3V + VSS) to (VCC + 0.3V) MAX7452 ................................................-0.3V to (VCC + 0.3V) Maximum Current into Any Pin ....................................50mA Continuous Power Dissipation (TA = +70C) 8-Pin SO (derate 18.9mW/C above +70C)..............1509mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead temperature (soldering, 10s) ..................................+300C
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
(VSUPPLY = 5V 5% (MAX7450), VSUPPLY = 3.3V 5% (MAX7451), VSUPPLY = +5V 5% (MAX7452), RL=150 to GND, CL = 0 to 20pF, GSET = 1, AGCD = 1, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Clamp Accuracy Back-Porch Level Input Range Clamp Response Time VBPLVL tCLAMP SYMBOL CONDITIONS MAX7450/MAX7451, relative to GND MAX7452, relative VBPLVL = 1.5V MAX7452 GSET = 0 GSET = 1 1.5 1.2 70 10 % 10 -6.0 -0.3 10 f = 100kHz tG dG d GSET = 0 GSET = 1 0.95 1.85 1 2 0.2 0.2 1.05 2.05 15 0.6 0.6 +6.0 +0.3 dB dB MHz V/V ns % Degrees MIN TYP MAX 50 50 2.4 2.0 UNITS mV V Lines
Blanking level at the output to 1% of final value GSET = 0, relative to VOUT = 1VP-P GSET = 1, relative to VOUT = 2VP-P
AGC Accuracy
AGCD = 0, VIN = 0.5VP-P to 2VP-P
AGC Input Range Gain Flatness Noise-Filter Cutoff Low-Frequency Gain Group-Delay Deviation Differential Gain Differential Phase GF Fc
AGCD = 0, relative to VIN = 1VP-P f = 5MHz relative to 100kHz
3.58/4.43MHz relative to 100kHz Five-step modulated staircase (VIN = 1VP-P) Five-step modulated staircase (VIN = 1VP-P)
2
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Video-Signal Conditioners with AGC and Back-Porch Clamp
ELECTRICAL CHARACTERISTICS (continued)
(VSUPPLY = 5V 5% (MAX7450), VSUPPLY = 3.3V 5% (MAX7451), VSUPPLY = +5V 5% (MAX7452), RL=150 to GND, CL = 0 to 20pF, GSET = 1, AGCD = 1, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER SYMBOL CONDITIONS Output signal peak-to-peak to RMS noise (100Hz to 5MHz) 18s, 100 IRE bar 130 lines, 18s, 100IRE bar 1 VIN = 1VP-P, dG / dP < 3% / degrees AGCD = 1 Power-Supply Rejection Ratio PSRR VCC + 100mVP-P, f = 3.5MHz MAX7450 Supply Current MAX7451 MAX7452 Logic-High Input Logic-Low Input Logic-High Output Logic-Low Output Input Current Logic-High Input Current Logic-Low VIH VIL VOH VOL IIH IIL ISOURCE = 500A ISINK = 500A Logic input sink Logic input source VCC 0.5 0.4 10 10 0.7 x VCC 0.3 x VCC AGCD = 0 with maximum gain 2 30 20 35 30 20 V V V V A A mA dB GSET = 0, VOUT = 1VP-P GSET = 1, VOUT = 2VP-P MIN 68 dB 65 0.2 0.5 5 2.4 % % A VP-P TYP MAX UNITS
MAX7450/MAX7451/MAX7452
Signal-to-Noise Ratio
SNR
Line Time Distortion Field Time Distortion Input Leakage Current Output Dynamic Range
HDIST VDIST IIN
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Video-Signal Conditioners with AGC and Back-Porch Clamp MAX7450/MAX7451/MAX7452
Typical Operating Characteristics
VSUPPLY = 5V 5% (MAX7450), VSUPPLY = 3.3V 5% (MAX7451), VSUPPLY = +5V 5% (MAX7452), RL= 150 to GND, CL = 0 to 20pF, GSET = 1, AGCD = 1. TA = +25C, unless otherwise noted.
GROUP DELAY vs. FREQUENCY
MAX7450 toc01
2T RESPONSE
DIFFERENTIAL PHASE (DEGREES) DIFFERENTIAL GAIN (%)
MAX7450 toc02
DIFFERENTIAL GAIN
0.2 0 -0.2 -0.4 1st 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 1st 2nd 3rd 4th 5th 6th 2nd 3rd 4th 5th 6th
MAX7450 toc03
60
0.4
50 GROUP DELAY (ns)
40 IN 200mV/div
30
DIFFERENTIAL PHASE
20
OUT 200mV/div 0.1 1 FREQUENCY (MHz) 10 t = 200ns/div
10
PASSBAND AMPLITUDE vs. FREQUENCY
MAX7450 toc04
AMPLITUDE vs. FREQUENCY
0 GAIN = 2V / V -10 AMPLITUDE (dB) -20 -30 -40 -50 -60 -70 GAIN = 1V / V
MAX7450 toc05
8 6 4 AMPLITUDE (dB) 2 0 -2 -4 -6 -8 -10 0.1 1 FREQUENCY (MHz) GAIN = 1V / V GAIN = 2V / V
10
10
0.1
1
10
100
FREQUENCY (MHz)
SUPPLY CURRENT vs. TEMPERATURE
MAX7450 toc06
BACK-PORCH VOLTAGE vs. TEMPERATURE
MAX7450 BACK-PORCH VOLTAGE (mV) -1 -2 -3 -4 -5 -6
MAX7450 toc07
35 MAX7450 33 SUPPLY CURRENT (mA)
0
31
29
27
25 -40 -15 10 35 60 85 TEMPERATURE (C)
-40
-15
10
35
60
85
TEMPERATURE (C)
4
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Video-Signal Conditioners with AGC and Back-Porch Clamp MAX7450/MAX7451/MAX7452
Typical Operating Characteristics (continued)
VSUPPLY = 5V 5% (MAX7450), VSUPPLY = 3.3V 5% (MAX7451), VSUPPLY = +5V 5% (MAX7452), RL= 150 to GND, CL = 0 to 20pF, GSET = 1, AGCD = 1. TA = +25C, unless otherwise noted.
OUTPUT BACK-PORCH LEVEL (MAX7450)
MAX7450 toc08
AGC RESPONSE ENVELOPE (VIN = 0.5VP-P)
MAX7450 toc09
AGC RESPONSE ENVELOPE (VIN = 2VP-P)
MAX7450 toc10
AGCD = 0 VOUT = 2VP-P IN AC-COUPLED 200mV/div 500mV/div OUT 200mV/div BACK-PORCH = 0V
AGCD = 0 VOUT = 2VP-P
500mV/div
1s
400ms/div
400ms/div
Pin Description
PIN MAX7450/ MAX7451 1 2 3 4 -- 5 6 7 8 -- MAX7452 1 2 3 -- 4 5 6 7 8 -- NAME FUNCTION Positive Power Supply. Connect +5V to VCC for the MAX7450/MAX7452. Connect +3.3V to VCC for the MAX7451. Bypass to GND with 1F and 0.1F capacitors as close to the pin as possible. Video Input. AC-couple video signal through a 0.1F capacitor. Ground Negative Power Supply. Connect -5V to VSS for the MAX7450. Connect -3.3V to VSS for the MAX7451. Bypass to GND with 1F and 0.1F capacitors as close to the pin as possible. Back-Porch Level Input. When gain = 2V/V (GSET = 1), output back-porch level is equal to BPLVL input. When gain = 1V/V (GSET = 0), output back-porch level is equal to VBPLVL/1.5. Automatic Gain-Control Disable Input. Disable AGC by driving AGCD to VCC. Enable AGC by driving AGCD to GND. Video Output Gain-Setting Input. Drive GSET high to set buffer gain to +6dB. Drive GSET low to set buffer gain to 0dB. Loss-of-Sync Logic Output. LOS is high when video sync is lost for more than 15 horizontal lines. LOS goes low when video sync is present. Exposed Pad. Connect to VSS (MAX7450/MAX7451). Connect to GND (MAX7452).
VCC IN GND VSS BPLVL AGCD OUT GSET LOS EP
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Video-Signal Conditioners with AGC and Back-Porch Clamp MAX7450/MAX7451/MAX7452
VCC GAIN SET (0dB OR +6dB)
VIDEO INPUT
IN
NOISE FILTER
6dB
0 OR +6dB
OUT
75
75
MAX7452
SYNC SEPARATOR AND AMPLITUDE DETECTOR
LOS AGCD
GND
BPLVL
Figure1. MAX7452 Functional Diagram
Detailed Description
As shown in Figure 1, the devices include a 2nd-order lowpass filter intended to reject out-of-band noise. The MAX7450/MAX7451 clamp the back-porch voltage to ground, and the MAX7452 clamps to a user-supplied reference voltage. These devices also include an automatic gain control (AGC), which automatically adjusts the gain to ensure the sync amplitude is normalized to a standard video level; an AGC disable function; and an output driver that drives a standard video load (150) with a full 2VP-P video signal (GSET = 1) or 1VPP video signal (GSET = 0). The clamp and the AGC work concurrently. Interaction between the two different control loops is eliminated by the large difference in time constants. The time constant of the clamp settles within 100 lines, while the AGC loop is digitally stepped so that it settles between 1000-64,000 lines. The AGC control works independently of the gain setting of the output buffer. The overall gain is the multiplication of the AGC gain and the output buffer gain. The maximum overall gain is +12dB and the minimum gain is -6dB.
Back-Porch Clamp
The MAX7450/MAX7451/MAX7452 feature a backporch clamp to set the output blanking level. The devices sense the voltage during back porch and feed back into a control system. The control system provides the appropriate DC-level shift to clamp the output to ground (MAX7450/MAX7451) or to a voltage set by VBPLVL (MAX7452). This restores the DC level for further video processing such as on-screen display (OSD) insertion and analog-to-digital conversion. The backporch clamp to ground also eliminates the need for large output-coupling capacitors that can introduce unwanted line-time distortion (tilt) and cost. This can also reduce board space. The feedback network and the on-chip capacitors introduce a finite settling time after power-up or after any dramatic shift in input voltage (see the Electrical Characteristics section). Back-Porch Level Input (MAX7452) The MAX7452 features an adjustable back-porch level at the output as shown in Figure 1. VBPLVL sets the back-porch clamp level. The back-porch clamp-output level is defined by the following equations. GSET = 1 (Gain = 2V / V), VBACKPORCHLEVEL = VBPLVL GSET = 0 (Gain = 1V / V), VBACKPORCHLEVEL = VBPLVL / 1.5
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Video-Signal Conditioners with AGC and Back-Porch Clamp
Table 1. Gain-Control Settings
AGCD 0 0 1 1 GSET 0 1 0 1 OUTPUT 1VP-P fixed 2VP-P fixed VOUT = VIN VOUT = 2VIN
Noise Filter
The MAX7450/MAX7451/MAX7452 feature a simple 2ndorder lowpass filter to reject out-of-band noise that may be introduced by the long cable connection between the cameras and the switching matrix.
MAX7450/MAX7451/MAX7452
LOS Detector
The LOS detector of the MAX7450/MAX7451/MAX7452 outputs a logic high when the sync is not present (loss of video signal) for at least 15 horizontal lines on the input. This can be used to indicate a fault condition of the camera or cable.
Automatic Gain Control (AGC)
The MAX7450/MAX7451/MAX7452 have an integrated automatic gain-control circuit to ensure the sync amplitude is normalized to the standard level, thus normalizing the overall amplitude to a standard level. The accuracy of the normalized amplitude assumes the ratio of active video to sync amplitude is correct in the input video signal. The gain is adjusted automatically by detecting and comparing the amplitude of the sync pulse to a fixed internal reference. If the sync amplitude is less than this value, the overall gain is increased until the sync amplitude equals this reference. However, if the sync amplitude is high, the overall gain is reduced accordingly. Disable the AGC loop by driving AGCD high. When designing the overall system, it is important to note that the AGC can correct for termination problems. First, disable the AGC and verify that the terminations are correct, and then enable the AGC for proper operation.
Applications Information
Connecting the MAX7450/MAX7451 to a Crosspoint Switch
The MAX7450/MAX7451/MAX7452 are designed to directly interface to a video crosspoint switching device such as those used in security systems (see Figure 2). The MAX7450/MAX7451 clamp the video output to GND, making the devices an ideal interface to the MAX4358 crosspoint switches and the MAX4455 OSD. The MAX7450/MAX7451 and the MAX4455 have their outputs referenced to ground, ensuring the amplitudes and the brightness of the OSD relative to the video signal are accurate.
Interfacing the MAX7452 to an ADC
The MAX7452 can be directly connected to an ADC or video decoder as shown in Figure 3. The video output of the MAX7452 is DC-coupled to a single-ended video input on the ADC. The voltage on the BPLVL pin sets the black level of the video signal at the output of the MAX7452. Use a stable voltage reference for the BPLVL voltage, ideally the same reference that is used
Output Buffer
The output buffer of the MAX7450/MAX7451/MAX7452 is designed to drive either standard video loads or high-impedance loads, independent of the buffer gain. Logic levels on GSET and AGCD set the gain of the MAX7450/MAX7451/MAX7452. Table 1 shows the different gain-setting configurations.
CAM 1
MAX7450 MAX7451
MAX4358 32 x 16 CROSSPOINT
MONITOR 1
CAM 32
MAX7450 MAX7451
MONITOR 16
MAX4455 OSD
MAX4455 OSD
Figure 2. MAX7450/MAX7451 in a 32 x 16 Crosspoint Application
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Video-Signal Conditioners with AGC and Back-Porch Clamp MAX7450/MAX7451/MAX7452
VCC GAIN SET (0dB OR +6dB)
VIDEO INPUT
IN
NOISE FILTER
6dB
0 OR +6dB
OUT
ADC DSP
MAX7452
SYNC SEPARATOR AND AMPLITUDE DETECTOR
REF
LOS AGCD
VIDEO DECODER
BPLVL VSS
Figure 3. MAX7452 Interfaced to a Video Decoder
for the analog-to-digital conversion. This voltage must be scaled by a ratio of two resistors to set the black level of the video signal to the appropriate level (to match the input range of the converter). If the ADC or video decoder has a built-in clamp circuit, the output of the MAX7452 must be AC-coupled into the ADC with the capacitor value recommended for the converter. In this situation, set the BPLVL on the MAX7452 to the midpoint of the specified range for optimum performance. In addition, the stability of this voltage is not critical, provided that it stays within the specified range.
Chip Information
TRANSISTOR COUNT: 6316 PROCESS: BiCMOS
Pin Configuration
TOP VIEW
Power-Supply Bypassing and Layout
Bypass all supply pins to GND with 0.1F and 1F capacitors. These capacitors filter higher frequencies in the MHz range. Place all external components as close to the devices as possible. Connect EP to V SS for the MAX7450/MAX7451. Connect EP to GND for the MAX7452. Placing the IC onto a copper area the size of the pad is recommended for proper power dissipation. Refer to the MAX7450 Evaluation Kit for a proven PCboard layout example.
VCC IN GND
1 2 3
8
LOS GSET OUT AGCD
MAX7450 MAX7451 MAX7452
7 6 5
VSS (MAX7450/MAX7451) 4 BPLVL (MAX7452)
SO-EP* *CONNECT EP TO VSS FOR THE MAX7450/MAX7451
8
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Video-Signal Conditioners with AGC and Back-Porch Clamp
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.)
8L, SOIC EXP. PAD.EPS
MAX7450/MAX7451/MAX7452
PACKAGE OUTLINE 8L SOIC, .150" EXPOSED PAD
21-0111
B
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 _____________________ 9 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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