LT1675

LT1675/LT1675-1 250MHz, Triple and Single RGB Multiplexer with Current Feedback Amplifiers configured for a fixed gain of 2, eliminating six external FEATURES s s s s s s s s s s 100MHz Pixel Switching – 3dB Bandwidth: 250MHz Small 16-Pin SSOP Package Channel Switching Time: 2.5ns Expandable to Larger Arrays Drives Cables Directly High Slew Rate: 1100V/µs Low Switching Transient: 50mV Shutdown Supply Current: 0mA Output Short-Circuit Protected gain setting resistors. The SPDT switches are designed to be break-before-make to minimize unwanted signals coupling to the input. The LT1675-1 is a single version with two inputs, a single output and is ideal for a single channel application such as video sync. APPLICATIONS s s s s s RGB Switching Workstation Graphics Pixel Switching Coaxial Cable Drivers High Speed Signal Processing DESCRIPTION The LT ®1675 is a high speed RGB multiplexer designed for pixel switching and fast workstation graphics. Included on chip are three SPDT switches and three current feedback amplifiers. The current feedback amplifiers drive double-terminated 50Ω or 75Ω cables and are The key to the LT1675 fast switching speed is Linear Technology’s proprietary high speed bipolar process. This MUX can toggle between sources in excess of 100MHz, has a slew rate over 1000V/µs and has a –3dB bandwidth of 250MHz. The speed and ease of use of the LT1675 make it ideal for high performance PCs, workstations and professional video monitors. The input-referred switching transient is only 50mVP-P and lasts just 5ns, making it virtually undetectable. Power supply requirements are ± 4V to ± 6V and power dissipation is only 300mW on ± 5V, or 100mW for the LT1675-1. The expandable feature uses the disable pin to reduce the power dissipation to near 0mW in the off parts. Unlike competitive solutions that are in bulky high pin count packages, the LT1675 is in a 16-lead narrow body SSOP. This small footprint, the size of an SO-8, results in a very clean high performance solution. The LT1675-1 is available in the tiny MSOP and the SO-8. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION High Speed RGB MUX LT1675 RED 1 75Ω +2 GREEN 1 75Ω BLUE 1 75Ω RED 2 75Ω GREEN 2 75Ω SELECT RGB1/RGB2 BLUE 2 75Ω +1 ENABLE 1675 TA01 +1 +1 75Ω CABLE +1 +2 +1 +2 +1 U U U Select Pin Switches Inputs at 100MHz V+ 75Ω CABLE SELECT LOGIC PIN 10 0V 1V RED OUT 0V 500mV/DIV 3V 1V/DIV VOUT RED 75Ω VOUT GREEN 75Ω 75Ω CABLE VOUT BLUE 75Ω RED 1 = 0V, RED 2 = 1V, R L = 100Ω MEASURED BETWEEN 50 Ω BACK TERMINATION AND 50 Ω LOAD 1675 TA02 V– 1 LT1675/LT1675-1 ABSOLUTE MAXIMUM RATINGS Supply Voltage ..................................................... ± 6.3V Inputs, ENABLE and SELECT, Current ................ ± 20mA Output Short-Circuit Duration (Note 2) ......... Continuous Specified Temperature Range (Note 3) ....... 0°C to 70°C PACKAGE/ORDER INFORMATION TOP VIEW VIN1 GND VIN2 V– 1 2 3 4 8 7 6 5 V+ ENABLE VOUT SELECT VIN1 1 GND 2 VIN2 3 V– 4 TOP VIEW 8 7 6 5 V+ ENABLE VOUT SELECT MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150°C, θJA = 250°C/ W S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 150°C/ W ORDER PART NUMBER LT1675CMS8-1 MS8 PART MARKING LTGX ORDER PART NUMBER LT1675CS8-1 Consult factory for Industrial and Military grade parts. 2 U U W WW U W (Note 1) Operating Temperature Range ................ – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Junction Temperature (Note 4) ............................ 150°C Lead Temperature (Soldering, 10 sec).................. 300°C TOP VIEW RED 1 GREEN 1 BLUE 1 GND GND RED 2 GREEN 2 BLUE 2 1 2 3 4 5 6 7 8 16 V + 15 VOUT RED 14 VOUT GREEN 13 VOUT BLUE 12 V – 11 V – 10 SELECT 9 ENABLE GN PACKAGE 16-LEAD PLASTIC SSOP NARROW TJMAX = 150°C, θJA = 120°C/ W S8 PART MARKING 16751 ORDER PART NUMBER LT1675CGN GN PART MARKING 1675 LT1675/LT1675-1 ELECTRICAL CHARACTERISTICS PARAMETER Output Offset Voltage Output Offset Matching Input Current Input Resistance PSRR DC Gain Error 0V to 1V CONDITIONS Any Input Selected 0°C ≤ TA ≤ 70°C, VS = ± 5V, RL = ∞, VIN = 0V LT1675 (Pins 1, 2, 3, 6, 7, 8), LT1675-1 (Pins 1, 3), ENABLE = 0V, unless otherwise specified. MIN q q q q q q q q q q q q q q q q q q q q q q q q q q q q q TYP 20 5 – 12 MAX 40 20 – 30 UNITS mV mV µA kΩ dB Between Outputs R1 to R2, G1 to G2, B1 to B2 Any Input Selected VIN = ± 1V VS =± 2.6V to ± 6V, Measured at Output VIN = 1V, RL = ∞ VIN = 1V, RL = 150Ω VIN = 1V, RL = 75Ω VIN = – 1V, RL = ∞ VIN = – 1V, RL = 150Ω VIN = – 1V, RL = 75Ω VIN = 2V, RL = ∞ VIN = 2V, RL = 150Ω VIN = 2V, RL = 75Ω VIN = – 2V, RL = ∞ VIN = – 2V, RL = 150Ω VIN = – 2V, RL = 75Ω 100 38 700 50 3 4 5 3 4 8 6 8 10 6 8 20 % % % % % % V V V V V V DC Gain Error 0V to –1V Output Voltage 3.1 2.8 2.4 – 3.1 – 2.7 – 2.3 1.1 50 25 8 3.4 3.0 2.8 – 3.3 – 3.0 – 2.6 1.5 70 33 1 11 0.3 450 150 90 30 42 100 14 33 600 200 180 60 0.8 2.0 Disabled Output Impedance Maximum Output Current Supply Current LT1675 LT1675-1 ENABLE Pin Current SELECT Pin Current SELECT Low SELECT High LT1675 LT1675-1 LT1675 LT1675-1 ENABLE Open VIN = ± 1V, VO = 0V ENABLE = 0V ENABLE = 4.7V ENABLE = 0V ENABLE = 4.7V ENABLE= 0V ENABLE= 0V SELECT = 0V SELECT = 0V SELECT (See Truth Table) SELECT (See Truth Table) kΩ mA mA µA mA µA µA µA µA µA V V 2 3 LT1675/LT1675-1 AC CHARACTERISTICS PARAMETER Slew Rate Full Power Bandwidth (Note 5) Small-Signal –3dB Bandwidth Gain Flatness Gain Matching Channel-to-Channel Select Time Delay Time Switching Time Enable Time Disable Time Input Pin Capacitance SELECT Pin Capacitance ENABLE Pin Capacitance LT1675 LT1675-1 LT1675 LT1675-1 Output Pin Capacitance (Disabled) Small-Signal Rise Time Propagation Delay Overshoot On-Channel to Off-Channel Crosstalk Chip Disable Crosstalk Channel Select Output Transient Differential Gain (Note 6) Differential Phase (Note 6) 0°C ≤ TA ≤ 70°C, VS = ± 5V, RL = 150Ω, VIN = 0V LT1675 (Pins 1, 2, 3, 6, 7, 8), LT1675-1 (Pins 1, 3), ENABLE = 0V, unless otherwise specified. CONDITIONS VOUT = 5VP-P VOUT =6VP-P Less Than 1dB Peaking Less Than 0.1dB R to G to B R1 to R2, G1 to G2, B1 to B2, LT1675-1 VIN1 to VIN2 R1 = 0V, R2 = 1V Measured from Time SELECT Pin Crosses Logic Threshold Time for VOUT to Go from 0V to 1V MIN TYP 1100 58 250 70 0.10 0.01 5.0 2.5 10 100 2 2.2 1.5 2.1 1.5 ENABLE Open VIN = 300mVP-P, RL = 100Ω VIN = 300mVP-P, RL = 100Ω VIN = 300mVP-P, RL = 100Ω Measured at 10MHz Measured at 10MHz, ENABLE Open Measured Between Back Termination and Load 4.4 1.85 3 10 60 90 50 0.07 0.05 MAX UNITS V/µs MHz MHz MHz dB dB ns ns ns ns pF pF pF pF pF pF ns ns % dB dB mVP-P % DEG The q denotes specifications that apply over the specified temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: May require a heat sink. Note 3: The LT1675/LT1675-1 are guaranteed to meet specified performance from 0°C to 70°C and are designed, characterized and expected to meet these extended temperature limits, but are not tested at – 40°C and 85°C. Guaranteed I grade parts are available; consult factory. Note 4: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: LT1675CGN: TJ = TA + (PD)(120°C/W) LT1675CMS8-1: TJ = TA + (PD)(250°C/W) LT1675CS8-1: TJ = TA + (PD)(150°C/W) Note 5: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2πVPEAK. Note 6: 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°. Nine identical MUXs were cascaded giving an effective resolution of 0.011% and 0.011°. LT1675 LT1675-1 BLUE OUT BLUE 1 BLUE 2 OFF VOUT VIN1 VIN2 OFF Truth Table SELECT 1 0 X ENABLE 0 0 1 RED OUT RED 1 RED 2 OFF GREEN OUT GREEN 1 GREEN 2 OFF 4 LT1675/LT1675-1 TYPICAL PERFORMANCE CHARACTERISTICS Gain and Phase vs Frequency 5 4 3 2 GAIN (dB) 1 0 –1 –2 –3 –4 CL = 0pF RL = 150Ω 1M 10M 100M FREQUENCY (Hz) GAIN PHASE 0 –20 –40 –60 PHASE (DEG) GAIN (dB) CL = 3pF –100 –120 –140 –160 –180 –200 1G 1675 G01 1 0 –1 –2 –3 –4 100k 1M 10M 100M FREQUENCY (Hz) 1G 1675 G02 GAIN (dB) –5 100k – 3dB Bandwidth vs Supply Voltage 300 280 260 RL = 150Ω CROSSTALK REJECTION (dB) CROSSTALK REJECTION (dB) FREQUENCY (MHz) 240 220 200 180 160 140 120 100 2 4 5 3 SUPPLY VOLTAGE (±V) 6 1675 G04 Crosstalk Rejection vs Frequency (Disabled) –10 70 POWER SUPPLY REJECTION RATIO (dB) –20 CROSSTALK REJECTION (dB) –30 –40 –50 –60 –70 –80 –90 –100 RS = 75Ω RL = 150Ω 40 30 20 10 0 –10 –20 –30 100k 1M –PSRR OUTPUT VOLTAGE (VP-P) –110 100k 1M 10M 100M FREQUENCY (Hz) UW 1675 G06 Frequency Response with Capacitive Loads 6 5 4 3 2 RL = 150Ω CL = 10pF CL = 5pF 6.5 6.4 6.3 6.2 6.1 6.0 5.9 5.8 5.7 5.6 Gain vs Frequency RL = 100Ω –80 CL = 0pF RG B 5.5 10k 100k 1M 10M FREQUENCY (Hz) 100M 1675 G03 Crosstalk Rejection vs Frequency –30 –40 –50 –60 –70 –80 –90 –100 –110 –120 –130 100k 1M 10M 100M FREQUENCY (Hz) 1G 1675 G05 Crosstalk Rejection vs Frequency 20 10 0 –10 –20 –30 –40 –50 –60 –70 –80 100k 1M 10M 100M FREQUENCY (Hz) 1G 1675 G23 RS = 75Ω RL = 150Ω R1 DRIVEN R2 SELECTED RS = 75Ω RL = 150Ω G1 DRIVEN R1 SELECTED Power Supply Rejection Ratio vs Frequency 60 50 +PSRR VS = ± 5V TA = 25°C RL = 150Ω 8 7 6 5 4 3 2 Undistorted Output Swing vs Frequency VS = ±5V RL = 150Ω 1G 10M 100M FREQUENCY (Hz) 1G 1675 G07 1M 10M 100M FREQUENCY (Hz) 1G 1675 G08 5 LT1675/LT1675-1 TYPICAL PERFORMANCE CHARACTERISTICS Output Impedance vs Frequency 10k DISABLED OUTPUT IMPEDANCE (Ω) 1k –40 –30 RL = 150Ω VO = 2VP-P INPUT BIAS CURRENT (µA) DISTORTION (dBc) 100 10 –70 ENABLED 1 100k –80 1M 10M 100M FREQUENCY (Hz) 1G 1675 G09 Output Short-Circuit Current vs Temperature 90 OUTPUT SHORT-CIRCUIT CURRENT (mA) 85 80 VS = ± 5V 3 GAIN ERROR (%) GAIN ERROR (%) 75 70 65 60 55 50 –50 –25 0 25 SOURCING VIN = 1V SINKING VIN = – 1V 50 75 TEMPERATURE (°C) 1675 G13 Output Voltage vs Input Voltage 4 3 VS = ± 5V TA = 25°C RL = ∞ RL = 75Ω SUPPLY CURRENT (mA) RL = 150Ω OUTPUT VOLTAGE (V) 125°C –55°C SUPPLY CURRENT (mA) 2 1 0 –1 –2 –3 –4 –2 –1 1 0 INPUT VOLTAGE (V) 6 UW 100 2 1675 G16 2nd and 3rd Harmonic Distortion vs Frequency 15 10 5 0 –5 –10 –15 –20 –25 –30 1 10 FREQUENCY (MHz) 100 LTXXXX 1675 G10 Input Bias Current vs Input Voltage VS = ± 5V 2ND –50 3RD –60 125°C –55°C 25°C –3 –2 –1 0 1 INPUT VOLTAGE (V) 2 3 1675 G12 Positive DC Gain Error vs Temperature 4 VS = ± 5V VIN = 1V RL = 75Ω 8 12 10 Negative DC Gain Error vs Temperature VS = ± 5V VIN = – 1V 2 RL = 150Ω RL = 75Ω 6 4 2 RL = 150Ω 1 125 0 –50 –25 0 25 50 75 100 125 0 –50 –25 TEMPERATURE (°C) 1675 G14 50 25 75 0 TEMPERATURE (°C) 100 125 1675 G15 Supply Current vs Supply Voltage 40 35 30 25 20 15 10 5 0 0 1 2 3 4 SUPPLY VOLTAGE (±V) 5 6 1675 G11 LT1675-1 Supply Current vs Supply Voltage 14 12 10 8 6 4 2 0 125°C –55°C 25°C RL = ∞ RL = ∞ 25°C 0 1 2 3 4 SUPPLY VOLTAGE (±V) 5 6 1675 G24 LT1675/LT1675-1 TYPICAL PERFORMANCE CHARACTERISTICS Input Bias Current vs Temperature –10 OUTPUT OFFSET VOLTAGE (mV) VS = ± 5V VIN = 0V INPUT BIAS CURRENT (µA) –11 20 VS = ± 5V 15 –12 –13 –50 –25 50 25 75 0 TEMPERATURE (°C) Toggling RED 2 to RED 1 3V SELECT PIN 10 0V RED OUT PIN 15 RED OUT PIN 15 1V/DIV 1V/DIV RED 1 IN RED 1 = 0V RED 2 = UNCORRELATED SINEWAVE RL = 150Ω, 10pF SCOPE PROBE Small-Signal Rise Time VGEN VOUT 0V RL = 100Ω MEASURED WITH FET PROBES ENABLE AND DISABLE OF UNCORRELATED SINEWAVE 1675 G22 RL = 150Ω UW Output Offset Voltage vs Temperature 10 5 100 125 0 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 125 1675 G17 1675 G18 Slew Rate 1V/DIV 2V/DIV 1675 G19 MEASURED AT PIN 15 RL = 150Ω, 10pF SCOPE PROBE SR = 1100V/µs 1675 G20 Enable and Disable 50mV/DIV 5V ENABLE PIN 9 0V RED OUT 0V PIN 15 2V/DIV 50mV/DIV 2V/DIV 1675 G21 7 LT1675/LT1675-1 PIN FUNCTIONS LT1675 RED 1 (Pin 1): Red 1 Input. The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT RED will clip. The input must be terminated. GREEN 1 (Pin 2): Green 1 Input. The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT GREEN will clip. The input must be terminated. BLUE 1 (Pin 3): Blue 1 Input. The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT BLUE will clip. The input must be terminated. GND (Pins 4, 5): Signal Ground. Connect to ground plane. RED 2 (Pin 6): Red 2 Input. The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT RED will clip. The input must be terminated. GREEN 2 (Pin 7): Green 2 Input. The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT GREEN will clip. The input must be terminated. BLUE 2 (Pin 8): Blue 2 Input. The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT BLUE will clip. The input must be terminated. ENABLE (Pin 9): Chip Enable. Ground this pin for normal operation. Take this pin to within 300mV of V +, or open to shut down the part. This pin is also used for router applications. When the part is disabled, the supply current is 1µA. SELECT (Pin 10): Channel Select. Use this pin to select between RGB1 inputs and RGB2 inputs. Use this pin for fast toggling. HIGH Selects RGB1. V – (Pins 11, 12): Negative Power Supply. Connect these pins to – 5V and bypass with good tantalum capacitor (4.7µF). The pin may also require a 0.1µF or 0.01µF depending on layout. VOUT BLUE (Pin 13): Blue Output. It is twice BLUE 1 or BLUE 2 depending on which channel is selected by Pin 10. VOUT BLUE drives 50Ω or 75Ω double-terminated cables. Do not add capacitance to this pin. VOUT GREEN (Pin 14): Green Output. It is twice GREEN 1 or GREEN 2 depending on which channel is selected by Pin 10. VOUT GREEN drives 50Ω or 75Ω double-terminated cables. Do not add capacitance to this pin. VOUT RED (Pin 15): Red Output. It is twice RED 1 or RED 2 depending on which channel is selected by Pin 10. VOUT RED drives 50Ω or 75Ω double-terminated cables. Do not add capacitance to this pin. V + (Pin 16): Positive Power Supply. Connect this pin to 5V and bypass with good tantalum capacitor (4.7µF). The pin may also require a 0.1µF or 0.01µF depending on layout. LT1675-1 VIN1 (Pin 1): The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT will clip. The input must be terminated. GND (Pin 2): Signal Ground. Connect to ground plane. VIN2 (Pin 3): The 1V video input signal to be switched is applied to this pin. If 2V are applied to this pin, VOUT will clip. The input must be terminated. V – (Pin 4): Connect this pin to – 5V and bypass with good tantalum capacitor (4.7µF). The pin may also require a 0.1µF or 0.01µF depending on layout. SELECT (Pin 5): Use this pin to select VIN1 or VIN2. Use this pin for fast toggling. HIGH Selects VIN1. VOUT (Pin 6): It is twice VIN1 or VIN2 depending on which channel is selected by Pin 5. VOUT drives 50Ω or 75Ω double-terminated cables. Do not add capacitance to this pin. ENABLE (Pin 7): Ground this pin for normal operation. Take this pin to within 300mV of V +, or open to shut down the part. This pin is also used for router applications. When the part is disabled, the supply current is 0.3µA. V + (Pin 8): Connect this pin to 5V and bypass with good tantalum capacitor (4.7µF). The pin may also require a 0.1µF or 0.01µF depending on layout. 8 U U U LT1675/LT1675-1 APPLICATIONS INFORMATION Power Supplies The LT1675 will function with supply voltages below ± 2V (4V total), however, to ensure a full 1VP-P video signal (2VP-P at the output pins), the power supply voltage should be between ± 4V to ± 6V. The LT1675 is designed to operate on ± 5V, and at no time should the supplies exceed ± 6V. The power supplies should be bypassed with quality tantalum capacitors. It may be necessary to add 0.01µF or 0.1µF in parallel with the tantalum capacitors if there is excessive ringing on the output waveform. Even though the LT1675 is well behaved, bypass capacitors should be placed as close to the LT1675 as possible. Smallest Package and PC Board Space The LT1675 has the internal gain set for + 2V/V or 6dB, because it is designed to drive a double-terminated 50Ω or 75Ω cable that has an inherent 6dB loss. There are several advantages to setting the gain internally. This topology eliminates six gain set resistors, reduces the pin count of the package and eliminates stray capacitance on the sensitivity feedback node. The LT1675 fits into the small SSOP package, and these advantages lead to the smallest PC board footprint with enhanced performance. The LT1675-1 eliminates two gain set resistors and is available in the tiny MSOP package and the cost-effective SO-8 package. Fast Switching The key to the LT1675 fast switching speed is Linear Technology’s proprietary high speed bipolar process. Internal switches can change state in less than 1ns, but the output of the MUX switches in about 2.5ns, as shown in Figure 1. The additional delay is due to the finite bandwidth and the slew rate of the current feedback amplifier that drives the cable. For minimum ringing, it is important to minimize the load capacitance on the output of the part. This is normally not a problem in a controlled impedance environment, but stray PC board capacitance and scope probe capacitance can degrade the pulse fidelity. Figure 2 shows the response of the output to various capacitive loads measured with a 10pF scope probe. 3V SELECT PIN 10 0V RED OUT PIN 15 500mV/DIV CL = 0pF 1V/DIV CL = 20pF RED 1 = 1V, RED 2 = 0V MEASURED BETWEEN 75Ω BACK TERMINATION AND 75Ω LOAD 1675 F01 Figure 1. Toggling at 25MHz U W U U CL = 10pF 2V/DIV MEASURED AT PIN 15 RL = 150Ω, 10pF SCOPE PROBE 1675 F02 Figure 2. Response to Capacitive Loads 9 LT1675/LT1675-1 APPLICATIONS INFORMATION Switching Transients This MUX includes fast current steering break-beforemake SPDT switches that minimize switching glitches. The switching transients of Figure 3 are input-referred (measured between 75Ω back termination and the 75Ω load). The glitch is only 50mVP-P and the duration is just 5ns. This transient is small and fast enough to not be visible on quality graphics terminals. Additionally, the break-before-make SPDT switch is open before the alternate channel is connected. This means there is no input feedthrough during switching. Figure 4 shows the amount of alternate channel that is coupled at the input. Expanding Inputs In video routing applications where the ultimate speed is not mandatory, as it is in pixel switching, it is possible to expand the number of MUX inputs by shorting the LT1675 outputs together and switching with the ENABLE pins. The internal gain set resistors have a nominal value of 750Ω and cause a 1500Ω shunt across the 75Ω cable termination. Figure 5 shows schematically the effect of expanding the number of inputs. The effect of this loading is to cause a gain error that can be calculated by the following formula:   1575Ω 75Ω   Gain Error (dB) = 6dB + 20log  n – 1  dB 1575Ω  75 + 75Ω   n –1 where n is total number of LT1675s. For example, using ten LT1675s (20 Red, 20 Green and 20 Blue) the Gain Error is only – 1.7dB per channel. Figure 6 shows a 4-input RGB router. The response from RED 1 Input to Red Output is shown in Figure 7 for a 25MHz square wave with Chip Select = 0V. In this case the Gain Error is – 0.23dB. Toggling with Chip Select between IC #1 and IC #2 is shown in Figure 8. In this case RED 1 Input is connected to 0V and RED 3 Input is connected to an uncorrelated sinewave. 3V SELECT PIN 10 0V 1V/DIV SELECT PIN 10 RED OUT PIN 15 0V RL = 150Ω, 10pF SCOPE PROBE 1675 F03 Figure 3. Input-Referred Switching Transient 10 U W U U 3V 1V/DIV 0V 50mV/DIV RED 1 IN 0V PIN 1 20mV/DIV RS = 75Ω 1675 F04 Figure 4. Switching Transient at RED 1 (Pin 1) LT1675/LT1675-1 APPLICATIONS INFORMATION n . . . 750Ω OFF 750Ω 75Ω OFF 750Ω R1 75Ω ON 750Ω 75Ω CABLE n = NUMBER OF LT1675s IN PARALLEL 1675 F05 75Ω RED 1 INPUT 750Ω ⇒ 75Ω 1575 n–1 R2 75Ω RED OUTPUT 750Ω Figure 5. Off Channels Load the Cable Termination with 1575Ω Each R1 AV = 2 75Ω R2 ENABLE LT1675 #1 R3 AV = + 2 75Ω RED OUT 75Ω R4 ENABLE LT1675 #2 CHIP SELECT 74HC04 1675 F06 Figure 6. Two LT1675s Build a 4-Input RGB Router U W U U 1V 500mV/DIV 0V 1V 500mV/DIV 0V CHIP SELECT = 0V, IC #2 DISABLED 1675 F07 Figure 7. 4-Input Router Response CHIP 5V SELECT 0V 5V/DIV RED 0V OUTPUT 1V/DIV RED 1 INPUT = 0V RED 3 INPUT = UNCORRELATED SINEWAVE 1675 F08 Figure 8. 4-Input Router Toggling 11 LT1675/LT1675-1 TYPICAL APPLICATIO S RGB Video Inverter LT1675 RED 97.6Ω +2 VIDEO IN GREEN 97.6Ω BLUE 97.6Ω 332Ω 332Ω +1 – + 332Ω 332Ω – 5V 10k 1.25V – LT1634 10k 0.714V + LT1399 COMPOSITE BLANKING 1675 TA03 This circuit is useful for viewing photographic negatives on video. A single channel can be used for composite or monochrome video. The inverting amplifier stages are only switched in during active video so the blanking, sync 12 U +1 V+ 75Ω CABLE VOUT RED 75Ω +1 75Ω CABLE +1 +2 VOUT GREEN 75Ω +2 75Ω CABLE VOUT BLUE 75Ω +1 V– SELECT +1 ENABLE + 332Ω 332Ω and color burst (if present) are not disturbed. To prevent video from swinging negative, a voltage offset equal to the peak video signal is added to the inverted signal. LT1675/LT1675-1 TYPICAL APPLICATIO S Logo or “Bug” Inserter LT1675 RED 75Ω +2 VIDEO IN GREEN 75Ω BLUE 75Ω +1 +2 113Ω CABLE VOUT BLUE 75Ω SELECT A 0 0 1 1 SELECT B 0 1 0 1 OUTPUT NO VIDEO, 100% WHITE VIDEO PLUS 66% WHITE VIDEO PLUS 33% WHITE VIDEO, NO WHITE +1 V– SELECT +1 ENABLE +1 +2 113Ω +1 CABLE VOUT GREEN 75Ω +1 V+ 113Ω CABLE VOUT RED 75Ω SELECT A SELECT B B LT1675 +1 V+ 226Ω 5V 10k 1.25V LT1634 10k 0.714V +1 +1 V– SELECT ENABLE 1675 TA05 This circuit highlights a section of the picture under control of a synchronous key signal. It can be used for adding the logo (also called a “bug”) you see in the bottom corner of commercial television pictures or any sort of overlay signal, such as a crosshair or a reticule. The key signal has 2 bits of control so there can be four levels of highlighting: unmodified video, video plus 33% white, video plus 66% white and 100% white. The two LT1675s are configured as a 2-bit DAC. The resistors on the outputs U A +2 +1 +1 +2 226Ω +1 +2 226Ω set the relative bit weights. The output of the LT1675 labeled B in the schematic is one half the weight of the A device. To properly match the 75Ω video cable, the output resistors are selected so the parallel combination of the two is 75 ohms. The output will never exceed peak white, which is 0.714V for this NTSC-related RGB video. The reference white signal is adjustable to lower than peak white to make the effect less intrusive, if desired. 13 LT1675/LT1675-1 SI PLIFIED SCHE ATIC OFF 750Ω 750Ω ENABLE LOGIC SELECT V+ GND V– 14 – V+ + W W (LT1675-1, LT1675 One Channel) V+ V– RED 1 RED 2 V– RED VOUT 1675 SS LT1675/LT1675-1 PACKAGE DESCRIPTION 0.015 ± 0.004 × 45° (0.38 ± 0.10) 0.007 – 0.0098 (0.178 – 0.249) 0.016 – 0.050 (0.406 – 1.270) 0° – 8° TYP * DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 0.007 (0.18) 0.021 ± 0.006 (0.53 ± 0.015) 0° – 6° TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) TYP 0.192 ± 0.004 (4.88 ± 0.10) 0.118 ± 0.004** (3.00 ± 0.102) * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 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. U Dimensions in inches (millimeters) unless otherwise noted. GN Package 16-Lead Plastic SSOP (Narrow 0.150) (LTC DWG # 05-08-1641) 0.189 – 0.196* (4.801 – 4.978) 0.053 – 0.068 (1.351 – 1.727) 0.004 – 0.0098 (0.102 – 0.249) 16 15 14 13 12 11 10 9 0.009 (0.229) REF 0.008 – 0.012 (0.203 – 0.305) 0.025 (0.635) BSC 0.229 – 0.244 (5.817 – 6.198) 0.150 – 0.157** (3.810 – 3.988) 1 23 4 56 7 8 GN16 (SSOP) 0398 MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 0.040 ± 0.006 (1.02 ± 0.15) 0.034 ± 0.004 (0.86 ± 0.102) 8 76 5 0.006 ± 0.004 (0.15 ± 0.102) MSOP (MS8) 1197 1 23 4 S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 8 7 6 5 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) TYP 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) SO8 0996 1 2 3 4 15 LT1675/LT1675-1 TYPICAL APPLICATION NTSC-Related Color Bar Generator 5V 74ACT04 CLOCK IS SUBCARRIER × 4 DIVIDED BY 91 OR 157.343kHz CLR ENP ENT CLK 5V A B C 6.04k D LOAD COMPOSITE BLANKING QC 1k +1 +2 75Ω CABLE G +1 74LS163 QB 1k +2 75Ω CABLE VOUT RED 75Ω VOUT GREEN 75Ω QA 1k 6.04k R +1 +2 6.04k B +1 LT1675 V+ 75Ω CABLE MAGENTA YELLOW GREEN BLACK WHITE CYAN BLUE RED 0.714V B 0 0.714V R 0 0.714V G 0 640Ω An RGB color bar test pattern is easily generated by dividing down a suitable clock. To form a stable pattern, the clock must be synchronous with the horizontal scan rate. Four times subcarrier, or 14.318MHz, is a readily available frequency, which when divided by 91, gives 157.343KHz. Dividing this signal by two, four and eight, gives the blue, read and green signals, respectively. This timing gives eight bars including white and black that fill the 52.6µs active video time. The digital signals are run RELATED PARTS PART NUMBER LT1203/LT1205 LT1204 LT1260 LT1398/LT1399 DESCRIPTION 150MHz Video MUX 4-Input Video MUX with 75MHz Current Feedback Amp Low Cost Dual and Triple 130MHz Current Feedback Amp with Shutdown Low Cost Dual and Triple 300MHz Current Feedback Amp with Shutdown COMMENTS 2-Input and 4-Input, 90dB Channel Separation, Wide Supply Range Drives Cables, Adjustable Gain, 90dB Channel Separation Drives Cables, Wide Supply Range, 0µA Shutdown Current Performance Upgrade for the LT1259/LT1260 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com U VOUT BLUE 75Ω –5V 10k –0.285V +1 V– SELECT +1 ENABLE COMPOSITE SYNC 1675 TA04 through a 74ACT04 inverter because the CMOS output swings rail-to-rail. The inverter output is scaled to make video (0.714V peak, for NTSC-related RGB). The LT1675 drives the cable and adds sync to the RGB signals by switching in –0.286V. If no sync is required, this voltage can be set to zero and composite blanking can be used to drive the select pin of the LT1675 in order to provide a more precise blanking level. 16751fs, sn16751 LT/TP 0199 4K • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 1998