Datasheet

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LT1204

4-Input Video Multiplexer

with 75MHz Current

Feedback Amplifier

ESCRIPTIO

The LT

1204 is a 4-input video multiplexer designed to

drive 75Ω cables and easily expand into larger routing

systems. Wide bandwidth, high slew rate, and low differ-

ential gain and phase make the LT1204 ideal for broadcast

quality signal routing. Channel separation and disable

isolation are greater than 90dB up to 10MHz. The channel-

to-channel output switching transient is only 40mV

P-P

with a 50ns duration, making the transition imperceptible

on high quality monitors.

A unique feature of the LT1204 is its ability to expand into

larger routing matrices. This is accomplished by a patent

pending circuit that bootstraps the feedback resistors in

the disable condition, raising the true output impedance of

the circuit. The effect of this feature is to eliminate cable

misterminations in large systems.

The large input and output signal levels supported by the

LT1204 when operated on ±15V supplies make it ideal for

general purpose analog signal selection and multiplexing.

A shutdown feature reduces the supply current to 1.5mA.

All Hostile Crosstalk

Surface Mount PCB Measurements

FREQUENCY (MHz)

–120

ALL HOSTILE CROSSTALK (dB)

–100

–80

–60

–40

10 100

1204 TA02

–20

= ±15V

IN 0

= GND

IN 1,2,3

= 0dBm

= 100Ω

■

0.1dB Gain Flatness > 30MHz

■

Channel Separation at 10MHz: 90dB

■

40mV Switching Transient, Input Referred

■

–3dB Bandwidth, A

= 2, R

= 150Ω: 75MHz

■

Channel-to-Channel Switching Time: 120ns

■

Easy to Expand for More Inputs

■

Large Input Range: ± 6V

■

0.04% Differential Gain, R

= 150Ω

■

0.06° Differential Phase, R

= 150Ω

■

High Slew Rate: 1000V/µs

■

Output Swing, R

= 400Ω: ±13V

■

Wide Supply Range: ±5V to ±15V

■

Broadcast Quality Video Multiplexing

■

Large Matrix Routing

■

Medical Imaging

■

Large Amplitude Signal Multiplexing

■

Programmable Gain Amplifiers

, LTC and LT are registered trademarks of Linear Technology Corporation.

ITY

–

CFA

IN0

75Ω

IN1

75Ω

IN2

75Ω

IN3

75Ω

LOGIC

–

S/D

ENABLE

15V

–15V

75Ω

OUT

8.2k

–15V

LT1204

6.8k

GND

REF

1204 TA01

Summary of content (20 pages)

PAGE 1
LT1204 4-Input Video Multiplexer with 75MHz Current Feedback Amplifier DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 0.1dB Gain Flatness > 30MHz Channel Separation at 10MHz: 90dB 40mV Switching Transient, Input Referred – 3dB Bandwidth, AV = 2, RL = 150Ω: 75MHz Channel-to-Channel Switching Time: 120ns Easy to Expand for More Inputs Large Input Range: ± 6V 0.04% Differential Gain, RL = 150Ω 0.
PAGE 2
LT1204 W W W AXI U U ABSOLUTE RATI GS Supply Voltage ..................................................... ±18V – Input Current (Pin 13) .................................... ±15mA +Input and Control/Logic Current (Note 1) ........ ±50mA Output Short-Circuit Duration (Note 2) ......... Continuous Specified Temperature Range (Note 3) ....... 0°C to 70°C Operating Temperature Range ............... – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Junction Temperature (Note 4) ...
PAGE 3
LT1204 ELECTRICAL CHARACTERISTICS 0°C ≤ TA ≤ 70°C, ±5V ≤ VS ≤ ±15V, VCM = 0V, Pin 8 grounded and pulse tested unless otherwise noted. SYMBOL CMRR PARAMETER CONDITIONS MIN TYP Input Voltage Range, Any Positive Input VS = ±5V, TA = 25°C 2.5 – 2.0 ±6.0 4.0 V V V V 55 58 dB dB VS = ±15V VS = ±15V, Pin 8 Voltage = – 5V ● ● 2.0 – 1.5 ±5.0 3.75 VS = ±5V, VCM = – 1.5V, 2V, TA = 25°C VS = ±15V, VCM = ±5V ● 48 48 Negative Input Current Common Mode Rejection VS = ±5V, VCM = – 1.
PAGE 4
LT1204 AC CHARACTERISTICS TA = 25°C, VS = ±15V, RF = RG = 1k, unless otherwise noted. SYMBOL PARAMETER CONDITIONS tr, tf Small-Signal Rise and Fall Time RL = 150Ω, VOUT = ±125mV SR Slew Rate (Note 10) RL = 400Ω tS TYP 5.6 400 MAX UNITS ns 1000 V/µs Channel Select Output Transient All VIN = 0V, RL = 400Ω, Input Referred 40 mV Settling Time 0.
PAGE 5
LT1204 W U TYPICAL AC PERFOR A CE Measurements taken from SO Demonstration Board #028. VS (V) AV RL (Ω) RF (Ω) RG (Ω) SMALL SIGNAL – 3dB BW (MHz) SMALL SIGNAL 0.1dB BW (MHz) SMALL SIGNAL PEAKING (dB) ±15 1 150 1k 1.1k 1.6k None None 88.5 95.6 48.3 65.8 0.1 0 ±12 1 150 1k 976 1.3k None None 82.6 90.2 49.1 63.6 0.1 0.1 ±5 1 150 1k 665 866 None None 65.5 68.2 43.6 42.1 0.1 0.1 ±15 2 150 1k 787 887 787 887 75.7 82.2 45.8 61.3 0 0.1 ±12 2 150 1k 750 845 750 845 71.
PAGE 6
LT1204 U W TYPICAL PERFOR A CE CHARACTERISTICS ±12V Frequency Response, AV = 1 ±5V Frequency Response, AV = 1 3 –40 2 1 –60 1 0 –80 VS = ±12V RL = 150Ω RF = 976Ω PHASE GAIN (dB) 2 GAIN –1 –100 GAIN (dB) –20 3 0 VS = ±5V RL = 150Ω RF = 655Ω PHASE –60 –80 GAIN –1 –100 –2 –120 –3 –140 –3 –140 –4 –160 –4 –160 –5 –180 –5 –180 –6 1M –200 –6 1M 10M 100M FREQUENCY (Hz) 1G –120 –2 –200 10M 100M FREQUENCY (Hz) PHASE 7 9 –40 8 –60 7 –100 –120 4 0 VS = ±5V RL = 15
PAGE 7
LT1204 U W TYPICAL PERFOR A CE CHARACTERISTICS Maximum Capacitive Load vs Feedback Resistor Maximum Undistorted Output vs Frequency 15 AV = 10 10 AV = 1 5 AV = 2 RL = 1k AV = 2 TA = 25°C ≤ 5dB PEAKING 1000 VS = ±5V VS = ±15V 100 10 FREQUENCY (MHz) 0 100 1 2 FEEDBACK RESISTOR (kΩ) –40 –50 –70 –80 CH1 –90 –100 CH2 –110 CH4 CH3 –40 –50 –60 –70 –80 ANY CHANNEL –90 –100 10 FREQUENCY (MHz) –70 –80 SHUTDOWN CROSSTALK –90 –100 DISABLE CROSSTALK –110 10 FREQUENCY (MHz) –110 1 100 10
PAGE 8
LT1204 U W TYPICAL PERFORMANCE CHARACTERISTICS 100 OUTPUT CURRENT (µA) 150 100 50 0 –50 SLOPE = 1/18k –100 –150 –200 –5 –4 –3 –2 –1 0 1 2 3 OUTPUT VOLTAGE (V) 4 0 VS = ±15V RF = RG = 1k 10 1 –2 –3 –4 –5 –6 –7 –8 1.
PAGE 9
LT1204 U W TYPICAL PERFOR A CE CHARACTERISTICS Settling Time to 1mV vs Output Step Enabled Supply Current vs Supply Voltage 10 VS = ±15V RF = RG = 1k 8 22 21 21 4 2 0 –2 –4 20 –55°C 19 18 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) OUTPUT STEP (V) 22 20 6 25°C 17 16 15 –6 14 –8 13 –10 Disabled and Shutdown Supply Current vs Supply Voltage 125°C 2 4 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) –55°C 16 15 –55°C, 25°C, 125°C 16 ISHDN 0 18 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (±V) 120
PAGE 10
LT1204 U W U UO APPLICATI S I FOR ATIO Capacitance on the Inverting Input Large-Signal Transient Response Current feedback amplifiers require resistive feedback from the output to the inverting input for stable operation. Take care to minimize the stray capacitance between the output and the inverting input. Capacitance on the inverting input to ground will cause peaking in the frequency response and overshoot in the transient response.
PAGE 11
LT1204 U W U UO APPLICATI S I FOR ATIO monitors. The reference pin has no effect when the LT1204 is operating on ±5V, and should be grounded. On supply voltages above ±8V, the range of voltages for Pin 8 should be between – 6.5V and – 7.5V. Reducing Pin 8 voltage below – 7.5V turns “on” the “off” tee switch, and the isolation between channels is lost.
PAGE 12
LT1204 W U U UO APPLICATI S I FOR ATIO When the decoder turns off the tee switch (Q2 on) the emitter base junctions of Q1 and Q3 become reversebiased while Q2 emitter absorbs current from I1. Not only do the reverse-biased emitter base junctions provide good isolation, but any signal at VIN0 coupling to Q1 emitter is further attenuated by the shunt impedance of Q2 emitter. Current from I2 is routed to any on switch.
PAGE 13
LT1204 U W U UO APPLICATI S I FOR ATIO SOL PC Board #028, Component Side GND V– V+ VOUT VIN0 ENABLE C4 VIN1 C2 C1 RO U1 RF A1 R3 C3 R1 RG R2 A0 VIN2 S/D (408) 432-1900 LT1204 VIDEO MUX DEMONSTRATION BOARD VIN3 REF 1204 AI08 13
PAGE 14
LT1204 W U U UO APPLICATI S I FOR ATIO Demonstration PC Board Schematic GND V – 1 VIN0 2 3 VIN1 4 5 VIN2 6 7 VIN3 8 V+ VIN0 GND VO VIN1 V– V+ + 16 C1 4.7µF C2 0.1µF C3 4.7µF C4 0.1µF RO 75Ω 15 14 + RF 750Ω 13 GND FB LT1204 12 VIN2 SHDN ENABLE GND VIN3 A1 REF A0 SHUTDOWN R3 10k 11 RG 750Ω ENABLE 10 RESISTORS R1, R2 AND R3 ARE PULL-DOWN AND PULL-UP RESISTORS FOR THE LOGIC AND ENABLE PINS. THEY MAY BE OMITTED IF THE LT1204 IS DRIVEN FROM TTL LEVELS OR FROM 5V CMOS.
PAGE 15
LT1204 W U U UO APPLICATI S I FOR ATIO Multiplexer Expansion Pin 11 and Pin 12 To expand the number of MUX inputs, LT1204s can be paralleled by shorting their outputs together. The multiplexer disable logic has been designed to prevent shootthrough current when two or more amplifiers have their outputs shorted together. (Shoot-through current is a spike of power supply current caused by both amplifiers being on at once.
PAGE 16
LT1204 W U U UO APPLICATI S I FOR ATIO improper cable termination due to feedback resistors loading the cable. The limit to the number of expanded inputs is set by the acceptable error budget of the system. For a 64-to-1 MUX we need sixteen LT1204s. The equivalent load resistance due to the feedback resistor REQ in Disable is 25k/15 = 1.67k. See Figure 3. VO = 16-to-1 MUX Response Using Disable vs Shutdown 4 GAIN (dB) This voltage represents a 2.1% loading error.
PAGE 17
LT1204 UO TYPICAL APPLICATI S Programable Gain Amplifier (PGA) Two LT1204s and seven resistors make a Programable Gain Amplifier with a 128-to-1 gain range. The gain is proportional to 2N where N is the 3-bit binary value of the select logic. An input attenuator alters the input signal Programable Gain Amplifier Accepts Inputs from 62.5mVP-P to 8VP-P VIN = 62.5mVP-P TO 8VP-P 1 3 5 7 13 499Ω 249Ω 124Ω 4-Input Differential Receiver + + LT1204 + #1 + – 1.
PAGE 18
LT1204 UO TYPICAL APPLICATI S Differential Receiver Response DIFFERENTIAL RECEIVER RESPONSE (dB) Differential Receiver Switching Waveforms CABLE OUTPUT LT1204 #2 OUTPUT A0 PIN 9 20 0 DIFFERENTIAL MODE RESPONSE –20 –40 COMMON MODE RESPONSE –60 10k 1204 TA05 VS = ±15V RL = 100Ω 100k 1M 10M FREQUENCY (Hz) 100M 1204 TA06 4-Input Twisted-Pair Driver It is possible to send and receive color composite video signals appreciable distances on a low cost twisted pair.
PAGE 19
LT1204 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N Package 16-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.770* (19.558) MAX 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 0.255 ± 0.015* (6.477 ± 0.381) 0.130 ± 0.005 (3.302 ± 0.127) 0.300 – 0.325 (7.620 – 8.255) 0.020 (0.508) MIN 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 0.045 – 0.065 (1.143 – 1.651) ) 0.065 (1.651) TYP 0.125 (3.175) MIN 0.018 ± 0.003 (0.457 ± 0.
PAGE 20
LT1204 U TYPICAL APPLICATION 4-Input Twisted-Pair Driver/Receiver VIN0 VIN1 75Ω VIN2 VIN3 + + + + – LT1204 1k 1k 2k 47Ω 1000 FT OF TWISTED PAIR + 91Ω 47Ω – + 75Ω – + – LT1193 300Ω LT1227 1204 TA07 18Ω 680pF 390Ω 300pF 300Ω 200Ω RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1203/LT1205 150MHz Video Multiplexer High Speed, but No Cable Driving LT1259/LT1260 Dual and Triple Current Feedback Amplifiers Low Cost, with Shutdown LT1675 RGB Multiplexer with Current Feedback Ampli