LT1468-2 200MHz, 30V/µs 16-Bit Accurate AV ≥ 2 Op Amp FEATURES DESCRIPTION n The LT®1468-2 is a precision high speed operational amplifier with 16-bit accuracy, decompensated to be stable in a gain of 2 or greater. The combination of precision and AC performance makes the LT1468-2 the optimum choice for high accuracy applications such as DAC current-to-voltage conversion and ADC buffers. The initial accuracy and drift characteristics of the input offset voltage and inverting input bias current are tailored for inverting applications. n n n n n n n n n n n n n n Stable in Gain AV ≥ 2 (AV = –1) 200MHz Gain Bandwidth Product 30V/μs Slew Rate Settling Time: 800ns (10V Step, 150μV) Specified at ±5V and ±15V Supplies Low Distortion, – 96.5dB for 100kHz, 10VP-P Maximum Input Offset Voltage: 75μV Maximum Input Offset Voltage Drift: 2μV/°C Maximum (–) Input Bias Current: 10nA Minimum DC Gain: 1000V/mV Minimum Output Swing into 2k: ±12.8V Input Noise Voltage: 5nV/√Hz Input Noise Current: 0.6pA/√Hz Total Input Noise Optimized for 1k < RS < 20k Available in an 8-Lead Plastic SO Package and 8-Lead DFN Package The 200MHz gain bandwidth ensures high open-loop gain at frequency for reducing distortion. In noninverting applications such as an ADC buffer, the low distortion and DC accuracy allow full 16-bit AC and DC performance. The high slew rate of the LT1468-2 improves large-signal performance in applications such as active filters and instrumentation amplifiers compared to other precision op amps. The LT1468-2 is specified on power supply voltages of ±5V and ±15V and from –40°C to 85°C. For a unity-gain stable op amp with same DC performance, see the LT1468 datasheet. APPLICATIONS n n n n n n 16-Bit DAC Current-to-Voltage Converter Precision Instrumentation ADC Buffer Low Distortion Active Filters High Accuracy Data Acquisition Systems Photodiode Amplifiers L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 16-Bit DAC I-to-V Converter Large Signal Transient, AV = –1 DAC INPUTS 16 6k ® LTC 1597 – LT1468-2 + VS = ±15V AV = –1 RF = RG = 2k CF = 22pF 10V 20pF 2k VOUT 2V/DIV 50pF 0V OPTIONAL NOISE FILTER OFFSET: VOS + IB (6kΩ) < 1LSB SETTLING TIME TO 150μV = 1.6μs SETTLING LIMITED BY 6k AND 20pF TO COMPENSATE DAC OUTPUT CAPACITANCE 14682 TA01 200ns/DIV 14682 TA02 14682f 1 LT1468-2 ABSOLUTE MAXIMUM RATINGS (Note 1) Total Supply Voltage (V+ to V –).................................36V Maximum Input Current (Note 2) ...........................10mA Output Short-Circuit Duration (Note 3) ............ Indefinite Operating Temperature Range ................. –40°C to 85°C Specified Temperature Range (Note 4) .... –40°C to 85°C Junction Temperature ........................................... 150°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) for S8 Only........................................................ 300°C PIN CONFIGURATION TOP VIEW NULL 1 –IN 2 +IN 3 + – V– 4 TOP VIEW 8 DNC* NULL 1 8 DNC* 7 V+ –IN 2 7 V+ 6 OUT +IN 3 6 VOUT 5 NULL V– 4 5 NULL S8 PACKAGE 8-LEAD PLASTIC SO DD PACKAGE 8-LEAD (3mm × 3mm) PLASTIC DFN *DO NOT CONNECT TJMAX = 150°C, θJA = 43°C/W EXPOSED PAD IS INTERNALLY CONNECTED TO V– TJMAX = 150°C, θJA = 190°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE LT1468CS8-2#PBF LT1468CS8-2#TRPBF 14682 8-Lead Plastic Small Outline 0°C to 70°C LT1468IS8-2#PBF LT1468IS8-2#TRPBF 14682 8-Lead Plastic Small Outline –40°C to 85°C LT1468ACDD-2#PBF LT1468ACDD-2#TRPBF LDSY 8-Lead (3mm × 3mm) Plastic DFN 0°C to 70°C LT1468AIDD-2#PBF LT1468AIDD-2#TRPBF LDSY 8-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C LT1468CDD-2#PBF LT1468CDD-2#TRPBF LDSY 8-Lead (3mm × 3mm) Plastic DFN 0°C to 70°C LT1468IDD-2#PBF LT1468IDD-2#TRPBF LDSY 8-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS TYP MAX UNITS VOS Input Offset Voltage S8 Package ±15V ± 5V 30 50 75 175 μV μV LT1468A, DD Package ±15V ± 5V 30 50 75 175 μV μV LT1468, DD Package ±15V ± 5V 100 150 200 300 μV μV ±5V to ±15V 13 50 IOS Input Offset Current VSUPPLY MIN nA 14682f 2 LT1468-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCM = 0V unless otherwise noted. SYMBOL PARAMETER – Inverting Input Bias Current + Noninverting Input Bias Current IB CONDITIONS VSUPPLY MIN TYP MAX UNITS ±5V to ±15V 3 ±10 nA ±40 ±5V to ±15V –10 Input Noise Voltage 0.1Hz to 10Hz ±5V to ±15V 0.3 en Input Noise Voltage f = 10kHz ±5V to ±15V 5 nV/√Hz in Input Noise Voltage f = 10kHz ±5V to ±15V RIN Input Resistance VCM = ±12.5V Differential CIN Input Capacitance ±15V Input Voltage Range + ±15V ±5V Input Voltage Range – ±15V ±5V IB CMRR Common Mode Rejection Ratio VCM = ±12.5V VCM = ±2.5V PSRR Power Supply Rejection Ratio VS = ±4.5V to ±15V AVOL Large-Signal Voltage Gain VOUT = ±12.5V, RL = 10k VOUT = ±12.5V, RL = 2k VOUT = ±2.5V, RL = 10k VOUT = ±2.5V, RL = 2k VOUT Output Swing IOUT ±15V ±15V 100 50 12.5 2.5 0.6 pA/√Hz 240 150 MΩ kΩ 4 pF 13.5 3.5 V V –14.3 –4.3 ±15V ±5V nA μVP-P –12.5 –2.5 V V 96 96 110 112 dB dB 100 112 dB ±15V ±15V ±5V ±5V 1000 500 1000 500 9000 5000 6000 3000 V/mV V/mV V/mV V/mV RL = 10k RL = 2k RL = 10k RL = 2k ±15V ±15V ± 5V ±5V ±13.0 ±12.8 ±3.0 ±2.8 ±13.6 ±13.5 ±3.6 ±3.5 V V V V Output Current VOUT = ±12.5V VOUT = ±2.5V ±15V ±5V ±15 ±15 ±22 ±22 mA mA ISC Short-Circuit Current VOUT = 0V, VIN = ±0.2V ±15V ±25 ±40 mA SR Slew Rate RL = 2k (Note 5) ±15V ± 5V 20 15 30 22 V/μs V/μs Full-Power Bandwidth 10V Peak, (Note 6) 3V Peak, (Note 6) ±15V ±5V 475 1160 kHz kHz GBW Gain Bandwidth f = 100kHz, RL = 2k ±15V ±5V 200 190 MHz MHz ts Settling Time 10V Step, 0.01%, AV = –1 10V Step, 150μV, AV = –1 5V Step, 0.01%, AV = –1 ±15V ±15V ±5V 650 800 550 ns ns ns RO Output Resistance AV = –1, f = 100kHz ±15V 0.02 IS Supply Current ±15V ±5V 3.9 3.6 140 130 Ω 5.2 5.0 mA mA The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. 0°C ≤ TA ≤ 70°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VSUPPLY VOS Input Offset Voltage S8 Package ±15V ± 5V LT1468A, DD Package LT1468, DD Package MIN TYP MAX UNITS ● ● 150 250 μV μV ±15V ± 5V ● ● 150 250 μV μV ±15V ± 5V ● ● 300 400 μV μV 14682f 3 LT1468-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. 0°C ≤ TA ≤ 70°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS Input VOS Drift (Note 7) VSUPPLY MIN ±5V to ±15V ● Input Offset Current ±5V to ±15V ● Input Offset Current Drift ±5V to ±15V Inverting Input Bias Current ±5V to ±15V Negative Input Current Drift ± 5V to ±15V IB Noninverting Input Bias Current ±5V to ±15V ● CMRR Common Mode Rejection Ratio ±15V ±5V ● ● IOS – IB + VCM = ±12.5V VCM = ±2.5V TYP MAX UNITS 0.7 2.0 μV/°C 65 nA 60 ● pA/°C ±15 40 nA pA/°C ±50 nA 94 94 dB dB PSRR Power Supply Rejection Ratio VS = ±4.5V to ±15V ● 98 dB AVOL Large-Signal Voltage Gain VOUT = ±12.5V, RL = 10k VOUT = ±12.5V, RL = 2k VOUT = ±2.5V, RL = 10k VOUT = ±2.5V, RL = 2k ±15V ±15V ±5V ±5V ● ● ● ● 500 250 500 250 V/mV V/mV V/mV V/mV VOUT Output Swing RL = 10k RL = 2k RL = 10k RL = 2k ±15V ±15V ±5V ±5V ● ● ● ● ±12.9 ±12.7 ±2.9 ±2.7 V V V V IOUT Output Current VOUT = ±12.5V VOUT = ±2.5V ±15V ±5V ● ● ±12.5 ±12.5 mA mA ISC Short-Circuit Current VOUT = 0V, VIN = ±0.2V ±15V ● ±17 mA SR Slew Rate RL = 2k (Note 5) ±15V ±5V ● ● 18 13 V/μs V/μs GBW Gain Bandwidth f = 100kHz, RL = 2k ±15V ± 5V ● ● 130 120 IS Supply Current ±15V ±5V ● ● 200 190 MHz MHz 6.5 6.3 mA mA The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. –40°C ≤ TA ≤ 85°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MAX UNITS VOS Input Offset Voltage S8 Package ±15V ± 5V ● ● 230 330 μV μV LT1468A, DD Package ±15V ± 5V ● ● 230 330 μV μV LT1468, DD Package ±15V ± 5V ● ● 400 500 μV μV ±5V to ±15V ● 2.5 μV/°C Input Offset Current ±5V to ±15V ● 80 nA Input Offset Current Drift ±5V to ±15V Inverting Input Bias Current ±5V to ±15V Negative Input Current Drift ±5V to ±15V Input VOS Drift IOS – IB + (Note 7) IB Noninverting Input Bias Current CMRR Common Mode Rejection Ratio VCM = ±12.5V VCM = ±2.5V PSRR Power Supply Rejection Ratio VS = ±4.5V to ±15V VSUPPLY MIN TYP 0.7 120 ● pA/°C ±30 80 nA pA/°C ±5V to ±15V ● ±15V ±5V ● ● 92 92 dB dB ● 96 dB ±60 nA 14682f 4 LT1468-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. –40°C ≤ TA ≤ 85°C, VCM = 0V unless otherwise noted. MIN VSUPPLY TYP MAX UNITS SYMBOL PARAMETER CONDITIONS AVOL Large-Signal Voltage Gain VOUT = ±12V, RL = 10k VOUT = ±10V, RL = 2k VOUT = ±2.5V, RL = 10k VOUT = ±2.5V, RL = 2k ±15V ±15V ±5V ±5V ● ● ● ● 300 150 300 150 VOUT Output Swing RL = 10k RL = 2k RL = 10k RL = 2k ±15V ±15V ±5V ±5V ● ● ● ● ±12.8 ±12.6 ±2.8 ±2.6 IOUT Output Current VOUT = ±12.5V VOUT = ±2.5V ±15V ±5V ● ● ±7 ±7 mA mA ISC Short-Circuit Current VOUT = 0V, VIN = ±0.2V ±15V ● ±12 mA SR Slew Rate RL = 2k (Note 5) ±15V ±5V ● ● 15 11 V/μs V/μs GBW Gain Bandwidth f = 100kHz, RL = 2k ±15V ±5V ● ● 110 100 IS Supply Current ±15V ±5V ● ● 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: The inputs are protected by back-to-back diodes and two 100Ω series resistors. If the differential input voltage exceeds 0.7V, the input current should be limited to 10mA. Input voltages outside the supplies will be clamped by ESD protection devices and input currents should also be limited to 10mA. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted indefinitely. V/mV V/mV V/mV V/mV V V V V 200 190 MHz MHz 7.0 6.8 mA mA Note 4: The LT1468C-2 is guaranteed to meet specified performance from 0°C to 70°C and is designed, characterized and expected to meet these extended temperature limits, but is not tested at – 40°C and at 85°C. The LT1468I-2 is guaranteed to meet the extended temperature limits. Note 5: Slew rate is measured between ±8V on the output with ±12V input for ±15V supplies and ±2V on the output with ±3V input for ±5V supplies. Note 6: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2πVP Note 7: This parameter is not 100% tested. TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Supply Voltage and Temperature Input Common Mode Range vs Supply Voltage V+ 7 5 4 25°C 3 –55°C 2 60 –1.0 INPUT BIAS CURRENT (nA) COMMON MODE RANGE (V) SUPPLY CURRENT (mA) 125°C 80 TA = 25°C ΔVOS < 100μV –0.5 6 Input Bias Current vs Input Common Mode Voltage –1.5 –2.0 2.0 1.5 1.0 V– 0 5 10 15 SUPPLY VOLTAGE (±V) 20 14682 G01 40 20 0 IB– IB+ –20 –40 –60 0.5 1 VS = ±15V TA = 25°C 0 3 9 12 6 SUPPLY VOLTAGE (±V) 15 18 14682 G02 –80 –15 –10 –5 5 10 0 INPUT COMMON MODE VOLTAGE (V) 15 14682 G03 14682f 5 LT1468-2 TYPICAL PERFORMANCE CHARACTERISTICS Input Bias Current vs Temperature Input Noise Spectral Density VS = ±15V INPUT VOLTAGE NOISE (nV/√Hz) IB– –10 IB+ –20 –30 –40 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 in 100 1 en 10 0.1 1 125 1 10 100 1k FREQUENCY (Hz) 14682 G06 Open-Loop Gain vs Resistive Load 5 140 Open-Loop Gain vs Temperature 160 TA = 25°C 0 VS = ±15V 135 OPEN-LOOP GAIN (dB) –10 –15 –20 –25 VS = ±15V VS = ±5V 130 125 120 115 –40 40 60 80 100 120 TIME AFTER POWER UP (s) 10 140 100 1k LOAD RESISTANCE (Ω) VS = ±5V 120 110 90 –50 –25 –1 V+ –0.5 –1.0 OUTPUT VOLTAGE SWING (V) RL = 10k –2 –3 –4 4 3 2 RL = 2k 1 RL = 10k TA = 25°C 0 60 VS = ±15V 85°C 25°C –40°C –1.5 –2.0 –2.5 2.5 2.0 1.5 1.0 20 14682 G10 125 Output Short-Circuit Current vs Temperature 40°C 85°C 25°C V– 0.5 5 10 15 SUPPLY VOLTAGE (±V) 100 14682 G09 Output Voltage Swing vs Load Current RL = 2k 50 25 75 0 TEMPERATURE (°C) 14682 G08 Output Voltage Swing vs Supply Voltage V+ 10k OUTPUT SHORT-CIRCUIT CURRENT (mA) 20 14682 G07 OUTPUT VOLTAGE SWING (V) 130 100 110 0 V 140 S0-8 ±15V –35 – RL = 2k 150 S0-8 ±5V –30 TIME (1s/DIV) 14682 G05 Warm-Up Drift vs Time OFFSET VOLTAGE DRIFT (μV) 0.01 100k 10k 14682 G04 –5 VS = ±15V OPEN-LOOP GAIN (dB) INPUT BIAS CURRENT (nA) 10 VS = ±15V TA = 25°C AV = 101 RS = 100k FOR in INPUT CURRENT NOISE (pA/√Hz) 20 0 0.1Hz to 10Hz Voltage Noise 10 1000 VOLTAGE NOISE (100nV/DIV) 30 –20 –15 –10 –5 0 10 5 OUTPUT CURRENT (mA) 15 20 14682 G11 55 VS = ±15V VIN = ±0.2V 50 45 SOURCE SINK 40 35 30 25 20 15 10 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 14682 G12 14682f 6 LT1468-2 TYPICAL PERFORMANCE CHARACTERISTICS Open-Loop Gain and Phase vs Frequency Gain vs Frequency, AV = –1 100 60 80 PHASE 60 GAIN (dB) 40 GAIN 30 20 20 0 TA = 25°C 10 AV = –1 RF = RG = 5.1k 0 CF = 5pF RL = 2k –10 100k 10k 1M 10M FREQUENCY (Hz) PHASE (DEG) 40 GAIN (dB) 50 Output Impedance vs Frequency 100 6 TA = 25°C 5 AV = –1 4 RF = RG = 2k CF = 6.8pF 3 RL = 500Ω 2 CL = 47pF CL = 22pF 1 0 NO CL –1 –2 –20 10 AV = 100 1 AV = 10 0.1 AV = –1 0.01 –3 –40 VS = ±15V TA = 25°C CL = 100pF OUTPUT IMPEDANCE (Ω) 70 –4 –60 100M –5 100k 1M 10M FREQUENCY (Hz) 100M 0.001 10k 100k 1M 10M FREQUENCY (Hz) 100M 14682 G14 14682 G13 14682 G15 Undistorted Output Swing vs Frequency, VS = ±5V Undistorted Output Swing vs Frequency, VS = ±15V OUTPUT VOLTAGE SWING (VP-P) OUTPUT VOLTAGE SWING (VP-P) 25 AV = –1 20 15 10 VS = ±15V 5 TA = 25°C RL = 2k THD<1% 0 1 10 100 FREQUENCY (kHz) 1000 10 9 8 8 6 7 4 6 AV = –1 5 4 3 VS = ±5V TA = 25°C 1 RL = 2k THD<1% 0 1 10 100 FREQUENCY (kHz) 2 14682 G16 2 VS = ±15V TA = 25°C RF = RG = 2.5k RL = 5k CF = 8pF AV = –1 0.01% 0.1% 0 –2 –4 0.1% –6 150μV –8 1000 2000 150μV –10 0.01% 0 100 200 300 400 500 600 700 800 900 1000 SETTLING TIME (ns) 14682 G17 Settling Time vs Output Step 14682 G18 Small-Signal Transient, AV = –1 10 VS = ±15V 8 Large-Signal Transient, AV = –1 VS = ±15V AV = –1 RF = RG = 2k CL = 22pF 10V 0.01% 6 OUTPUT STEP (V) Settling Time vs Output Step 10 OUTPUT STEP (V) 30 2V/DIV 4 2 20mV/DIV 0 –2 –4 –6 –8 –10 0.01% VS = ±15V TA = 25°C RF = RG = 1k RL = 5k INTO DIODES CF = 22pF AV = 2 RL = 511Ω/30pF 0V 200ns/DIV 50ns/DIV 14682 G20 14682 G21 0 100 200 300 400 500 600 700 800 900 1000 SETTLING TIME (ns) 14682 G19 14682f 7 LT1468-2 APPLICATIONS INFORMATION The LT1468-2 may be inserted directly into many operational amplifier applications improving both DC and AC performance, provided that the nulling circuitry is removed. The suggested nulling circuit for the LT1468-2 is shown below. V+ 3 + LT1468-2 2 76 Offset Nulling 0.1μF 2.2μF 0.1μF 2.2μF 4 – 5 1 100k V– 14682 AI01 Gain of 2 Stable The LT1468-2 is a decompensated version of the LT1468. The precision DC performance is identical, but the internal compensation capacitors have been reduced to a point where the op amp needs a gain of 2 or greater in order to be stable. In general, for applications where the gain around the op amp is ≥ 2, the decompensated version should be used, because it will give the best AC performance. In applications where the gain is < 2, the unity-gain stable version should be used. The appropriate way to define the ‘gain’ is as the inverse of the feedback ratio from output to differential input, including all relevant parasitics. Moreover, as with all feedback loops, the stability of the loop depends on the value of that feedback ratio at frequencies where the total loop-gain would cross unity. Therefore, it is possible to have circuits in which the gain at DC is lower than the gain at high frequency, and these circuits can be stable even with a non unity-gain stable op amp. An example is many current-output DAC buffer applications. and minimize leakage (i.e., 1.5GΩ of leakage between an input and a 15V supply will generate 10nA—equal to the maximum IB– specification.) Board leakage can be minimized by encircling the input circuitry with a guard ring operated at a potential close to that of the inputs. For inverting configurations tie the ring to ground, in noninverting connections tie the ring to the inverting input (note the input capacitance will increase which may require a compensating capacitor as discussed below.) Microvolt level error voltages can also be generated in the external circuitry. Thermocouple effects caused by temperature gradients across dissimilar metals at the contacts to the inputs can exceed the inherent drift of the amplifier. Air currents over device leads should be minimized, package leads should be short, and the two input leads should be as close together as possible and maintained at the same temperature. Make no connection to Pin 8. This pin is used for factory trim of the inverting input current. The parallel combination of the feedback resistor and gain setting resistor on the inverting input can combine with the input capacitance to form a pole that can cause peaking or even oscillations. A feedback capacitor of the value: CF = (RG)(CIN/RF) may be used to cancel the input pole and optimize dynamic performance. For applications where the DC noise gain is one, and a large feedback resistor is used, CF should be less than or equal to one half of CIN. An example would be a DAC I-to-V converter as shown on the front page of this data sheet where the DAC can have many tens of pF of output capacitance. Nulling Input Capacitance Layout and Passive Components The LT1468 requires attention to detail in board layout in order to maximize DC and AC performance. For best AC results (for example fast settling time) use a ground plane, short lead lengths, and RF-quality bypass capacitors (0.01μF to 0.1μF) in parallel with low ESR bypass capacitors (1μF to 10μF tantalum). For best DC performance, use “star” grounding techniques, equalize input trace lengths RF CF RG – CIN VIN LT1468-2 VOUT + 14682 AI02 14682f 8 LT1468-2 APPLICATIONS INFORMATION Input Considerations Each input of the LT1468-2 is protected with a 100Ω series resistor and back-to-back diodes across the bases of the input devices. If the inputs can be pulled apart, the input current should be limited to less than 10mA with an external series resistor. Each input also has two ESD clamp diodes—one to each supply. If an input is driven above the supply, limit the current with an external resistor to less than 10mA. The LT1468-2 employs bias current cancellation at the inputs. The inverting input current is trimmed at zero common mode voltage to minimize errors in inverting applications such as I-to-V converters. The noninverting input current is not trimmed and has a wider variation and therefore a larger maximum value. As the input offset current can be greater than either input current, the use of balanced source resistance is NOT recommended as it actually degrades DC accuracy and also increases noise. The input bias currents vary with common mode voltage as shown in the Typical Performance Characteristics. The cancellation circuitry was not designed to track this common mode voltage because the settling time would have been adversely affected. The LT1468 inputs can be driven to the negative supply and to within 0.5V of the positive supply without phase reversal. As the input moves closer than 0.5V to the positive supply, the output reverses phase. Total Input Noise The curve of Total Noise vs Unmatched Source Resistance in the Typical Performance Characteristics shows that with source resistance below 1k, the voltage noise of the amplifier dominates. In the 1k to 20k region the increase in noise is due to the source resistance. Above 20k the input current noise component is larger than the resistor noise. Input Stage Protection R1 100Ω +IN Q1 Q2 R2 100Ω –IN 14682 AI03 14682f 9 LT1468-2 SIMPLIFIED SCHEMATIC V+ I1 I5 I2 Q10 Q8 +IN Q1 Q2 –IN Q5 Q9 Q7 Q3 I3 I4 OUT Q6 Q4 BIAS Q11 C I6 V– 14682 SS 14682f 10 LT1468-2 PACKAGE DESCRIPTION S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 7 8 .245 MIN 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) 2 3 4 .053 – .069 (1.346 – 1.752) .008 – .010 (0.203 – 0.254) .004 – .010 (0.101 – 0.254) 0°– 8° TYP .016 – .050 (0.406 – 1.270) .050 (1.270) BSC .014 – .019 (0.355 – 0.483) TYP 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) SO8 0303 DD Package 8-Lead (3mm × 3mm) Plastic DFN (LTC DWG # 05-08-1210) .005 (0.127) MIN .520 (13.208) MAX 8 7 6 .020 – .060 (0.508 – 1.524) 5 .290 (7.366) TYP PIN NO. 1 IDENT 1 2 3 4 .485 (12.319) MAX .008 – .015 (0.203 – 0.381) .300 (7.620) REF .125 .054 (3.175) (1.372) MIN TYP .015 – .023 (0.381 – 0.584) .165 (4.191) MAX .100 (2.54) BSC D8 0801 14682f 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. 11 LT1468-2 TYPICAL APPLICATION 16-Bit ADC Buffer 22pF 1k 1k – 16 BITS 200Ω LT1468-2 VIN + LTC1605 1000pF 33.2k CAP 14682 TA04 2.2μF RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1167 Precision Instrumentation Amplifier Single Resistor Gain Set, 0.04% Max Gain Error, 10ppm Max Gain Nonlinearity LT1468 Single 200MHz, 30V/μs, 16-Bit Accurate AV ≥ 2 Op Amp 75μV VOS(MAX) LT1468-2 Single 90MHz, 22V/μs, 16-Bit Accurate Op Amp 75μV VOS(MAX) LT1469 Dual 200MHz, 30V/μs, 16-Bit Accurate AV ≥ 2 Op Amp 75μV VOS(MAX) LT1469-2 Dual 90MHz, 22V/μs, 16-Bit Accurate Op Amp 75μV VOS(MAX) LTC1595/LTC1596 16-Bit Serial Multiplying IOUT DACs ±1LSB Max INL/DNL, Low Glitch, DAC8043 16-Bit Upgrade LTC1597 16-Bit Parallel Multiplying IOUT DAC ±1LSB Max INL/DNL, Low Glitch, On-Chip Bipolar Resistors LTC1604 16-Bit, 333ksps Sampling ADC ± 2.5V Input, SINAD = 90dB, THD = –100dB LTC1605 Single 5V, 16-Bit, 100ksps Sampling ADC Low Power, ±10V Inputs, Parallel/Byte Interface 14682f 12 Linear Technology Corporation LT 0808 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008