lt1203/lt1205 - 150mhz video multiplexers
TRANSCRIPT
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LT1203/LT1205
150MHz Video Multiplexers
–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
SFEATURE D
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ESCRIPTIOThe LT1203 is a wideband 2-input video multiplexerdesigned for pixel switching and broadcast quality rout-ing. The LT1205 is a dual version that is configured as a4-input, 2-output multiplexer.
These multiplexers act as SPDT video switches with 10nstransition times at toggle rates up to 30MHz. The – 3dBbandwidth is 150MHz and 0.1dB gain flatness is 30MHz.Many parts can be tied together at their outputs by usingthe enable feature which reduces the power dissipationand raises the output impedance to 10MΩ. Output capaci-tance when disabled is only 3pF and the LT1203 peaks lessthan 3dB into a 50pF load. Channel crosstalk and disableisolation are greater than 90dB up to 10MHz. An on-chipbuffer interfaces to fast TTL or CMOS logic. Switchingtransients are only 50mV with a 25ns duration. TheLT1203 and LT1205 outputs are protected against shortsto ground.
The LT1203/LT1205 are manufactured using LinearTechnology’s proprietary complementary bipolar process.The LT1203 is available in both the 8-lead PDIP and SOpackage while the LT1205 is available in the 16-leadnarrow body SO package.
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PPLICATITYPICAL
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+1
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LT1205
LOGIC
V+LOGIC
VOUT RED
VOUT GREEN
VOUT BLUE
LT1203 • TA01
EN
RED 1
CHANNEL SELECT
RED 2
GREEN 1
GREEN 2
BLUE 1
BLUE 2
V–
V–
V–
EN
V+
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LT1203
LOGIC
EN
V+
High Speed RGB MUX Large-Signal Response
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PPLICATI Broadcast Quality Video Multiplexing Picture-in-Picture Switching HDTV Computer Graphics Title Generation Video Crosspoint Matrices Video Routers
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LT1203/LT1205
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ARBSOLUTE XI TI SSupply Voltage ...................................................... ±18VSignal Input Current (Note 1) ............................ ±20mALogic Input Current (Note 2).............................. ±50mAOutput Short-Circuit Duration (Note 3) ........ ContinuousSpecified Temperature Range (Note 4) ....... 0°C to 70°C
Operating Temperature Range ............... – 40°C to 85°CStorage Temperature Range ................ –65°C to 150°CJunction Temperature (Note 5) ............................ 150°CLead Temperature (Soldering, 10 sec) ................. 300°C
ORDER PARTNUMBER
LT1203CN8*LT1203CS8*
S8 PART MARKING
1203
*See Note 4Consult factory for Industrial and Military grade parts.
ORDER PARTNUMBER
LT1205CS*
TJMAX = 150°C, θJA = 100°C/W
TOP VIEW
S PACKAGE 16-LEAD PLASTIC SOIC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VINO
GND
VIN1
V –
VIN2
GND
VIN3
V–
V+
VOUT1
EN1
LOGIC 1
V+
VOUT2
EN2
LOGIC 2
1
2
3
4
8
7
6
5
TOP VIEW
VIN0
GND
VIN1
V–
V+
VOUT
EN
LOGIC
N8 PACKAGE 8-LEAD PLASTIC DIP
S8 PACKAGE 8-LEAD PLASTIC SOIC
TJMAX = 150°C, θJA = 100°C/W (N)TJMAX = 150°C, θJA = 150°C/W (S)
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PACKAGE/ORDER I FOR ATIO
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VOS Output Offset Voltage Any Input Selected 10 30 mV
Output Offset Matching Between Outputs 0.3 5 mV
∆VOS/∆T Output Offset Drift 40 µV/°C
IIN Input Current 0.6 5 µA
RIN Input Resistance VS = ±5V, VIN = ±2V 1 5 MΩVS = ±15V, VIN = ±2V 2 5 MΩ
CIN Input Capacitance Input Selected 2.6 pFInput Deselected 2.6 pF
COUT Disabled Output Capacitance EN Pin Voltage ≤ 0.8V 2.8 pF
VIN Input Voltage (Note 1) VS = ±5V ±2 ±2.8 VVS = ±15V ±2 ±3.0 V
PSRR Power Supply Rejection Ratio VS = ±4.5 to ±15V 60 70 dB
Gain Error VS = ±15V, VIN = ±2V, RL = 1k 2 4 %VS = ±15V, VIN = ±2V, RL = 400Ω 6 10 %VS = ±5V, VIN = ±2V, RL = 1k 3 6 %
ELECTRICAL C CHARA TERISTICS0°C ≤ TA ≤ 70°C, ±5V ≤ VS ≤ ±15V, RL = 1k, pulse tested, EN pin open or high, unless otherwise noted.
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LT1203/LT1205
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
SR Slew Rate (Note 6) 180 300 V/µs
FPBW Full Power Bandwidth (Note 7) VOUT = 2VP-P 28.6 47.7 MHz
tSEL Channel-to-Channel Select Time (Note 8) RL = 10k 25 35 ns
Enable Time (Note 9) RL = 1k 25 35 ns
Disable Time (Note 9) RL = 1k 20 35 ns
tr, tf 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
tS 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
ELECTRICAL C CHARA TERISTICS0°C ≤ TA ≤ 70°C, ±5V ≤ VS ≤ ±15V, RL = 1k, pulse tested, EN pin open or high, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VOUT Output Voltage VS = ±15V, VIN = ±2V, RL = 400Ω ±1.8 ±1.90 VVS = ±5V, VIN = ±2V, RL = 1k ±1.8 ±1.94 V
Overload Swing (Note 1) VS = ±15V, VIN = ±5V ±0.9 ±1.5 VVS = ±5V, VIN = ±5V ±0.9 ±1.5 V
IOUT Output Current VS = ±15V, VIN = ±2V, RL = 400Ω ±4.5 ±4.75 mAVS = ±5V, VIN = ±2V, RL = 1k ±1.8 ±2.00 mA
ROUT Enabled Output Resistance EN Pin Voltage = 2V, VOUT = ±2V, VS = ±15V 20 42 ΩDisabled Output Resistance EN Pin Voltage = 0.5V, VOUT = ±2V, VS = ±15V 1 10 MΩ
IS Supply Current (LT1203) EN Pin Voltage = 2V 10.0 14 mAEN Pin Voltage = 0.5V 5.8 8 mA
Supply Current (LT1205) EN Pin Voltage = 2V 20.0 28 mAEN Pin Voltage = 0.5V 11.6 16 mA
VIL Logic Low Logic Pin 0.8 V
VIH Logic High Logic Pin 2 V
Enable Low EN Pin 0.5 V
Enable High EN Pin 2 V
IIL Digital Input Current Low LT1203 Pin 5, LT1205 Pins 9, 13 = 0V 1.5 6.5 µA
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
C CHARA TERISTICSAC TA = 25°C, VS = ±15V, RL = 1k, EN pin open or high, unless otherwise noted.
The denotes specifications which apply over the specifiedtemperature range.Note 1: The analog inputs (pins 1, 3 for the LT1203, pins 1, 3, 5, 7 for theLT1205) are protected against ESD and overvoltage with internal SCRs.
For inputs ≤±2.8V the SCR will not fire. Voltages above 2.8V will fire theSCR and the DC current should be limited to 20mA. To turn off the SCRthe pin voltage must be reduced to less than 1V or the current reduced toless than 600µA.
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LT1203/LT1205
Note 2: The digital inputs (pins 5, 6 for the LT1203, pins 9, 10, 13, 14 forthe LT1205) are protected against ESD and overvoltage with internalSCRs. For inputs ≤±6V the SCR will not fire. Voltages above 6V will firethe SCR and the DC current should be limited to 50mA. To turn off theSCR the pin voltage must be reduced to less than 2V or the currentreduced to less than 10mA.Note 3: A heat sink may be required depending on the power supplyvoltage.Note 4: Commercial grade parts are designed to operate over thetemperature range of –40°C to 85°C but are neither tested nor guaranteedbeyond 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 powerdissipation 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 whileoperating on ±15V supplies, RL = 1k.Note 7: Full power bandwidth is calculated from the slew ratemeasurement:
FPBW = SR/2πVPEAK
Note 8: For the LT1203, apply 1VDC to pin 1 and measure the time for theappearance 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 whenpin 5 goes from 0V to 5V. Apply 1VDC to pin 3 and measure the time forthe appearance of 0.5V at pin 7 when pin 5 goes from 0V to 5V. Apply1VDC to pin 3 and measure the time for disappearance of 0.5V at pin 7when pin 5 goes from 5V to 0V. For the LT1205 the same test isperformed on both MUXs.Note 9: For the LT1203, apply 1VDC to pin 1 and measure the time for theappearance 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 0.2Vat pin 7 when pin 6 goes from 5V to 0V. Pin 5 voltage = 0V. Apply 1VDCto pin 3 and measure the time for the appearance of 0.5V at pin 7 whenpin 6 goes from 0V to 5V. Pin 5 voltage = 5V. Apply 1VDC to pin 3 andmeasure the time for disappearance of 0.2V at pin 7 when pin 5 goes from5V to 0V. Pin 5 voltage = 5V. For the LT1205 the same test is performedon both MUXs.Note 10: VIN = 0dBm (0.223VRMS) at 10MHz on one input with the otherinput selected and RS = 10Ω. For disable crosstalk all inputs are drivensimultaneously. In disable the output impedance is very high and signalcouples across the package; the load impedance determines the crosstalk.Note 11: Differential gain and phase are measured using a TektronixTSG120 YC/NTSC signal generator and a Tektronix 1780R videomeasurement set. The resolution of this equipment is 0.1% and 0.1°.Ten identical MUXs were cascaded giving an effective resolution of0.01% and 0.01°.
TYPICAL PERFOR A CE CHARACTERISTICSW U
LOGIC EN VOUT
0 1 VIN0
1 1 VIN1
0 0* HIGH ZOUT
1 0 HIGH ZOUT
*Must be ≤0.5V
TRUTH TABLE
FREQUENCY (MHz)1
–1GAIN
(dB)
PHASE (DEG)
0
1
2
3
10 100 1000
LT1203/05 • TPC02
–2
–3
–4
–5
4
5
–120
–100
–80
–60
–40
–140
–160
–180
–200
–20
0VS = ±15V TA = 25°C RL = ∞
FREQUENCY (MHz)1
–1GAIN
(dB)
PHASE (DEG)
0
1
2
3
10 100 1000
LT1203/05 • TPC01
–2
–3
–4
–5
4
5
–120
–100
–80
–60
–40
–140
–160
–180
–200
–20
0VS = ±5V TA = 25°C RL = ∞
±5V Frequency Response ±15V Frequency Response
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TYPICAL PERFOR A CE CHARACTERISTICSW U
Frequency Responsewith Capacitive Loads
Disable Rejectionvs Frequency
Crosstalk Rejectionvs Frequency
Output Impedance (Enabled)vs Frequency
Crosstalk Rejectionvs Frequency
SUPPLY VOLTAGE (±V)0
FREQ
UENC
Y (M
Hz)
160
180
18
LT1203/05 • TPC03
140
1202 6 8 10 12 14 164
200TA = 25°C RL = 10k PEAKING ≤ 0.5dB
FREQUENCY (MHz)1
–5
GAIN
(dB)
–3
–1
1
3
10 100
LT1203/05 • TPC04
–4
–2
0
2
4
5VS = ±15V TA = 25°C RL = ∞
CL = 100pF
CL = 50pF
CL = 20pF
CL = 10pF
FREQUENCY (MHz)1
–110
CROS
STAL
K RE
JECT
ION
(dB)
–100
–90
–80
–70
–30
10 100
LT1203/05 • TPC05
–60
–50
–40VS = ±15V TA = 25°C RL = ∞
RS = 0Ω
RS = 10Ω
RS = 37.5Ω
RS = 75Ω
FREQUENCY (MHz)1
–110
CROS
STAL
K RE
JECT
ION
(dB)
–100
–90
–80
–70
–30
10 100
LT1203/05 • TPC06
–60
–50
–40TA = 25°C RS = 0Ω RL = ∞
VS = ±5V VS = ±15V
FREQUENCY (MHz)1
–70
–80
–90
–100
–110
–120
DISA
BLE
REJE
CTIO
N (d
B)
– 60
–50
–40
–30
10 100
LT1203/05 • TPC07
–20VS = ±15V TA = 25°C
RL = ∞
RL = 1k
RL = 100Ω
RL = 10Ω
FREQUENCY (MHz)
0
30
20
10
70
60
50
40
LT1203/05 • TPC08
POW
ER S
UPPL
Y RE
JECT
ION
RATI
O (d
B)
1 10010
VS = ±15V TA = 25°C RL = ∞ RS = 0Ω–PSRR
+PSRR
Supply Currentvs Supply Voltage (Enabled)
Supply Currentvs Supply Voltage (Disabled)
FREQUENCY (Hz)
20
OUTP
UT IM
PEDA
NCE
(Ω)
40
30
60
80
100
10k 1M 100M10M
LT1203/05 • TPC09
10100k
VS = ±15V TA = 25°C
SUPPLY VOLTAGE (±V)0
7.6
SUPP
LY C
URRE
NT (m
A)
8.4
9.6
4 8 10 18
LT1203/05 • TPC10
8.0
9.2
8.8
2 6 12 14 16
LT1203 RL = ∞
125° 25°
–55°
SUPPLY VOLTAGE (±V)0
4.4
SUPP
LY C
URRE
NT (m
A)
4.8
4 8 10 18
LT1203/05 • TPC11
4.6
5.2
5.0
2 6 12 14 16
125°
25°
LT1203 RL = ∞
–55°
– 3dB Bandwidthvs Supply Voltage
Power Supply Rejection Ratiovs Frequency
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LT1203/LT1205
TYPICAL PERFOR A CE CHARACTERISTICSW U
TEMPERATURE (°C)–50
5
6
8
25 75
LT1203/05 • TPC12
4
3
–25 0 50 100 125
2
1
7
GAIN
ERR
OR (%
)
VS = ±15V VIN = –2V TO 2V
RL = 400Ω
RL = 1k
Gain Error vs Temperature
INPUT VOLTAGE (V)–4
INPU
T BI
AS C
URRE
NT (µ
A)
0.4
0.6
0.8
4
LT1203/05 • TPC13
0.2
0
–0.4–2 0 2
–0.2
1.2
1.0
–3 –1 1 3
125°C
25°C
–55°C
VS = ±15V RL = ∞
INPUT VOLTAGE (V)–5
OUTP
UT V
OLTA
GE (V
) 2
4
3
LT1203/05 • TPC14
0
–2
–4–3 –1 1 5
1
3
–1
–3
2–4 –2 0 4
VS = ±15V TA = 25°C RL = 1k
Output Voltage vs Input Voltage
Small-Signal Rise Time
RL = 1k
VIN0 to VIN1 Select TimeVIN1 to VIN0 Select Time
Settling Time to 1mV and 10mVvs Output Step
SETTLING TIME (ns)0
OUTP
UT S
TEP
(V)
1.0
2.0
400
LT1203/05 • TPC15
0
–1.0
–2.0100 200 300 500
0.5
1.5
–0.5
–1.5
10mV
10mV
1mV
1mV
VS = ±15V RL = 1k
LT1203/05 • TPC16
VS = ±15VRL = 10k
LT1203/05 • TPC17 LT1203/05 • TPC18VS = ±15VRL = 10k
LOGIC(PIN 5)
VOUT(PIN 7)
LOGIC(PIN 5)
VOUT(PIN 7)
Input Bias Current vs Input Voltage
VINO = 1VVIN1 = 0V
VINO = 1VVIN1 = 0V
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LT1203/LT1205
TYPICAL PERFOR A CE CHARACTERISTICSW U
Channel 1 Disable
VS = ±15VRL = 1k
LT1203/05 • TPC19 VS = ±15VRL = 1k
Channel 1 Enable
LT1203/05 • TPC20
Input Protection
The logic inputs have ESD protection (≥2kV) and short-ing them to 12V or 15V will cause excessive current toflow. Limit the current to less than 50mA when drivingthe logic above 6V. The analog inputs are protectedagainst ESD and overvoltage with internal SCRs. Forinputs ≥±2.8V the SCRs will fire and the DC currentshould 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. Charac-teristics change very little over this voltage range. It is notnecessary to use equal value supplies however, the outputoffset voltage will change. The offset will change about300µV per volt of supply mismatch. The LT1203/LT1205have a very wide bandwidth yet are tolerant of powersupply bypassing. The power supplies should be by-passed with a 0.1µF or 0.01µF ceramic capacitor within 0.5inch of the part.
Circuit Layout
Use a ground plane to ensure a low impedance ground isavailable throughout the PCB layout. Separate the inputs
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LT1203 Channel-to-Channel Switching Transient
with ground plane to ensure high channel separation. Forminimum peaking, maximum bandwidth and maximumgain flatness sockets are not recommended because theycan add considerable stray inductance and capacitance. Ifa socket must be used, use a low profile, low capacitancesocket such as the SamTec ISO-308.
Switching Transients
The LT1203/LT1205 use input buffers to ensure switchingtransients do not couple to other video equipment sharingthe input line. Output switching transients are about50mVP-P with a 20ns duration and input transients are
OUTPUT50mV/DIV
INPUT20mV/DIV
LOGIC(PIN 5)
RS = 50Ω LT1203/05 • AI01
VINO = 1VVIN1 = 0V
VINO = 1VVIN1 = 0V
EN(PIN 6)
VOUT(PIN 7)
VOUT(PIN 7)
EN(PIN 6)
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OUTPUT1V/DIV
LT1203/05 • AI02RS = 50ΩNOTE: 50 TIMES LARGER THAN LT1203 TRANSIENT
LT1203/05 • AI03
OUTPUT(PIN 7)
CHANNEL 1 = 0VCHANNEL 2 = 2MHz SINEWAVE
LOGIC(PIN 5)
LT1203 Switching Inputs
only 10mVP-P. A photo of the switching transients from aCMOS MUX shows glitches to be 50 times larger than onthe LT1203. Also shown is the output of the LT1203switching on and off a 2MHz sinewave cleanly and withoutabnormalities.
Pixel Switching
The multiplexers are fabricated on LTC's ComplementaryBipolar Process to attain fast switching speed, high band-width, and a wide supply voltage range compatible withtraditional video systems. Channel-to-channel switchingtime and Enable time are both 25ns, therefore delay is thesame when switching between channels or between ICs.To demonstrate the switching speed of the LT1203/LT1205the RGB MUX of Figure 1 is used to switch RGB Worksta-tion inputs with a 22ns pixel width. Figure 2a is a photoshowing the Workstation output and RGB MUX output.The slight rise time degradation at the RGB MUX output isdue to the bandwidth of the LT1260 current feedbackamplifier used to drive the 75Ω cable. In Figure 2b, theLT1203 switches to an input at zero at the end of the firstpixel and removes the following pixels.
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5
6
7
8
16
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13
1
2
3
4
8
7
6
5
12
116
15
14
13
12
11
10
9
2
3
4
5
6
7
8
LT1260
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10
9
+1
+1
+1
LT1205
LT1203/05 • F01
+1
+1
LT1203
R4 75Ω
J4 GREEN 2
J7 LOGIC
R6 75Ω C1
0.1µF
C2 0.1µF
C3 4.7µF
C4 4.7µF
J6 BLUE 2
R8* 10k
R13 1.5k
R15 1.5k
R9* 10k
*OPTIONAL
R14 1.5k
R7* 10k
R5 75Ω
J5 BLUE 1
R3 75Ω
J3 GREEN 1
R2 75Ω
J2 RED 2
R1 75Ω
J1 RED 1
–
+
–
+
–
+
R12 1.5k
R10 1.5k
V+ V –
R11 1.5k
R
G
B
+ +
GND
J8 ENABLE
J9 RED
J10 GREEN
J11 BLUE
R16 75Ω
R17 75Ω
R18 75Ω
Figure 1. RGB MUX
INPUT1V/DIV
LOGICCONTROL
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LT1203/LT1205
WORKSTATIONOUTPUT
LT1203/05 • F02a
Figure 2a. Workstation and RGB MUX Output
LT1203/05 • F02b
Figure 2b. RGB MUX Output Switched to GroundAfter One Pixel
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FREQUENCY (MHz)1
–2
GAIN
(dB)
–1
0
1
2
10 100 1000
LT1203/05 • F04
–3
–4
3
4
G
R, B
VS = ±15V RL = 150Ω RF = RG = 1.3k
Input Expansion
The output impedance of the LT1203/LT1205 is typically20Ω when enabled and 10MΩ when disabled or notselected. This high disabled output impedance allows theoutput of many LT1205s to be shorted together to formlarge crosspoint arrays. With their outputs shorted to-gether, shoot-through current is low because the “on”channel is disabled before the “off” channel is activated.
ENABLEIC #1
Timing and Supply Current Waveforms
ENABLEIC #2
VOUT1V/DIV
IS10mA/DIV
5V/DIV
5V/DIV
LT1203/05 • AI04
Four LT1205s are used in Figure 5 to form a 16-to-1multiplexer which is very space efficient and uses only sixSO packages. In this application 15 switches are turned offand only one is active. An attenuator is formed by the 15deselected switches and the active device which has an
Figure 4. RGB MUX Frequency Response ofDemonstration Board #041
RGB MUXOUTPUT
WORKSTATIONOUTPUT
RGB MUXOUTPUT
Demonstration Board
A Demonstration Board (#041) of the RGB MUX in Figure1 has been fabricated and its layout is shown in Figure 3.The small-signal bandwidth of the RGB MUX is set by thebandwidth of the LT1260. The stray capacitance of thesurface mount feedback resistors RF and RG restricts the–3dB bandwidth to about 95MHz. The bandwidth can beimproved by about 20% using the through-hole LT1260and components. A frequency response plot in Figure 4shows that the R, G, and B amplifiers have slightlydifferent frequency responses. The difference in the Gamplifier is due to different output trace routing tofeedback resistor R13.
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LT1203/LT1205
( 4 0 8 ) 4 3 2 - 1 9 0 0 L T 1 2 0 3 / L T 1 2 0 5 F A S T S W I T C H I N G R G B M U L T I P L E X E R D E M O B O A R D
R9
R8C2C1
R15 C4
B
G
R
R1
R2
G1
G2
B1
B2
R14
R11U3
U1
U2
R10
041A
ENABLELOGIC
R16
R18
R17
C3
GNDV+V–
R13
R12
R7
R1
R2
R3
R4
R5
R6COPYWRITE '93 MADE IN USA
LT1205/03 • F03
Figure 3. Demo Board #041 Layout
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LT1203/LT1205
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+1
+1
+1
+1U1
LT1205
16
9
10
11
12
13
14
15 C2 0.1µF
C7 0.1µF
1
R1 75Ω
C1 0.1µF
8
7
6
5
4
3
2
+1
+1
+1
+1U2
LT1205
16
9
10
11
12
13
14
15
1
8
7
6
5
4
3
2
1
5V
816
4
5
6
A
B
C
D
EN
3
2
15
7
2
3
7
4
6OUTPUT
OPTIONAL RX 10k
9
10
11
12
13
14A
G2A
G2B
G1
C
B
Y0
Y7
Y6
Y5
Y4
Y3
Y2
Y1
+1
+1
+1
+1U3
LT1205
16
9
10
11
12
13
14
15
1
8
7
6
5
4
3
2
+1
+1
+1
U4 LT1205
16
9
LT1203/05 • F05
10
11
12
13
14
15
1
8CH15
CH0
7
6
5
4
3
2
GND15V–15V
RF 1.6k
RG 1.6k
RS 75Ω
C5 4.7µF
+
C6 4.7µF+
–
+U6
LT1252
U5 74HCT238
R16 75Ω
C4 0.1µF
C3 0.1µF
+1
D X L L L L L L L L H H H H H H H H
C X L L L L H H H H L L L L H H H H
B X L L H H L L H H L L H H L L H H
A X L H L H L H L H L H L H L H L H
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
SELECTLOGIC
TRUTH TABLE
OUTPUTENABLE EN
Figure 5. 16-to-1 Multiplexer and Truth Table
12
LT1203/LT1205
output impedance of only 25Ω at 10MHz. This attenuatoris responsible for the outstanding All Hostile CrosstalkRejection of 90dB at 10MHz with 15 input signals.
Several suggestions to attain this high rejection include:
1. Mount the feedback resistors for the surface mountLT1252 on the back side of the PC board.
2. Keep the feedback trace (pin 3) of the LT1252 as shortas possible.
3. Route V + and V – for the LT1205s on the component(top) side and under the devices (between inputs andoutputs).
4. Use the backside of the PC board as a solid groundplane. Connect the LT1205 device grounds and by-pass capacitors grounds as vias to the backsideground plane.
U
SA
O
PPLICATI
WU U
I FOR ATIO
16-to-1 MUX, Switching LT1205 Enable Lines
1V
0V
0V
RF = RG = 1.6kRL = 100Ω
VIN4 = 0VVIN0 = 1V
LT1203/05 • AI05
16-to-1 Multiplexer All Hostile Crosstalk Rejection
16-to-1 MUX Response
FREQUENCY (MHz)1
GAIN
(dB)
–6
–4
–2
0
10 100
LT1203/05 • AI07
2VS = ±15V RL = 100Ω RF = RG = 1.6k
Each “off” switch has 2.8pF of output capacitance and 15“off” switches tied together represent a 48pF load to theone active switch. In this case the active device will peakabout 3dB at 50MHz. An attribute of current feedbackamplifiers is that the bandwidth can easily be adjusted bychanging the feedback resistors, and in this applicationthe LT1252’s bandwidth is reduced to about 60MHz using1.6k feedback resistors. This has the effect of reducing thepeaking in the MUX to 0.25dB and flattening the responseto 0.05dB at 30MHz.
4 × 4 Crosspoint
The compact high performance 4 × 4 crosspoint shown inFigure 6 uses four LT1205s to route any input to any or alloutputs. The complete crosspoint uses only six SO pack-ages and less than six square inches of PC board space.The LT1254 quad current feedback amplifier serves as acable driver with a gain of 2. A ±5V supply is used to ensurethat the maximum 150°C junction temperature of theLT1254 is not exceeded in the SO package. With thissupply voltage the crosspoint can operate at a 70°Cambient temperature and drive 2V (peak or DC) into adouble-terminated 75Ω video cable. The feedback resis-tors of these output amplifiers have been optimized forthis supply voltage. The –3dB bandwidth of the crosspointis over 100MHz with only 0.8dB of peaking. All HostileCrosstalk Rejection is 85dB at 10MHz when a shortedinput is routed to all outputs. To obtain this level ofperformance it is necessary to follow techniques similar to
SELECTLINE C
FREQUENCY (MHz)1
–120
HOST
ILE
CROS
STAL
K RE
JECT
ION
(dB)
–100
–80
–60
–40
10 100
LT1203/05 • AI06
–20VS = ±15V RS = 10Ω RL = 100Ω
5V
13
LT1203/LT1205
+1
+1
+1
+1U1
LT1205
16
9
10
11
12
13
14
15
C2 0.1µF1
R1 75Ω
C1 0.1µF
8
7
6
5
4
3
2
+1
+1
+1
+1U2
LT1205
16
9
10
11
12
13
14
15
1
8
7
6
5
4
3
2
10
9
8
4
11
OUTPUT 2 J7
+1
+1
+1
+1U3
LT1205
16 U5 74HC04
9
10
11
12
13
14
15
1
8
7
6
5
4
3
2
+1
+1
+1
U4 LT1205
16
9
A
LT1203/05 • F06
10
11
12
13
14
15
1
8
CH3 J4
CH0 J1
7
6
5
4
3
2
R2 75Ω
CH1 J2
R3 75Ω
CH2 J3
GND
B
5V–5V
R13 820Ω
R14 820Ω
C6 4.7µF
R19 75Ω
C5 4.7µF
R7 10k
–
+
R4 75Ω
C4 0.1µF
SELECT LOGIC OUTPUT 0
A BSELECT LOGIC
OUTPUT 1
A BSELECT LOGIC
OUTPUT 2
A BSELECT LOGIC
OUTPUT 3
C3 0.1µF
+1
A L L H H
B L H L H
CH0 CH1 CH2 CH3
SELECT LOGIC
TRUTH TABLE
INPUT CHANNEL
U6 C LT1254
12
13
14
OUTPUT 3 J8
R15 820Ω
R16 820Ω
R20 75Ω
R8 10k
–
+U6 D
LT1254
5
6
7
OUTPUT 1 J6
R11 820Ω
R12 820Ω
R18 75Ω
R6 10k
–
+U6 B
LT1254
3
2
1
OUTPUT 0 J5
R9 820Ω
R10 820Ω
R17 75Ω
–
+U6 A
LT1254
+
+
R5 10k
Figure 6. 4 × 4 Crosspoint and Truth Table
U
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PPLICATI
WU U
I FOR ATIO
14
LT1203/LT1205
U
SA
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PPLICATI
WU U
I FOR ATIOthose used in the 16-to-1 crosspoint with one additionalsuggestion: Surround the LT1205 output traces by groundplane and route them away from the (–) inputs of theother three LT1254s.
Each pair of logic inputs labeled Select Logic Output isused to select a particular output. The truth table is usedto select the desired input and is applied to each pair oflogic inputs. For example, to route Channel 1 Input to
Output 3, the 4th pair of logic inputs labeled Select LogicOutput 3 is coded A = Low and B = High. To routeChannel 3 Input to all outputs, set all eight logic inputsHigh. Channel 3 is the default input with all logic inputsopen. To shut off all channels a pair of LT1259s can besubstituted for the LT1254. The LT1259 is a dual currentfeedback amplifier with a shutdown pin that reduces thesupply current to 0µA.
Response of All Four Inputs for the 4 × 4 Crosspoint
FREQUENCY (MHz)1
GAIN
(dB)
2
0
–2
–4
–6
–810 100
LT1203/05 • AI08
200
VS = ±5V RF = RG = 820Ω RL = 100Ω
LT1203/05 • AI10CHANNEL 0 = 1VCHANNEL 2 = 0V
4 × 4 Crosspoint, Switching Channel 0 to Channel 2
INPUT AOF SELECT
LOGICOUTPUT 0
5V
0V
4 × 4 Crosspoint, All Hostile Rejection
FREQUENCY (MHz)1
–120HOST
ILE
CROS
STAL
K RE
JECT
ION
(dB)
–100
–80
–60
–40
10 100
VS = ±5V RL = 100Ω RS = 0Ω
LT1203/05 • AI09
15
LT1203/LT1205
OFF IN 0
GND
LOGIC
ENABLE
V–
LT1203/05 • SS
V+
OUTIN 1
–2V
2V
V–
V–
V+
V+
LOGIC
SI PLIFIED SCHE ATICW W
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 represen-tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Dimensions in inches (millimeters) unless otherwise noted.PACKAGE DESCRIPTIOU
N8 Package8-Lead Plastic DIP
N8 0392
0.045 ± 0.015 (1.143 ± 0.381)
0.100 ± 0.010 (2.540 ± 0.254)
0.065 (1.651)
TYP
0.045 – 0.065 (1.143 – 1.651)
0.130 ± 0.005 (3.302 ± 0.127)
0.020 (0.508)
MIN
0.018 ± 0.003 (0.457 ± 0.076)
0.125 (3.175)
MIN
1 2 3 4
8 7 6 5
0.250 ± 0.010 (6.350 ± 0.254)
0.400 (10.160)
MAX
0.009 – 0.015 (0.229 – 0.381)
0.300 – 0.320 (7.620 – 8.128)
0.325+0.025 –0.015+0.635 –0.3818.255( )
16
LT1203/LT1205
PACKAGE DESCRIPTIOU
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package8-Lead Plastic SOIC
1 2 3 4
0.150 – 0.157* (3.810 – 3.988)
8 7 6 5
0.189 – 0.197* (4.801 – 5.004)
0.228 – 0.244 (5.791 – 6.197)
0.016 – 0.050 0.406 – 1.270
0.010 – 0.020 (0.254 – 0.508)
× 45°
0°– 8° TYP0.008 – 0.010
(0.203 – 0.254)
SO8 0294
0.053 – 0.069 (1.346 – 1.752)
0.014 – 0.019 (0.355 – 0.483)
0.004 – 0.010 (0.101 – 0.254)
0.050 (1.270)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
0.016 – 0.050 0.406 – 1.270
0.010 – 0.020 (0.254 – 0.508)
× 45°
0° – 8° TYP0.008 – 0.010
(0.203 – 0.254)
1 2 3 4 5 6 7 8
0.150 – 0.157* (3.810 – 3.988)
16 15 14 13
0.386 – 0.394* (9.804 – 10.008)
0.228 – 0.244 (5.791 – 6.197)
12 11 10 9
SO16 0893
0.053 – 0.069 (1.346 – 1.752)
0.014 – 0.019 (0.355 – 0.483)
0.004 – 0.010 (0.101 – 0.254)
0.050 (1.270)
TYP
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm).
S Package16-Lead Plastic SOIC
LINEAR TECHNOLOGY CORPORATION 1994
LT/GP 0494 10K • PRINTED IN USALinear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7487(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977