Semiconductor
January 1999
T
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DUC
PRO LACEME 747
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CA3256
25MHz, BiMOS Analog
Video Switch and Amplifier
[ /Title
(CA32
56)
/Sub-
ject
(25MH
z,
BiMO
S Ana-
log
Video
Switch
and
Ampli-
fier)
/Autho
r ()
/Key-
words
(Har-
ris
Semi-
con-
ductor,
4x1,
video
cross-
point
switch,
multi-
plexer
multi-
plexor,
cable
driver,
5x1,
moni
tor out-
put,
adjust-
able
gain,
Features
• 5 Multiplex Video Channels
- 1 Independent Channel
- 4 Channels with Enable
• 4 LED Channel Indicator Outputs
• Wideband Video Amplifier . . . . . . . . 25MHz Unity Gain
• Adjustable Video Amplifier Gain
• High Signal-Drive Capability
Description
The CA3256 BiMOS analog video switch has five channels
of CMOS multiplex switching for general-purpose video-
signal control. One of four CMOS channels may be selected
in parallel with channel 5. The CMOS switches are inputs to
the video amplifier but may be used in bilateral switching
between channels 1 to 4 and channel 5. The analog
switches of channels 1 to 4 are digitally controlled with logic
level conversion and binary decoding to select 1 of 4
channels. The enable function controls channels 1 to 4 but
does not affect channel 5. LED output drivers are selected
with the channel 1-to-4 switch selection to indicate the ON-
channel. Channel 5 may be used as a monitor output for
data or signal information on channels 1 to 4. The
transmission gate switches shown in the block diagram of
the CA3256 are configured in a “T” design to minimize
feedthrough. When the switch is off, the shunt or center of
the “T” is grounded.
The amplifier has high input impedance to minimize the R
ON
transmission gate insertion loss. The amplifier output imped-
ance is typically 5Ω in a complementary symmetry output.
The amplifier can directly drive a nominal 75Ω coaxial cable
to provide line-to-line video switching. The gain of the ampli-
fier is programmable by different feedback resistor values
between pins 8 and 9. Compensation may also be used
between these pins for an optimally flat frequency response.
An internal regulated 5V bias reference with temperature
compensation permits stable direct-coupled output drive and
minimizes DC offset during signal switching.
Applications
• Video Multiplex Switch
• 75Ω Video Amplifier/Line Driver
• Video Signal-Level Control
• Monitor Switching Control
• TV/CATV Audio/Video Switch
• Video Signal Adder/Fader Control
Part Number Information
PART NUMBER
CA3256E
CA3256M
TEMP.
RANGE (
o
C)
-40 to 85
-40 to 85
PACKAGE
18 Ld PDIP
20 Ld SOIC
PKG.
NO.
E18.3
M20.3
Pinouts
CA3256
(PDIP)
TOP VIEW
CA3256
(SOIC)
TOP VIEW
IN 3
LED 4
IN 4
GND
V-
ENABLE
CONTROL C
FEEDBACK
AMP OUT
1
2
3
4
5
6
7
8
9
18 CONTROL B
17 IN 2
16 CONTROL A
15 IN 1
14 V+
13 IN/OUT 5
12 LED 1
11 LED 2
10 LED 3
IN3
LED4
IN4
GND
V-
ENABLE
CONTROL C
FEEDBACK
AMP OUT
1
2
3
4
5
6
7
8
9
20 CONTROL B
19 IN2
18 CONTROL A
17 NC
16 IN1
15 V+
14 IN/OUT5
13 NC
12 LED1
11 LED2
LED3 10
CAUTION: These devices are sensitive to electrostatic discharge. Users should follow proper IC Handling Procedures.
Copyright
©
Harris Corporation 1999
File Number
1769.5
8-1
CA3256
Block Diagram
IN/OUT
5
13
V+ 14
4
3
3
1
2
17
1
15
V+
BIAS
REG
V-
TG
FEED BACK
8
1K
10K
AMPLIFIER
OUTPUT
9
-
+
10K
4
LED DRIVER
OUTPUTS
12
CHANNEL 1
TG
11
ENABLE 6
LOGIC
LEVEL
CONV.
BINARY
TO
1 OF 4
WITH
ENABLE
CHANNEL 2
TG
10
CHANNEL 3
A 16
B 18
TG
V- 5
C
7
IN
TG
SW
CONTROL
OUT
IN
OUT
IN
OUT
TG
2
CHANNEL 4
SW
OPEN
SW
CLOSED
(DIP PIN OUT)
Switch Control Logic
CHANNEL
NUMBER
1
2
3
4
5 + (1-4) (Note)
5
None
C
0
0
0
0
1
1
0
X
A
0
0
1
1
Channel 1-4
Channel 5 Only
X
B
0
1
0
1
ENABLE
1
1
1
1
1
0
0
NOTE: For Maximum Video Bandwidth, Use Single Channel Selections
8-2
CA3256
Absolute Maximum Ratings
DC Supply Voltage Range (V+ to V-) . . . . . . . . . . . . . . . . . . . . . 18V
Control Input Voltage Range, All Inputs . . . . . . . . . . . . . . . . V+ to V-
Signal Input Voltage Range, Channel 1-5 . . . . . . . . . . . . . . . .3V
P-P
Amplifier Output Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30mA
DC LED Sink Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30mA
Thermal Information
Thermal Resistance (Typical, Note 1)
θ
JA
(
o
C/W)
PDIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70
SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
75
Maximum Junction Temperature (Die). . . . . . . . . . . . . . . . . . . . 175
o
C
Maximum Junction Temperature (Plastic Package) . . . . . . . . 150
o
C
Maximum Storage Temperature Range . . . . . . . . . -65
o
C to 150
o
C
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . . 300
o
C
(SOIC - Lead Tips Only)
Operating Conditions
Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . -40
o
C to 85
o
C
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation
of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE:
1.
θ
JA
is measured with the component mounted on an evaluation PC board in free air.
Electrical Specifications
T
A
= 25
o
C, V+ = 12V; V- = GND
SYMBOL
TYPICAL VALUES
10 to 17
I
CC
SWITCH
20
AMPLIFIER
35
-0.8 A
OL
10
25
-
-
10
5
2.5
7
5
1
1
-
0.5
30
16
dB
dB
MHz
MHz
dB
dB
kΩ
Ω
V
P-P
V
P-P
V
%
Degree
dB
µs
mA
mA
V
UNITS
V
mA
PARAMETER
Power Supply Voltage V+ to V-
Power Supply Current
Open Loop Gain
Programmable Gain, FB Adjustment Range
Full Power Bandwidth
Unity Gain Bandwidth, 1kΩ, 7pF Compensation
Insertion Loss
Signal Feedthrough, 5MHz
Input Impedance
Output Impedance
Maximum Input Voltage
Maximum Output Voltage, Clipped
Reference Bias Output Voltage (V
8
- V-)
Differential Gain
Differential Phase
Off Isolation, Channel to Channel, Z
IN
= 75Ω
LLC Switch Turn On/Off Time Delay
Maximum LED Sink Current
Typical Output Source Current
Channel Control Switch A, B, C and E
N
Threshold
(Notes 2, 3)
A
OL
-
-
-
-
-0.8
-66
Z
IN
Z
OUT
V
I(MAX)
V
O(MAX)
-
-
3
-
-
-
-
-66
-
-
-
V
TH
Approximately (V+ - V-)/2
CAUTION: Connect the V- power supply voltage before or during the V+ turn-on.
NOTES:
2. Threshold value is referenced to GND.
3. V
TH
is restricted by the equation, V
TH
< V+ -1.
8-3
CA3256
Electrical Specifications
T
A
= 25
o
C, V+ = 12V, V
LED
= 12V, V- = GND, Pin 4 = GND, Feedback Switch Closed, V
HIGH
= 9V, V
LOW
= 3V
(See Figure 1), Unless Otherwise Specified
INPUTS
CH 1
PARAMETERS
Supply Current,
V
LED
= 0V
Dual Supply Current
V+ = +7V, V- = -5V
Amplifier Output
Voltage, Open Loop
V
LED
= 0V
Amplifier Output
Voltage, Closed Loop,
V
LED
= 0V
I
OUT (MAX)
(Source)
Open Loop
I
OUT (MAX)
(Sink)
Open Loop
Input Leakage
Channel 1-5
Channel Control
Input A, B, C,
Enable Leakage
LED Off Voltage, V
OFF
LED On Voltage, V
ON
Switch Resistance,
R
DS
R
DS
Match
Amplifier Output
Offset, V
O
, Feedback
Switch Closed
V+ = +7V, V- = -5V
Closed Loop Gain
NOTES:
4. V
OUT
= +7V.
5. V
OUT
= +3V.
6. DIP Pinout.
0V
0V
CH 2
CH 3
CH 4
CH 5
A
CHANNEL SWITCH CONTROL
B
C
ENABLE
NOTE 6
TEST
PIN 6
PIN#
3V
14
PIN 15 PIN 17 PIN 1
0V
0V
0V
PIN 3 PIN 13 PIN 16 PIN 18 PIN 7
0V
0V
3V
3V
3V
MIN
10
TYP MAX UNITS
16
22
mA
0V
0V
0V
0V
0V
0V
0V
0V
7V
14/5
10
20
26
mA
0V
0V
0V
0V
0V
3V
3V
3V
3V
9
6
8.5
10
V
0V
0V
0V
0V
0V
3V
3V
3V
3V
9
4.8
5.1
5.4
V
0V
0V
0V
0V
0V
3V
3V
3V
3V
9
Note 4
9
Note 5
1, 3, 15,
17
6, 7, 16,
18
-
-70
-25
mA
0V
0V
0V
0V
0V
3V
3V
3V
3V
10
16
-
mA
3V
3V
3V
3V
3V
3V
3V
3V
3V
-15
5
15
nA
0V
0V
0V
0V
0V
Measure at 3V, 9V each;
Enable and Channel
Switching Control Inputs
Select Channel 0-5
-20
10
20
nA
0V
0V
0V
0V
0V
2, 10,
11, 12
2, 10,
11, 12
9V
11.97 11.99
-
V
0V
0V
0V
0V
0V
Select Channel 0-5
-
0.1
0.3
V
±100µA
Input Each Switch,
Channel 1-4 + 5
Select Channel
1-4
9V
0.8
1.1
1.4
kΩ
Calculation: (Max R
DS
- Min R
DS
)/Min R
DS
0V
0V
0V
0V
0V
0V
7V
-
9
-
-100
3.6
45
5
100
%
mV
3V
0V
0V
0V
0V
3V
3V
3V
9V
9
-0.5
-0.1
0.5
dB
8-4
CA3256
Test Circuits
V-
5
V+
14
V
BIAS
(V- +5V)
10K
IN 1
15
TG-1
10K
OUTPUT
AMP
1.1K
IN 2
17
TG-2
1.1K
IN 3
1
TG-3
1.1K
IN 4
3
LLC ENABLE
AND CHAN 1-4
SELECT
TG-5
TG-4
1.1K
4
2
3
10
2
11
1
12
V
LED
+12 V
+12 V
FEEDBACK
8
FEEDBACK
SWITCH
BIAS
REG
1K
AMP
OUT
9
+
IN/OUT 5
13
6 ENABLE
16 A
18 B
7 C
4
GND
CONTROL INPUTS (CHANNEL SELECT)
FIGURE 1. CA3256 TEST CIRCUIT (DIP PINOUT)
Application Information
CMOS analog switches are available in a wide variety of
forms, and have been known and used for some time. There
are a number of advantages to using the CMOS transmis-
sion gate as a switch:
•
•
•
•
•
•
•
•
•
Ideal Suitability to Series Cascade Arrangements
Simple Multiple Parallel Input Switching Arrangements
No Bipolar Junctions and, Hence, No Offset
Very Low Power Consumption
Wide Signal-Swing Capability
Fast Multiplexing and Video Switching
Wide Bandwidth
Low R
ON
Channel Resistance
Bidirectional Signal Handling
speed as advantages, the price is high in voltage offset and cur-
rent drain. The integrated device solution that is offered here is
in the use of the BiMOS technology, where both the CMOS and
bipolar processes complement each other to provide CMOS
switching with bipolar amplifiers. The BiMOS process allows
several CMOS switches to be coupled to a bipolar drive-ampli-
fier in the same process to exploit the best of two technologies.
Other advantages are gained when the BiMOS process is
used for an IC video-switch amplifier design. The BiMOS
process calls for a P-substrate and, therefore, isolated N-epi-
taxial wells can be built for both N and P channel parts. The
boats provide for better isolation of the N and P channels.
The N and P wells in a transmission-gate cell can be
switched between source and rail; therefore, they have a
smaller body effect on both N and P devices, which results in
better gain linearity. Where desired, oxide capacitors are
available for bipolar amplifier compensation.
CA3256 Video-Switch Amplifier
The Block Diagram shows the functional diagram of the
CA3256, which consists of five MOS channels, each com-
prising a three-element T-switch. The output of the five
switches is made common and fed into the input of a bipolar
An Integrated Video-Switch Amplifier
Commonly, integrated video-switch amplifiers have been fabri-
cated in the bipolar technology using differential amplifiers in a
current-switching mode. In this form, two differential pairs are
needed for two input-signal sources. The handling of multiple
sources is very much more complex. The advantages of the
CMOS video-switch amplifier have already been noted. While
the bipolar video switch has high output drive and switching
8-5
FPGA/CPLD
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