MAXIM MAX7481ETI+

19-0671; Rev 0; 11/06
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
Features
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
150Ω 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 DirectDrive™ 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 -40°C to +85°C extended temperature range.
♦ 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, < 1µA (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)
Ordering Information
PART
TEMP RANGE
PINPACKAGE
MAX7481ETI+
-40°C to +85°C
28 TQFN-EP*
T2855-6
MAX7482ETI+
-40°C to +85°C
28 TQFN-EP*
T2855-6
Applications
Portable Media Devices
Digital Camcorders
PKG
CODE
+Denotes lead-free package.
*EP = Exposed pad.
Digital Cameras
Pin Configuration appears at end of data sheet.
Simplified Block Diagram
VIDEO
DAC
PLAYBACK SIGNAL FLOW
OUT4
VIDEO
ADC
MAX7481
MAX7482
0V
IN1
LPF
OUT1
IN3
0V
IN5
P/R
VIDEO
PROCESSOR
CVBSON
YCON
OUT3
CONTROL
LOGIC
OUT2
IN2
VIDEO
DAC
LPF
0V
IN4
VIDEO
ADC
0V
OUT5
RECORD SIGNAL FLOW
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX7481/MAX7482
General Description
MAX7481/MAX7482
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
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 = +70°C)
28-Pin TQFN (derate 21.3mW/°C above +70°C) .......1702mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
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 = +25°C, C1 = C2 = 1µF, C3 = C4 = C5 = 0.1µF, load at OUT1–OUT5 = 150Ω to GND, RBIAS = 100kΩ to
GND, unless otherwise noted. See the Functional Diagram/Typical Application Circuit.)
PARAMETER
SYMBOL
Passband Flatness
Stopband Attenuation
CONDITIONS
MIN
f = 100kHz to 4.2MHz
-1
f = 27MHz
35
TYP
MAX
UNITS
+1
dB
dB
Differential Gain Error
dG
5-step modulated staircase
0.2
%
Differential Phase Error
dP
5-step modulated staircase
0.3
Degrees
Peak signal (2VP-P) to RMS noise,
f = 100kHz to 4.2MHz
72
dB
Signal-to-Noise Ratio
SNR
IN1, VIN = -0.10V to 0.92V
1.15
IN2, VIN = -0.09V to 0.92V
Input Dynamic Swing
VRANGE
AC-coupled
Input Leakage Current
IN4
0.90
IN5
1.15
10
MAX7481: All outputs
MAX7482: OUT4, OUT5
5.5
6
6.5
MAX7482: OUT1, OUT2,
OUT3
6.5
7
7.5
f = 100kHz
Output Black Level Variation
Group-Delay Deviation
1.15
IIN
Low Frequency Gain
Clamp Settling Time
0.83
IN3
TCLAMP
TG
VP-P
µA
dB
OUT1, OUT2, OUT4
±150
OUT3, OUT5
±200
To 5% with a 100 IRE step
Deviation from 100kHz to 4.2MHz
mV
300
Lines
4
ns
Line-Time Distortion
HDIST
Deviation in a line with an 18µs, 100 IRE
bar; 1 line = 63.5µs
0.3
%
Field-Time Distortion
VDIST
Deviation in 130 lines with an 18µs, 100 IRE
bar
0.5
%
Channel-to-Channel Crosstalk
XTALK
f = 100kHz to 4.2MHz
2
-60
_______________________________________________________________________________________
dB
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
(VCC = CPVCC = +3.0V, TA = +25°C, C1 = C2 = 1µF, C3 = C4 = C5 = 0.1µF, load at OUT1–OUT5 = 150Ω to GND, RBIAS = 100kΩ to
GND, unless otherwise noted. See the Functional Diagram/Typical Application Circuit.)
PARAMETER
Power-Supply Rejection Ratio
SYMBOL
PSRR
CONDITIONS
VCC = +2.7V to +3.6V
MIN
TYP
MAX
50
UNITS
dB
CHARGE PUMP
Switching Frequency
250
kHz
LOGIC SIGNALS (CVBSON, P/R, YCON)
Logic-Low Threshold
VIL
VCC = +2.7V to +3.6V
Logic-High Threshold
VIH
VCC = +2.7V to +3.6V
Logic Input Current
IIL
0.5
V
10
µA
3.6
V
1.5
V
SUPPLY
Supply Voltage Range
Quiescent Supply Current
VCC,
CPVCC
ICC
Shutdown Supply Current
ISHDN
Bias Voltage
VBIAS
2.7
ICC = IVCC +
ICPVCC, no
load, P/R =
GND, playback
mode
CVBSON = YCON = GND
9
18
CVBSON = VCC, YCON =
GND
19
33
CVBSON = GND, YCON
= VCC
28
42
CVBSON = YCON = VCC
40
52
1
10
mA
ISHDN = IVCC + ICPVCC; SHDN = VCC, P/R =
GND, CVBSON = YCON = VCC
1
µA
V
_______________________________________________________________________________________
3
MAX7481/MAX7482
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = CPVCC = +3.0V, TA = +25°C, unless otherwise noted.)
INPUT = 1VP-P
-40
INPUT = 1VP-P
2
-20
-40
-60
-60
1
1
10
FREQUENCY (MHz)
FREQUENCY (MHz)
MAX7482
PASSBAND FLATNESS
MAX7481
GROUP-DELAY RESPONSE
INPUT = 1VP-P
110
GROUP DELAY (ns)
3
120
2
1
0
-1
100
90
80
1
10
120
INPUT = 1VP-P
110
100
90
80
70
60
60
0.1
0.1
1
FREQUENCY (MHz)
10
0.1
2T RESPONSE
12.5T RESPONSE
MAX7481 toc07
4
1
FREQUENCY (MHz)
FREQUENCY (MHz)
200ns/div
10
MAX7482
GROUP-DELAY RESPONSE
70
-2
1
FREQUENCY (MHz)
GROUP DELAY (ns)
INPUT = 1VP-P
0.1
100
MAX7481 toc05
4
-1
-3
0.1
100
10
MAX7481 toc04
0.1
0
-2
-80
-80
1
MAX7481 toc06
-20
0
3
OUTPUT AMPLITUDE (dB)
OUTPUT AMPLITUDE (dB)
0
20
MAX7481 toc02
INPUT = 1VP-P
MAX7481 toc01
20
OUTPUT AMPLITUDE (dB)
MAX7481
PASSBAND FLATNESS
MAX7482
FREQUENCY RESPONSE
MAX7481 toc03
MAX7481
FREQUENCY RESPONSE
OUTPUT AMPLITUDE (dB)
MAX7481/MAX7482
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
MAX7481 toc08
IN1
200mV/div
IN1
200mV/div
OUT1
200mV/div
OUT1
200mV/div
400ns/div
_______________________________________________________________________________________
10
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
0
-0.01
-0.05
-0.02
-0.05
FIELD SQUARE-WAVE RESPONSE
FIELD SQUARE-WAVE RESPONSE
-0.13
MAX7481 toc11
MAX7481 toc10
MAX7481 toc09
DIFFERENTIAL GAIN (%)
0.05
0
-0.05
-0.10
-0.15
-0.20
-0.25
DIFFERENTIAL PHASE (deg)
DIFFERENTIAL GAIN
vs. DIFFERENTIAL PHASE
0
1st
-0.07
2nd
-0.12
-0.15
3rd
4th
-0.24
5th
IN1
500mV/div
IN3
500mV/div
OUT1
500mV/div
OUT4
500mV/div
-0.37
6th
STEP
2ms/div
2ms/div
Pin Description
PIN
NAME
FUNCTION
1
CPVCC
2, 14, 17, 20
GND
Charge-Pump Positive Power Supply. Bypass with a 1µF capacitor to CPGND.
3
IN2
Video Input 2
4
IN1
Video Input 1
5
OUT5
Video Output 5
6
OUT4
Video Output 4
Ground
7, 13, 23
VCC
Positive Power Supply. Bypass with a 1µF capacitor to GND.
8
BIAS
Bias Current Setting Control. Connect a 100kΩ ±1% resistor from BIAS to GND.
9
SHDN
Shutdown Input. Drive high to put device in shutdown mode.
10
P/R
11
CVBSON
12
YCON
15
IN3
16
OUT1
Video Output 1
18
OUT3
Video Output 3
19
IN5
21
OUT2
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 Input 5
Video Output 2
_______________________________________________________________________________________
5
MAX7481/MAX7482
Typical Operating Characteristics (continued)
(VCC = CPVCC = +3.0V, TA = +25°C, unless otherwise noted.)
MAX7481/MAX7482
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
Pin Description (continued)
PIN
NAME
FUNCTION
22
IN4
Video Input 4
24
VSS
Negative Power Supply. Connect to CPVSS.
25
CPVSS
26
C1N
27
CPGND
28
C1P
Charge-Pump Flying Capacitor Positive Terminal. Connect a low-ESR 1µF capacitor from C1P to C1N.
EP
Exposed Pad. Internally connected to GND. Do not route any PCB traces directly under the package.
Connect EP to GND for improved heat dissipation.
—
Charge-Pump Negative Power Supply. Bypass with a low-ESR 1µF capacitor to CPGND.
Charge-Pump Flying Capacitor Negative Terminal. Connect a low-ESR 1µF capacitor from C1P to C1N.
Charge-Pump Power Ground
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 75Ω 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.
6
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 150Ω). 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 220µF to 3000µF. 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
_______________________________________________________________________________________
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
OUTPUT
500mV/div
INPUT
500mV/div
0V
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
75Ω 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 75Ω resistor serves as a back-termination resistor in
playback mode and provides the cable termination in
record mode.
Record Mode
Bidirectional Video Filter and Buffer
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 75Ω load termination to ground. The inputs IN3,
IN4, and IN5 are AC-coupled with a 0.1µF 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.
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 150Ω
load DC-coupled to GND. The output buffers can drive
an AC-coupled load provided that the load impedance
is greater than 5kΩ.
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.
_______________________________________________________________________________________
7
MAX7481/MAX7482
INPUT
500mV/div
MAX7481/MAX7482
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
VIDEO
ADC
MAX7481
MAX7482
S1
VIDEO
DAC
75Ω
LPF
S2
S6
0.1μF
S3
VIDEO
PROCESSOR
0.1μF
P/R
CVBSON
YCON
CONTROL
LOGIC
S7
VIDEO
DAC
75Ω
S5
S4
LPF
75Ω
S8
0.1μF
VIDEO
ADC
Figure 3. Signal Flow Diagram
Clamp
In record mode, signals are AC-coupled into IN3, IN4,
and IN5 through small 0.1µF 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.
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
8
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.
_______________________________________________________________________________________
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
MAX7481/MAX7482
Table 1. Input/Output Truth Table
P/R
High
High
High
High
PLAYBACK
Low
Low
RECORD
Low
Low
CVBSON
YCON
OUT3
(CVBS)
OUT1 (Y) AND
OUT2 (C)
OUT4
(Y, CVBS)
OUT5
(C)
IN3 AND IN4
(Y, C)
IN5
(CVBS)
IN1
(Y)
IN2
(C)
Low
Low
Not Active
Not Active
GND
GND
Not Used
Not Used
Active
Active
Low
High
Not Active
Active
GND
GND
Not Used
Not Used
Active
Active
Active
High
Low
Active
Not Active
GND
GND
Not Used
Not Used
Active
High
High
Active
Active
GND
GND
Not Used
Not Used
Active
Active
Low
Low
GND
GND
GND
GND
Not Used
Not Used
Not Used
Not Used
Not Used
Low
High
GND
GND
Active
Active
Active
Not Used
Not Used
High
Low
GND
GND
Active
GND
Not Used
Active
Not Used
Not Used
High
High
GND
GND
GND
GND
Not Used
Not Used
Not Used
Not Used
VIDEO
ADC
OUT4
VIDEO
DAC
IN1
MAX7481
MAX7482
S1
OUT1
75Ω
LPF
S6
S2
S3
IN3
0.1μF
IN5
0.1μF
P/R = LOW
CVBSON
YCON
VIDEO
DAC
IN2
OUT3
CONTROL
LOGIC
75Ω
S7
S5
S4
OUT2
75Ω
LPF
S8
VIDEO
ADC
OUT5
IN4
0.1μF
Figure 4. Signal Flow Diagram for Playback Mode
Short-Circuit Protection
The MAX7481/MAX7482 typical application circuit
includes a 75Ω 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
MAX7481/MAX7482
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
VIDEO
ADC
OUT4
VIDEO
DAC
IN1
MAX7481
MAX7482
75Ω
S2
S1
LPF
S6
IN3
0.1μF
S3
IN5
P/R = HIGH
CVBSON
YCON
75Ω
S7
VIDEO
DAC
IN2
S4
75Ω
S5
LPF
S8
YCON = HIGH
VIDEO
ADC
0.1μF
CONTROL
LOGIC
IN4
0.1μF
OUT5
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.
BIAS
Connect a 100kΩ resistor with 1% accuracy or better
from BIAS to GND to create the bias current used
throughout the MAX7481/MAX7482.
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 10µA in shutdown mode.
The MAX7481/MAX7482 also feature advanced powerdown modes that turn off the output buffers not in use
10
OUTPUT
BUFFER
OUT1, OUT2, OUT3
75Ω
SINGLE
CONNECTION
75Ω
CABLE
IN3, IN4, IN5
0.1μF
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.
______________________________________________________________________________________
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
MAX7481
MAX7482
IN1
DAC
+6dB OR +7dB
OUT1
150Ω
LOWPASS FILTER
CLAMP
75Ω
Y
IN3
C3 = 0.1μF
OUT4
ADC
+6dB
+6dB OR +7dB
0.1μF
OUT3
75Ω
P/R
CVBS
CVBSON
IN5
YCON
C5 = 0.1μF
+6dB OR +7dB
IN2
DAC
OUT2
LOWPASS FILTER
75Ω
150Ω
C
CLAMP
IN4
C4 = 0.1μF
ADC
OUT5
REGULATOR
+6dB
0.1μF
CHARGE PUMP
GND
VCC
BIAS
SHDN CPVCC CPGND
C1P
100kΩ
1μF
VCC
C1 = 1μF
VSS
C1N CPVSS
C2 = 1μF
1μF
VCC
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
1µF capacitor to GND, placed as close as possible to
the device. Bypass the charge-pump supply (CPVCC)
with a 1µF capacitor to CPGND, placed as close as
possible to the device. Connect CPV SS to V SS and
bypass with a low-ESR 1µF capacitor to CPGND as
close as possible to the device.
______________________________________________________________________________________
11
MAX7481/MAX7482
Functional Diagram/Typical Application Circuit
Pin Configuration
Chip Information
PROCESS: BiCMOS
GND
OUT3
GND
OUT1
IN3
21
IN5
TOP VIEW
OUT2
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.
20
19
18
17
16
15
IN4 22
14
GND
VCC 23
13
VCC
VSS 24
MAX7481
MAX7482
CPVSS 25
C1N 26
CPGND 27
4
5
6
7
OUT4
VCC
3
OUT5
2
IN1
1
IN2
+
GND
C1P 28
CPVCC
MAX7481/MAX7482
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
TQFN
12
______________________________________________________________________________________
12
YCON
11
CVBSON
10
P/R
9
SHDN
8
BIAS
Bidirectional Video Filters/Buffers for Composite
and S-Video Portable Media Devices
QFN THIN.EPS
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
© 2006 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX7481/MAX7482
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.)