LT1675/LT1675-1 250MHz, Triple and Single RGB Multiplexer with Amplifiers FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ configured for a fixed gain of 2, eliminating six external gain setting resistors. The SPDT switches are designed to be break-before-make to minimize unwanted signals coupling to the input. 100MHz Pixel Switching – 3dB Bandwidth: 250MHz Channel Switching Time: 2.5ns Expandable to Larger Arrays Drives Cables Directly High Slew Rate: 1100V/µs Low Switching Transient: 50mV Shutdown Supply Current: 100µA Output Short-Circuit Protected Available in Small 16-Pin SSOP Package 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. 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. 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. U APPLICATIO S ■ ■ ■ ■ ■ RGB Switching Workstation Graphics Pixel Switching Coaxial Cable Drivers High Speed Signal Processing U DESCRIPTIO 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 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. All other trademarks are the property of their respective owners. U TYPICAL APPLICATIO High Speed RGB MUX Clocking Between 2 DC Levels at 100MHz LT1675 RED 1 3V V+ +1 75Ω 75Ω CABLE +2 VOUT RED +1 GREEN 1 LOGIC INPUT PIN 10 75Ω 0V 75Ω 75Ω +1 BLUE 1 CABLE +2 1V/DIV 1V VOUT GREEN RED OUT 500mV/DIV 75Ω 75Ω +1 RED 2 75Ω CABLE VOUT BLUE +2 75Ω GREEN 2 0V RED INPUT 1 = 0VDC, RED INPUT 2 = 1VDC MEASURED BETWEEN 50Ω BACK TERMINATION AND 50Ω LOAD 75Ω +1 V– +1 ENABLE 1675 TA02 75Ω SELECT RGB1/RGB2 BLUE 2 75Ω 1675 TA01 16751fb 1 LT1675/LT1675-1 U W W W ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage ..................................................... ±6.3V Inputs, ENABLE and SELECT, Current ................ ±20mA Output Short-Circuit Duration (Note 2) ......... Continuous Specified Temperature Range ..................... 0°C to 70°C Operating Temperature Range (Note 3) .. – 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 W U U PACKAGE/ORDER INFORMATION VIN1 GND VIN2 V– 1 2 3 4 TOP VIEW TOP VIEW TOP VIEW 8 7 6 5 V+ ENABLE VOUT SELECT MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150°C, θJA = 250°C/ W RED 1 1 16 V + GREEN 1 2 15 VOUT RED BLUE 1 3 14 VOUT GREEN VOUT GND 4 13 VOUT BLUE SELECT GND 5 12 V – RED 2 6 11 V – GREEN 2 7 10 SELECT BLUE 2 8 9 VIN1 1 8 V+ GND 2 7 ENABLE VIN2 3 6 V– 4 5 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 150°C/ W ENABLE GN PACKAGE 16-LEAD PLASTIC SSOP NARROW TJMAX = 150°C, θJA = 120°C/ W ORDER PART NUMBER LT1675CMS8-1 MS8 PART MARKING LTGX ORDER PART NUMBER LT1675CS8-1 S8 PART MARKING 16751 ORDER PART NUMBER LT1675CGN GN PART MARKING 1675 Order Options Tape and Reel: Add #TR Lead Free: Add #PBF, Lead Free Tape and Reel: Add #TRPBF, Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. 16751fb 2 LT1675/LT1675-1 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the specified temperature range, otherwise specifications are at TA = 25°C. VS = ±5V, RL = ∞, VIN = 0V LT1675 (Pins 1, 2, 3, 6, 7, 8), LT1675-1 (Pins 1, 3), ENABLE = 0V, unless otherwise specified. PARAMETER CONDITIONS Output Offset Voltage Any Input Selected ● 20 50 mV Output Offset Matching Between Outputs R1 to R2, G1 to G2, B1 to B2 ● 5 20 mV Input Current Any Input Selected ● – 12 – 30 µA Input Resistance VIN = ±1V ● 100 700 kΩ PSRR VS =±2.6V to ±6V, Measured at Output ● 38 50 dB DC Gain Error 0V to 1V VIN = 1V, RL = ∞ VIN = 1V, RL = 150Ω VIN = 1V, RL = 75Ω ● ● 3 4 5 6 8 10 % % % DC Gain Error 0V to –1V VIN = –1V, RL = ∞ VIN = –1V, RL = 150Ω VIN = –1V, RL = 75Ω ● ● 3 4 8 6 8 20 % % % Output Voltage VIN = 2V, RL = ∞ VIN = 2V, RL = 150Ω VIN = 2V, RL = 75Ω ● ● ● 3.1 2.7 2.4 3.4 3.0 2.8 V V V VIN = – 2V, RL = ∞ VIN = – 2V, RL = 150Ω VIN = – 2V, RL = 75Ω ● ● ● – 3.1 – 2.6 – 2.3 – 3.3 – 3.0 – 2.6 V V V Disabled Output Impedance ENABLE Open ● 1.1 1.5 Maximum Output Current VIN = ±1V, VO = 0V ● 50 70 LT1675 ENABLE = 0V ENABLE = 4.7V ● ● 25 33 1 42 100 mA µA LT1675-1 ENABLE = 0V ENABLE = 4.7V ● ● 8 11 0.3 14 33 mA µA LT1675 ENABLE= 0V ● 450 600 µA LT1675-1 ENABLE= 0V ● 150 200 µA LT1675 SELECT = 0V ● 90 180 µA LT1675-1 SELECT = 0V ● 30 60 µA SELECT Low SELECT (See Truth Table) ● SELECT High SELECT (See Truth Table) ● Supply Current ENABLE Pin Current SELECT Pin Current MIN TYP MAX 2.0 kΩ mA 0.8 2 UNITS V V 16751fb 3 LT1675/LT1675-1 AC CHARACTERISTICS TA = 25°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. PARAMETER CONDITIONS Slew Rate VOUT = 5VP-P Full Power Bandwidth (Note 5) Small-Signal –3dB Bandwidth MIN TYP MAX UNITS 1100 V/µs VOUT =6VP-P 58 MHz Less Than 1dB Peaking 250 MHz Gain Flatness Less Than 0.1dB 70 MHz Gain Matching R to G to B R1 to R2, G1 to G2, B1 to B2, LT1675-1 VIN1 to VIN2 0.10 0.01 dB dB Channel-to-Channel Select Time Delay Time Switching Time R1 = 0V, R2 = 1V Measured from Time SELECT Pin Crosses Logic Threshold Time for VOUT to Go from 0V to 1V 5.0 2.5 ns ns Enable Time 10 ns Disable Time 100 ns Input Pin Capacitance 2 pF LT1675 2.2 pF LT1675-1 1.5 pF LT1675 2.1 pF LT1675-1 1.5 pF ENABLE Open 4.4 pF Small-Signal Rise Time VIN = 300mVP-P, RL = 100Ω 1.85 ns Propagation Delay VIN = 300mVP-P, RL = 100Ω 3 ns Overshoot VIN = 300mVP-P, RL = 100Ω 10 % SELECT Pin Capacitance ENABLE Pin Capacitance Output Pin Capacitance (Disabled) On-Channel to Off-Channel Crosstalk Measured at 10MHz 60 dB Chip Disable Crosstalk Measured at 10MHz, ENABLE Open 90 dB Channel Select Output Transient Measured Between Back Termination and Load 50 mVP-P Differential Gain (Note 6) 0.07 % Differential Phase (Note 6) 0.05 DEG 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°. Truth Table LT1675 SELECT LT1675-1 ENABLE RED OUT GREEN OUT BLUE OUT VOUT 1 0 RED 1 GREEN 1 BLUE 1 VIN1 0 0 RED 2 GREEN 2 BLUE 2 VIN2 X 1 OFF OFF OFF OFF 16751fb 4 LT1675/LT1675-1 U W TYPICAL PERFORMANCE CHARACTERISTICS Frequency Response with Capacitive Loads Gain and Phase vs Frequency 5 4 PHASE 6 –20 5 Gain vs Frequency 6.5 RL = 150Ω 4 –60 3 CL = 5pF 6.2 1 –80 2 CL = 3pF 6.1 6.3 GAIN (dB) –100 GAIN (dB) 0 PHASE (DEG) –40 GAIN 1 0 –120 –2 –140 –1 5.8 –160 –2 5.7 –180 –3 5.6 CL = 0pF RL = 150Ω –4 –5 100k 1M 10M 100M FREQUENCY (Hz) CL = 0pF –4 100k –200 1G 1M 10M 100M FREQUENCY (Hz) – 3dB Bandwidth vs Supply Voltage –40 CROSSTALK REJECTION (dB) 220 200 180 160 140 –50 –60 –80 –90 –100 –110 –130 100k 1M 10M 100M FREQUENCY (Hz) –30 –40 –50 –60 –80 100k 1G 70 –10 POWER SUPPLY REJECTION RATIO (dB) –30 –40 –50 –60 –70 –80 –90 –100 1G 1675 G06 1M 10M 100M FREQUENCY (Hz) Undistorted Output Swing vs Frequency 8 VS = ±5V TA = 25°C RL = 150Ω 60 50 40 VS = ±5V RL = 150Ω 7 +PSRR 30 1G 1675 G23 Power Supply Rejection Ratio vs Frequency Crosstalk Rejection vs Frequency (Disabled) 10M 100M FREQUENCY (Hz) –20 1675 G05 1675 G04 1M 0 –10 –70 100 RS = 75Ω RL = 150Ω RS = 75Ω RL = 150Ω G1 DRIVEN R1 SELECTED 10 –70 –120 6 100M Crosstalk Rejection vs Frequency RS = 75Ω RL = 150Ω R1 DRIVEN R2 SELECTED 120 –110 100k 1M 10M FREQUENCY (Hz) 20 OUTPUT VOLTAGE (VP-P) FREQUENCY (MHz) 240 5 4 3 SUPPLY VOLTAGE (±V) 100k 1675 G03 CROSSTALK REJECTION (dB) RL = 150Ω 260 –20 B 5.5 10k 1G –30 2 R G Crosstalk Rejection vs Frequency 300 280 5.9 1675 G02 1675 G01 CROSSTALK REJECTION (dB) 6.0 –1 –3 RL = 100Ω 6.4 CL = 10pF 2 3 GAIN (dB) 0 –PSRR 20 10 0 –10 6 5 4 3 –20 –30 100k 1M 10M 100M FREQUENCY (Hz) 1G 1675 G07 2 1M 10M 100M FREQUENCY (Hz) 1G 1675 G08 16751fb 5 LT1675/LT1675-1 U W TYPICAL PERFORMANCE CHARACTERISTICS 10k 15 –30 RL = 150Ω VO = 2VP-P DISABLED INPUT BIAS CURRENT (µA) 100 2ND –50 3RD –60 10 –70 10M 100M FREQUENCY (Hz) 10 FREQUENCY (MHz) 1 1G –3 SINKING VIN = –1V 60 VS = ±5V VIN = –1V 10 RL = 75Ω GAIN ERROR (%) 70 3 2 Negative DC Gain Error vs Temperature 12 3 SOURCING VIN = 1V 75 –1 0 1 INPUT VOLTAGE (V) –2 1675 G12 VS = ±5V VIN = 1V 80 RL = 150Ω 2 8 RL = 75Ω 6 4 1 2 55 RL = 150Ω 0 25 50 75 100 0 –50 –25 125 TEMPERATURE (°C) 0 25 50 75 100 40 0 –1 –2 SUPPLY CURRENT (mA) 1 14 30 125°C 25 –55°C 20 25°C 15 10 0 –4 –2 –1 1 0 INPUT VOLTAGE (V) 2 1675 G16 RL = ∞ 12 10 125°C 8 –55°C 25°C 6 4 2 5 –3 125 LT1675-1 Supply Current vs Supply Voltage RL = ∞ 35 RL = 75Ω RL = 150Ω 100 1675 G15 Supply Current vs Supply Voltage RL = ∞ 2 50 25 75 0 TEMPERATURE (°C) 1675 G14 Output Voltage vs Input Voltage VS = ±5V TA = 25°C 125 TEMPERATURE (°C) 1675 G13 4 0 –50 –25 SUPPLY CURRENT (mA) 50 –50 –25 OUTPUT VOLTAGE (V) –55°C 25°C –20 100 4 VS = ±5V GAIN ERROR (%) OUTPUT SHORT-CIRCUIT CURRENT (mA) 90 3 125°C –15 Positive DC Gain Error vs Temperature Output Short-Circuit Current vs Temperature 65 –5 –10 LTXXXX 1675 G10 1675 G09 85 0 –30 –80 1M 5 –25 ENABLED 1 100k VS = ±5V 10 –40 1k DISTORTION (dBc) OUTPUT IMPEDANCE (Ω) Input Bias Current vs Input Voltage 2nd and 3rd Harmonic Distortion vs Frequency Output Impedance vs Frequency 0 1 2 3 4 SUPPLY VOLTAGE (±V) 5 6 1675 G11 0 0 1 2 3 4 SUPPLY VOLTAGE (±V) 5 6 1675 G24 16751fb 6 LT1675/LT1675-1 U W TYPICAL PERFORMANCE CHARACTERISTICS Input Bias Current vs Temperature Output Offset Voltage vs Temperature –10 20 VS = ±5V OUTPUT OFFSET VOLTAGE (mV) INPUT BIAS CURRENT (µA) VS = ±5V VIN = 0V –11 –12 –13 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 15 10 5 0 –50 –25 125 50 25 75 0 TEMPERATURE (°C) 1675 G17 100 125 1675 G18 Slew Rate Toggling RED 2 to RED 1 3V SELECT PIN 10 RED 1 IN 1V/DIV RED OUT PIN 15 2V/DIV 1V/DIV 0V RED OUT PIN 15 1V/DIV RED 1 = 0V RED 2 = UNCORRELATED SINEWAVE RL = 150Ω, 10pF SCOPE PROBE MEASURED AT PIN 15 RL = 150Ω, 10pF SCOPE PROBE SR = 1100V/µs 1675 G19 Small-Signal Rise Time 1675 G20 Enable and Disable 50mV/DIV VGEN 5V 2V/DIV ENABLE PIN 9 0V VOUT 50mV/DIV RED OUT 0V PIN 15 2V/DIV 0V RL = 100Ω MEASURED WITH FET PROBES 1675 G21 ENABLE AND DISABLE OF UNCORRELATED SINEWAVE 1675 G22 RL = 150Ω 16751fb 7 LT1675/LT1675-1 U U U 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 is applied to this pin, VOUT RED will clip. The input must be terminated. 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. GREEN 1 (Pin 2): Green 1 Input. The 1V video input signal to be switched is applied to this pin. If 2V is applied to this pin, VOUT GREEN will clip. The input must be terminated. V – (Pins 11, 12): Negative Power Supply. Connect these pins to – 5V and bypass with a good tantalum capacitor (4.7µF). The pin may also require a 0.1µF or 0.01µF depending on layout. BLUE 1 (Pin 3): Blue 1 Input. The 1V video input signal to be switched is applied to this pin. If 2V is 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 is 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 is 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 is 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. 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 a 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 is 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 is 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. 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 a 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. 16751fb 8 LT1675/LT1675-1 U W U U 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 a 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. 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 Smallest Package and PC Board Space 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. 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 sensitive feedback node. The LT1675 fits into the small 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 1V/DIV SELECT PIN 10 CL = 20pF 2V/DIV CL = 10pF 0V RED OUT PIN 15 500mV/DIV CL = 0pF RED 1 = 1V, RED 2 = 0V MEASURED BETWEEN 75Ω BACK TERMINATION AND 75Ω LOAD Figure 1. Toggling at 25MHz MEASURED AT PIN 15 RL = 150Ω, 10pF SCOPE PROBE 1675 F02 1675 F01 Figure 2. Response to Capacitive Loads 16751fb 9 LT1675/LT1675-1 U W U U 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 75 Ω ⎟ ⎜ Gain Error (dB) = 6dB + 20log ⎜ n – 1 ⎟ dB 1575 Ω ⎜ 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 3V 1V/DIV SELECT PIN 10 1V/DIV SELECT PIN 10 0V 0V RED OUT PIN 15 0V 50mV/DIV RL = 150Ω, 10pF SCOPE PROBE 1675 F03 Figure 3. Input-Referred Switching Transient RED 1 IN 0V PIN 1 20mV/DIV RS = 75Ω 1675 F04 Figure 4. Switching Transient at RED 1 (Pin 1) 16751fb 10 LT1675/LT1675-1 U U W U APPLICATIONS INFORMATION n . . . 750Ω R1 75Ω AV = 2 OFF 75Ω 750Ω ⇒ 75Ω 750Ω OFF 75Ω 1575 n–1 750Ω R2 R2 75Ω ENABLE LT1675 #1 R1 75Ω 750Ω CABLE n = NUMBER OF LT1675s IN PARALLEL ON 750Ω 75Ω 1675 F05 R3 AV = +2 Figure 5. Off Channels Load the Cable Termination with 1575Ω Each 75Ω RED OUT 75Ω R4 ENABLE LT1675 #2 CHIP SELECT 1675 F06 74HC04 Figure 6. Two LT1675s Build a 4-Input RGB Router CHIP 5V SELECT 0V 1V RED 1 INPUT 5V/DIV 500mV/DIV 0V RED 0V OUTPUT 1V RED OUTPUT 1V/DIV 500mV/DIV 0V CHIP SELECT = 0V, IC #2 DISABLED Figure 7. 4-Input Router Response 1675 F07 RED 1 INPUT = 0V RED 3 INPUT = UNCORRELATED SINEWAVE 1675 F08 Figure 8. 4-Input Router Toggling 16751fb 11 LT1675/LT1675-1 U TYPICAL APPLICATIO S RGB Video Inverter LT1675 RED V+ +1 97.6Ω 75Ω CABLE +2 VIDEO IN VOUT RED +1 GREEN 75Ω 97.6Ω 75Ω +1 BLUE CABLE +2 VOUT GREEN 75Ω 97.6Ω 332Ω 75Ω CABLE 332Ω +1 VOUT BLUE +2 75Ω – + 332Ω V– +1 332Ω – SELECT +1 ENABLE + 5V 332Ω 10k 332Ω 1.25V – LT1634 10k 0.714V + COMPOSITE BLANKING 1675 TA03 LT1399 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 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. 16751fb 12 LT1675/LT1675-1 U TYPICAL APPLICATIO S Logo or “Bug” Inserter LT1675 RED V+ +1 75Ω CABLE 113Ω +2 VIDEO IN VOUT RED +1 GREEN 75Ω 75Ω CABLE 113Ω +2 +1 BLUE VOUT GREEN 75Ω 75Ω CABLE 113Ω +1 VOUT BLUE +2 75Ω SELECT A 0 0 1 1 SELECT B 0 1 0 1 V– +1 OUTPUT NO VIDEO, 100% WHITE VIDEO PLUS 66% WHITE VIDEO PLUS 33% WHITE VIDEO, NO WHITE SELECT +1 ENABLE A SELECT A SELECT B B LT1675 V+ +1 226Ω +2 +1 226Ω +1 +2 +1 +2 226Ω 5V +1 10k 1.25V LT1634 10k V– SELECT 0.714V +1 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 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. 16751fb 13 LT1675/LT1675-1 W W SI PLIFIED SCHE ATIC (LT1675-1, LT1675 One Channel) V+ V– RED 1 OFF RED 2 V– + V+ – RED VOUT 750Ω 750Ω ENABLE LOGIC V+ SELECT GND V– 1675 SS 16751fb 14 LT1675/LT1675-1 U PACKAGE DESCRIPTION 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) 0.015 ± 0.004 × 45° (0.38 ± 0.10) 0.007 – 0.0098 (0.178 – 0.249) 0.053 – 0.068 (1.351 – 1.727) 0.009 (0.229) REF 16 15 14 13 12 11 10 9 0.004 – 0.0098 (0.102 – 0.249) 0° – 8° TYP 0.016 – 0.050 (0.406 – 1.270) 0.008 – 0.012 (0.203 – 0.305) 0.229 – 0.244 (5.817 – 6.198) 0.025 (0.635) BSC * 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 0.150 – 0.157** (3.810 – 3.988) 1 2 3 4 7 6 5 5 6 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) 0.007 (0.18) 0.034 ± 0.004 (0.86 ± 0.102) 8 0° – 6° TYP 0.021 ± 0.006 (0.53 ± 0.015) SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) TYP 0.006 ± 0.004 (0.15 ± 0.102) 0.118 ± 0.004** (3.00 ± 0.102) 0.192 ± 0.004 (4.88 ± 0.10) MSOP (MS8) 1197 1 * 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 4 2 3 S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 8 7 6 5 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) *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 0.050 (1.270) TYP 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) SO8 0996 1 2 3 4 16751fb 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. 15 LT1675/LT1675-1 U 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 LT1675 B 6.04k QA V+ +1 1k 74LS163 6.04k 75Ω CABLE +2 R VOUT BLUE +1 QB B 75Ω 1k C 6.04k 75Ω G +1 QC D CABLE +2 VOUT RED 75Ω 1k LOAD COMPOSITE BLANKING +1 75Ω CABLE VOUT GREEN +2 BLACK RED BLUE MAGENTA CYAN GREEN WHITE YELLOW 75Ω –5V V– +1 SELECT 10k –0.285V 0.714V B +1 ENABLE 640Ω 0 0.714V R COMPOSITE SYNC 0 1675 TA04 0.714V G 0 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, red 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 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. RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT6555 650 MHz RGB Multiplexing Amplifier 2200V/µs Slew Rate, 2:1 Input MUX LT1203/LT1205 150MHz Video MUX 2-Input and 4-Input, 90dB Channel Separation, Wide Supply Range LT1204 4-Input Video MUX with 75MHz Current Feedback Amp Drives Cables, Adjustable Gain, 90dB Channel Separation LT1260 Low Cost Dual and Triple 130MHz Current Feedback Amp with Shutdown Drives Cables, Wide Supply Range, 0µA Shutdown Current LT1398/LT1399 Low Cost Dual and Triple 300MHz Current Feedback Amp with Shutdown Performance Upgrade for the LT1259/LT1260 16751fb 16 Linear Technology Corporation LT/LT 0605 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1998