LT1187CN8

LT1187 Low Power Video Difference Amplifier FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION The LT®1187 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/ms, 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. , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 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 Available in 8-Lead PDIP and SO Packages APPLICATIONS ■ ■ ■ ■ Line Receivers Video Signal Processing Cable Drivers Tape and Disc Drive Systems TYPICAL APPLICATION Cable Sense Amplfier for Loop Through Connections with DC Adjust V IN 5V 3 CABLE VDC 2 1 8 VOLTAGE GAIN (dB) 40 Closed-Loop Gain vs Frequency VS = ±5V RL = 1k + – + – 30 6 7 LT1187 4 –5V 1k VOUT 20 10 0 1k –10 0.1 LT1187 • TA01 1 10 FREQUENCY (MHz) 100 LT1187 • TA02 1187fa 1 LT1187 ABSOLUTE MAXIMUM RATINGS Total Supply Voltage (V+ to V–) .................................18V Differential Input Voltage ..........................................±6V Input Voltage.............................................................±VS Output Short-Circuit Duration (Note 2) .........Continuous Operating Temperature Range LT1187C .................................................. 0°C to 70°C LT1187I ............................................... –40°C to 85°C LT1187M (OBSOLETE) ...................... –55°C to 150°C Junction Temperature (Note 3) Plastic Packages (CN8, CS8) ............................ 150°C Ceramic Packages (CJ8, MJ8) (OBSOLETE) ..... 175°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C (Note 1) PACKAGE/ORDER INFORMATION TOP VIEW +/REF 1 –IN 2 +IN 3 V– 4 8 7 6 5 –/FB V+ OUT S/D ORDER PART NUMBER LT1187CN8 LT1187CS8 LT1187IN8 S8 PART MARKING 1187 LT1187MJ8 LT1187CJ8 N8 PACKAGE S8 PACKAGE 8-LEAD PDIP 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 100°C/W (N8) TJMAX = 150°C, θJA = 150°C/W (S8) J8 PACKAGE 8-LEAD CERDIP TJMAX = 175°C, θJA = 100°C/W Consider the N8 or S8 Packages for Alternate Source OBSOLETE PACKAGE 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. ±5V ELECTRICAL CHARACTERISTICS SYMBOL VOS IOS IB en in RIN CIN VIN LIM CMRR PSRR VOUT PARAMETERS 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 4) 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 5) S8 Package Either Input Either Input fO = 10kHz fO = 10kHz Differential Either Input (Note 6) 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 4) VO = ±1V, AV = 10, RL = 1k (Notes 7, 11) VO = 1VP-P (Note 8) AV = 10 AV = 50, VO = ±1.5V, 20% to 80% (Note 11) RL= 1k, VO = ±125mV, 50% to 50% VO = ±50mV 3V Step, 0.1% (Note 9) RL = 1k, AV = 4 (Note 10) RL = 1k, AV = 4 (Note 10) MIN LT1187C/I/M MAX 2.0 2.0 0.2 ±0.5 65 1.5 100 2.0 ±380 100 85 ±4.0 ±7.0 ±6.8 0.2 165 53 5.7 230 26 0 100 0.6 0.8 MAX 10 11 1.0 ±2.0 UNITS mV µA µA nV/√Hz pA/√Hz kΩ pF mV V dB dB V V V % V/µs MHz MHz ns ns % ns % DEGP-P 1187fa –2.5 70 70 ±3.8 ±6.7 ±6.4 100 3.5 GE SR FPBW BW tr, tf tPD ts Diff AV Diff Ph Gain Error Slew Rate Full Power Bandwidth Small-Signal Bandwidth Rise Time, Fall Time Propagation Delay Overshoot Settling Time Differential Gain Differential Phase 1.0 150 325 2 LT1187 ±5V ELECTRICAL CHARACTERISTICS SYMBOL IS IS/D tON tOFF PARAMETERS Supply Current Shutdown Supply Current Shutdown Pin Current Turn-On Time Turn-On Time CONDITIONS Pin 5 at V– Pin 5 at V– Pin 5 from V– to Ground, RL = 1k Pin 5 from Ground to V–, RL = 1k TA = 25°C (Note 4) 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 LT1187C/I/M MAX 13 0.8 5 500 600 MAX 16 1.5 25 UNITS mA mA µA ns ns TA = 25°C (Note 4) 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. 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 CONDITIONS Either Input (Note 5) SO Package Either Input Either Input VCM = 2.0V to 3.5V RL = 300Ω to Ground (Note 4) VO = 1.5V to 3.5V AV = 10 Pin 5 at V– Pin 5 at V– MIN LT1187C/I/M TYP 2.0 2.0 0.2 ±0.5 100 4.0 0.15 130 5.3 12 0.8 5 MAX 10 12 1.0 ±2.0 3.5 UNITS mV mV µA µA V dB V V V/µs MHz mA mA µA 5V ELECTRICAL CHARACTERISTICS + – VOUT High VOUT Low 2.0 70 3.6 0.4 15 1.5 25 ±5V ELECTRICAL CHARACTERISTICS SYMBOL VOS ΔVOS/ΔT 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 –55°C ≤ TA ≤ 125°C (Note 4) 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 5) 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 4) VO = ±1V, AV = 10, RL = 1k Pin 5 at V– (Note 12) Pin 5 at V– –2.5 70 60 ±3.7 ±6.6 ±6.4 MIN LT1187M TYP 2.0 8.0 0.2 ±0.5 100 85 ±4.0 ±7.0 ±6.8 0.2 13 0.8 5 MAX 15 1.5 ±3.5 3.5 UNITS mV mV/°C µA µA V dB dB V V V % mA mA µA GE IS IS/D Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current 1.2 17 1.5 25 1187fa 3 LT1187 ±5V ELECTRICAL CHARACTERISTICS SYMBOL VOS ΔVOS/ΔT 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 0°C ≤ TA ≤ 70°C (LT1187C) –40°C ≤ TA ≤ 85°C (LT1187I) (Note 4) 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 5) 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 4) VO = ±1V, AV = 10, RL = 1k Pin 5 at V– (Note 12) Pin 5 at V– –2.5 70 65 ±3.7 ±6.6 ±6.4 MIN LT1187C/I TYP 2.0 9.0 0.2 ±0.5 100 85 ±4.0 ±7.0 ±6.8 0.2 13 0.8 5 MAX 12 1.5 ±3.5 3.5 UNITS mV mV/°C µA µA V dB dB V V V % mA mA µA GE IS IS/D Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current 1.0 17 1.5 25 0°C ≤ TA ≤ 70°C (LT1187C) –40°C ≤ TA ≤ 85°C (LT1187I) (Note 4) 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. SYMBOL VOS ΔVOS/ΔT 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 CONDITIONS Either Input (Note 5) SO Package Either Input Either Input VCM = 2.0V to 3.5V RL = 300Ω to Ground (Note 4) Pin 5 at V– (Note 12) Pin 5 at V– 2.0 70 3.5 MIN LT1187C/I TYP 2.0 2.0 9.0 0.2 ±0.5 100 4.0 0.15 12 0.8 5 MAX 12.0 13.0 1.5 ±3.5 3.5 UNITS mV mV µV/°C µA µA V dB V V mA mA µA 5V ELECTRICAL CHARACTERISTICS + – VOUT High VOUT Low 0.4 16 1.5 25 Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted continuously. Note 3: TJ is calculated from the ambient temperature TA 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 4: When RL = 1k is specified, the load resistor is RFB1 + RFB2, but when RL = 300Ω is specified, then an additional 430Ω is added to the output such that (RFB1 + RFB2) in parallel with 430Ω is RL = 300Ω. Note 5: VOS measured at the output (Pin 6) is the contribution from both input pair and is input referred. Note 6: VIN LIM is the maximum voltage between –VIN and +VIN (Pin 2 and Pin 3) for which the output can respond. Note 7: Slew rate is measured between ±0.5V on the output, with a VIN step of ±0.75V, AV = 3 and RL = 1k. Note 8: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2πVP. Note 9: Settling time measurement techniques are shown in “Take the Guesswork Out of Settling Time Measurements,” EDN, September 19, 1985. Note 10: NTSC (3.58MHz). Note 11: 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 12: See Application section for shutdown at elevated temperatures. Do not operate shutdown above TJ > 125°C. 1187fa 4 LT1187 TYPICAL PERFORMANCE CHARACTERISTICS Input Bias Current vs Common Mode Voltage 3.0 2.5 INPUT BIAS CURRENT (µA) 2.0 1.5 1.0 0.5 0 –0.5 – 5 – 4 –3 –2 –1 0 1 2 3 COMMON MODE VOLTAGE (V) 4 5 –55°C 25°C 125°C – 400 –50 –25 50 0 25 75 TEMPERATURE (°C) 100 125 INPUT BIAS CURRENT (nA) 0 VS = ±5V 100 +IB Input Bias Current vs Temperature V+ –0.5 COMMON MODE RANGE (V) –1.0 –1.5 –2.0 Common Mode Voltage vs Temperature V + = 1.8V TO 9V –100 IOS –200 –IB 2.0 1.5 1.0 0.5 V– – 50 –25 0 25 75 50 TEMPERATURE (°C) 100 125 V + = –1.8V TO –9V –300 LT1187 • TPC01 LT1187 • TPC02 LT1187 • TPC03 Equivalent Input Noise Voltage vs Frequency 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 VS = ±5V TA = 25°C RS = 0Ω 12 10 8 6 4 2 0 Equivalent Input Noise Current vs Frequency VS = ±5V TA = 25°C RS = 100k SUPPLY CURRENT (mA) 16 Supply Current vs Supply Voltage 14 – 55°C 25°C 12 125°C 10 10 100 1k 10k FREQUENCY (Hz) 100k 8 0 2 4 6 8 ± SUPPLY VOLTAGE (V) 10 LT1187 • TPC04 LT1187 • TPC05 LT1187 • TPC06 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 VS/D = – VEE + 0.6V VS/D = –VEE + 0.4V –0.05 0 Gain Error vs Temperature VS = ± 5V VOUT = ± 2V AV = 10 RL = 1k 8 Open-Loop Gain vs Temperature VS = ± 5V VO = ± 3V RL = 1k OPEN-LOOP GAIN (kV/V) 6 –0.10 4 RL = 500Ω –0.15 2 –0.20 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 0 –50 –25 0 50 25 75 TEMPERATURE (°C) 100 125 LT1187 • TPC07 LT1187 • TPC08 LT1187 • TPC09 1187fa 5 LT1187 TYPICAL PERFORMANCE CHARACTERISTICS Gain, Phase vs Frequency 100 80 VOLTAGE GAIN (dB) 60 40 20 0 –20 100k GAIN PHASE VS = ±5V TA = 25°C RL = 1k 100 80 PHASE MARGIN (DEG) 60 40 20 0 –20 1M 10M FREQUENCY (Hz) 100M LT1187 • TPC11 Open-Loop Voltage Gain vs Load Resistance 16k OPEN-LOOP VOLTAGE GAIN (V/V) GAIN BANDWIDTH PRODUCT (MHz) 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 8k 40 4k 0 100 30 1k LOAD RESISTANCE (Ω) 10k LT1187 • TPC10 0 2 4 8 6 ± SUPPLY VOLTAGE (V) 10 LT1187 • TPC12 Gain Bandwidth Product and Unity Gain Phase Margin vs Temperature 60 GAIN BANDWIDTH PRODUCT (MHz) VS = ±5V RL = 1k 65 100 Output Impedance vs Frequency COMMON-MODE REJECTION RATIO (dB) VS = ±5V TA = 25°C 80 Common Mode Rejection Ratio vs Frequency VS = ±5V TA = 25°C RL = 1k 50 GAIN BANDWIDTH PRODUCT 55 OUTPUT IMPEDANCE (Ω) 70 PHASE MARGIN (DEG) 10 60 40 UNITY GAIN PHASE MARGIN 45 1.0 AV = 10 50 AV = 2 30 –50 35 125 0.1 40 –25 25 75 0 50 TEMPERATURE (°C) 100 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 30 100k 1M 10M FREQUENCY (Hz) 100M LT1187 • TPC15 LT1187 • TPC13 LT1187 • TPC14 Power Supply Rejection Ratio vs Frequency 80 POWER SUPPLY REJECTION RATIO (dB) OUTPUT SHORT-CIRCUIT CURRENT (mA) VS = ± 5V TA = 25°C VRIPPLE = ± 300mV 36 35 34 33 32 31 Output Short-Circuit Current vs Temperature VS = ± 5V OUTPUT SATURATION VOLTAGE (V) V+ – 0.7 –0.8 –0.9 –1.0 –1.1 0.5 0.4 0.3 0.2 ±Output Swing vs Supply Voltage 125°C 25°C –55°C RL = 1k ±1.8V ≤ VS ≤ ± 9V 125°C 25°C –55°C 2 4 6 8 ± SUPPLY VOLTAGE (V) 10 60 40 +PSRR –PSRR 20 0 –20 1k 10k 1M 100k FREQUENCY (Hz) 10M 100M 30 – 50 –25 50 0 25 75 TEMPERATURE (°C) 100 125 0.1 V– 0 LT1187 • TPC16 LT1187 • TPC17 LT1187 • TPC18 1187fa 6 LT1187 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage Swing vs Load Resistance 5 VS = ± 5V OUTPUT VOLTAGE SWING (V) 3 TA = – 55°C TA = 25°C TA = 125°C SLEW RATE (V/µs) 250 Slew Rate vs Temperature VS = ± 5V RL = 1k VO = ± 0.5V AV = 2 –SLEW RATE 4 Output Voltage Step vs Settling Time, AV = 2 VS = ± 5V TA = 25°C RL = 1k OUTPUT VOLTAGE STEP (V) 2 10mV 1 200 +SLEW RATE 0 –1 TA = 25°C –3 TA = 125°C TA = – 55°C –2 10mV –5 10 100 LOAD RESISTANCE (Ω) 1000 LT1187 • TPC19 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 Harmonic Distortion vs Output Voltage –30 VS = ± 5V TA = 25°C –35 RL = 1k f = 1MHz AV = 10 –40 –45 –50 –55 –60 0 1 4 3 5 2 OUTPUT VOLTAGE (VP-P) 6 7 Large-Signal Transient Response DISTORTION (dBc) HD3 HD2 INPUT IN LIMITING, AV = 3, SR = 180V/µs LT1187 • TPC22 LT1187 • TPC23 Small-Signal Transient Response Small-Signal Transient Response AV = 2, RFB = 1k, OVERSHOOT = 25% LT1187 • TPC24 AV = 2, RFB = 1k, OVERSHOOT = 25% LT1187 • TPC25 1187fa 7 LT1187 APPLICATIONS INFORMATION 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 VIN 3 2 5 V+ V IN 3 2 S/D 5 V+ 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. 1 +/REF 8 –/FB 4 7 + – LT1187 6 VOUT 1 +/REF 8 –/FB 4 7 + – LT1187 6 VOUT V– RFB AV = + RFB + RG RG V– RFB RFB + RG RG 7 V+ RG RG AV = – 6 S/D 3 2 5 V+ VIN DIFF VOUT V IN RG 3 2 7 + – LT1187 S/D 5 V+ Q1 6 VOUT 3 Q2 RE 1.1k Q3 Q4 RE 1.1k 8 RG RFB 7 + – LT1187 VIN DIFF VIN 1 +/REF 8 –/FB 4 6 1 +/REF 8 –/FB 4 + RS 2 – RS + 1 REF RREF V– RFB RFB + RG RG V– RFB 345mA 350mA 4 V– ILT1187 • F01 RG VO = (VIN DIFF + VIN) VO = ( RFB + RG RG ( VIN DIFF – (R ( G RFB VIN LT1187 • AI01 Figure 1. Simplified Input Stage Schematic 1187fa 8 LT1187 APPLICATIONS INFORMATION 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 CLOSED-LOOP VOLTAGE GAIN (dB) 8 7 6 5 4 3 CFB = 10pF CFB = 5pF CFB = 0pF AV = 2, WITH 8pF FEEDBACK CAPACITOR LT1187 • AI05 Small-Signal Transient Response Extending the Input Range Figure 1 shows a simplified schematic of the LT1187. In normal operation 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 Pins 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. 2 VS = ± 5V T = 25°C 1 AA = 2 V 0 RFB = 900Ω RG = 900Ω –1 100k 1M 10M FREQUENCY (Hz) 100M LT1187 • AI03 Small-Signal Transient Response AV = 2, OVERSHOOT = 25%, RFB = RG = 1k LT1187 • AI04 1187fa 9 LT1187 APPLICATIONS INFORMATION LT1187 in Unity Gain 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 bi-directional “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 twisted-pair receiver converts signals from differential to single-ended. 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 (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 shut down 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 AV = 2, RFB = RG = 1k LT1187 • AI07 LT1187 • AI08 1187fa 10 LT1187 APPLICATIONS INFORMATION 1.5MHz Square Wave Input and Equalized Response Through 1000 Feet of Twisted-Pair Multiburst Pattern Passed Through 1000 Feet of Twisted-Pair LT1187 • AI09 LT1187 • AI10 Bi-Directional Video Bus TRANSMIT 1 3 75Ω 1k 2 TRANSMIT 2 3 1k 75Ω + LT1195 6 6 + LT1195 – 1k 1k – 2 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 – + + – + – 5 LT1187 2 3 + + 5 – LT1187 + – R 300Ω FB 3 3 2 1 8 15Ω 75Ω 6 6 75Ω 1000pF RG 300Ω 50Ω RFB 300Ω RECEIVE 2 LT1187 • AI11 1187fa 11 LT1187 SIMPLIFIED SCHEMATIC VBIAS + VBIAS + 7 V+ + – 3 CFF 2 +V CM +V 6 VOUT * 5 S/D 1 +/REF 8 –/FB * SUBSTRATE DIODE, DO NOT FORWARD BIAS 4 V– LT1187 • SS 1187fa 12 LT1187 PACKAGE DESCRIPTION J8 Package J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic) Hermetic) 8-Lead CERDIP (Narrow (Reference LTC DWG 05-08-1110) (Reference LTC DWG # 05-08-1110) CORNER LEADS OPTION CORNER LEADS OPTION (4 PLCS) (4 PLCS) .405 .405 (10.287) (10.287) MAX 8 7 6 5 .005 (0.127) (0.127) M IN MIN .023 .045 .023 – .045 (0.584 – 1.143) LEAD HALF LEAD OPTION OPTION .045 .068 .045 – .068 (1.143 1.650) (1.143 – 1.650) LEAD FULL LEAD OPTION OPTION .300 BSC BSC (7.62 BSC) BSC) .025 .025 (0.635) (0.635) RAD TYP 1 2 3 .220 – .310 .220 .310 (5.588 – 7.874) (5.588 7.874) 4 .200 .200 (5.080) (5.080) MAX MAX .015 .060 .015 – .060 (0.381 1.524) (0.381 – 1.524) .008 .018 .008 – .018 (0.203 – 0.457) (0.203 0° – 15° .045 .065 .045 – .065 (1.143 1.651) (1.143 – 1.651) .014 .026 .014 – .026 (0.360 – 0.660) (0.360 0.660) .100 .100 (2.54) (2.54) BSC BSC NOTE: DIMENSIONS APPLY TO SOLDER NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR LEADS OR TIN PLATE LEADS .125 .125 3.175 MIN J8 0801 0801 OBSOLETE PACKAGE 1187fa 13 LT1187 PACKAGE DESCRIPTION N8 Package 8-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .400* (10.160) MAX 8 7 6 5 .255 ± .015* (6.477 ± 0.381) 1 .300 – .325 (7.620 – 8.255) 2 3 4 .130 ± .005 (3.302 ± 0.127) .045 – .065 (1.143 – 1.651) .008 – .015 (0.203 – 0.381) +.035 .325 –.015 8.255 +0.889 –0.381 .065 (1.651) TYP .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 1002 ( ) .100 (2.54) BSC INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) NOTE: 1. DIMENSIONS ARE 1187fa 14 LT1187 PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .045 ±.005 .050 BSC 8 .189 – .197 (4.801 – 5.004) NOTE 3 7 6 5 .245 MIN .160 ±.005 .228 – .244 (5.791 – 6.197) .150 – .157 (3.810 – 3.988) NOTE 3 .030 ±.005 TYP RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 0°– 8° TYP 1 2 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) .014 – .019 (0.355 – 0.483) TYP .050 (1.270) BSC SO8 0303 1187fa 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 LT1187 RELATED PARTS PART NUMBER LT1189 LT1193 LT1194 LT1206 LT1354 LT6552 LT6559 DESCRIPTION Low Power Video Difference Amplifier Adjustable Gain Video Difference Amplifier Gain = 10 Video Difference Amplifier 250mA Out, 900V/µs, 60MHz CFA 1mA, 12MHz 400V/µs Op Amplifier 3.3V Video Difference Amplifier Low Cost 5V/±5V Triple Video Amplifier with Shutdown 1187fa 16 Linear Technology Corporation (408) 432-1900 ● FAX: (408) 434-0507 ● LT 1006 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com © LINEAR TECHNOLOGY CORPORATION 1993