LT1187MJ8

LT1187 Low Power Video Difference Amplifier FEATURES s s s s s s s s s s s DESCRIPTIO Differential or Single-Ended Gain Block (Adjustable) –3dB Bandwidth, AV = ± 2 50MHz Slew Rate 165V/µs Low Supply Current 13mA Output Current ± 20mA CMRR at 10MHz 40dB LT1193 Pin Compatible Low Cost Single 5V Operation Drives Cables Directly Output Shutdown The LT1187 is a difference amplifier optimized for operation on ± 5V, or a single 5V supply, and gain ≥ 2. This versatile amplifier features uncommitted high input impedance (+) and (–) inputs, and can be used in differential or single-ended configurations. Additionally, a second set of inputs give gain adjustment and DC control to the difference amplifier. The LT1187’s high slew rate, 165V/µs, wide bandwidth, 50MHz, and ± 20mA output current require only 13mA of supply current. The shutdown feature reduces the power dissipation to a mere 15mW, and allows multiple amplifiers to drive the same cable. The LT1187 is a low power version of the popular LT1193, and is available in 8-pin miniDIPs and SO packages. For applications with gains of 10 or more, see the LT1189 data sheet. APPLICATI s s s s S Line Receivers Video Signal Processing Cable Drivers Tape and Disc Drive Systems TYPICAL APPLICATI Cable Sense Amplifier for Loop Through Connections with DC Adjust 40 V IN 5V CABLE VDC 2 1 8 + – LT1187 + – 4 –5V 1k 7 6 VOUT Closed-Loop Gain vs Frequency 30 VOLTAGE GAIN (dB) 3 20 10 0 1k LT1187 • TA01 –10 0.1 U VS = ±5V RL = 1k 1 10 FREQUENCY (MHz) 100 LT1187 • TA02 UO UO 1 LT1187 ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW +/REF –IN +IN V– 1 2 3 4 8 7 6 5 –/FB V+ OUT S/D Total Supply Voltage (V + to V –) ............................. 18V Differential Input Voltage ........................................ ± 6V Input Voltage .......................................................... ± VS Output Short Circuit Duration (Note 1) ........ Continuous Operating Temperature Range LT1187M ..................................... – 55°C to 150°C LT1187C............................................. 0°C to 70°C Junction Temperature (Note 2) Plastic Package (CN8,CS8) ......................... 150°C Ceramic Package (CJ8,MJ8) ....................... 175°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................ 300°C ORDER PART NUMBER LT1187MJ8 LT1187CJ8 LT1187CN8 LT1187CS8 S8 PART MARKING 1187 J8 PACKAGE N8 PACKAGE 8-LEAD HERMETIC DIP 8-LEAD PLASTIC DIP S8 PACKAGE 8-LEAD PLASTIC SOIC LT1187 • POI01 TJMAX = 175°C, θJA = 100°C/W (J8) TJMAX = 150°C, θJA = 100°C/W (N8) TJMAX = 150°C, θJA = 150°C/W (S8) Consult factory for Industrial grade parts. +5V ELECTRICAL CHARACTERISTICS – SYMBOL VOS IOS IB en in RIN CIN VIN LIM CMRR PSRR VOUT PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Noise Voltage Input Noise Current Input Resistance Input Capacitance Input Voltage Limit Input Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Output Voltage Swing TA = 25°C, (Note 3) VS = ± 5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. CONDITIONS Either Input, (Note 4) SOIC Package Either Input Either Input fO = 10kHz fO = 10kHz Differential Either Input (Note 5) –2.5 VCM = – 2.5V to 3.5V VS = ± 2.375V to ± 8V VS = ± 5V, RL = 1k, AV = 50 VS = ± 8V, RL = 1k, AV = 50 VS = ± 8V, RL = 300Ω, AV = 50, (Note 3) GE SR FPBW BW tr, tf tPD ts Diff AV Diff Ph IS Gain Error Slew Rate Full Power Bandwidth Small Signal Bandwidth Rise Time, Fall Time Propagation Delay Overshoot Settling Time Differential Gain Differential Phase Supply Current Shutdown Supply Current Pin 5 at V – VO = ±1V, AV = 10, RL = 1k (Note 6, 10) VO = 1VP-P, (Note 7) AV = 10 AV = 50, VO = ±1.5V, 20% to 80% (Note 10) RL= 1k, VO = ±125mV, 50% to 50% VO = ± 50mV 3V Step, 0.1%, (Note 8) RL = 1k, AV = 4, (Note 9) RL = 1k, AV = 4, (Note 9) 150 100 70 70 ± 3.8 ± 6.7 ± 6.4 100 85 ± 4.0 ±7.0 ± 6.8 0.2 165 53 5.7 230 26 0 100 0.6 0.8 13 0.8 16 1.5 325 1.0 % V/µs MHz MHz ns ns % ns % DEGP-P mA mA MIN LT1187M/C TYP MAX 2.0 10 2.0 11 0.2 ± 0.5 65 1.5 100 2.0 ± 380 3.5 1.0 ±2.0 UNITS mV mV µA µA nV/√Hz pA/√Hz kΩ pF mV V dB dB V 2 U W U U WW W LT1187 +5V ELECTRICAL CHARACTERISTICS – SYMBOL IS/D tON tOFF PARAMETER Shutdown Pin Current Turn On Time Turn Off Time CONDITIONS Pin 5 at V – Pin 5 from V – to Ground, RL = 1k Pin 5 from Ground to V –, RL = 1k TA = 25°C, (Note 3) VS = ± 5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1187M/C TYP MAX 5 500 600 25 UNITS µA ns ns 5V ELECTRICAL CHARACTERISTICS + – SYMBOL VOS IOS IB CMRR VOUT SR BW IS IS/D PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Output Voltage Swing Slew Rate Small-Signal Bandwidth Supply Current Shutdown Supply Current Shutdown Pin Current Pin 5 at V – TA = 25°C, (Note 3) VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. CONDITIONS Either Input, (Note 4) SOIC Package Either Input Either Input 2.0 VCM = 2.0V to 3.5V RL = 300Ω to Ground (Note 3) VO = 1.5V to 3.5V AV = 10 VOUT High VOUT Low 70 3.6 100 4.0 0.15 130 5.3 12 0.8 5 Pin 5 at V – 15 1.5 25 0.4 V/µs MHz mA mA µA MIN LT1187M/C TYP MAX 2.0 2.0 0.2 ± 0.5 10 12 1.0 ± 2.0 3.5 UNITS mV mV µA µA V dB V +5V ELECTRICAL CHARACTERISTICS – SYMBOL VOS ∆VOS /∆T IOS IB CMRR PSRR VOUT PARAMETER Input Offset Voltage Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Output Voltage Swing Either Input Either Input CONDITIONS –55°C ≤ TA ≤ 125°C, (Note 3) VS = ± 5V, VREF = 0V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to ground, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1187M TYP MAX 2.0 8.0 0.2 ± 0.5 –2.5 VCM = – 2.5V to 3.5V VS = ±2.375V to ± 8V VS = ± 5V, RL = 1k, AV = 50 VS = ± 8V, RL = 1k, AV = 50 VS = ± 8V, RL = 300Ω, AV = 50, (Note 3) GE IS IS/D Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current Pin 5 at V –, (Note 11) Pin 5 at V – UNITS mV µV/°C µA µA V dB dB V Either Input, (Note 4) 15 1.5 ± 3.5 3.5 70 60 ± 3.7 ± 6.6 ± 6.4 100 85 ± 4.0 ± 7.0 ± 6.8 0.2 13 0.8 5 1.2 17 1.5 25 VO = ±1V, AV = 10, RL = 1k % mA mA µA 3 LT1187 +5V ELECTRICAL CHARACTERISTICS 0°C ≤ TA ≤ 70°C, (Note 3) – = ±5V, V = 0V, R = 900Ω from pins 6 to 8, R = 100Ω from pin 8 to ground, R = R V S REF FB1 FB2 L FB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1187C TYP MAX 2.0 9.0 0.2 ± 0.5 – 2.5 70 65 ± 3.7 ± 6.6 ± 6.4 100 85 ± 4.0 ± 7.0 ± 6.8 0.2 13 0.8 5 1.0 17 1.5 25 % mA mA µA 12 1.5 ± 3.5 3.5 UNITS mV µV/°C µA µA V dB dB V SYMBOL VOS ∆VOS /∆T IOS IB CMRR PSRR VOUT PARAMETER Input Offset Voltage Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Output Voltage Swing CONDITIONS Either Input, (Note 4) Either Input Either Input VCM = – 2.5V to 3.5V VS = ±2.375V to ±8V VS = ±5V, RL = 1k, AV = 50 VS = ±8V, RL = 1k, AV = 50 VS = ±8V, RL = 300Ω, AV = 50, (Note 3) GE IS IS/D Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current VO = ±1V, AV = 10, RL = 1k Pin 5 at V , (Note 11) Pin 5 at V – – 5V ELECTRICAL CHARACTERISTICS + – SYMBOL VOS ∆VOS/∆T IOS IB CMRR VOUT IS IS/D PARAMETER Input Offset Voltage Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common-Mode Rejection Ratio Output Voltage Swing Supply Current Shutdown Supply Current Shutdown Pin Current Either Input Either Input CONDITIONS 0°C ≤ TA ≤ 70°C, (Note 3) VS = 5V, VS = 0V, VREF = 2.5V, RFB1 = 900Ω from pins 6 to 8, RFB2 = 100Ω from pin 8 to VREF, RL = RFB1 + RFB2 = 1k, CL ≤ 10pF, pin 5 open. MIN LT1187C TYP MAX 2.0 2.0 9.0 0.2 ± 0.5 2.0 VCM = 2.0V to 3.5V RL = 300Ω to Ground (Note 3) Pin 5 at V –, (Note 11) Pin 5 at V – VOUT High VOUT Low 70 3.5 100 4.0 0.15 12 0.8 5 0.4 16 1.5 25 mA mA µA 1.5 ± 3.5 3.5 12.0 13.0 UNITS mV mV µV/°C µA µA V dB V Either Input, (Note 4) SOIC Package Note 1: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted continuously. Note 2: TJ is calculated from the ambient temperature T A and power dissipation PD according to the following formulas: LT1187MJ8,LT1187CJ8: TJ = TA + (PD × 100°C/W) LT1187CN8: TJ = TA + (PD × 100°C/W) LT1187CS8: TJ = TA + (PD × 150°C/W) Note 3: When RL = 1k is specified, the load resistor is RFB1 + RFB2, but when RL = 300 Ω is specified, then an additional 430 Ω is added to the output such that (RFB1 + RFB2) in parallel with 430Ω is RL = 300Ω. Note 4: VOS measured at the output (pin 6) is the contribution from both input pair, and is input referred. Note 5: VIN LIM is the maximum voltage between –V IN and +VIN (pin 2 and pin 3) for which the output can respond. Note 6: Slew rate is measured between ±0.5V on the output, with a VIN step of ±0.75V, AV = 3 and RL = 1k. Note 7: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2πVp. Note 8: Settling time measurement techniques are shown in “Take the Guesswork Out of Settling Time Measurements,” EDN, September 19, 1985. Note 9: NTSC (3.58MHz). Note 10: AC parameters are 100% tested on the ceramic and plastic DIP packaged parts (J8 and N8 suffix) and are sample tested on every lot of the SO packaged parts (S8 suffix). Note 11: See Application section for shutdown at elevated temperatures. Do not operate shutdown above T J > 125°C. 4 LT1187 TYPICAL PERFOR A CE CHARACTERISTICS Input Bias Current vs Common-Mode Voltage 3.0 VS = ±5V 2.5 INPUT BIAS CURRENT (µA) 2.0 1.5 1.0 0.5 0 –55°C 25°C 125°C –5 –4 –3 –2 –1 0 1 2 3 COMMON-MODE VOLTAGE (V) 4 5 COMMON-MODE RANGE (V) INPUT BIAS CURRENT (nA) –0.5 Equivalent Input Noise Voltage vs Frequency VS = ±5V TA = 25°C RS = 0Ω EQUIVALENT INPUT NOISE CURRENT (pA/√Hz) EQUIVALENT INPUT NOISE VOLTAGE (nV/√Hz) 600 500 400 300 200 100 0 10 100 1k 10k FREQUENCY (Hz) 100k 8 6 4 2 0 10 100 1k 10k FREQUENCY (Hz) 100k SUPPLY CURRENT (mA) Shutdown Supply Current vs Temperature 6 SHUTDOWN SUPPLY CURRENT (mA) VS = ±5V 5 GAIN ERROR (%) 4 3 VS/D = –VEE + 0.2V 2 1 VS/D = –VEE 0 –50 –25 50 0 25 75 TEMPERATURE (°C) 100 125 –0.20 –50 –25 –0.05 VS/D = – VEE + 0.6V VS/D = –VEE + 0.4V OPEN-LOOP GAIN (kV/V) UW LT1187 • TPC01 Input Bias Current vs Temperature 100 +IB Common-Mode Voltage vs Temperature V+ –0.5 V + = 1.8V TO 9V 0 –1.0 –1.5 –2.0 –100 IOS –200 –IB 2.0 1.5 1.0 0.5 V– – 50 –25 V + = –1.8V TO –9V –300 – 400 –50 –25 0 25 75 50 TEMPERATURE (°C) 100 125 0 25 75 50 TEMPERATURE (°C) 100 125 LT1187 • TPC02 LT1187 • TPC03 Equivalent Input Noise Current vs Frequency 12 10 VS = ±5V TA = 25°C RS = 100k 16 Supply Current vs Supply Voltage 14 – 55°C 25°C 12 125°C 10 8 0 2 4 6 8 ±SUPPLY VOLTAGE (V) 10 LT1187 • TPC04 LT1187 • TPC05 LT1187 • TPC06 Gain Error vs Temperature 0 VS = ± 5V VOUT = ± 2V AV = 10 RL = 1k 8 Open-Loop Gain vs Temperature VS = ± 5V VO = ± 3V 6 RL = 1k –0.10 4 RL = 500Ω –0.15 2 0 25 50 75 TEMPERATURE (°C) 100 125 0 –50 –25 25 75 0 50 TEMPERATURE (°C) 100 125 LT1187 • TPC07 LT1187 • TPC08 LT1187 • TPC09 5 LT1187 TYPICAL PERFOR A CE CHARACTERISTICS Gain, Phase vs Frequency 100 80 VOLTAGE GAIN (dB) OPEN-LOOP VOLTAGE GAIN (V/V) 80 PHASE MARGIN (DEG) GAIN BANDWIDTH PRODUCT (MHz) PHASE 60 40 20 0 –20 100k GAIN 1M 10M FREQUENCY (Hz) Gain Bandwidth Product and Unity Gain Phase Margin vs Temperature 60 65 VS = ±5V RL = 1k GAIN BANDWIDTH PRODUCT 100 COMMON-MODE REJECTION RATIO (dB) GAIN BANDWIDTH PRODUCT (MHz) 50 55 OUTPUT IMPEDANCE (Ω) 40 UNITY GAIN PHASE MARGIN 30 –50 –25 25 75 0 50 TEMPERATURE (°C) Power Supply Rejection Ratio vs Frequency 80 36 OUTPUT SHORT CIRCUIT CURRENT (mA) POWER SUPPLY REJECTION RATIO (dB) OUTPUT SATURATION VOLTAGE (V) 60 +PSRR –PSRR VS = ± 5V TA = 25°C VRIPPLE = ± 300mV 40 20 0 –20 1k 10k 1M 100k FREQUENCY (Hz) 10M 100M 6 UW VS = ±5V TA = 25°C RL = 1k 100M LT1187 • TPC11 Open-Loop Voltage Gain vs Load Resistance 100 16k VS = ±5V VO = ±3V TA = +25˚C 60 Gain Bandwidth Product vs Supply Voltage AV = 20dB TA = – 55°C TA = 25°C 50 TA = 125˚C 12k 60 40 20 0 8k 40 4k –20 0 100 30 1k LOAD RESISTANCE (Ω) 10k 0 2 4 8 6 ±SUPPLY VOLTAGE (V) 10 LT1187 • TPC12 Output Impedance vs Frequency 80 VS = ±5V TA = 25°C Common-Mode Rejection Ratio vs Frequency VS = ±5V TA = 25°C RL = 1k 70 PHASE MARGIN (DEG) 10 60 45 1.0 AV = 10 50 AV = 2 35 125 0.1 40 100 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 30 100k 1M 10M FREQUENCY (Hz) 100M LT1187 • TPC15 LT1187 • TPC13 LT1187 • TPC14 Output Short Circuit Current vs Temperature VS = ± 5V 35 34 33 32 31 30 – 50 V+ – 0.7 –0.8 –0.9 ± Output Swing vs Supply Voltage 125°C 25°C –1.0 –1.1 0.5 0.4 0.3 0.2 0.1 V– 0 2 –55°C 4 6 8 ±SUPPLY VOLTAGE (V) 10 –55°C RL = 1k ±1.8V ≤ VS ≤ ± 9V 125°C 25°C –25 50 0 25 75 TEMPERATURE (°C) 100 125 LT1187 • TPC16 LT1187 • TPC17 LT1187 • TPC18 LT1187 TYPICAL PERFOR A CE CHARACTERISTICS Output Voltage Swing vs Load Resistance 5 VS = ± 5V OUTPUT VOLTAGE SWING (V) 3 TA = – 55°C TA = 25°C 1 TA = 125°C 250 VS = ± 5V RL = 1k VO = ± 0.5V AV = 2 OUTPUT VOLTAGE STEP (V) SLEW RATE (V/µs) –1 TA = 25°C –3 TA = 125°C TA = – 55°C –5 10 100 LOAD RESISTANCE (Ω) 1000 LT1187 • TPC19 Harmonic Distortion vs Output Voltage –30 –35 DISTORTION (dBc) –40 –45 –50 –55 –60 0 1 4 3 5 2 OUTPUT VOLTAGE (VP-P) 6 7 VS = ± 5V TA = 25°C RL = 1k f = 1MHz AV = 10 Small-Signal Transient Response AV = 2, RFB = 1k, OVERSHOOT = 25% LT1187 • TPC24 UW Slew Rate vs Temperature 4 Output Voltage Step vs Settling Time, AV = 2 VS = ± 5V TA = 25°C RL = 1k 2 10mV –SLEW RATE 200 +SLEW RATE 0 –2 10mV 150 –50 –25 –4 0 25 50 75 TEMPERATURE (°C) 100 125 40 50 60 70 80 SETTLING TIME (ns) 90 100 LT1187 • TPC20 LT1187 • TPC21 Large-Signal Transient Response HD3 HD2 INPUT IN LIMITING, AV = 3, SR = 180V/ µs LT1187 • TPC22 LT1187 • TPC23 Small-Signal Transient Response AV = 2, RFB = 1k, OVERSHOOT = 25% LT1187 • TPC25 7 LT1187 APPLICATIO S I FOR ATIO U Power Supply Bypassing The LT1187 is quite tolerant of power supply bypassing. In some applications a 0.1µF ceramic disc capacitor placed 1/2 inch from the amplifier is all that is required. In applications requiring good settling time, it is important to use multiple bypass capacitors. A 0.1µF ceramic disc in parallel with a 4.7µF tantalum is recommended. Calculating the Output Offset Voltage Both input stages contribute to the output offset voltage at pin 6. The feedback correction forces balance in the input stages by introducing an Input VOS at pin 8. The complete expression for the output offset voltage is: VOUT = (VOS + IOS(RS) + IB(RREF)) × (RFB+RG)/RG + IB(RFB) RS represents the input source resistance, typically 75Ω, and RREF represents the finite source impedance from the DC reference voltage, for VREF grounded, RREF = 0Ω. The IOS is normally a small contributor and the expression simplifies to: VOUT = VOS(RFB+RG)/RG + IB(RFB) If RFB is limited to 1k the last term of the equation contributes only 2mV, since IB is less than 2µA. RFB + RG RG 6 VOUT The primary use of the LT1187 is in converting high speed differential signals to a single-ended output. The LT1187 video difference amplifier has two uncommitted high input impedance (+) and (–) inputs. The amplifier has another set of inputs which can be used for reference and feedback. Additionally, this set of inputs give gain adjust and DC control to the difference amplifier. The voltage gain of the LT1187 is set like a conventional operational amplifier. Feedback is applied to pin 8, and it is optimized for gains of 2 or greater. The amplifier can be operated single-ended by connecting either the (+) or (–) inputs to the +/REF (pin 1). The voltage gain is set by the resistors: (RFB + RG)/RG. Like the single-ended case, the differential voltage gain is set by the external resistors: (RFB + RG)/RG. The maximum input differential signal for which the output will respond is approximately ±0.38V. S/D 5 VIN S/D V+ V IN 3 7 + 2 – LT1187 1 +/REF 8 –/FB 4 V– RFB AV = + 6 VOUT RG RFB + RG RG S/D V+ 5 3 7 + 2 – LT1187 1 +/REF 8 –/FB 4 V– RFB RFB + RG RG VIN DIFF VIN 6 VIN DIFF VOUT V IN RG RG VO = (VIN DIFF + VIN) VO = 8 W RG U U V+ 5 3 7 + 2 – LT1187 1 +/REF 8 –/FB 4 V– RFB AV = – 7 V+ 6 S/D V+ 5 3 7 + 2 – LT1187 1 +/REF 8 –/FB 4 V– RFB RFB 6 VOUT Q1 3 Q2 RE 1.1k Q3 Q4 RE 1.1k 8 RG + RS 2 – RS + 1 REF RREF 345µA 350µA 4 V– ILT1187 • AI02 ( RFB + RG RG (V IN DIFF – ( R (V G RFB IN LT1187 • AI01 Figure 1. Simplified Input Stage Schematic LT1187 APPLICATIO S I FOR ATIO Operating with Low Closed-Loop Gains The LT1187 has been optimized for closed-loop gains of 2 or greater. For a closed-loop gain of 2 the response peaks about 2dB. Peaking can be eliminated by placing a capacitor across the feedback resistor, (feedback zero). This peaking shows up as time domain overshoot of about 25%. Closed-Loop Voltage Gain vs Frequency 9 8 7 6 5 4 3 2 1 0 –1 100k VS = ± 5V TA = 25°C AV = 2 RFB = 900Ω RG = 900Ω 1M 10M FREQUENCY (Hz) 100M LT1187 • AI03 CLOSED-LOOP VOLTAGE GAIN (dB) CFB = 0pF CFB = 5pF CFB = 10pF Small-Signal Transient Response AV = 2, OVERSHOOT = 25%, RFB = RG = 1k LT1187 • AI04 U Small-Signal Transient Response AV = 2, WITH 8pF FEEDBACK CAPACITOR LT1187 • AI05 W U U Extending the Input Range Figure 1 shows a simplified schematic of the LT1187. In normal operation the REF pin 1 is grounded or taken to a DC offset control voltage and differential signals are applied between pins 2 and 3. The input responds linearly until all of the 345µA current flows through the 1.1k resistor and Q1 (or Q2) turns off. Therefore the maximum input swing is 380mVP or 760mVP-P. The second differential pair, Q3 and Q4, is running at slightly larger current so that when the first input stage limits, the second stage remains biased to maintain the feedback. Occasionally it is necessary to handle signals larger than 760mVP-P at the input. The LT1187 input stage can be tricked to handle up to 1.5VP-P. To do this, it is necessary to ground pin 3 and apply the differential input signal between pin 1 and 2. The input signal is now applied across two 1.1k resistors in series. Since the input signal is applied to both input pairs, the first pair will run out of bias current before the second pair, causing the amplifier to go open-loop. The results of this technique are shown in the following scope photo. 9 LT1187 APPLICATIO S I FOR ATIO LT1187 in Unity Gain A B C (A) STANDARD INPUTS, PINS 2 TO 3, VIN = 1.0VP-P (B) EXTENDED INPUTS, PINS 2 TO 2, VIN = 1.0VP-P (C) EXTENDED INPUTS, PINS 1 TO 2, VIN = 2.0VP-P LT1187 • AI06 Using the Shutdown Feature The LT1187 has a unique feature that allows the amplifier to be shutdown for conserving power, or for multiplexing several amplifiers onto a common cable. The amplifier will shutdown by taking pin 5 to V –. In shutdown, the amplifier dissipates 15mW while maintaining a true high impedance output state of 20k in parallel with the feedback resistors. For MUX applications, the amplifiers may be configured inverting, noninverting, or differential. When the output is loaded with as little 1k from the amplifier’s feedback resistors, the amplifier shuts off in 600ns. This shutoff can be under the control of HC CMOS operating between 0V and –5V. The ability to maintain shutoff is shown on the curve Shutdown Supply Current vs Temperature in the Typical 1MHz Sine Wave Gated Off with Shutdown Pin SHUTDOWN VOUT AV = 2, RFB = RG = 1k LT1187 • AI07 LT1187 • AI08 10 U Performance Characteristics section. At very high elevated temperature it is important to hold the shutdown pin close to the negative supply to keep the supply current from increasing. Send Color Video Over Twisted-Pair With an LT1187 it is possible to send and receive color composite video signals more than 1000 feet on a low cost twisted-pair. A bidirectional “video bus” consists of the LT1195 op amp and the LT1187 video difference amplifier. A pair of LT1195s at TRANSMIT 1, is used to generate differential signals to drive the line which is back-terminated in its characteristic impedance. The LT1187, twistedpair receiver, converts signals from differential to singleended. Topology of the LT1187 provides for cable compensation at the amplifier’s feedback node as shown. In this case, 1000 feet of twisted-pair is compensated with 1000pF and 50Ω to boost the 3dB bandwidth of the system from 750kHz to 4MHz. This bandwidth is adequate to pass a 3.58MHz chroma subcarrier, and the 4.5MHz sound subcarrier. Attenuation in the cable can be compensated by lowering the gain set resistor RG. At TRANSMIT 2, another pair of LT1195s serve the dual function to provide cable termination via low output impedance, and generate differential signals for TRANSMIT 2. Cable termination is made up of a 15Ω and 33Ω attenuator to reduce the differential input signal to the LT1187. Maximum input signal for the LT1187 is 760mVP-P. 1.5MHz Square Wave Input and Unequalized Response Through 1000 Feet of Twisted-Pair W U U LT1187 APPLICATIO S I FOR ATIO U Multiburst Pattern Passed Through 1000 Feet of Twisted-Pair LT1187 • AI10 1.5MHz Square Wave Input and Equalized Response Through 1000 Feet of Twisted-Pair TRANSMIT 1 3 75Ω 1k 2 + LT1195 6 6 – 1k 1k 1k 1k 1k 2 – LT1195 6 33Ω S/D 33Ω 33Ω 15Ω 15Ω 15Ω 1000 FEET TWISTED-PAIR 33Ω S/D 3 2 1 8 1000pF 50Ω RG 300Ω RECEIVE 1 6 LT1195 3 + + – LT1187 + – R 5 FB 75Ω 6 300Ω RECEIVE 2 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. W 3 2 1 8 U U LT1187 • AI09 Bidirectional Video Bus TRANSMIT 2 3 1k 75Ω + LT1195 – 2 1k – + + – + – 5 LT1187 2 3 15Ω 6 75Ω 1000pF RG 300Ω 50Ω RFB 300Ω LT1187 • AI11 11 LT1187 SI PLIFIED SCHE ATIC 7 V+ VBIAS VBIAS +3 CFF –2 +V 5 S/D 1 +/REF 8 –/FB * SUBSTRATE DIODE, DO NOT FORWARD BIAS PACKAGE DESCRIPTIO 0.290 – 0.320 (7.366 – 8.128) J8 Package 8-Lead Hermetic DIP 0.008 – 0.018 (0.203 – 0.460) 0.385 ± 0.025 (9.779 ± 0.635) 0.300 – 0.320 (7.620 – 8.128) N8 Package 8-Lead Plastic DIP 0.009 – 0.015 (0.229 – 0.381) ( +0.025 0.325 –0.015 +0.635 8.255 –0.381 ) 0.010 – 0.020 × 45° (0.254 – 0.508) S8 Package 8-Lead Plastic SOIC 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U W W CM +V 6 VOUT * 4 V– LT1187 • SS Dimensions in inches (millimeters) unless otherwise noted. 0.405 (10.287) MAX 8 7 6 5 CORNER LEADS OPTION (4 PLCS) 0.200 (5.080) MAX 0.015 – 0.060 (0.381 – 1.524) 0.005 (0.127) MIN 0.023 – 0.045 (0.58 – 1.14) HALF LEAD OPTION 0° – 15° 0.045 – 0.065 (1.14 – 1.65) FULL LEAD OPTION 0.025 (0.635) RAD TYP 1 2 3 0.220 – 0.310 (5.588 – 7.874) 4 0.045 – 0.065 (1.14 – 1.65) 0.014 – 0.026 (0.360 – 0.660) 0.125 3.175 0.100 ± 0.010 MIN (2.540 ± 0.254) 0.045 – 0.065 (1.143 – 1.651) 0.130 ± 0.005 (3.302 ± 0.127) 0.400 (10.160) MAX 8 7 6 5 0.065 (1.651) TYP 0.125 (3.175) MIN 0.020 (0.508) MIN 0.250 ± 0.010 (6.350 ± 0.254) 0.045 ± 0.015 (1.143 ± 0.381) 0.100 ± 0.010 (2.540 ± 0.254) 1 2 3 4 0.018 ± 0.003 (0.457 ± 0.076) 0.189 – 0.197 (4.801 – 5.004) 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0.228 – 0.244 (5.791 – 6.197) 8 7 6 5 0.008 – 0.010 (0.203 – 0.254) 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) BSC 0.150 – 0.157 (3.810 – 3.988) 1 2 3 4 BA/LT/GP 0293 10K REV0 © LINEAR TECHNOLOGY CORPORATION 1993