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. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ 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 ■ ■ ■ ■ 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. Line Receivers Video Signal Processing Cable Drivers Tape and Disc Drive Systems , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Cable Sense Amplfier for Loop Through Connections with DC Adjust Closed-Loop Gain vs Frequency 40 V IN 5V CABLE 2 VDC 1 8 + – + – 30 7 LT1187 6 VOUT 4 –5V VOLTAGE GAIN (dB) 3 VS = ±5V RL = 1k 20 10 1k 0 1k –10 0.1 LT1187 • TA01 1 10 FREQUENCY (MHz) 100 LT1187 • TA02 1187fa 1 LT1187 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) 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 ORDER PART NUMBER TOP VIEW +/REF 1 8 –/FB –IN 2 7 V+ +IN 3 6 OUT V– 4 5 S/D LT1187CN8 LT1187CS8 LT1187IN8 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) S8 PART MARKING 1187 J8 PACKAGE 8-LEAD CERDIP TJMAX = 175°C, θJA = 100°C/W LT1187MJ8 LT1187CJ8 OBSOLETE PACKAGE Consider the N8 or S8 Packages for Alternate Source 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 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. SYMBOL VOS PARAMETERS Input Offset Voltage IOS IB en in RIN CIN VIN LIM 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 CMRR PSRR VOUT 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 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 –2.5 70 70 ±3.8 ±6.7 ±6.4 100 150 LT1187C/I/M MAX 2.0 2.0 0.2 ±0.5 65 1.5 100 2.0 ±380 MAX 10 11 1.0 ±2.0 3.5 100 85 ±4.0 ±7.0 ±6.8 0.2 165 53 5.7 230 26 0 100 0.6 0.8 1.0 325 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 LT1187 ±5V ELECTRICAL CHARACTERISTICS 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. SYMBOL IS IS/D tON tOFF PARAMETERS Supply Current Shutdown Supply Current Shutdown Pin Current Turn-On Time Turn-On Time CONDITIONS MIN Pin 5 at V– Pin 5 at V– Pin 5 from V– to Ground, RL = 1k Pin 5 from Ground to V–, RL = 1k LT1187C/I/M MAX 13 0.8 5 500 600 MAX 16 1.5 25 UNITS mA mA µA ns ns 5V ELECTRICAL CHARACTERISTICS + – 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 PARAMETER Input Offset Voltage IOS IB Input Offset Current Input Bias Current Input Voltage Range Common Mode Rejection Ratio Output Voltage Swing CMRR VOUT SR BW IS IS/D 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) MIN VOUT High VOUT Low 2.0 70 3.6 VO = 1.5V to 3.5V AV = 10 Pin 5 at V– Pin 5 at V– 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 0.4 15 1.5 25 UNITS mV mV µA µA V dB V V V/µs MHz mA mA µA ±5V ELECTRICAL CHARACTERISTICS –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. SYMBOL VOS ΔVOS/ΔT IOS IB CMRR PSRR VOUT GE IS IS/D 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 Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current CONDITIONS Either Input (Note 5) MIN 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 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 1.2 17 1.5 25 UNITS mV mV/°C µA µA V dB dB V V V % mA mA µA 1187fa 3 LT1187 ±5V ELECTRICAL CHARACTERISTICS 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. SYMBOL VOS ΔVOS/ΔT IOS IB CMRR PSRR VOUT GE IS IS/D 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 Gain Error Supply Current Shutdown Supply Current Shutdown Pin Current CONDITIONS Either Input (Note 5) MIN 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 –2.5 70 65 ±3.7 ±6.6 ±6.4 Pin 5 at V– (Note 12) Pin 5 at V– 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 1.0 17 1.5 25 UNITS mV mV/°C µA µA V dB dB V V V % mA mA µA 5V ELECTRICAL CHARACTERISTICS + – 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 PARAMETER Input Offset Voltage ΔVOS/ΔT IOS IB Input VOS Drift Input Offset Current Input Bias Current Input Voltage Range Common Mode Rejection Ratio Output Voltage Swing CMRR VOUT IS IS/D Supply Current Shutdown Supply Current Shutdown Pin Current CONDITIONS Either Input (Note 5) SO Package MIN 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– 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. VOUT High VOUT Low 2.0 70 3.5 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 0.4 16 1.5 25 UNITS mV mV µV/°C µA µA V dB V V mA mA µA 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 V+ 100 VS = ±5V 1.5 1.0 –55°C 0.5 25°C 0 +IB 0 –100 COMMON MODE RANGE (V) INPUT BIAS CURRENT (nA) INPUT BIAS CURRENT (µA) 2.0 –IB IOS –200 –300 125°C – 5 – 4 –3 –2 –1 0 1 2 3 COMMON MODE VOLTAGE (V) – 400 –50 5 4 –25 50 0 25 75 TEMPERATURE (°C) 300 200 100 0 1k 10k FREQUENCY (Hz) 12 10 8 6 4 V + = –1.8V TO –9V Supply Current vs Supply Voltage 16 100 25°C 12 125°C 10 1k 10k FREQUENCY (Hz) 8 100k 5 2 GAIN ERROR (%) –0.05 VS/D = –VEE + 0.2V 4 6 8 ±SUPPLY VOLTAGE (V) 10 LT1187 • TPC06 Open-Loop Gain vs Temperature VS = ±5V VOUT = ±2V AV = 10 RL = 1k VS = ±5V VS/D = –VEE + 0.4V 2 0 Gain Error vs Temperature 0 3 – 55°C 14 LT1187 • TPC05 6 125 100 LT1187 • TPC03 0 10 100k VS/D = –VEE + 0.6V 0 25 75 50 TEMPERATURE (°C) 2 Shutdown Supply Current vs Temperature SHUTDOWN SUPPLY CURRENT (mA) 1.5 1.0 V– – 50 –25 125 VS = ±5V TA = 25°C RS = 100k LT1187 • TPC04 4 100 SUPPLY CURRENT (mA) 400 EQUIVALENT INPUT NOISE CURRENT (pA/√Hz) EQUIVALENT INPUT NOISE VOLTAGE (nV/√Hz) VS = ±5V TA = 25°C RS = 0Ω 100 2.0 Equivalent Input Noise Current vs Frequency Equivalent Input Noise Voltage vs Frequency 500 –1.5 –2.0 LT1187 • TPC02 LT1187 • TPC01 600 –1.0 0.5 –0.5 10 V + = 1.8V TO 9V –0.5 2.5 –0.10 –0.15 8 VS = ±5V VO = ±3V RL = 1k OPEN-LOOP GAIN (kV/V) 3.0 Common Mode Voltage vs Temperature Input Bias Current vs Temperature 6 4 RL = 500Ω 2 1 VS/D = –VEE 0 –50 –25 50 0 25 75 TEMPERATURE (°C) 100 125 LT1187 • TPC07 –0.20 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 LT1187 • TPC08 0 –50 –25 0 50 25 75 TEMPERATURE (°C) 100 125 LT1187 • TPC09 1187fa 5 LT1187 TYPICAL PERFORMANCE CHARACTERISTICS Open-Loop Voltage Gain vs Load Resistance Gain, Phase vs Frequency 60 40 GAIN 20 20 0 PHASE MARGIN (DEG) VOLTAGE GAIN (dB) 80 60 40 16k 0 –20 100k 12k 8k 4k –20 1M 10M FREQUENCY (Hz) 60 VS = ±5V VO = ±3V TA = 25°C GAIN BANDWIDTH PRODUCT (MHz) PHASE 80 100 VS = ±5V TA = 25°C RL = 1k OPEN-LOOP VOLTAGE GAIN (V/V) 100 1k LOAD RESISTANCE (Ω) –25 25 75 0 50 TEMPERATURE (°C) 100 10 AV = 10 1.0 35 125 0.1 10k 1k 100k 1M FREQUENCY (Hz) LT1187 • TPC13 36 +PSRR –PSRR 20 0 –20 1k 10k 1M 100k FREQUENCY (Hz) 10M 2 4 8 6 ±SUPPLY VOLTAGE (V) 100M LT1187 • TPC16 10M Common Mode Rejection Ratio vs Frequency VS = ±5V TA = 25°C RL = 1k 70 60 50 40 30 100k 100M 1M 10M FREQUENCY (Hz) 34 33 32 31 30 – 50 –25 50 0 25 75 TEMPERATURE (°C) 100 125 LT1187 • TPC17 100M LT1187 • TPC15 V+ – 0.7 VS = ±5V 35 10 LT1187 • TPC12 OUTPUT SATURATION VOLTAGE (V) VS = ± 5V TA = 25°C VRIPPLE = ±300mV 40 0 Output Short-Circuit Current vs Temperature OUTPUT SHORT-CIRCUIT CURRENT (mA) POWER SUPPLY REJECTION RATIO (dB) 60 40 LT1187 • TPC14 Power Supply Rejection Ratio vs Frequency 80 TA = 125°C 80 VS = ±5V TA = 25°C AV = 2 30 –50 50 10k COMMON-MODE REJECTION RATIO (dB) OUTPUT IMPEDANCE (Ω) 45 100 PHASE MARGIN (DEG) GAIN BANDWIDTH PRODUCT (MHz) 65 55 UNITY GAIN PHASE MARGIN 40 TA = 25°C Output Impedance vs Frequency GAIN BANDWIDTH PRODUCT 50 TA = – 55°C LT1187 • TPC10 Gain Bandwidth Product and Unity Gain Phase Margin vs Temperature VS = ±5V RL = 1k AV = 20dB 30 0 100 100M LT1187 • TPC11 60 Gain Bandwidth Product vs Supply Voltage ±Output Swing vs Supply Voltage –0.8 125°C –0.9 25°C –1.0 –1.1 0.5 –55°C RL = 1k ±1.8V ≤ VS ≤ ±9V 0.4 125°C 25°C 0.3 –55°C 0.2 0.1 V– 0 2 4 6 8 ±SUPPLY VOLTAGE (V) 10 LT1187 • TPC18 1187fa 6 LT1187 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage Swing vs Load Resistance 250 TA = –55°C SLEW RATE (V/µs) TA = 25°C TA = 125°C 1 –1 TA = 25°C –3 TA = 125°C 10 4 VS = ±5V RL = 1k VO = ±0.5V AV = 2 –SLEW RATE 200 +SLEW RATE TA = –55°C –5 100 LOAD RESISTANCE (Ω) 150 –50 –25 1000 LT1187 • TPC19 VS = ±5V TA = 25°C RL = 1k 10mV 2 0 –2 10mV –4 0 25 50 75 TEMPERATURE (°C) 100 125 40 50 60 70 80 SETTLING TIME (ns) 90 100 LT1187 • TPC21 LT1187 • TPC20 Harmonic Distortion vs Output Voltage Large-Signal Transient Response –30 DISTORTION (dBc) OUTPUT VOLTAGE SWING (V) VS = ±5V OUTPUT VOLTAGE STEP (V) 5 3 Output Voltage Step vs Settling Time, AV = 2 Slew Rate vs Temperature VS = ±5V TA = 25°C –35 RL = 1k f = 1MHz AV = 10 –40 HD3 HD2 –45 –50 –55 –60 0 1 4 3 5 2 OUTPUT VOLTAGE (VP-P) 6 7 INPUT IN LIMITING, AV = 3, SR = 180V/µs LT1187 • TPC23 LT1187 • TPC22 Small-Signal Transient Response AV = 2, RFB = 1k, OVERSHOOT = 25% Small-Signal Transient Response 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 S/D V+ 7 + – LT1187 1 +/REF 8 –/FB 4 6 V IN VOUT 5 3 2 7 + – LT1187 AV = + 6 1 +/REF 8 –/FB 4 V– RFB RG V+ RG RG AV = – 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) VOUT If RFB is limited to 1k the last term of the equation contributes only 2mV, since IB is less than 2µA. V– RFB RFB + RG Power Supply Bypassing 7 V+ RFB + RG RG 6 S/D VIN DIFF VIN 3 2 5 S/D V+ 7 + – LT1187 1 +/REF 8 –/FB 4 6 3 2 VIN DIFF VOUT V IN 5 V+ 7 + – LT1187 1 +/REF 8 –/FB 4 RG V– RFB RFB Q1 6 VOUT 3 + RS V– RFB 2 – RS Q2 RE 1.1k 345mA Q3 + 1 REF RREF Q4 8 RG RE 1.1k 350mA 4 V– RG VO = (VIN DIFF + VIN) RFB + RG RG VO = ( RFB + RG RG ( VIN DIFF – RFB (R ( G ILT1187 • F01 VIN LT1187 • AI01 Figure 1. Simplified Input Stage Schematic 1187fa 8 LT1187 APPLICATIONS INFORMATION Small-Signal Transient Response 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 CLOSED-LOOP VOLTAGE GAIN (dB) 9 8 7 CFB = 0pF AV = 2, WITH 8pF FEEDBACK CAPACITOR LT1187 • AI05 6 5 Extending the Input Range CFB = 5pF 4 3 CFB = 10pF 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 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. 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 (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 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 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 + 1k 75Ω TRANSMIT 2 + LT1195 2 6 6 3 1k LT1195 – – 1k 1k 1k 1k 1k 2 1k – 6 LT1195 3 + 6 33Ω S/D 75Ω 6 75Ω 2 + 5 – LT1187 + – R 33Ω 33Ω 15Ω 3 15Ω 2 1 15Ω 1 8 8 FB 300Ω 1000pF RG 300Ω RECEIVE 2 50Ω + – + – 1000pF 50Ω + 3 S/D 3 2 1000 FEET TWISTED-PAIR 2 LT1195 33Ω 15Ω – 5 LT1187 6 75Ω RFB 300Ω RG 300Ω RECEIVE 1 LT1187 • AI11 1187fa 11 LT1187 SIMPLIFIED SCHEMATIC VBIAS + 3 – 2 + VBIAS 7 V+ + CM CFF +V 6 VOUT +V * 4 V– 5 S/D 1 +/REF 8 –/FB * SUBSTRATE DIODE, DO NOT FORWARD BIAS LT1187 • SS 1187fa 12 LT1187 PACKAGE DESCRIPTION J8 Package 8-Lead CERDIP (Narrow .300 Inch, Hermetic) (Reference LTC DWG # 05-08-1110) CORNER LEADS OPTION (4 PLCS) .023 – .045 (0.584 – 1.143) HALF LEAD OPTION .045 – .068 (1.143 – 1.650) FULL LEAD OPTION .005 (0.127) MIN .405 (10.287) MAX 8 7 6 5 .025 (0.635) RAD TYP .220 – .310 (5.588 – 7.874) 1 2 .300 BSC (7.62 BSC) 3 4 .200 (5.080) MAX .015 – .060 (0.381 – 1.524) .008 – .018 (0.203 – 0.457) 0° – 15° NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS .045 – .065 (1.143 – 1.651) .014 – .026 (0.360 – 0.660) .100 (2.54) BSC .125 3.175 MIN J8 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 1 2 3 4 .255 ± .015* (6.477 ± 0.381) .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 8.255 +0.889 –0.381 ) .045 – .065 (1.143 – 1.651) .130 ± .005 (3.302 ± 0.127) .065 (1.651) TYP .100 (2.54) BSC .120 (3.048) .020 MIN (0.508) MIN .018 ± .003 (0.457 ± 0.076) N8 1002 NOTE: 1. DIMENSIONS ARE INCHES MILLIMETERS *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm) 1187fa 14 LT1187 PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 .245 MIN 7 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) 3 4 .053 – .069 (1.346 – 1.752) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN 2 .014 – .019 (0.355 – 0.483) TYP 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) .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 DESCRIPTION LT1189 Low Power Video Difference Amplifier LT1193 Adjustable Gain Video Difference Amplifier LT1194 Gain = 10 Video Difference Amplifier LT1206 250mA Out, 900V/µs, 60MHz CFA LT1354 1mA, 12MHz 400V/µs Op Amplifier LT6552 3.3V Video Difference Amplifier LT6559 Low Cost 5V/±5V Triple Video Amplifier with Shutdown 1187fa 16 Linear Technology Corporation LT 1006 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 1993