LINER LT1205 150mhz video multiplexer Datasheet

LT1203/LT1205
150MHz Video Multiplexers
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DESCRIPTIO
FEATURES
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– 3dB Bandwidth: 150MHz
0.1dB Gain Flatness: 30MHz
Channel-to-Channel Switching Time: 25ns
Turn-On/Turn-Off Time: 25ns
High Slew Rate: 300V/µs
Disabled Output Impedance: 10MΩ
50mV Switching Transient
Channel Separation at 10MHz: > 90dB
Differential Gain: 0.02%
Differential Phase: 0.02°
Wide Supply Range: ±5V to ±15V
Output Short-Circuit Protected
Push-Pull Output
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APPLICATI
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Broadcast Quality Video Multiplexing
Picture-in-Picture Switching
HDTV
Computer Graphics
Title Generation
Video Crosspoint Matrices
Video Routers
These multiplexers act as SPDT video switches with 10ns
transition times at toggle rates up to 30MHz. The – 3dB
bandwidth is 150MHz and 0.1dB gain flatness is 30MHz.
Many parts can be tied together at their outputs by using
the enable feature which reduces the power dissipation
and raises the output impedance to 10MΩ. Output capacitance when disabled is only 3pF and the LT1203 peaks less
than 3dB into a 50pF load. Channel crosstalk and disable
isolation are greater than 90dB up to 10MHz. An on-chip
buffer interfaces to fast TTL or CMOS logic. Switching
transients are only 50mV with a 25ns duration. The
LT1203 and LT1205 outputs are protected against shorts
to ground.
The LT1203/LT1205 are manufactured using Linear
Technology’s proprietary complementary bipolar process.
The LT1203 is available in both the 8-lead PDIP and SO
package while the LT1205 is available in the 16-lead
narrow body SO package.
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The LT1203 is a wideband 2-input video multiplexer
designed for pixel switching and broadcast quality routing. The LT1205 is a dual version that is configured as a
4-input, 2-output multiplexer.
TYPICAL APPLICATI
Large-Signal Response
High Speed RGB MUX
CHANNEL SELECT
RED 1
RED 2
V+
+1
EN
+1
V–
GREEN 1
GREEN 2
LT1205
+1
V+
V+
+1
LT1203
BLUE 2
+1
V–
VOUT GREEN
LOGIC
V–
BLUE 1
LOGIC
EN
+1
VOUT RED
EN
VOUT BLUE
LOGIC
LT1203 • TA01
1
LT1203/LT1205
W W
W
AXI U
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ABSOLUTE
RATI GS
Supply Voltage ...................................................... ±18V
Signal Input Current (Note 1) ............................ ±20mA
Logic Input Current (Note 2).............................. ±50mA
Output Short-Circuit Duration (Note 3) ........ Continuous
Specified Temperature Range (Note 4) ....... 0°C to 70°C
Operating Temperature Range ............... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Junction Temperature (Note 5) ............................ 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
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PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
V+
VIN0 1
8
GND 2
7
VOUT
VIN1 3
6
EN
–
5
LOGIC
V
4
LT1203CN8*
LT1203CS8*
N8 PACKAGE
S8 PACKAGE
8-LEAD PLASTIC DIP 8-LEAD PLASTIC SOIC
S8 PART MARKING
TJMAX = 150°C, θJA = 100°C/W (N)
TJMAX = 150°C, θJA = 150°C/W (S)
1203
TOP VIEW
VINO 1
16 V +
GND 2
15 VOUT1
VIN1 3
14 EN1
V–
LT1205CS*
13 LOGIC 1
4
VIN2 5
12 V +
GND 6
11 VOUT2
VIN3 7
10 EN2
V–
ORDER PART
NUMBER
9
8
LOGIC 2
S PACKAGE
16-LEAD PLASTIC SOIC
TJMAX = 150°C, θJA = 100°C/W
*See Note 4
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
0°C ≤ TA ≤ 70°C, ±5V ≤ VS ≤ ±15V, RL = 1k, pulse tested, EN pin open or high, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VOS
Output Offset Voltage
Any Input Selected
Output Offset Matching
Between Outputs
∆VOS/∆T
Output Offset Drift
IIN
Input Current
RIN
Input Resistance
VS = ±5V, VIN = ±2V
VS = ±15V, VIN = ±2V
CIN
Input Capacitance
Input Selected
Input Deselected
COUT
Disabled Output Capacitance
EN Pin Voltage ≤ 0.8V
VIN
Input Voltage (Note 1)
VS = ±5V
VS = ±15V
●
●
±2
±2
Power Supply Rejection Ratio
VS = ±4.5 to ±15V
●
60
70
Gain Error
VS = ±15V, VIN = ±2V, RL = 1k
VS = ±15V, VIN = ±2V, RL = 400Ω
VS = ±5V, VIN = ±2V, RL = 1k
●
●
●
PSRR
2
MIN
TYP
MAX
●
10
30
●
0.3
5
●
40
●
0.6
●
●
1
2
UNITS
mV
mV
µV/°C
5
µA
5
5
MΩ
MΩ
2.6
2.6
pF
pF
2.8
pF
±2.8
±3.0
V
V
2
6
3
dB
4
10
6
%
%
%
LT1203/LT1205
ELECTRICAL CHARACTERISTICS
0°C ≤ TA ≤ 70°C, ±5V ≤ VS ≤ ±15V, RL = 1k, pulse tested, EN pin open or high, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
VOUT
Output Voltage
VS = ±15V, VIN = ±2V, RL = 400Ω
VS = ±5V, VIN = ±2V, RL = 1k
●
●
Overload Swing (Note 1)
VS = ±15V, VIN = ±5V
VS = ±5V, VIN = ±5V
●
●
IOUT
Output Current
VS = ±15V, VIN = ±2V, RL = 400Ω
VS = ±5V, VIN = ±2V, RL = 1k
●
●
±4.5
±1.8
±4.75
±2.00
ROUT
Enabled Output Resistance
Disabled Output Resistance
EN Pin Voltage = 2V, VOUT = ±2V, VS = ±15V
EN Pin Voltage = 0.5V, VOUT = ±2V, VS = ±15V
●
●
20
10
42
1
Ω
MΩ
Supply Current (LT1203)
EN Pin Voltage = 2V
EN Pin Voltage = 0.5V
●
●
10.0
5.8
14
8
mA
mA
Supply Current (LT1205)
EN Pin Voltage = 2V
EN Pin Voltage = 0.5V
●
●
20.0
11.6
28
16
mA
mA
VIL
Logic Low
Logic Pin
●
VIH
Logic High
Logic Pin
●
Enable Low
EN Pin
●
Enable High
EN Pin
●
IIL
Digital Input Current Low
LT1203 Pin 5, LT1205 Pins 9, 13 = 0V
●
1.5
6.5
IIH
Digital Input Current High
LT1203 Pin 5, LT1205 Pins 9, 13 = 5V
●
10
200
nA
IEN
Enable Pin Current
LT1203 Pin 6, LT1205 Pins 10, 14
●
20
80
µA
IS
AC CHARACTERISTICS
MIN
TYP
±1.8
±1.8
±1.90
±1.94
±0.9
±0.9
MAX
UNITS
V
V
±1.5
±1.5
V
V
mA
mA
0.8
V
2
V
0.5
V
2
V
µA
TA = 25°C, VS = ±15V, RL = 1k, EN pin open or high, unless otherwise noted.
SYMBOL
PARAMETER
SR
Slew Rate (Note 6)
FPBW
Full Power Bandwidth (Note 7)
tSEL
Channel-to-Channel Select Time (Note 8) RL = 10k
Enable Time (Note 9)
RL = 1k
25
35
ns
25
35
ns
Disable Time (Note 9)
RL = 1k
20
35
ns
Small-Signal Rise and Fall Time
VOUT = 250mVP-P, 10% to 90%
2.6
ns
Propagation Delay
VOUT = 250mVP-P
2.9
ns
Overshoot
VOUT = 250mVP-P
5
%
Crosstalk (Note 10)
RS = 10Ω
90
dB
Chip Disabled Crosstalk (Note 10)
RL = 10Ω, EN Pin Voltage ≤ 0.8V
110
dB
Channel Select Output Transient
All VIN = 0V
50
mVP-P
Settling Time
1%, VOUT = 1V
30
ns
Differential Gain (Note 11)
VS = ±15V, RL = 10k
0.02
%
Differential Phase (Note 11)
VS = ±15V, RL = 10k
0.02
DEG
Insertion Loss
RL = 100k, CL = 30pF, VOUT = 500mVP-P, f = 1MHz
0.02
dB
tr, tf
tS
CONDITIONS
MIN
180
300
V/µs
VOUT = 2VP-P
28.6
47.7
MHz
The ● denotes specifications which apply over the specified
temperature range.
Note 1: The analog inputs (pins 1, 3 for the LT1203, pins 1, 3, 5, 7 for the
LT1205) are protected against ESD and overvoltage with internal SCRs.
TYP
MAX
UNITS
For inputs ≤ ±2.8V the SCR will not fire. Voltages above 2.8V will fire the
SCR and the DC current should be limited to 20mA. To turn off the SCR
the pin voltage must be reduced to less than 1V or the current reduced to
less than 600µA.
3
LT1203/LT1205
Note 2: The digital inputs (pins 5, 6 for the LT1203, pins 9, 10, 13, 14 for
the LT1205) are protected against ESD and overvoltage with internal
SCRs. For inputs ≤ ±6V the SCR will not fire. Voltages above 6V will fire
the SCR and the DC current should be limited to 50mA. To turn off the
SCR the pin voltage must be reduced to less than 2V or the current
reduced to less than 10mA.
Note 3: A heat sink may be required depending on the power supply
voltage.
Note 4: Commercial grade parts are designed to operate over the
temperature range of – 40°C to 85°C but are neither tested nor guaranteed
beyond 0°C to 70°C. Industrial grade parts specified and tested over
– 40°C to 85°C are available on special request, consult factory.
Note 5: TJ is calculated from the ambient temperature TA and the power
dissipation PD according to the following formulas:
LT1203CN8: TJ = TA + (PD × 100°C/W)
LT1203CS8: TJ = TA + (PD × 150°C/W)
LT1205CS: TJ = TA + (PD × 100°C/W)
Note 6: Slew rate is measured at ±2.0V on a ±2.5V output signal while
operating on ±15V supplies, RL = 1k.
Note 7: Full power bandwidth is calculated from the slew rate
measurement:
FPBW = SR/2πVPEAK
Note 8: For the LT1203, apply 1VDC to pin 1 and measure the time for the
appearance of 0.5V at pin 7 when pin 5 goes from 5V to 0V. Apply 1VDC
to pin 1 and measure the time for disappearance of 0.5V at pin 7 when
pin 5 goes from 0V to 5V. Apply 1VDC to pin 3 and measure the time for
the appearance of 0.5V at pin 7 when pin 5 goes from 0V to 5V. Apply
1VDC to pin 3 and measure the time for disappearance of 0.5V at pin 7
when pin 5 goes from 5V to 0V. For the LT1205 the same test is
performed on both MUXs.
Note 9: For the LT1203, apply 1VDC to pin 1 and measure the time for the
appearance of 0.5V at pin 7 when pin 6 goes from 0V to 5V. Pin 5 voltage
= 0V. Apply 1VDC to pin 1 and measure the time for disappearance of 0.2V
at pin 7 when pin 6 goes from 5V to 0V. Pin 5 voltage = 0V. Apply 1VDC
to pin 3 and measure the time for the appearance of 0.5V at pin 7 when
pin 6 goes from 0V to 5V. Pin 5 voltage = 5V. Apply 1VDC to pin 3 and
measure the time for disappearance of 0.2V at pin 7 when pin 5 goes from
5V to 0V. Pin 5 voltage = 5V. For the LT1205 the same test is performed
on both MUXs.
Note 10: VIN = 0dBm (0.223VRMS) at 10MHz on one input with the other
input selected and RS = 10Ω. For disable crosstalk all inputs are driven
simultaneously. In disable the output impedance is very high and signal
couples across the package; the load impedance determines the crosstalk.
Note 11: Differential gain and phase are measured using a Tektronix
TSG120 YC/NTSC signal generator and a Tektronix 1780R video
measurement set. The resolution of this equipment is 0.1% and 0.1°.
Ten identical MUXs were cascaded giving an effective resolution of
0.01% and 0.01°.
TRUTH TABLE
LOGIC
EN
VOUT
0
1
VIN0
1
1
VIN1
0
0*
HIGH ZOUT
1
0
HIGH ZOUT
*Must be ≤0.5V
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TYPICAL PERFOR A CE CHARACTERISTICS
±5V Frequency Response
±15V Frequency Response
–20
4
–40
3
2
–60
2
–60
1
–80
1
–80
0
–100
0
–100
–1
–120
VS = ±5V
TA = 25°C
RL = ∞
4
–20
–40
–1
–120
–2
–140
–2
–140
–3
–160
–3
–160
–4
–180
–4
–180
–200
1000
–5
–5
1
10
100
FREQUENCY (MHz)
LT1203/05 • TPC01
4
0
VS = ±15V
TA = 25°C
RL = ∞
1
10
100
FREQUENCY (MHz)
–200
1000
LT1203/05 • TPC02
PHASE (DEG)
GAIN (dB)
3
GAIN (dB)
5
PHASE (DEG)
0
5
LT1203/LT1205
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TYPICAL PERFOR A CE CHARACTERISTICS
– 3dB Bandwidth
vs Supply Voltage
Frequency Response
with Capacitive Loads
5
TA = 25°C
RL = 10k
PEAKING ≤ 0.5dB
–30
VS = ±15V
TA = 25°C
RL = ∞
4
3
180
CL = 50pF
GAIN (dB)
2
160
CL = 10pF
CL = 100pF
1
0
–1
–2
140
–3
6
4
8
10
12
14
16
1
18
10
FREQUENCY (MHz)
SUPPLY VOLTAGE (±V)
Crosstalk Rejection
vs Frequency
–30
DISABLE REJECTION (dB)
–80
VS = ±5V
– 90
VS = ±15V
70
– 40
–50
RL = ∞
– 60
–70
RL = 1k
–80
–90
RL = 100Ω
–100
RL = 10Ω
–110
–120
–110
1
10
FREQUENCY (MHz)
100
10
FREQUENCY (MHz)
1
125°
SUPPLY CURRENT (mA)
30
20
20
10
1
LT1203/05 • TPC08
LT1203
RL = ∞
–55°
8.8
8.4
7.6
100M
LT1203/05 • TPC09
100
10
FREQUENCY (MHz)
Supply Current
vs Supply Voltage (Disabled)
8.0
1M
10M
FREQUENCY (Hz)
+PSRR
30
25°
9.2
100k
40
5.2
LT1203
RL = ∞
40
VS = ±15V
TA = 25°C
RL = ∞
RS = 0Ω
0
100
9.6
VS = ±15V
TA = 25°C
60
10
10k
–PSRR
50
Supply Current
vs Supply Voltage (Enabled)
100
80
60
LT1203/05 • TPC07
LT1203/05 • TPC06
Output Impedance (Enabled)
vs Frequency
100
LT1203/05 • TPC05
SUPPLY CURRENT (mA)
CROSSTALK REJECTION (dB)
–70
10
FREQUENCY (MHz)
Power Supply Rejection Ratio
vs Frequency
VS = ±15V
TA = 25°C
–30
–100
OUTPUT IMPEDANCE (Ω)
1
–20
TA = 25°C
RS = 0Ω
RL = ∞
– 60
RS = 0Ω
RS = 10Ω
–90
Disable Rejection
vs Frequency
–50
RS = 37.5Ω
–80
LT1203/05 • TPC04
LT1203/05 • TPC03
– 40
RS = 75Ω
–70
100
POWER SUPPLY REJECTION RATIO (dB)
2
– 60
–110
–5
0
–50
–100
–4
120
VS = ±15V
TA = 25°C
RL = ∞
– 40
CL = 20pF
CROSSTALK REJECTION (dB)
200
FREQUENCY (MHz)
Crosstalk Rejection
vs Frequency
5.0
25°
125°
4.8
–55°
4.6
4.4
0
2
4
6
8 10 12 14
SUPPLY VOLTAGE (±V)
16
18
LT1203/05 • TPC10
0
2
4
6
8 10 12 14
SUPPLY VOLTAGE (±V)
16
18
LT1203/05 • TPC11
5
LT1203/LT1205
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TYPICAL PERFOR A CE CHARACTERISTICS
Gain Error vs Temperature
Input Bias Current vs Input Voltage
8
1.2
RL = 400Ω
6
GAIN ERROR (%)
1.0
5
4
3
RL = 1k
2
VS = ±15V
RL = ∞
3
125°C
0.8
OUTPUT VOLTAGE (V)
VS = ±15V
VIN = –2V TO 2V
INPUT BIAS CURRENT (µA)
7
Output Voltage vs Input Voltage
4
25°C
0.6
–55°C
0.4
0.2
0
50
25
75
0
TEMPERATURE (°C)
100
– 0.4
–4
125
2
1
0
–1
–2
–3
– 0.2
1
–50 –25
VS = ±15V
TA = 25°C
RL = 1k
–3
–2
1
2
–1 0
INPUT VOLTAGE (V)
LT1203/05 • TPC12
3
4
–4
–5 – 4 –3 –2 –1 0 1 2
INPUT VOLTAGE (V)
Small-Signal Rise Time
2.0
VS = ±15V
RL = 1k
1.5
10mV
1mV
OUTPUT STEP (V)
1.0
0.5
0
–0.5
–1.0
10mV
1mV
–1.5
–2.0
0
100
300
400
200
SETTLING TIME (ns)
500
RL = 1k
LT1203/05 • TPC16
LT1203/05 • TPC15
VIN1 to VIN0 Select Time
VIN0 to VIN1 Select Time
LOGIC
(PIN 5)
LOGIC
(PIN 5)
VOUT
(PIN 7)
VOUT
(PIN 7)
VS = ±15V VINO = 1V
RL = 10k VIN1 = 0V
6
LT1203/05 • TPC17
VS = ±15V VINO = 1V
RL = 10k VIN1 = 0V
4
5
LT1203/05 • TPC14
LT1203/05 • TPC13
Settling Time to 1mV and 10mV
vs Output Step
3
LT1203/05 • TPC18
LT1203/LT1205
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TYPICAL PERFOR A CE CHARACTERISTICS
Channel 1 Enable
Channel 1 Disable
EN
(PIN 6)
EN
(PIN 6)
VOUT
(PIN 7)
VOUT
(PIN 7)
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APPLICATI
VS = ±15V VINO = 1V
RL = 1k
VIN1 = 0V
LT1203/05 • TPC19
VINO = 1V
VIN1 = 0V
LT1203/05 • TPC20
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VS = ±15V
RL = 1k
S I FOR ATIO
Input Protection
The logic inputs have ESD protection (≥ 2kV) and shorting them to 12V or 15V will cause excessive current to
flow. Limit the current to less than 50mA when driving
the logic above 6V. The analog inputs are protected
against ESD and overvoltage with internal SCRs. For
inputs ≥ ±2.8V the SCRs will fire and the DC current
should be limited to 20mA.
Power Supplies
The LT1203/LT1205 will operate from ±5V (10V total) to
±15V (30V total) and is specified over this range. Characteristics change very little over this voltage range. It is not
necessary to use equal value supplies however, the output
offset voltage will change. The offset will change about
300µV per volt of supply mismatch. The LT1203/LT1205
have a very wide bandwidth yet are tolerant of power
supply bypassing. The power supplies should be bypassed with a 0.1µF or 0.01µF ceramic capacitor within 0.5
inch of the part.
Circuit Layout
Use a ground plane to ensure a low impedance ground is
available throughout the PCB layout. Separate the inputs
with ground plane to ensure high channel separation. For
minimum peaking, maximum bandwidth and maximum
gain flatness sockets are not recommended because they
can add considerable stray inductance and capacitance. If
a socket must be used, use a low profile, low capacitance
socket such as the SamTec ISO-308.
Switching Transients
The LT1203/LT1205 use input buffers to ensure switching
transients do not couple to other video equipment sharing
the input line. Output switching transients are about
50mVP-P with a 20ns duration and input transients are
LT1203 Channel-to-Channel Switching Transient
OUTPUT
50mV/DIV
INPUT
20mV/DIV
LOGIC
(PIN 5)
RS = 50Ω
LT1203/05 • AI01
7
LT1203/LT1205
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APPLICATI
S I FOR ATIO
CMOS MUX Channel-to-Channel Switching Transient
only 10mVP-P. A photo of the switching transients from a
CMOS MUX shows glitches to be 50 times larger than on
the LT1203. Also shown is the output of the LT1203
switching on and off a 2MHz sinewave cleanly and without
abnormalities.
OUTPUT
1V/DIV
Pixel Switching
INPUT
1V/DIV
The multiplexers are fabricated on LTC's Complementary
Bipolar Process to attain fast switching speed, high bandwidth, and a wide supply voltage range compatible with
traditional video systems. Channel-to-channel switching
time and Enable time are both 25ns, therefore delay is the
same when switching between channels or between ICs.
To demonstrate the switching speed of the LT1203/LT1205
the RGB MUX of Figure 1 is used to switch RGB Workstation inputs with a 22ns pixel width. Figure 2a is a photo
showing the Workstation output and RGB MUX output.
The slight rise time degradation at the RGB MUX output is
due to the bandwidth of the LT1260 current feedback
amplifier used to drive the 75Ω cable. In Figure 2b, the
LT1203 switches to an input at zero at the end of the first
pixel and removes the following pixels.
LOGIC
CONTROL
LT1203/05 • AI02
RS = 50Ω
NOTE: 50 TIMES LARGER THAN LT1203 TRANSIENT
LT1203 Switching Inputs
LOGIC
(PIN 5)
OUTPUT
(PIN 7)
LT1203/05 • AI03
CHANNEL 1 = 0V
CHANNEL 2 = 2MHz SINEWAVE
J8
ENABLE
V+
J7
LOGIC
C4
4.7µF
+
R10
1.5k
16
J1
RED 1
1
1
2
J2
RED 2
R2
75Ω
3
4
J3
GREEN 1
R3
75Ω
J5
BLUE 1
R5
75Ω
5
J4
GREEN 2
R4
75Ω
6
7
8
J6
BLUE 2
+1
2
15
14
+1
LT1205
R7*
10k
13
3
4
R
4
5
10
R8*
10k
9
8
+1
LT1203
R14
1.5k
7
6
5
7
R9*
10k
8
R15
1.5k
*OPTIONAL
C1
0.1µF
Figure 1. RGB MUX
R16
75Ω
J9
RED
13
–
+
G
12
R17
75Ω
J10
GREEN
11
6
R13
1.5k
15
14
3
R12
1.5k
11
+1
+1
+
12
+1
2
–
16
C2
0.1µF
1
R6
75Ω
8
GND
+
R11
1.5k
C3
4.7µF
R1
75Ω
V–
+
B
–
10
9
LT1260
LT1203/05 • F01
R18
75Ω
J11
BLUE
LT1203/LT1205
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APPLICATI
S I FOR ATIO
4
VS = ±15V
RL = 150Ω
RF = RG = 1.3k
3
2
GAIN (dB)
WORKSTATION
OUTPUT
1
R, B
0
G
–1
–2
RGB MUX
OUTPUT
–3
–4
1
LT1203/05 • F02a
10
100
FREQUENCY (MHz)
1000
LT1203/05 • F04
Figure 2a. Workstation and RGB MUX Output
Figure 4. RGB MUX Frequency Response of
Demonstration Board #041
Input Expansion
WORKSTATION
OUTPUT
The output impedance of the LT1203/LT1205 is typically
20Ω when enabled and 10MΩ when disabled or not
selected. This high disabled output impedance allows the
output of many LT1205s to be shorted together to form
large crosspoint arrays. With their outputs shorted together, shoot-through current is low because the “on”
channel is disabled before the “off” channel is activated.
RGB MUX
OUTPUT
Timing and Supply Current Waveforms
LT1203/05 • F02b
Figure 2b. RGB MUX Output Switched to Ground
After One Pixel
ENABLE
IC #1
ENABLE
IC #2
5V/DIV
5V/DIV
Demonstration Board
A Demonstration Board (#041) of the RGB MUX in Figure
1 has been fabricated and its layout is shown in Figure 3.
The small-signal bandwidth of the RGB MUX is set by the
bandwidth of the LT1260. The stray capacitance of the
surface mount feedback resistors RF and RG restricts the
– 3dB bandwidth to about 95MHz. The bandwidth can be
improved by about 20% using the through-hole LT1260
and components. A frequency response plot in Figure 4
shows that the R, G, and B amplifiers have slightly
different frequency responses. The difference in the G
amplifier is due to different output trace routing to
feedback resistor R13.
VOUT
1V/DIV
IS
10mA/DIV
LT1203/05 • AI04
Four LT1205s are used in Figure 5 to form a 16-to-1
multiplexer which is very space efficient and uses only six
SO packages. In this application 15 switches are turned off
and only one is active. An attenuator is formed by the 15
deselected switches and the active device which has an
9
LT1203/LT1205
041A
R1
LOGIC
ENABLE
V–
V+
GND
R1
R
R2
R2
U1
R3
R11
R7
R10 C3
U3
R12
G1
R17
G
R13
C1
U2
G2
R16
C2
R18
R8
R14
R15 C4
R9
B
R4
B1
R5
B2
(408) 432-1900
LT1203/LT1205 FAST SWITCHING
RGB MULTIPLEXER DEMO BOARD
R6
COPYWRITE '93
MADE IN USA
LT1205/03 • F03
Figure 3. Demo Board #041 Layout
10
LT1203/LT1205
W
U
U
UO
APPLICATI
S I FOR ATIO
–15V
15V
GND
5V
C1
0.1µF
A
16
1
CH0
R1
75Ω
15
16
+1
C2
0.1µF
14
2
15
3
14
13
13
12
12
11
11
10
10
9
9
7
4
5
6
7
8
1
+1
+1
+1
U1
LT1205
3
4
5
6
7
8
4
5
6
7
8
1
4
5
6
7
8
R16
75Ω
C3
0.1µF
B
Y2
C
B
1
2
C
3
D
Y3
U5
Y4 74HCT238
Y5
G1
Y6
G2B
Y7
G2A
EN
6
5
4
14
+1
13
12
+1
+
11
10
+1
U2
LT1205
C5
4.7µF
2
U6
LT1252
9
3
7
+
–
6
RS
75Ω
OUTPUT
4
RF
1.6k
C6
4.7µF
16
+1
RG
1.6k
15
14
+1
13
TRUTH TABLE
12
+1
11
10
+1
U3
LT1205
9
16
+1
2
3
Y1
15
2
3
A
OPTIONAL
RX
10k
+
1
8
Y0
16
+1
2
CH15
C7
0.1µF
15
14
+1
13
12
+1
11
10
+1
U4
LT1205
9
C4
0.1µF
LT1203/05 • F05
D
X
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
LOGIC
SELECT
C
B
A
X
X
X
L
L
L
L
L
H
L
H
L
L
H
H
H
L
L
H
L
H
H
H
L
H
H
H
L
L
L
L
L
H
L
H
L
L
H
H
H
L
L
H
L
H
H
H
L
H
H
H
ENABLE
EN
OUTPUT
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
OFF
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH8
CH9
CH10
CH11
CH12
CH13
CH14
CH15
Figure 5. 16-to-1 Multiplexer and Truth Table
11
LT1203/LT1205
W
U
U
UO
APPLICATI
S I FOR ATIO
16-to-1 MUX Response
output impedance of only 25Ω at 10MHz. This attenuator
is responsible for the outstanding All Hostile Crosstalk
Rejection of 90dB at 10MHz with 15 input signals.
Several suggestions to attain this high rejection include:
16-to-1 MUX, Switching LT1205 Enable Lines
5V
SELECT
LINE C
0V
0
GAIN (dB)
1. Mount the feedback resistors for the surface mount
LT1252 on the back side of the PC board.
2. Keep the feedback trace (pin 3) of the LT1252 as short
as possible.
3. Route V + and V – for the LT1205s on the component
(top) side and under the devices (between inputs and
outputs).
4. Use the backside of the PC board as a solid ground
plane. Connect the LT1205 device grounds and bypass capacitors grounds as vias to the backside
ground plane.
VS = ±15V
RL = 100Ω
RF = RG = 1.6k
2
–2
–4
–6
1
10
FREQUENCY (MHz)
100
LT1203/05 • AI07
Each “off” switch has 2.8pF of output capacitance and 15
“off” switches tied together represent a 48pF load to the
one active switch. In this case the active device will peak
about 3dB at 50MHz. An attribute of current feedback
amplifiers is that the bandwidth can easily be adjusted by
changing the feedback resistors, and in this application
the LT1252’s bandwidth is reduced to about 60MHz using
1.6k feedback resistors. This has the effect of reducing the
peaking in the MUX to 0.25dB and flattening the response
to 0.05dB at 30MHz.
4 × 4 Crosspoint
1V
0V
VIN4 = 0V
VIN0 = 1V
LT1203/05 • AI05
RF = RG = 1.6k
RL = 100Ω
16-to-1 Multiplexer All Hostile Crosstalk Rejection
HOSTILE CROSSTALK REJECTION (dB)
–20
VS = ±15V
RS = 10Ω
RL = 100Ω
–40
–60
–80
–100
–120
1
10
FREQUENCY (MHz)
100
LT1203/05 • AI06
12
The compact high performance 4 × 4 crosspoint shown in
Figure 6 uses four LT1205s to route any input to any or all
outputs. The complete crosspoint uses only six SO packages and less than six square inches of PC board space.
The LT1254 quad current feedback amplifier serves as a
cable driver with a gain of 2. A ±5V supply is used to ensure
that the maximum 150°C junction temperature of the
LT1254 is not exceeded in the SO package. With this
supply voltage the crosspoint can operate at a 70°C
ambient temperature and drive 2V (peak or DC) into a
double-terminated 75Ω video cable. The feedback resistors of these output amplifiers have been optimized for
this supply voltage. The – 3dB bandwidth of the crosspoint
is over 100MHz with only 0.8dB of peaking. All Hostile
Crosstalk Rejection is 85dB at 10MHz when a shorted
input is routed to all outputs. To obtain this level of
performance it is necessary to follow techniques similar to
LT1203/LT1205
W
U
U
UO
APPLICATI
S I FOR ATIO
–5V
5V
GND
3
C1
0.1µF
CH0
J1
1
R1
75Ω
2
3
4
5
6
7
8
C2
0.1µF
16
+1
2
4
5
CH1
J2
6
7
R2
75Ω
8
R3
75Ω
R5
10k
13
R10
820Ω
12
+1
11
10
+1
U1
LT1205
5
9
R6
10k
16
+1
+
U6 B
LT1254
–
R11
820Ω
R12
820Ω
14
+1
+
12
+1
11
10
10
+1
U2
LT1205
9
9
16
+1
15
14
6
7
8
C5
4.7µF
13
3
5
OUTPUT 1
J6
15
2
4
7
R18
75Ω
OUTPUT 0
J5
–
+
+1
4
–
R19
75Ω
8
U6 C
LT1254
CH2
J3
1
1
R17
75Ω
R9
820Ω
14
+1
2
3
U6 A
LT1254
15
6
1
+
OUTPUT 2
J7
11
R13
820Ω
U5
74HC04
R7
10k
R14
820Ω
C6
4.7µF
+
13
12
+1
11
12
10
+1
U3
LT1205
9
13
+
R20
75Ω
14
U6 D
LT1254
OUTPUT 3
J8
–
R15
820Ω
1
16
+1
3
4
5
CH3
J4
6
7
8
R4
75Ω
C3
0.1µF
R8
10k
15
2
14
+1
R16
820Ω
13
TRUTH TABLE
12
+1
SELECT LOGIC
11
A
L
L
H
H
10
+1
U4
LT1205
9
C4
0.1µF
B
L
H
L
H
INPUT
CHANNEL
CH0
CH1
CH2
CH3
LT1203/05 • F06
B
A
SELECT LOGIC
OUTPUT 0
A
B
SELECT LOGIC
OUTPUT 1
A
B
SELECT LOGIC
OUTPUT 2
A
B
SELECT LOGIC
OUTPUT 3
Figure 6. 4 × 4 Crosspoint and Truth Table
13
LT1203/LT1205
U
W
U
UO
APPLICATI
S I FOR ATIO
those used in the 16-to-1 crosspoint with one additional
suggestion: Surround the LT1205 output traces by ground
plane and route them away from the (–) inputs of the
other three LT1254s.
Each pair of logic inputs labeled Select Logic Output is
used to select a particular output. The truth table is used
to select the desired input and is applied to each pair of
logic inputs. For example, to route Channel 1 Input to
Output 3, the 4th pair of logic inputs labeled Select Logic
Output 3 is coded A = Low and B = High. To route
Channel 3 Input to all outputs, set all eight logic inputs
High. Channel 3 is the default input with all logic inputs
open. To shut off all channels a pair of LT1259s can be
substituted for the LT1254. The LT1259 is a dual current
feedback amplifier with a shutdown pin that reduces the
supply current to 0µA.
Response of All Four Inputs for the 4 × 4 Crosspoint
4 × 4 Crosspoint, All Hostile Rejection
HOSTILE CROSSTALK REJECTION (dB)
2
GAIN (dB)
0
–2
–4
–6
VS = ±5V
RF = RG = 820Ω
RL = 100Ω
VS = ±5V
RL = 100Ω
RS = 0Ω
–40
–60
–80
–100
–120
–8
1
10
FREQUENCY (MHz)
100 200
1
10
FREQUENCY (MHz)
LT1203/05 • AI08
LT1203/05 • AI09
4 × 4 Crosspoint, Switching Channel 0 to Channel 2
5V
INPUT A
OF SELECT
LOGIC
OUTPUT 0
0V
CHANNEL 0 = 1V
CHANNEL 2 = 0V
14
100
LT1203/05 • AI10
LT1203/LT1205
W
W
SI PLIFIED SCHE ATIC
V+
2V
V–
OFF
IN 0
V–
IN 1
OUT
V+
ENABLE
V+
LOGIC
–2V
LOGIC
V–
GND
LT1203/05 • SS
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
N8 Package
8-Lead Plastic DIP
0.400
(10.160)
MAX
8
7
6
5
0.250 ± 0.010
(6.350 ± 0.254)
1
0.300 – 0.320
(7.620 – 8.128)
0.009 – 0.015
(0.229 – 0.381)
(
+0.025
0.325 –0.015
8.255
+0.635
–0.381
)
2
0.045 – 0.065
(1.143 – 1.651)
3
4
0.130 ± 0.005
(3.302 ± 0.127)
0.065
(1.651)
TYP
0.045 ± 0.015
(1.143 ± 0.381)
0.100 ± 0.010
(2.540 ± 0.254)
0.125
(3.175)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
0.020
(0.508)
MIN
N8 0392
15
LT1203/LT1205
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic SOIC
0.189 – 0.197*
(4.801 – 5.004)
7
8
5
6
0.150 – 0.157*
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
3
2
4
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
SO8 0294
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
S Package
16-Lead Plastic SOIC
0.386 – 0.394*
(9.804 – 10.008)
16
15
14
13
12
11
10
9
0.150 – 0.157*
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
2
3
4
5
6
7
8
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0° – 8° TYP
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
0.050
(1.270)
TYP
SO16 0893
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
16
Linear Technology Corporation
LT/GP 0494 10K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
 LINEAR TECHNOLOGY CORPORATION 1994