19-4238; Rev 2; 11/08
KIT
ATION
EVALU
E
L
B
AVAILA
Low-Power Video Switches
for Dual SCART Connectors
Features
The MAX9655/MAX9656 dual SCART switches route
video signals between a set-top box decoder chip and
two external SCART connectors. Under the control of the
TV_SEL logic input, the MAX9655 selects whether the
CVBS and RGB signals from the encoder or the VCR
SCART are routed to the TV SCART. The CVBS signal
from the encoder is always routed to the VCR SCART.
The MAX9656 is similar to the MAX9655 except that
under the control of the VCR_SEL logic input, the
MAX9656 selects whether the CVBS signal from the
encoder or the TV SCART is routed to the VCR SCART.
The MAX9656 also features a low-power shutdown
mode, in which quiescent current falls to 35µA.
The incoming video signals must be AC-coupled to the
inputs, which have sync-tip clamps to set the internal
DC level. After the input stages, multiplexers select
which video signals are routed to the reconstruction filters and output amplifiers. The reconstruction filters are
optimized for standard-definition signals and typically
have ±1dB passband flatness out to 9.5MHz and 47dB
attenuation at 27MHz.
The amplifiers have 2V/V gain, and the outputs can be
DC-coupled to a 75Ω load, which is the equivalent of
two video loads, or AC-coupled to a 150Ω load.
♦ Dual SCART Support for Video Signals
♦ Supports CVBS Input from TV SCART (MAX9656)
♦ Reconstruction Filters with 9.5MHz Passband and
47dB Attenuation at 27MHz
♦ Fixed Gain of 2V/V
♦ Input Sync-Tip Clamps
♦ 2.7V to 3.6V Single-Supply Operation
Ordering Information
PIN-PACKAGE
TV SCART CVBS
RETURN SUPPORT
MAX9655AEE+
16 QSOP
No
MAX9656AEP+
20 QSOP
Yes
PART
Note: All devices are specified over the -40°C to +125°C operating temperature range.
+Denotes a lead-free/RoHS-compliant package.
Pin Configurations and Typical Application Circuits appear
at end of data sheet.
Applications
SCART Set-Top Boxes
Functional Diagram
VDD
TV_SEL
MAX9655
0
BUFFER
ENC_B_IN
LPF
2V/V
TV_B_OUT
1
ENC_G_IN
CLAMPREF
UNKNOWN
BIAS
0
ENC_R_IN
300mV
BUFFER
1
LPF
2V/V
LPF
2V/V
LPF
2V/V
LPF
2V/V
TV_G_OUT
ENC_CVBS_IN
CLAMPREF
0
VCR_B_IN
BUFFER
1
TV_R_OUT
VCR_G_IN
CLAMPREF
0
BUFFER
VCR_R_IN
1
VCR_CVBS_IN
TV_CVBS_OUT
CLAMPREF
BUFFER
TV_SEL
0
VCR_CVBS_OUT
CLAMPREF
GND
________________________________________________________________ Maxim Integrated Products
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
MAX9655/MAX9656
General Description
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
ABSOLUTE MAXIMUM RATINGS
Supply Voltage
VDD to GND ...........................................................-0.3V to +4V
All Video and Logic Input Pins..................(GND - 0.3V) to +4V
Duration of Output Short Circuit to VDD or GND ........Continuous
Continuous Input Current
All Video and Logic Input Pins .....................................±20mA
Continuous Power Dissipation (TA = +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)............727mW
Operating Temperature Range .........................-40°C to +125°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
(VDD = 3.3V, VGND = 0, V SHDN = VDD, VCR_SEL = VDD, TV_SEL = VDD, RL = 150Ω to GND, TA = TMIN to TMAX, unless otherwise
noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
Supply Voltage Range
VDD
Guaranteed by power-supply rejection test
Quiescent Supply Current
IDD
No load
Shutdown Supply Current
ISHDN
Input Voltage
Input Resistance
Sync-Tip Clamp Level
MIN
TYP
MAX
2.7
3.3
3.6
V
21
45
mA
35
70
µA
VSHDN = TV_SEL = VCR_SEL = GND
(MAX9656 only)
Unselected input
VDD/3
Unselected input
0.23
Sync Crush
0.3
1.05
3.0V ≤ VDD ≤ 3.6V
Sync-tip clamp; percentage reduction in
sync pulse (0.3VP-P); guaranteed by input
clamping current measurement
1.2
Input Clamping Current
1
Maximum Input Source
Resistance
300
DC Voltage Gain
AV
RL = 150Ω to GND
(Note 2)
VDD = 2.7V, 0V ≤ VIN
≤ 1.05V
VDD = 3.0V, 0V ≤ VIN
≤ 1.2V
DC Gain Mismatch
Guaranteed by output-voltage swing
Output Level
Measured at output, CIN_ = 0.1µF to GND
Output-Voltage Swing
2
kΩ
0.39
2.7V ≤ VDD ≤ 3.6V
Guaranteed by outputvoltage swing
Input Voltage Range
V
222
VCLP
UNITS
V
VP-P
2
%
2
µA
Ω
1.96
2
2.04
1.96
2
2.04
V/V
-2
0.218
0.3
Measured at output, VDD = 2.7V, VIN =
VCLP to (VCLP +1.05V), RL = 150Ω to -0.2V
2.1
Measured at output, VDD = 2.7V, VIN =
VCLP to (VCLP +1.05V), RL = 150Ω to VDD/2
2.1
Measured at output, VDD = 3.0V, VIN =
VCLP to (VCLP +1.2V), RL = 150Ω to -0.2V
2.4
Measured at output, VDD = 3.0V, VIN =
VCLP to (VCLP +1.2V), RL = 150Ω to VDD/2
2.4
Measured at output, VDD = 3.135V, VIN =
VCLP to (VCLP +1.05V), RL = 75Ω to -0.2V
2.1
_______________________________________________________________________________________
+2
%
0.39
V
VP-P
Low-Power Video Switches
for Dual SCART Connectors
(VDD = 3.3V, VGND = 0, V SHDN = VDD, VCR_SEL = VDD, TV_SEL = VDD, RL = 150Ω to GND, TA = TMIN to TMAX, unless otherwise
noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Output Short-Circuit Current
Output Resistance
ROUT
CONDITIONS
Standard-Definition
Reconstruction Filter
TYP
140
Short to VDD (sinking)
70
VOUT = 1.5V, -10mA ≤ ILOAD ≤ +10mA
2.7V ≤ VDD ≤ 3.6V
Power-Supply Rejection Ratio
MIN
Short to GND (sourcing)
Ω
64
20
VOUT = 2VP-P, reference frequency is
100kHz, ±1dB passband flatness
9.5
f = 5.5MHz
0.1
f = 9.5MHz
-1
f = 10MHz
-3
f = 27MHz
-47
UNITS
mA
0.2
48
f = 1MHz, 100mVP-P
VOUT = 2VP-P, reference
frequency is 100kHz
MAX
dB
MHz
dB
Differential Gain
DG
5-step modulated staircase of 129mV step
size and 286mV peak-to-peak subcarrier
amplitude, f = 4.43MHz
0.4
%
Differential Phase
DP
5-step modulated staircase of 129mV step
size and 286mV peak-to-peak subcarrier
amplitude, f = 4.43MHz
0.45
deg
Group-Delay Distortion
100kHz ≤ f ≤ 5MHz, outputs are 2VP-P
9
ns
Peak Signal to RMS Noise
100kHz ≤ f ≤ 5MHz
71
dB
2T Pulse Response
2T = 200ns
0.2
K%
2T Bar Response
2T = 200ns; bar time is 18µs; the beginning
2.5% and the ending 2.5% of the bar time
are ignored
0.2
K%
2T Pulse-to-Bar K Rating
2T = 200ns; bar time is 18µs; the beginning
2.5% and the ending 2.5% of the bar time
are ignored
0.3
K%
Nonlinearity
5-step staircase
0.1
%
Output Impedance
f = 5.5MHz
8.07
Ω
f = 15kHz
-82
f = 4.43MHz
-78
f = 30MHz
-68
All-Hostile Crosstalk
Output-to-Input Crosstalk
dB
dB
LOGIC SIGNALS (MAX9655: TV_SEL, MAX9656: TV_SEL, VCR_SEL, SHDN)
Logic-Low Threshold
VIL
TA = +25°C
Logic-High Threshold
VIH
TA = +25°C
Logic Input Current
IIN
TA = +25°C
0.3 x
VDD
0.7 x
VDD
V
V
10
µA
Note 1: All devices are 100% production tested at TA = +25°C. Specifications over temperature limits are guaranteed by design.
Note 2: Voltage gain (AV) is a two-point measurement in which the output-voltage swing is divided by the input-voltage swing.
_______________________________________________________________________________________
3
MAX9655/MAX9656
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VDD = 3.3V, VGND = 0, V SHDN = VDD, RL = 150Ω to GND, TA = +25°C.)
SMALL-SIGNAL GAIN
vs. FREQUENCY
VIN = 50mVP-P
NOTE: GAIN IS NORMALIZED TO 0dB
3
2
1
0
-10
-15
-20
GAIN (dB)
-25
-30
-35
-6
-7
10M
1M
10M
FREQUENCY (Hz)
LARGE-SIGNAL GAIN
vs. FREQUENCY
LARGE-SIGNAL GAIN FLATNESS
vs. FREQUENCY
VIN = 1VP-P
NOTE: GAIN IS NORMALIZED TO 0dB
0
-5
3
2
VIN = 1VP-P
NOTE: GAIN IS NORMALIZED TO 0dB
1
100M
0
-10
-15
-20
-25
GAIN (dB)
GAIN (dB)
100k
100M
FREQUENCY (Hz)
MAX9655 toc04
1M
MAX9655 toc03
100k
-30
-35
-40
-45
-1
-2
-3
-4
-5
-6
-7
-50
1M
10M
1M
10M
FREQUENCY (Hz)
VIDEO CROSSTALK
vs. FREQUENCY
VIDEO GROUP DELAY DISTORTION
vs. FREQUENCY
120
110
100
90
GROUP DELAY (ns)
VIN = 1VP-P
NOTE: GAIN IS NORMALIZED TO 0dB
-40
-60
ALL-HOSTILE
-80
2 ADJACENT CHANNELS
-100
-120
1M
VIN = 1VP-P
NOTE: GAIN IS NORMALIZED TO 0dB
100M
80
70
60
50
40
30
20
10
0
1 ADJACENT CHANNEL
100k
100k
100M
FREQUENCY (Hz)
MAX9655 toc05
100k
10M
FREQUENCY (Hz)
4
-3
-5
-45
-50
-20
-2
-4
-40
0
-1
MAX9655 toc06
GAIN (dB)
-5
10
5
VIN = 50mVP-P
NOTE: GAIN IS NORMALIZED TO 0dB
MAX9655 toc02
SMALL-SIGNAL GAIN FLATNESS
vs. FREQUENCY
MAX9655 toc01
10
5
0
GAIN (dB)
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
100M
100k
1M
10M
FREQUENCY (Hz)
_______________________________________________________________________________________
100M
Low-Power Video Switches
for Dual SCART Connectors
VOLTAGE GAIN
vs. TEMPERATURE
VIDEO PSRR
vs. FREQUENCY
2.08
2.06
VOLTAGE GAIN (V/V)
-30
-40
-50
MAX9655 toc08
VDD = 3.3V + 100mVP-P
-20
-60
2.04
2.02
2.00
1.98
1.96
1.94
-70
1.92
1.90
-80
100k
1M
-50
100M
10M
-25
0
2
3
4
5
0.8
0.6
0.4
0.2
0
-0.2
-0.4
DIFFERENTIAL PHASE (deg)
DIFFERENTIAL PHASE
f = 3.58MHz
0
1
2
3
2T RESPONSE
100ns/div
4
DIFFERENTIAL GAIN (%)
1
MAX9655 toc09
DIFFERENTIAL GAIN (%)
DIFFERENTIAL PHASE (deg)
f = 3.58MHz
0
50
75
100
125
DIFFERENTIAL GAIN
DIFFERENTIAL GAIN
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
25
TEMPERATURE (°C)
FREQUENCY (Hz)
5
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
f = 4.43MHz
0
1
2
3
5
DIFFERENTIAL PHASE
0.8
0.6
0.4
0.2
0
-0.2
-0.4
f = 4.43MHz
0
1
2
3
12.5T RESPONSE
MAX9655 toc11
4
MAX9655 toc10
PSRR (dB)
2.10
MAX9655 toc07
0
-10
4
5
MAX9655 toc12
IN
200mV/div
IN
200mV/div
OUT
400mV/div
OUT
400mV/div
400ns/div
_______________________________________________________________________________________
5
MAX9655/MAX9656
Typical Operating Characteristics (continued)
(VDD = 3.3V, VGND = 0, V SHDN = VDD, RL = 150Ω to GND, TA = +25°C.)
Typical Operating Characteristics (continued)
(VDD = 3.3V, VGND = 0, V SHDN = VDD, RL = 150Ω to GND, TA = +25°C.)
FIELD SQUARE WAVE
NTC-7 VIDEO TEST SIGNAL
MAX9655 toc13
IN
500mV/div
OUT
1V/div
OUT
1V/div
2ms/div
VIDEO SYNC-TIP CLAMP CURRENT
vs. TEMPERATURE
VIDEO SYNC-TIP CLAMP VOLTAGE
vs. TEMPERATURE
0.36
0.34
0.32
0.30
MAX4617 toc16
0.38
1.04
SYNC-TIP CLAMP CURRENT (μA)
MAX4617 toc15
1.02
1.00
0.98
0.96
0.94
0.92
0.28
0.90
0.26
-25
0
25
50
75
100
-50
125
-25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
SYNC-TIP CLAMP CURRENT
vs. INPUT VOLTAGE
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
MAX9655 toc17
500
400
300
200
100
0
23.0
QUIESCENT SUPPLY CURRENT (mA)
-50
125
MAX4617 toc18
SYNC-TIP CLAMP VOLTAGE (V)
0.40
22.5
22.0
21.5
21.0
20.5
20.0
-100
0
0.2
0.4
0.6
0.8
1.0
INPUT VOLTAGE (V)
6
MAX9655 toc14
IN
500mV/div
10μs/div
SYNC-TIP CLAMP CURRENT (μA)
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
1.2
1.4
1.6
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
_______________________________________________________________________________________
Low-Power Video Switches
for Dual SCART Connectors
PIN
NAME
FUNCTION
MAX9655
MAX9656
1
2
ENC_B_IN
2
3
ENC_G_IN
Encoder Green Video Input. AC-couple the signal through a 0.1µF capacitor.
3
4
ENC_R_IN
Encoder Red Video Input. AC-couple the signal through a 0.1µF capacitor.
4
5
ENC_CVBS_IN
5
6
VCR_B_IN
VCR SCART Blue Video Input. AC-couple the signal through a 0.1µF capacitor.
6
7
VCR_G_IN
VCR SCART Green Video Input. AC-couple the signal through a 0.1µF capacitor.
Encoder Blue Video Input. AC-couple the signal through a 0.1µF capacitor.
Encoder Composite Video Input. AC-couple the signal through a 0.1µF capacitor.
7
8
VCR_R_IN
8
9
VCR_CVBS_IN
VCR SCART Red Video Input. AC-couple the signal through a 0.1µF capacitor.
9
11
GND
10
13
VCR_CVBS_OUT
11
14
TV_CVBS_OUT
12
15
TV_R_OUT
TV SCART Red Video Output. The sync tip is biased at 0.3V.
13
16
TV_G_OUT
TV SCART Green Video Output. The sync tip is biased at 0.3V.
14
17
TV_B_OUT
TV SCART Blue Video Output. The sync tip is biased at 0.3V.
15
18
TV_SEL
16
19
VDD
—
1
TV_CVBS_IN
—
10
N.C.
—
12
SHDN
—
20
VCR_SEL
VCR SCART Composite Video Input. AC-couple the signal through a 0.1µF capacitor.
Ground
VCR SCART Composite Video Output. The sync tip is biased at 0.3V.
TV SCART Composite Video Output. The sync tip is biased at 0.3V.
TV SCART Output Selection. Connect to GND to route the encoder video signals
to the TV SCART outputs. Connect to VDD to route the VCR SCART video signals
to the TV SCART outputs.
Positive Power Supply. Bypass with 0.1µF ceramic capacitors to GND.
Television SCART Composite Video Input. AC-couple the signal through a 0.1µF
capacitor.
No Connection. Not internally connected.
Active-Low Shutdown Logic Input. Connect to GND to place device in shutdown.
Connect to VDD for normal operation.
VCR SCART Output Selection. Connect to GND to route ENC_CVBS_IN to the
VCR SCART CVBS output. Connect to VDD to route TV_CVBS_IN to the VCR
SCART CVBS output.
Detailed Description
A MAX9655 or a MAX9656 can comprise the video portion of a low-cost, dual SCART solution in set-top boxes
with a subset of the full SCART functions. The
MAX9655/MAX9656 select whether the CVBS, red,
green, and blue video signals from the encoder or the
VCR SCART are routed to the TV SCART. The
MAX9655/MAX9656 support the output of one CVBS
signal to the VCR SCART. In the MAX9655, the CVBS
signal from the encoder is routed to the VCR SCART.
In the MAX9656, the CVBS signal routed to the VCR
SCART can come from the encoder or TV SCART. In
the typical usage case, the VCR (or DVD recorder)
records a television program from the set-top box. In
such a case, the encoder would be the source of the
CVBS signal. Support for the TV SCART CVBS return
path is useful when a person wants to record on his
VCR (or more likely DVD recorder) a television program
received through the television’s antenna. The television program is transmitted from the television to the
set-top box and then to the VCR.
Both the MAX9655 and MAX9656 have integrated
reconstruction filters so that when the encoder video
signals are routed to the TV SCART or the VCR SCART,
the steps and spikes left by the video digital-to-analog
converter (DAC) are smoothed away. Although the
incoming video signals from the VCR SCART are
assumed to be filtered already, the reconstruction filter
has wide enough bandwidth so that the video signals
from the VCR SCART are not degraded.
_______________________________________________________________________________________
7
MAX9655/MAX9656
Pin Description
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
The incoming video signals can have any DC bias
because the input sync-tip clamps restore the
DC level. The output amplifiers have a gain of 2V/V.
The MAX9655/MAX9656 operate from a single 3.3V
supply and consume low quiescent power and low
average power. In addition, the MAX9656 also has
shutdown mode.
Table 1. TV_SEL Logic (Applicable to
Both the MAX9655 and the MAX9656)
LOGIC STATE
Operating Modes
TV_SEL controls whether the encoder or VCR video signals are sent to the TV SCART. See Table 1.
On the MAX9656, VCR_SEL controls whether the CVBS
signal from the TV SCART or the encoder is sent to the
VCR SCART. SHDN controls whether the device is on
or off. See Tables 2 and 3. In shutdown, the outputs of
the MAX9656 are high impedance.
Low
Encoder video signals are routed to the
TV SCART.
High
VCR SCART video signals are routed to
the TV SCART.
Table 2. VCR_SEL Logic (Only Applicable
to the MAX9656)
Input
Every video signal must be AC-coupled to the
MAX9655/MAX9656 through 0.1µF capacitors. The
MAX9655/MAX9656 have sync-tip clamps and bias circuits to restore the DC level of the video signal after the
input coupling capacitor. When a video input is selected, the input has a sync-tip clamp, which accepts
video signals that have sync pulses or that reach their
minimum level during sync. Composite video with
blanking and sync (CVBS) is an example of a video signal with sync pulses. The red, green, and blue signals
in an RGBS signal set are examples of signals that
return to their blank level during sync. The sync-tip voltage is internally set to 300mV.
When a video input is not selected, the inputs to the
MAX9655 and the MAX9656 do not distort the video
signal in case the video source is driving video signals
to another video circuit such as a video multiplexer.
The inputs are biased at VDD/3, which is sufficiently
above ground so that the ESD diodes never forward
bias as the video signal changes. The input resistance
MODE
LOGIC STATE
MODE
Low
CVBS signal from encoder is routed to the
VCR SCART.
High
CVBS signal from the TV SCART is routed
to the VCR SCART.
Table 3. SHDN Logic (Only Applicable to
the MAX9656)
LOGIC STATE
MODE
Low
Off
High
On
is 220kΩ, which presents negligible loading on the
video current DAC. The sole exception to this condition
is ENC_CVBS_IN (MAX9655), in which the input circuit
is always a sync-tip clamp. Table 4 summarizes which
input circuit is active on the inputs of the MAX9655
depending on TV_SEL. Table 5 summarizes which input
circuit is active on the inputs of the MAX9656 depending on TV_SEL and VCR_SEL.
Table 4. MAX9655 Input Circuit of Input as Determined by State of TV_SEL
8
INPUT
INPUT CIRCUIT
(TV_SEL = LOW)
INPUT CIRCUIT
(TV_SEL = HIGH)
Bias
ENC_B_IN
Sync-tip clamp
ENC_G_IN
Sync-tip clamp
Bias
ENC_R_IN
Sync-tip clamp
Bias
ENC_CVBS_IN
Sync-tip clamp
Sync-tip clamp
VCR_B_IN
Bias
Sync-tip clamp
VCR_G_IN
Bias
Sync-tip clamp
VCR_R_IN
Bias
Sync-tip clamp
VCR_CVBS_IN
Bias
Sync-tip clamp
_______________________________________________________________________________________
Low-Power Video Switches
for Dual SCART Connectors
MAX9655/MAX9656
Table 5. MAX9656 Input Circuit of Input as Determined by State of TV_SEL
INPUT
INPUT CIRCUIT
(TV_SEL = LOW)
INPUT CIRCUIT
(TV_SEL = HIGH)
ENC_B_IN
Sync-tip clamp
Bias
ENC_G_IN
Sync-tip clamp
Bias
Sync-tip clamp
Bias
ENC_R_IN
ENC_CVBS_IN
Sync-tip clamp
(VCR_SEL = 0)
Sync-tip clamp (VCR_SEL = 1)
Sync-tip clamp (VCR_SEL = 0)
Bias
(VCR_SEL = 1)
TV_CVBS_IN
Bias
(VCR_SEL = 0)
Sync-tip clamp
(VCR_SEL = 1)
Bias
(VCR_SEL = 0)
Sync-tip clamp
(VCR_SEL = 1)
VCR_B_IN
Bias
Sync-tip clamp
VCR_G_IN
Bias
Sync-tip clamp
VCR_R_IN
Bias
Sync-tip clamp
VCR_CVBS_IN
Bias
Sync-tip clamp
Note: VCR_SEL = X (don’t care), except where noted.
When the MAX9656 is in shutdown, its inputs are
biased at the same voltage and present the same input
resistance as unselected inputs.
Video Filter
The MAX9655/MAX9656 video filter features ±1dB
passband out to 9.5MHz and 47dB attenuation at
27MHz, making the filter suitable for standard-definition
video signals from all sources (e.g., broadcast and
DVD). Broadcast video signals are channel limited:
NTSC signals have 4.2MHz bandwidth, and PAL signals have 5MHz bandwidth. Video signals from a DVD
player, however, are not channel limited; so the bandwidth of DVD video signals can approach the Nyquist
limit of 6.75MHz. Recommendation: ITU-R BT.601-5
specifies 13.5MHz as the sampling rate for standarddefinition video. Therefore, the maximum bandwidth of
the signal is 6.75MHz. To ease the filtering requirements, most modern video systems oversample by two
times, clocking the video current DAC at 27MHz.
Outputs
The video output amplifiers can both source and sink
load current, allowing output loads to be DC- or ACcoupled. The amplifier output stage needs approximately 300mV of headroom from either supply rail. The
devices have an internal level-shift circuit that positions
the sync tip at approximately 300mV at the output.
If the supply voltage is greater than 3.135V (5% below
a 3.3V supply), each amplifier can drive two DC-coupled video loads to ground. If the supply is less than
3.135V, each amplifier can drive only one DC-coupled
or AC-coupled video load.
Applications Information
Audio Switch for Dual SCART Connectors
In addition to video signals, SCART connectors also
support left and right audio signals that are full duplex.
Figure 1 shows a matching audio switch for the
MAX9655. Notice that it can be made from low-cost,
discrete components. It is assumed that the set-top box
chip generates the left and right audio signals directly,
or the set-top box chip sends an I2S stream to a stereo
audio DAC that generates the left and right audio signals. In both cases, the audio signals are filtered and
amplified by a dual audio op amp before they are presented to the audio switch.
Figure 2 shows a matching audio switch for the
MAX9656. Similar to how the MAX9656 handles video
signals, the audio signals from the set-top box chip or
the audio signals from the TV SCART are routed to the
VCR SCART.
AC-Coupling the Outputs
The outputs can be AC-coupled since the output stage
can source and sink current as shown in Figure 3.
Coupling capacitors should be 220µF or greater to
keep the highpass filter, formed by the 150Ω equivalent
resistance of the video transmission line, to a corner
frequency of 4.8Hz or below. The frame rate of PAL
systems is 25Hz. The corner frequency should be well
below the frame rate.
_______________________________________________________________________________________
9
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
12V
12V
12V
0.1μF
9.5kΩ
100kΩ
16
10μF
180pF
0.1μF
2
7
15
+
12V
1MΩ
10μF
DAC
8
4.7kΩ
4.7kΩ
1.2kΩ
2
100kΩ
8
1
2.7nF
2.7nF
3
0.1μF
+
300kΩ
10μF
1
3
TV_SEL
12V
U1
1/2 LM833
4
9, 10, 11
TV
SCART
8
7
4
100kΩ
10μF
SDATA
DEMSCLK
LRCK
1
MCLK
4
5
3
2
3
10μF
15 +
1
+
12V
1MΩ
100kΩ
5.1kΩ
U0
CS4334
6
2
U2
HEF4053
21
21
+
5.1kΩ
10μF
9.5kΩ
12V
180pF
10μF
DAC
5
4.7kΩ
1.2kΩ
4.7kΩ
100kΩ
10μF
6
10μF
+
2.7nF
2.7nF
+
7
300kΩ
+
2
6
3
1/2 LM833
5
100kΩ
1MΩ
4
VCR
SCART
6
12V
12V
10kΩ
12V
10kΩ
10μF
3.3V
TV_SEL
JU0
TV_SEL
10kΩ
2N3904
3.3V
VCR_SEL
JU1
100kΩ
10μF
+
VCR_SEL
+
10kΩ
21
1MΩ
100kΩ
2N3904
Figure 1. Audio Switch for the MAX9655
10
1
______________________________________________________________________________________
Low-Power Video Switches
for Dual SCART Connectors
MAX9655/MAX9656
12V
12V
0.1μF
16
10μF
12V
9.5kΩ
180pF
0.1μF
10μF
15+
3
+
1MΩ
7
100kΩ
12V
10μF
DAC
8
4.7kΩ
4.7kΩ
1.2kΩ
0.1μF
2
TV_SEL
8
+
300kΩ
3
U1
1/2 LM833
4
7
1
3
10μF
15 +
1
MCLK
4
5
12V
1MΩ
2
3
100kΩ
6
2
U2
HEF4053
5.1kΩ
U0
CS4334
4
100kΩ
10μF
+
SDATA
DEMSCLK
LRCK
TV
SCART
8
12V
1
2.7nF
2.7nF
9, 10, 11
21
21
+
5.1kΩ
10μF
9.5kΩ
180pF
DAC
4.7kΩ
5
4.7kΩ
1.2kΩ
2.7nF
2.7nF
12V
6
7
300kΩ
1/2 LM833
5
2
6
16
1
10μF
3
15 +
10μF
2
6
+
1MΩ
12V
12V
10kΩ
3.3V
TV_SEL
JU0
0.1μF
12V
+
TV_SEL
10kΩ
2N3904
100kΩ
VCR
SCART
10kΩ
3.3V
VCR_SEL
JU1
VCR_SEL
VCR_SEL
10kΩ
8
9, 10, 11
7
4
12V
100kΩ
2N3904
3
10μF
15 +
1
10μF
5
+
1MΩ
100kΩ
U2
HEF4053
21
21
Figure 2. Audio Switch for the MAX9656
______________________________________________________________________________________
11
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
Table 6. Quiescent and Average Power
Consumption for MAX9655/MAX9656
MEASUREMENTS
POWER
CONSUMPTION
(mW)
MAX9655
MAX9656
CONDITIONS
TV_B_OUT
Quiescent Power
Consumption
Average Power
Consumption
69
No load.
LPF
220μF
AV = 2V/V
75Ω
175 (MAX9655)
200 (MAX9656)
150Ω to ground on
each output. 50%
flat field signal on
each input.
TV_G_OUT
LPF
75Ω
Power Consumption
The quiescent power consumption and average power
consumption of the MAX9655/MAX9656 are very low
because of the 3.3V operation and low-power circuit
design. Quiescent power consumption is defined when
the MAX9655/MAX9656 are operating without loads
and without any video signals.
Average power consumption represents the normal
power consumption when the devices drive real video
signals into real video loads. It is measured when the
MAX9655/MAX9656 drive a 150Ω load to ground with
a 50% flat field, which serves as a proxy for a real
video signal.
Table 6 shows the quiescent and average power consumption of the MAX9655/MAX9656.
TV_R_OUT
LPF
220μF
AV = 2V/V
TV SCART
220μF
AV = 2V/V
75Ω
TV_CVBS_OUT
LPF
AV = 2V/V
LPF
AV = 2V/V
220μF
75Ω
VCR_CVBS_OUT
220μF
75Ω
TO VCR SCART
Figure 3. AC-Coupled Outputs
Power-Supply Bypassing and Ground
The MAX9655/MAX9656 operate from a single-supply
voltage down to 2.7V, allowing for low-power operation.
Bypass V DD to GND with a 0.1µF capacitor. Place
all external components as close as possible to
the device.
Chip Information
PROCESS: BiCMOS
12
______________________________________________________________________________________
Low-Power Video Switches
for Dual SCART Connectors
+3.3V
0.1μF
MPEG
DECODER
VDD
TV_SEL
GPIO
DAC
ENC_B_IN
B
DAC
G
MAX9655
0
0.1μF
BUFFER
75Ω
TV_B_OUT
LPF
2V/V
75Ω
ENC_G_IN
DAC
1
R
75Ω
0.1μF
CLAMPREF
0
DAC
CVBS
ENC_R_IN
75Ω
BUFFER
TV_G_OUT
LPF
0.1μF
2V/V
75Ω
1
ENC_CVBS_IN
TV
SCART
CLAMPREF
0
0.1μF
75Ω
BUFFER
TV_R_OUT
LPF
VCR_B_IN
75Ω
0.1μF
VCR
SCART
2V/V
1
75Ω
CLAMPREF
VCR_G_IN
0.1μF
75Ω
0
BUFFER
VCR_R_IN
TV_CVBS_OUT
LPF
2V/V
75Ω
0.1μF
75Ω
1
CLAMPREF
VCR_CVBS_IN
0.1μF
BUFFER
75Ω
VCR_CVBS_OUT
LPF
0
2V/V
75Ω
TVSEL
CLAMPREF
GND
______________________________________________________________________________________
13
MAX9655/MAX9656
Typical Application Circuits
Low-Power Video Switches
for Dual SCART Connectors
MAX9655/MAX9656
Typical Application Circuits (continued)
+3.3V
0.1μF
MPEG
DECODER
VDD
SHDN
TV_SEL
GPIO
TV_CVBS_IN
GPIO
0.1μF
75Ω
DAC
MAX9656
ENC_B_IN
B
0
0.1μF
DAC
G
BUFFER
75Ω
TV_B_OUT
LPF
2V/V
75Ω
ENC_G_IN
DAC
1
R
75Ω
0.1μF
CLAMPREF
0
DAC
CVBS
ENC_R_IN
75Ω
BUFFER
TV_G_OUT
LPF
0.1μF
2V/V
75Ω
1
ENC_CVBS_IN
TV
SCART
CLAMPREF
0
0.1μF
75Ω
BUFFER
TV_R_OUT
LPF
VCR_B_IN
75Ω
0.1μF
VCR
SCART
2V/V
1
75Ω
CLAMPREF
VCR_G_IN
0.1μF
0
75Ω
BUFFER
TV_CVBS_OUT
LPF
VCR_R_IN
2V/V
75Ω
0.1μF
1
75Ω
CLAMPREF
VCR_SEL
VCR_CVBS_IN
1
0.1μF
75Ω
BUFFER
VCR_CVBS_OUT
LPF
0
2V/V
75Ω
TVSEL
VCRSEL
0
CLAMPREF
GND
14
______________________________________________________________________________________
Low-Power Video Switches
for Dual SCART Connectors
TOP VIEW
ENC_B_IN 1
+
+
16 VDD
TV_CVBS_IN 1
ENC_G_IN 2
15 TV_SEL
ENC_B_IN 2
ENC_R_IN 3
14 TV_B_OUT
ENC_G_IN 3
13 TV_G_OUT
ENC_R_IN 4
ENC_CVBS_IN 4
MAX9655
ENC_CVBS_IN 5
20 VCR_SEL
19 VDD
18 TV_SEL
17 TV_B_OUT
MAX9656
16 TV_G_OUT
VCR_B_IN 5
12 TV_R_OUT
VCR_G_IN 6
11 TV_CVBS_OUT
VCR_B_IN 6
15 TV_R_OUT
VCR_R_IN 7
10 VCR_CVBS_OUT
VCR_G_IN 7
14 TV_CVBS_OUT
VCR_R_IN 8
13 VCR_CVBS_OUT
VCR_CVBS_IN 8
9
QSOP
GND
VCR_CVBS_IN 9
12 SHDN
N.C. 10
11 GND
QSOP
______________________________________________________________________________________
15
MAX9655/MAX9656
Pin Configurations
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
16 QSOP
E16-4
21-0055
20 QSOP
E20-1
21-0055
QSOP.EPS
MAX9655/MAX9656
Low-Power Video Switches
for Dual SCART Connectors
16
______________________________________________________________________________________
Low-Power Video Switches
for Dual SCART Connectors
REVISION
NUMBER
REVISION
DATE
0
3/08
Initial release
1
10/08
Removed future product reference from MAX9656, updated Shutdown Supply
Current parameter, updated Table 6
2
11/08
Updated Shutdown Supply Current maximum value in EC table.
DESCRIPTION
PAGES
CHANGED
—
1, 2, 12
2
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 ____________________ 17
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX9655/MAX9656
Revision History
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