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19-0671; Rev 0; 11/06
Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices
General Description
The MAX7481/MAX7482 bidirectional video filters/ buffers provide the reconstruction filter and line drive buffer for both composite (CVBS) and S-Video (Y/C) video signals in playback mode, and anti-aliasing in record mode for portable media devices. Each channel consists of a lowpass filter and an output buffer capable of driving a full 2VP-P video signal into one standard 150 load (DC-coupled to ground). In record mode, the MAX7481/MAX7482 output buffers have a gain of +6dB. In playback mode, the MAX7481 output buffers have a gain of +6dB and the MAX7482 output buffers have a gain of +7dB. The MAX7481/MAX7482 feature DirectDriveTM by utilizing an internal negative charge pump and regulator to maintain the output blanking level at ground, eliminating the need for a negative supply voltage, a large output coupling capacitor, or a sag correction configuration. The MAX7481/MAX7482 operate from a single +2.7V to +3.6V power supply. These devices are available in a space-saving 28-pin TQFN package and operate over the -40C to +85C extended temperature range.
Features
Composite and S-Video, Video-Playback and VideoRecord Interface for Portable Video Devices Saves Space by Sharing Connectors in Portable Devices DirectDrive Eliminates Expensive AC-Coupling Capacitors Blanking Level at Ground with Single Supply Composite and Y/C Signals Advanced Power-Down Modes for Extended Battery Life Low Supply Current in Shutdown Mode, < 1A (typ) Filter Response Ideal for NTSC and PAL +6dB (MAX7481) or +7dB (MAX7482) Gain +2.7V to +3.6V Single-Supply Operation Small, 28-Pin, TQFN Package (5mm x 5mm)
MAX7481/MAX7482
Ordering Information
PART MAX7481ETI+ MAX7482ETI+ TEMP RANGE -40C to +85C -40C to +85C PINPACKAGE 28 TQFN-EP* 28 TQFN-EP* PKG CODE T2855-6 T2855-6
Applications
Portable Media Devices Digital Camcorders Digital Cameras
+Denotes lead-free package. *EP = Exposed pad.
Pin Configuration appears at end of data sheet.
Simplified Block Diagram
VIDEO ADC OUT4
PLAYBACK SIGNAL FLOW
MAX7481 MAX7482
VIDEO DAC
0V
IN1 LPF OUT1
IN3 IN5 P/R VIDEO PROCESSOR CVBSON YCON CONTROL LOGIC OUT3
0V
VIDEO DAC
IN2 LPF
OUT2
0V IN4
VIDEO ADC
0V
OUT5
RECORD SIGNAL FLOW
________________________________________________________________ Maxim Integrated Products
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
ABSOLUTE MAXIMUM RATINGS
VCC to GND ............................................................. -0.3V to +4V IN1-IN5 to GND..........................................-0.3V to (VCC + 0.3V) OUT1-OUT5 to GND ....................................-1.8V to (VCC + 0.3V) OUT1-OUT5 to GND (Shutdown) .................-0.3V to (VCC + 0.3V) BIAS, SHDN, P/R, YCON, CVBSON to GND....................................................-0.3V to (VCC + 0.3V) CPVCC to CPGND ....................................................-0.3V to +4V C1P to GND............................................... -0.3V to (VCC + 0.3V) C1N to GND ............................................... (VSS - 0.3V) to +0.3V CPGND to GND.....................................................-0.1V to +0.1V CPVSS to VSS .........................................................-0.1V to +0.1V VSS to GND........................................................... -3.6V to +0.3V Continuous Current IN1-IN5, BIAS, CVBSON, YCON, C1P, C1N................50mA Output Short-Circuit Current.............................................90mA Continuous Power Dissipation (TA = +70C) 28-Pin TQFN (derate 21.3mW/C above +70C) .......1702mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +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
(VCC = CPVCC = +3.0V, TA = +25C, C1 = C2 = 1F, C3 = C4 = C5 = 0.1F, load at OUT1-OUT5 = 150 to GND, RBIAS = 100k to GND, unless otherwise noted. See the Functional Diagram/Typical Application Circuit.)
PARAMETER Passband Flatness Stopband Attenuation Differential Gain Error Differential Phase Error Signal-to-Noise Ratio dG dP SNR SYMBOL f = 27MHz 5-step modulated staircase 5-step modulated staircase Peak signal (2VP-P) to RMS noise, f = 100kHz to 4.2MHz IN1, VIN = -0.10V to 0.92V IN2, VIN = -0.09V to 0.92V Input Dynamic Swing VRANGE AC-coupled Input Leakage Current IIN MAX7481: All outputs MAX7482: OUT4, OUT5 Low Frequency Gain f = 100kHz MAX7482: OUT1, OUT2, OUT3 Output Black Level Variation Clamp Settling Time Group-Delay Deviation Line-Time Distortion Field-Time Distortion Channel-to-Channel Crosstalk TCLAMP TG HDIST VDIST XTALK OUT1, OUT2, OUT4 OUT3, OUT5 To 5% with a 100 IRE step Deviation from 100kHz to 4.2MHz Deviation in a line with an 18s, 100 IRE bar; 1 line = 63.5s Deviation in 130 lines with an 18s, 100 IRE bar f = 100kHz to 4.2MHz -60 300 4 0.3 0.5 6.5 7 7.5 150 200 mV Lines ns % % dB 5.5 6 IN3 IN4 IN5 CONDITIONS f = 100kHz to 4.2MHz MIN -1 35 0.2 0.3 72 1.15 0.83 1.15 0.90 1.15 10 6.5 dB A VP-P TYP MAX +1 UNITS dB dB % Degrees dB
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices
ELECTRICAL CHARACTERISTICS (continued)
(VCC = CPVCC = +3.0V, TA = +25C, C1 = C2 = 1F, C3 = C4 = C5 = 0.1F, load at OUT1-OUT5 = 150 to GND, RBIAS = 100k to GND, unless otherwise noted. See the Functional Diagram/Typical Application Circuit.)
PARAMETER Power-Supply Rejection Ratio CHARGE PUMP Switching Frequency LOGIC SIGNALS (CVBSON, P/R, YCON) Logic-Low Threshold Logic-High Threshold Logic Input Current SUPPLY Supply Voltage Range VCC, CPVCC CVBSON = YCON = GND ICC = IVCC + ICPVCC, no load, P/R = GND, playback mode CVBSON = VCC, YCON = GND CVBSON = GND, YCON = VCC CVBSON = YCON = VCC Shutdown Supply Current Bias Voltage ISHDN VBIAS ISHDN = IVCC + ICPVCC; SHDN = VCC, P/R = GND, CVBSON = YCON = VCC 2.7 9 19 28 40 1 1 3.6 18 33 mA 42 52 10 A V V VIL VIH IIL VCC = +2.7V to +3.6V VCC = +2.7V to +3.6V 1.5 10 0.5 V V A 250 kHz SYMBOL PSRR CONDITIONS VCC = +2.7V to +3.6V MIN 50 TYP MAX UNITS dB
MAX7481/MAX7482
Quiescent Supply Current
ICC
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
Typical Operating Characteristics
(VCC = CPVCC = +3.0V, TA = +25C, unless otherwise noted.)
MAX7481 FREQUENCY RESPONSE
MAX7481 toc01
MAX7482 FREQUENCY RESPONSE
MAX7481 toc02
MAX7481 PASSBAND FLATNESS
INPUT = 1VP-P 2 OUTPUT AMPLITUDE (dB) 1 0 -1 -2 -3
MAX7481 toc03
20 INPUT = 1VP-P OUTPUT AMPLITUDE (dB) 0
20 INPUT = 1VP-P OUTPUT AMPLITUDE (dB) 0
3
-20
-20
-40
-40
-60
-60
-80 0.1 1 10 100 FREQUENCY (MHz)
-80 0.1 1 10 100 FREQUENCY (MHz)
0.1
1 FREQUENCY (MHz)
10
MAX7482 PASSBAND FLATNESS
MAX7481 toc04
MAX7481 GROUP-DELAY RESPONSE
MAX7481 toc05
MAX7482 GROUP-DELAY RESPONSE
INPUT = 1VP-P 110 GROUP DELAY (ns) 100 90 80 70 60
MAX7481 toc06
4 INPUT = 1VP-P 3 OUTPUT AMPLITUDE (dB) 2 1 0 -1 -2 0.1 1 FREQUENCY (MHz)
120 INPUT = 1VP-P 110 GROUP DELAY (ns) 100 90 80 70 60
120
10
0.1
1 FREQUENCY (MHz)
10
0.1
1 FREQUENCY (MHz)
10
2T RESPONSE
MAX7481 toc07
12.5T RESPONSE
MAX7481 toc08
IN1 200mV/div
IN1 200mV/div
OUT1 200mV/div
OUT1 200mV/div
200ns/div
400ns/div
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices
Typical Operating Characteristics (continued)
(VCC = CPVCC = +3.0V, TA = +25C, unless otherwise noted.)
DIFFERENTIAL GAIN vs. DIFFERENTIAL PHASE
DIFFERENTIAL GAIN (%) 0.05 0 -0.05 -0.10 -0.15 -0.20 -0.25 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 0 -0.01 -0.05 -0.02 -0.05 -0.13
MAX7481 toc09
MAX7481/MAX7482
FIELD SQUARE-WAVE RESPONSE
MAX7481 toc10
FIELD SQUARE-WAVE RESPONSE
MAX7481 toc11
IN1 500mV/div
IN3 500mV/div
DIFFERENTIAL PHASE (deg)
0
-0.07
-0.12
-0.15
-0.24
-0.37
OUT1 500mV/div
OUT4 500mV/div
1st
2nd
3rd
4th
5th
6th
STEP
2ms/div
2ms/div
Pin Description
PIN 1 2, 14, 17, 20 3 4 5 6 7, 13, 23 8 9 10 11 12 15 16 18 19 21 NAME CPVCC GND IN2 IN1 OUT5 OUT4 VCC BIAS SHDN P/R CVBSON YCON IN3 OUT1 OUT3 IN5 OUT2 Ground Video Input 2 Video Input 1 Video Output 5 Video Output 4 Positive Power Supply. Bypass with a 1F capacitor to GND. Bias Current Setting Control. Connect a 100k 1% resistor from BIAS to GND. Shutdown Input. Drive high to put device in shutdown mode. Playback/Record Logic Input. Drive high for record mode and pull low for playback mode. CVBS Select Logic Input. Drive high for composite video on output OUT3 in playback mode and output OUT4 in record mode. See Table 1. Y/C Select Logic Input. Drive high to enable Y/C video on outputs OUT1 and OUT2 in playback mode and on outputs OUT4 and OUT5 in record mode. See Table 1. Video Input 3 Video Output 1 Video Output 3 Video Input 5 Video Output 2 FUNCTION Charge-Pump Positive Power Supply. Bypass with a 1F capacitor to CPGND.
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
Pin Description (continued)
PIN 22 24 25 26 27 28 -- NAME IN4 VSS CPVSS C1N CPGND C1P EP Video Input 4 Negative Power Supply. Connect to CPVSS. Charge-Pump Negative Power Supply. Bypass with a low-ESR 1F capacitor to CPGND. Charge-Pump Flying Capacitor Negative Terminal. Connect a low-ESR 1F capacitor from C1P to C1N. Charge-Pump Power Ground Charge-Pump Flying Capacitor Positive Terminal. Connect a low-ESR 1F capacitor from C1P to C1N. Exposed Pad. Internally connected to GND. Do not route any PCB traces directly under the package. Connect EP to GND for improved heat dissipation. FUNCTION
Detailed Description
The MAX7481/MAX7482 bidirectional video filters and buffers are ideal for portable video applications where low-voltage, low-power operation is critical and applications that require both analog video inputs and outputs. The MAX7481/MAX7482 provide the reconstruction filter and line drivers for both composite video (CVBS) and Y/C (S-Video) for playback, while providing antialiasing filters and drivers for recording. In playback mode, the IN1 and IN2 inputs are enabled while the IN3, IN4, and IN5 inputs are disabled. The MAX7481/MAX7482 provide the filtered Y/C outputs at OUT1 and OUT2, and the composite output at OUT3. In record mode, IN1 and IN2 are disabled while IN3, IN4, and IN5 are enabled. Switches connecting OUT1 to GND, OUT2 to GND, and OUT3 to GND are turned on. These switches provide low-impedance paths to ground so that the same 75 external resistors that connect the playback outputs (OUT1, OUT2, and OUT3) and the external device can be used as terminating resistors for the recording signal source. Inputs IN3, IN4, and IN5 require AC-coupling capacitors because the signal from the external video source can be DC level-shifted and an internal clamp uses these capacitors to restore the blanking level to GND. The internal clamp operates only on signals coming from the external source due to the uncertainty in the DC offset. The gain in either direction is fixed at +6dB for the MAX7481. The MAX7482 output buffers have a gain of +7dB in playback mode and +6dB in record mode. The MAX7481/MAX7482 feature DirectDrive technology that allows the blanking level to stay at GND in a single supply system. The MAX7481/MAX7482 internally generate a negative supply voltage from an inverting charge pump and internal linear regulator. The regulated negative supply allows output buffers to drive 2VP-P video signals without exceeding operating voltage limits.
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Comparison Between DirectDrive Output and AC-Coupled Output
DirectDrive refers to the connection of the video signal from the MAX7481/MAX7482 to an external device without requiring large series AC-coupling capacitors in a single supply system. The actual level of the video signal varies less with a DirectDrive output than an ACcoupled output. The video-signal average can change greatly depending upon the picture content. With an AC-coupled output, the average changes according to the time constant formed by the series capacitor and series resistance (usually 150). For example, Figure 1 shows an AC-coupled video signal alternating between a completely black screen and a completely white screen. Notice the excursion of the video signal as the screen changes. With a DirectDrive amplifier, the black level is held at ground. The video signal is constrained between -0.3V to +0.7V. Figure 2 shows the video signal from a DirectDrive amplifier with the same input signal as the AC-coupled system. The large series AC-coupling capacitors create a highpass filter. Since the lowest frequency in video is the frame rate, which can be between 24Hz and 30Hz, the pole of the highpass filter should ideally be an order of magnitude lower in frequency than the frame rate. Therefore, the AC-coupling capacitor must be very large, typically from 220F to 3000F. For space-constrained equipment, the series capacitor is unacceptable. Changing from a single series capacitor to a SAG network that requires two smaller capacitors can reduce space, but increases cost.
Playback Mode
Playback mode takes the video signal from the video processor and provides the reconstruction filter and line drive for both composite and Y/C video outputs. Figure 3 shows a signal flow diagram and Figure 4 shows the signal flow from the video processor to an external media
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
INPUT 500mV/div
INPUT 500mV/div 0V
OUTPUT 500mV/div
0V
OUTPUT 1V/div
2ms/div
2ms/div
Figure 1. AC-Coupled Output
Figure 2. DirectDrive Output
device, such as a display in playback mode. In playback mode, internal switches S1, S2, S4, and S5 close the path from the video processor to the filter upon driving CVBSON and/or YCON high. Driving either YCON or CVBSON high enables the signal path from the video processor through the filter. Switches S6, S7, and S8 are open and not in the signal path in playback mode. Driving YCON high drives the Y signal to OUT1 and C signal to OUT2 while enabling CVBSON combines the Y and C signals to form composite video and output on OUT3. Both composite and Y/C video can be active in this mode. Pull P/R low for playback mode.
Connection Sharing for Inputs and Outputs Outputs OUT1, OUT2, and OUT3 and inputs IN3, IN4, and IN5 can share one connector to save space. Figure 6 shows a possible interface at OUT1/OUT2/ OUT3 and IN3/IN4/IN5. In record mode, the switch closes, OUT1/OUT2/OUT3 go to GND, and the external 75 resistor looks like a load-termination resistor. Figure 4 shows that in playback mode, IN3/IN4/IN5 are not used and the switches to GND are open. The external 75 resistor serves as a back-termination resistor in playback mode and provides the cable termination in record mode.
Record Mode
Record mode takes the video signal from an external video source and provides anti-aliasing for both composite and Y/C signals. Figure 5 shows the signal flow from the external video source to the video processor. Upon driving P/R high, switches S1, S2, S4, and S5 change states so that the signals utilize the same filters and now route to the video processor. Switches S6, S7, and S8 all close to ground so that the incoming signal sees a 75 load termination to ground. The inputs IN3, IN4, and IN5 are AC-coupled with a 0.1F capacitor that works with an internal clamping circuit. Enabling CVBSON drives the video signal from IN5 through the upper filter and outputs at OUT4. In this mode, OUT5 is disabled and pulled to GND. Enabling YCON drives the Y signal from IN3 through the upper filter to output at OUT4 and the C signal from IN4 through the lower filter to output at OUT5. Switch S3 connects OUT4 to either the Y channel if YCON is high, or the composite video channel if CVBSON is high. Driving both CVBSON and YCON high results in an invalid state, resulting in all output buffers shutting down and pulling to GND.
Bidirectional Video Filter and Buffer
The MAX7481/MAX7482 output buffers are designed to drive both Y/C channels as well as composite video. The output buffers use the internally generated negative supply to shift the blanking level of video outputs (composite and Y only) to ground so that the active video signal is above ground and the negative sync pulse is below ground. The C signal is shifted so that it is centered at GND. The output buffers are capable of driving a full 2VP-P video signal into a standard 150 load DC-coupled to GND. The output buffers can drive an AC-coupled load provided that the load impedance is greater than 5k. The MAX7481/MAX7482 utilize the same filter in both playback and record modes by using switches that route the signals through different paths in the two modes (see Figure 3). Switches S1-S8 change states depending on the mode of operation and control input settings. The use of these internal switches enables utilizing a single filter in both modes for a unique solution in space constrained and cost-sensitive applications.
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
VIDEO ADC VIDEO DAC S1 LPF S2
MAX7481 MAX7482
75 S6 S3 0.1F
VIDEO PROCESSOR
P/R CVBSON YCON CONTROL LOGIC S7
0.1F
75 75
VIDEO DAC
S4 LPF
S5 S8
0.1F VIDEO ADC
Figure 3. Signal Flow Diagram
Clamp In record mode, signals are AC-coupled into IN3, IN4, and IN5 through small 0.1F capacitors. The clamp circuit internally DC-restores the signal for optimal performance of the circuit so that the OUT4 blanking level sits at GND and the OUT5 signal is centered at GND. Do not connect any resistors in series or parallel with clamp capacitors.
YCON high for outputs OUT1 and OUT2 to be active and/or drive CVBSON high to combine IN1 and IN2 into composite video and output on OUT3. Pull both control inputs low to disable outputs and power down the output buffers. OUT4 and OUT5 are always disabled in playback mode. In record mode, drive YCON high and CVBSON low to output Y/C format video on OUT4 and OUT5 or drive CVBSON high and YCON low to output composite video on OUT4. Pull both control inputs low to disable OUT4 and OUT5 and power down the output buffers. Driving both CVBSON and YCON high in record mode results in an invalid state and all output buffers power down. The Y signal inputs on IN3, C signal inputs on IN4, and composite signal inputs on IN5. OUT4 is shared between the composite signal and Y signal. The composite or Y signal that outputs on OUT4 has the blanking level set to GND with the sync tip below GND and active video above GND. The C signal that outputs on OUT5 is centered at GND. The outputs get levelshifted by the bias of the video processor input after the AC-coupling capacitors.
Analog Inputs/Outputs
Figures 4 and 5 show the signal flow diagrams for playback and record modes. P/R controls the mode of operation, while CVBSON and YCON select which outputs are enabled. Table 1 shows the various combinations of inputs and outputs that can be selected. In playback mode, inputs IN1 and IN2 are active and the outputs are selected by driving CVBSON and YCON. IN1 receives the composite or luma (Y) signal and level-shifts the signal by approximately 350mV at the output such that the sync tip is below GND and the active video is above GND. IN2 receives the chroma (C) signal and level-shifts by approximately 500mV at the output such that the signal is centered at GND. Drive
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
Table 1. Input/Output Truth Table
P/R Low Low Low Low High High High High PLAYBACK CVBSON Low Low High High Low Low High High YCON Low High Low High Low High Low High OUT3 (CVBS) Not Active Not Active Active Active GND GND GND GND OUT1 (Y) AND OUT2 (C) Not Active Active Not Active Active GND GND GND GND OUT4 (Y, CVBS) GND GND GND GND GND Active Active GND OUT5 (C) GND GND GND GND GND Active GND GND IN3 AND IN4 (Y, C) Not Used Not Used Not Used Not Used Not Used Active Not Used Not Used IN5 (CVBS) Not Used Not Used Not Used Not Used Not Used Not Used Active Not Used IN1 (Y) Active Active Active Active Not Used Not Used Not Used Not Used IN2 (C) Active Active Active Active Not Used Not Used Not Used Not Used
RECORD
VIDEO ADC
OUT4
MAX7481 MAX7482
S1 LPF S2 S3 S6 IN3 IN5 0.1F
VIDEO DAC
IN1
OUT1
75
P/R = LOW CVBSON YCON CONTROL LOGIC S7 OUT3
0.1F
75
VIDEO DAC
IN2
S4 LPF
S5 S8
OUT2
75
VIDEO ADC
OUT5
IN4
0.1F
Figure 4. Signal Flow Diagram for Playback Mode
Short-Circuit Protection The MAX7481/MAX7482 typical application circuit includes a 75 back-termination resistor that limits shortcircuit current if an external short is applied to the video output. The MAX7481/MAX7482 provide additional output short-circuit protection to prevent damage in applications where amplifier output can be directly shorted.
Charge Pump and Linear Regulator
Portable video applications have space constraints that limit the use of AC-coupling capacitors and power constraints that limit the use of batteries to generate the negative supply rail. The MAX7481/MAX7482 simplify and reduce space and power constraints by integrating a charge pump and linear regulator to create a lownoise negative supply from a single positive supply. The charge pump inverts the positive supply to create
9
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
VIDEO ADC OUT4
MAX7481 MAX7482
S1 LPF S2 S6 IN3 S3 P/R = HIGH CVBSON YCON CONTROL LOGIC S7 75 IN5 0.1F 0.1F 75
VIDEO DAC
IN1
VIDEO DAC
IN2
S4 LPF
S5 S8 IN4
75
YCON = HIGH VIDEO ADC OUT5
0.1F
Figure 5. Signal Flow Diagram for Record Mode
a raw negative voltage that is fed into a linear regulator. The linear regulator filters out the charge-pump noise for a clean negative supply rail. The use of an integrated charge pump facilitates a direct connection without the use of large series AC-coupling capacitors in a single supply system.
OUTPUT BUFFER
OUT1, OUT2, OUT3
75
SINGLE CONNECTION
BIAS
Connect a 100k resistor with 1% accuracy or better from BIAS to GND to create the bias current used throughout the MAX7481/MAX7482.
IN3, IN4, IN5 0.1F
75 CABLE
Power-Down Modes
The MAX7481/MAX7482 feature a shutdown mode that significantly reduces power consumption. Drive SHDN high to put the MAX7481/MAX7482 in shutdown mode. In shutdown mode, the video filters, output buffers, charge pump, and linear regulator are turned off, and all video output drivers are pulled to GND. The MAX7481/MAX7482 consume less than 10A in shutdown mode. The MAX7481/MAX7482 also feature advanced powerdown modes that turn off the output buffers not in use
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Figure 6. Single Connector for Input and Output
during normal operation. In playback mode, the record output buffers are turned off and in record mode, the playback output buffers are turned off. CVBSON and YCON further reduce power dissipation by turning off output buffers not in use. The MAX7481/MAX7482 are designed to extend battery life in portable video applications.
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices
Functional Diagram/Typical Application Circuit
MAX7481/MAX7482
DAC 150
IN1
MAX7481 MAX7482
+6dB OR +7dB OUT1
CLAMP
LOWPASS FILTER
75 Y IN3 C3 = 0.1F
ADC
OUT4 0.1F
+6dB +6dB OR +7dB OUT3 75
P/R
CVBS IN5 C5 = 0.1F +6dB OR +7dB
CVBSON YCON
DAC 150
IN2 LOWPASS FILTER
OUT2 75 C IN4 C4 = 0.1F
CLAMP
ADC
OUT5 0.1F
+6dB
REGULATOR
CHARGE PUMP VCC GND 100k 1F VCC C1 = 1F VCC C2 = 1F BIAS SHDN CPVCC CPGND C1P C1N CPVSS VSS
1F
Applications Information
Power-Supply Considerations
The MAX7481/MAX7482 operate from a +2.7V to +3.6V single supply and require proper layout and bypassing. For best performance, place components as close as possible to the device. Proper grounding improves performance, minimizes crosstalk, and prevents any switching noise from coupling into the video signal. Connect GND (pin 2) and
CPGND together at a single point on the PCB. Route CPGND and all traces carrying switching transients away from GND traces and components in the video signal path. Bypass each analog supply (VCC) with a 1F capacitor to GND, placed as close as possible to the device. Bypass the charge-pump supply (CPVCC) with a 1F capacitor to CPGND, placed as close as possible to the device. Connect CPV SS to V SS and bypass with a low-ESR 1F capacitor to CPGND as close as possible to the device.
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices MAX7481/MAX7482
Exposed Pad and Heat Dissipation
The MAX7481/MAX7482 are available in TQFN packages that have an exposed pad on the bottom. This pad is electrically connected to GND and can be soldered to the ground plane for improved thermal conductivity. Do not route signals directly under the package.
OUT2 GND IN5
Pin Configuration
OUT3 OUT1 16 GND IN3 15 14 13 12 GND VCC YCON CVBSON P/R SHDN BIAS 11 10 9 + 1 CPVCC 2 GND 3 IN2 4 IN1 5 OUT5 6 OUT4 7 VCC 8
TOP VIEW
21 IN4 22 VCC 23 VSS 24 CPVSS 25 C1N 26 CPGND 27 C1P 28
20
19
18
17
Chip Information
PROCESS: BiCMOS
MAX7481 MAX7482
TQFN
12
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Bidirectional Video Filters/Buffers for Composite and S-Video Portable Media Devices
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.)
MAX7481/MAX7482
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 ____________________ 13
(c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
QFN THIN.EPS

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