Precision 20 MHz CMOS Rail-to-Rail Input/Output Operational Amplifiers AD8616/AD8618 APPLICATIONS Barcode scanners Battery-powered instrumentation Multipole filters Sensors ASIC input or output amplifier Audio Photodiode amplification OUT A 1 AD8616 –IN A 2 +IN A 3 TOP VIEW V– 4 (Not to Scale) 8 V+ 7 OUT B 6 –IN B 5 +IN B 04648-0-001 PIN CONFIGURATIONS OUT A 1 AD8616 –IN A 2 +IN A 3 TOP VIEW V– 4 (Not to Scale) 8 V+ 7 OUT B 6 –IN B 5 +IN B 04648-0-002 Figure 1. 8-Lead MSOP (RM-8) Figure 2. 8-Lead SOIC (R-8) OUT A –IN A +IN A V+ +IN B –IN B OUT B 1 14 AD8618 8 7 OUT D –IN D +IN D V– +IN C –IN C OUT C 04648-0-048 Low offset voltage: 65 µV max Single-supply operation: 2.7 V to 5.5 V Low noise: 8 nV/√Hz Wide bandwidth: >20 MHz Slew rate: 12 V/µs High output current: 150 mA No phase reversal Low input bias current: 1 pA Low supply current: 2 mA Unity gain stable Figure 3. 14-Lead TSSOP (RU-14) 14 OUT D OUT A 1 –IN A 2 13 –IN D +IN A 3 V+ 4 12 +IN D AD8618 11 V– +IN B 5 10 +IN C –IN B 6 9 –IN C OUT B 7 8 OUT C 04648-0-049 FEATURES Figure 4. 14-Lead SOIC (R-14) GENERAL DESCRIPTION The AD8616/AD8618 are dual/quad, rail-to-rail, input and output, single-supply amplifiers featuring very low offset voltage, wide signal bandwidth, and low input voltage and current noise. The parts use a patented trimming technique that achieves superior precision without laser trimming. The AD8616/AD8618 are fully specified to operate from 2.7 V to 5 V single supplies. The combination of 20 MHz bandwidth, low offset, low noise, and very low input bias current make these amplifiers useful in a wide variety of applications. Filters, integrators, photodiode amplifiers, and high impedance sensors all benefit from the combination of performance features. AC applications benefit from the wide bandwidth and low distortion. The AD8616/ AD8618 offer the highest output drive capability of the DigiTrimTM family, which is excellent for audio line drivers and other low impedance applications. Applications for the parts include portable and low powered instrumentation, audio amplification for portable devices, portable phone headsets, bar code scanners, and multipole filters. The ability to swing rail to rail at both the input and output enables designers to buffer CMOS ADCs, DACs, ASICs, and other wide output swing devices in single-supply systems. The AD8616/AD8618 are specified over the extended industrial (–40°C to +125°C) temperature range. The AD8616 is available in 8-lead MSOP and narrow SOIC surface mount packages; the MSOP version is available in tape and reel only. The AD8618 is available in 14-lead SOIC and 14-lead TSSOP packages. Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved. AD8616/AD8618 TABLE OF CONTENTS Specifications..................................................................................... 3 Driving Capacitive Loads.......................................................... 12 VS = 5 V.......................................................................................... 3 Overload Recovery Time .......................................................... 13 VS = 2.7 V....................................................................................... 4 D/A Conversion ......................................................................... 13 Absolute Maximum Ratings............................................................ 5 Low Noise Applications ............................................................. 13 Thermal Resistance ...................................................................... 5 High Speed Photodiode Preamplifier...................................... 14 ESD Caution.................................................................................. 5 Active Filters ............................................................................... 14 Typical Performance Characteristics ............................................. 6 Power Dissipation ...................................................................... 14 Applications..................................................................................... 12 Power Calculations for Varying or Unknown Loads............. 15 Input Overvoltage Protection ................................................... 12 Outline Dimensions ....................................................................... 16 Output Phase Reversal............................................................... 12 Ordering Guide .......................................................................... 16 REVISION HISTORY 4/04—Data Sheet Changed from Rev. 0 to Rev. A Added AD8618................................................................Universal Updated Outline Dimensions ................................................... 16 1/04—Revision 0: Initial Version Rev. A | Page 2 of 16 AD8616/AD8618 SPECIFICATIONS VS = 5 V @VCM = VS/2, TA = 25°C, unless otherwise noted. Table 1. Parameter INPUT CHARACTERISTICS Offset Voltage Symbol Conditions VOS Offset Voltage Drift Input Bias Current ∆VOS/∆T IB VS = 3.5 V @ VCM = 0.5 V and 3.0 V VCM = 0 V to 5 V −40°C < TA < +125°C −40°C < TA < +125°C Min Typ Max Unit 23 80 65 500 800 7 1 50 500 0.5 50 250 5 µV µV µV µV/°C pA pA pA pA pA pA V dB V/mV pF pF 1.5 0.2 −40°C < TA < +85°C −40°C < TA < +125°C Input Offset Current IOS 0.1 −40°C < TA < +85°C −40°C < TA < +125°C Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Input Capacitance OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Peak-to-Peak Noise Voltage Noise Density Current Noise Density Channel Separation CMRR AVO CDIFF CCM VCM = 0 V to 4.5 V RL = 2 kΩ, VO = 0.5 V to 5 V VOH IL = 1 mA IL = 10 mA −40°C < TA < +125°C IL = 1 mA IL = 10 mA −40°C < TA < +125°C VOL IOUT ZOUT 0 80 105 4.98 4.88 4.7 100 1500 2.6 10 4.99 4.92 7.5 70 15 100 200 ±150 3 f = 1 MHz, AV = 1 PSRR ISY VS = 2.7 V to 5.5 V VO = 0 V −40°C < TA < +125°C SR ts GBP ØO RL = 2 kΩ To 0.01% 12 <0.5 24 73 V/µs µs MHz Degrees en p-p en 0.1 Hz to 10 Hz f = 1 kHz f = 10 kHz f = 1 kHz f = 10 kHz f = 100 kHz 2.4 8 6 0.05 –115 –110 µV nV/√Hz nV/√Hz pA/√Hz dB dB in Cs Rev. A | Page 3 of 16 70 90 1.7 V V V mV mV mV mA Ω 2.0 2.5 dB mA mA AD8616/AD8618 VS = 2.7 V @VCM = VS /2, TA = 25°C, unless otherwise noted. Table 2. Parameter INPUT CHARACTERISTICS Offset Voltage Symbol Conditions VOS Offset Voltage Drift Input Bias Current ∆VOS/∆T IB VS = 3.5 V @ VCM = 0.5 V and 3.0 V VCM = 0 V to 2.7 V −40°C < TA < +125°C −40°C < TA < +125°C Min Typ Max Unit 23 80 65 500 800 7 1 50 500 0.5 50 250 2.7 µV µV µV µV/°C pA pA pA pA pA pA V dB V/mV pF pF 1.5 0.2 −40°C < TA < +85°C −40°C < TA < +125°C Input Offset Current IOS 0.1 −40°C < TA < +85°C −40°C < TA < +125°C Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Input Capacitance OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Peak-to-Peak Noise Voltage Noise Density Current Noise Density Channel Separation CMRR AVO CDIFF CCM VCM = 0 V to 2.7 V RL = 2 kΩ, VO = 0.5 V to 2.2 V VOH IL = 1 mA −40°C < TA < +125°C IL = 1 mA −40°C < TA < +125°C VOL IOUT ZOUT 0 84 55 2.65 2.6 100 150 2.6 10 2.68 11 25 30 ±50 3 f = 1 MHz, AV = 1 PSRR ISY VS = 2.7 V to 5.5 V VO = 0 V −40°C < TA < +125°C SR ts GBP ØO RL = 2 kΩ To 0.01% 12 <0.3 22 50 V/µs µs MHz Degrees en p-p en 0.1 Hz to 10 Hz f = 1 kHz f = 10 kHz f = 1 kHz f = 10 kHz f = 100 kHz 2.1 8 6 0.05 –115 –110 µV nV/√Hz nV/√Hz pA/√Hz dB dB in Cs Rev. A | Page 4 of 16 70 90 1.7 V V mV mV mA Ω 2 2.5 dB mA mA AD8616/AD8618 ABSOLUTE MAXIMUM RATINGS Table 3. AD8616/AD8618 Stress Ratings Parameter Supply Voltage Input Voltage Differential Input Voltage Ouput Short-Circuit Duration to GND Storage Temperature Operating Temperature Range Lead Temperature Range (Soldering 60 sec) Junction Temperature THERMAL RESISTANCE Rating 6V GND to VS ±3 V Indefinite –65°C to +150°C –40°C to +125°C 300°C 150°C θJA is specified for the worst-case conditions, i.e., θJA is specified for device soldered in circuit board for surface-mount packages. Table 4. Package Type 8-Lead MSOP (RM) 8-Lead SOIC (R) 14-Lead SOIC (R) 14-Lead TSSOP (RU) θJA 210 158 120 180 Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. A | Page 5 of 16 θJC 45 43 36 35 Unit °C/W °C/W °C/W °C/W AD8616/AD8618 TYPICAL PERFORMANCE CHARACTERISTICS 350 2200 300 INPUT BIAS CURRENT (pA) 1800 NUMBER OF AMPLIFIERS VS = ±2.5V VS = 5V TA = 25°C VCM = 0V TO 5V 2000 1600 1400 1200 1000 800 600 250 200 150 100 400 50 –700 –500 –300 –100 100 300 500 0 04648-0-003 0 700 OFFSET VOLTAGE (µV) 0 25 Figure 5. Input Offset Voltage Distribution 75 100 125 Figure 8. Input Bias Current vs. Temperature 22 1000 VS = 5V TA = 25°C VS = ±2.5V TA = –40°C TO +125°C VCM = 0V 20 18 100 16 14 VSY – VOUT (mV) NUMBER OF AMPLIFIERS 50 TEMPERATURE (°C) 04648-0-006 200 12 10 8 6 SOURCE 10 SINK 1 4 0 2 4 6 8 10 0.1 0.001 04648-0-004 0 12 TCVOS (µV/°C) 0.1 1 10 100 LOAD CURRENT (mA) Figure 6. Offset Voltage Drift Distribution Figure 9. Output Voltage to Supply Rail vs. Load Current 500 120 VS = 5V TA = 25°C 400 VS = 5V 100 300 OUTPUT VOLTAGE (mV) 10mA LOAD 200 100 0 –100 –200 80 60 40 –300 20 –500 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 COMMON-MODE VOLTAGE (V) 0 –40 –25 –10 5 20 35 50 65 80 95 110 TEMPERATURE (°C) Figure 10. Output Voltage Swing vs. Temperature Figure 7. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews) Rev. A | Page 6 of 16 125 04648-0-008 1mA LOAD –400 04648-0-005 INPUT OFFSET VOLTAGE (µV) 0.01 04648-0-007 2 AD8616/AD8618 90 20 45 0 0 –45 20 –90 100M 0 –20 –40 1k 10k 100k 1M 10M 60 40 FREQUENCY (Hz) 04648-0-009 GAIN (dB) 40 80 1k 100k 1M 10M FREQUENCY (Hz) Figure 11. Open-Loop Gain and Phase vs. Frequency Figure 14. Common-Mode Rejection Ratio vs. Frequency 5.0 120 VS = ±2.5V VS = 5.0V VIN = 4.9V p-p TA = 25°C RL = 2kΩ AV = 1 4.5 4.0 3.5 100 80 3.0 PSRR (dB) OUTPUT SWING (V p-p) 10k D8616-0-012 135 VS = ±2.5V 100 CMRR (dB) 60 120 PHASE (Degrees) 80 225 VS = ±2.5V TA = 25°C 180 φM = 74° 100 2.5 2.0 60 40 1.5 1.0 20 1k 10k 100k 1M 10M FREQUENCY (Hz) 0 04648-0-010 0 1k 10k Figure 12. Closed-Loop Output Voltage Swing 10M 50 VS = ±2.5V VS = 5V RL = ∞ TA = 25°C AV = 1 SMALL SIGNAL OVERSHOOT (%) 45 80 70 60 50 40 30 AV = 100 20 AV = 1 AV = 10 10 40 35 30 25 20 15 –OS 10 +OS 10k 100k 1M 10M FREQUENCY (Hz) 100M 04648-0-011 5 Figure 13. Output Impedance vs. Frequency 0 10 100 1000 CAPACITANCE (pF) Figure 16. Small-Signal Overshoot vs. Load Capacitance Rev. A | Page 7 of 16 04648-0-014 90 OUTPUT IMPEDANCE (Ω) 1M Figure 15. PSRR vs. Frequency 100 0 1k 100k FREQUENCY (Hz) 04648-0-013 0.5 AD8616/AD8618 56 VOLTAGE NOISE DENSITY (nV/ Hz) 2.0 VS = 2.7V 1.8 VS = 5V 1.6 1.4 1.2 1.0 0.8 0.6 0.4 42 35 28 21 14 –10 5 20 35 50 65 80 95 110 125 0 0 Figure 17. Supply Current vs. Temperature 1 2 3 4 5 6 FREQUENCY (kHz) 7 8 9 10 04648-0-018 –25 TEMPERATURE (°C) Figure 20. Voltage Noise Density vs. Frequency 2000 VS = 5V RL = 10kΩ CL = 200pF AV = 1 1800 VOLTAGE (50mV/DIV) 1600 1400 1200 1000 800 600 400 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) TIME (1µs/DIV) Figure 21. Small-Signal Transient Response Figure 18. Supply Current vs. Supply Voltage VS = 5V RL = 10kΩ CL = 200pF AV = 1 72 VS = 5V MKR @ 8.72 VOLTAGE (500mV/DIV) 63 04648-0-019 200 04648-0-016 54 45 36 27 18 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 FREQUENCY (kHz) 1.0 04648-0-017 9 TIME (1µs/DIV) Figure 22. Large-Signal Transient Response Figure 19. Voltage Noise Density vs. Frequency Rev. A | Page 8 of 16 04648-0-020 SUPPLY CURRENT PER AMPLIFIER (µA) 49 7 0.2 0 –40 VOLTAGE NOISE DENSITY (nV/ Hz) VS = 5V MKR @ 6.70 2.2 04648-0-015 SUPPLY CURRENT PER AMPLIFIER (mA) 2.4 AD8616/AD8618 0.1 1400 VS = ±2.5V VIN = 0.5V rms AV = 1 BW = 22kHz RL = 100kΩ VS = 2.7V TA = 25°C VCM = 0V TO 2.7V NUMBER OF AMPLIFIERS 1200 THD+N (%) 0.01 0.001 1000 800 600 400 200 100 1k 20k FREQUENCY (Hz) 0 –700 –500 –300 –100 100 300 500 04648-0-024 20 04648-0-021 0.0001 700 OFFSET VOLTAGE (µV) Figure 23. THD + N Figure 26. Input Offset Voltage Distribution 500 VS = ±2.5V VIN = 2V p-p AV = 10 VS = 2.7V TA = 25°C VOLTAGE (2V/DIV) INPUT OFFSET VOLTAGE (µV) 400 300 200 100 0 –100 –200 –300 TIME (200ns/DIV) –500 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 COMMON-MODE VOLTAGE (V) Figure 24. Settling Time 04648-0-025 04648-0-022 –400 Figure 27. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews) 500 VS = 2.7V VS = 3.5V TA = 25°C VOLTAGE (1µV/DIV) INPUT OFFSET VOLTAGE (µV) 400 300 200 100 0 –100 –200 –300 Figure 25. 0.1 Hz to 10 Hz Input Voltage Noise –500 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 COMMON-MODE VOLTAGE (V) Figure 28. Input Offset Voltage vs. Common-Mode Voltage (200 Units, Five Wafer Lots Including Process Skews) Rev. A | Page 9 of 16 04648-0-026 TIME (1s/DIV) 04648-0-023 –400 AD8616/AD8618 2.7 1000 VS = 2.7V TA = 25°C 2.1 SOURCE 10 OUTPUT SWING (V p-p) 100 VSY – VOUT (mV) VS = 2.7V VIN = 2.6V p-p TA = 25°C RL = 2kΩ AV = 1 2.4 SINK 1 1.8 1.5 1.2 0.9 0.6 0.1 0.001 0 0.1 1 10 1k 04648-0-027 0.01 LOAD CURRENT (mA) 1M 10M Figure 32. Closed-Loop Output Voltage Swing vs. Frequency 18 50 VS = 2.7V VS = ±1.35V RL = ∞ TA = 25°C AV = 1 45 16 SMALL SIGNAL OVERSHOOT (%) VOH @ 1mA LOAD 14 12 10 VOL @ 1mA LOAD 8 6 4 40 35 30 25 –OS +OS 20 15 10 2 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 0 04648-0-028 0 –40 10 225 VS = ±1.35V TA = 25°C 180 φM = 51° 135 90 20 45 0 0 –20 –45 –40 –90 –60 –135 –80 –180 –100 1k 10k 100k 1M 10M –225 100M FREQUENCY (Hz) VOLTAGE NOISE DENSITY (nV/ Hz) 40 PHASE (Degrees) 60 64 VS = 2.7V MKR @ 7.47 56 48 40 32 24 16 8 04648-0-029 80 1000 Figure 33. Small-Signal Overshoot vs. Load Capacitance Figure 30. Output Voltage Swing vs. Temperature 100 100 CAPACITANCE (pF) 04648-0-0331 5 Figure 31. Open-Loop Gain and Phase vs. Frequency 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 FREQUENCY (kHz) 0.8 0.9 Figure 34. Voltage Noise Density vs. Frequency Rev. A | Page 10 of 16 1.0 04648-0-032 OUTPUT VOLTAGE (mV) 100k FREQUENCY (Hz) Figure 29. Output Voltage to Supply Rail vs. Load Current GAIN (dB) 10k 04648-0-030 0.3 AD8616/AD8618 VS = 2.7V RL = 10kΩ CL = 200pF AV = 1 VS = 2.7V MKR @ 5.91 42 36 VOLTAGE (500mV/DIV) VOLTAGE NOISE DENSITY (nV/ Hz) 48 30 24 18 12 0 1 2 3 4 5 6 7 8 9 FREQUENCY (kHz) 10 Figure 37. Large-Signal Transient Response Figure 35. Voltage Noise Density vs. Frequency 04648-0-034 VOLTAGE (50mV/DIV) VS = 2.7V RL = 10kΩ CL = 200pF AV = 1 TIME (1µs/DIV) TIME (1µs/DIV) Figure 36. Small-Signal Transient Response Rev. A | Page 11 of 16 04648-0-035 0 04648-0-033 6 AD8616/AD8618 APPLICATIONS The AD8616/AD8618 have internal protective circuitry that allows voltages exceeding the supply to be applied at the input. AD8616/AD8618. One simple technique for compensation is the snubber, which consists of a simple RC network. With this circuit in place, output swing is maintained and the amplifier is stable at all gains. It is recommended, however, not to apply voltages that exceed the supplies by more than 1.5 V at either input of the amplifier. If a higher input voltage is applied, series resistors should be used to limit the current flowing into the inputs. Figure 40 shows the implementation of the snubber, which reduces overshoot by more than 30% and eliminates ringing, which can cause instability. Using the snubber does not recover the loss of bandwidth incurred from a heavy capacitive load. The input current should be limited to <5 mA. The extremely low input bias current allows the use of larger resistors, which allows the user to apply higher voltages at the inputs. The use of these resistors adds thermal noise, which contributes to the overall output voltage noise of the amplifier. For example, a 10 kΩ resistor has less than 13 nV/√Hz of thermal noise and less than 10 nV of error voltage at room temperature. OUTPUT PHASE REVERSAL VS = ±2.5V AV = 1 CL = 500pF VOLTAGE (100mV/DIV) INPUT OVERVOLTAGE PROTECTION Phase reversal can cause permanent damage to the amplifier and lock-ups to systems with feedback loops. TIME (2µs/DIV) Figure 39. Driving Heavy Capacitive Loads without Compensation VS = ±2.5V VIN = 6V p-p AV = 1 RL = 10kΩ VCC + – V– V+ 200Ω 500pF + VOUT – VIN 200mV VEE 500pF 04648-0-038 VOLTAGE (2V/DIV) 04648-0-037 The AD8616/AD8618 are immune to phase inversion, a phenomenon that occurs when the voltage applied at the input of the amplifier exceeds the maximum input common mode. DRIVING CAPACITIVE LOADS Although the AD8616/AD8618 are capable of driving capacitive loads of up to 500 pF without oscillating, a large amount of overshoot is present when operating at frequencies above 100 kHz. This is especially true when the amplifier is configured in positive unity gain (worst case). When such large capacitive loads are required, the use of external compensation is highly recommended. This reduces the overshoot and minimizes ringing, which in turn improves the frequency response of the VS = ±2.5V AV = 1 RS = 200Ω CS = 500pF CL = 500pF TIME (10µs/DIV) 04648-0-039 Figure 38. No Phase Reversal VOLTAGE (100mV/DIV) TIME (2ms/DIV) 04648-0-036 Figure 40. Snubber Network Figure 41. Driving Heavy Capacitive Loads Using the Snubber Network Rev. A | Page 12 of 16 AD8616/AD8618 5V OVERLOAD RECOVERY TIME REFS REFF 1/2 AD8616 DIN SCLK AD5542 VOUT UNIPOLAR OUTPUT LDAC* DGND AGND Figure 44. Buffering DAC Output Although the AD8618 typically has less than 8 nV/√Hz of voltage noise density at 1 kHz, it is possible to reduce it further. A simple method is to connect the amplifiers in parallel, as shown in Figure 45. The total noise at the output is divided by the square root of the number of amplifiers. In this case, the total noise is approximately 4 nV/√Hz at room temperature. The 100 Ω resistor limits the current and provides an effective output resistance of 50 Ω. 0V 04648-0-040 0V –50mV VDD CS LOW NOISE APPLICATIONS VS = ±2.5V RL = 10kΩ AV = 100 VIN = 50mV +2.5V 0.1µF 0.1µF SERIAL INTERFACE 10µF + 04648-0-042 Overload recovery time is the time it takes the output of the amplifier to come out of saturation and recover to its linear region. Overload recovery is particularly important in applications where small signals must be amplified in the presence of large transients. Figure 42 and Figure 43 show the positive and negative overload recovery times of the AD8616. In both cases, the time elapsed before the AD8616 comes out of saturation is less than 1 µs. In addition, the symmetry between the positive and negative recovery times allows for excellent signal rectification without distortion to the output signal. 2.5V 3 VIN V+ R1 2 1 V– R3 100Ω 10Ω TIME (1µs/DIV) R2 Figure 42. Positive Overload Recovery 1kΩ VS = ±2.5V RL = 10kΩ AV = 100 VIN = 50mV 3 V+ R4 2 1 V– R6 100Ω 10Ω –2.5V 0V R5 VOUT 1kΩ 0V 3 V+ R7 2 1 R9 V– 100Ω 10Ω R8 +50mV 04648-0-041 V+ Figure 43. Negative Overload Recovery R10 2 1 V– R12 100Ω 10Ω D/A CONVERSION The AD8616 can be used at the output of high resolution DACs. Their low offset voltage, fast slew rate, and fast settling time make the parts suitable to buffer voltage output or current output DACs. Figure 44 shows an example of the AD8616 at the output of the AD5542. The AD8616’s rail-to-rail output and low distortion help maintain the accuracy needed in data acquisition systems and automated test equipment. Rev. A | Page 13 of 16 R11 1kΩ Figure 45. Noise Reduction 04648-0-043 TIME (1µs/DIV) 1kΩ 3 AD8616/AD8618 10 HIGH SPEED PHOTODIODE PREAMPLIFIER The AD8616/AD8618 are excellent choices for I-to-V conversions. The very low input bias, low current noise, and high unity gain bandwidth of the parts make them suitable, especially for high speed photodiode preamps. The total input capacitance, C1, is the sum of the diode capacitance and that of the op amp. This creates a feedback pole and causes degradation of the phase margin, making the op amp unstable. It is therefore necessary to use a capacitor in the feedback to compensate for this pole. –10 –20 –30 –40 0.1 1 10 100 1k 10k 100k 1M FREQUENCY (Hz) 04648-0-046 In high speed photodiode applications, the diode is operated in a photoconductive mode (reverse biased). This lowers the junction capacitance at the expense of an increase in the amount of dark current that flows out of the diode. GAIN (dB) 0 Figure 48. Second-Order Butterworth Low-Pass Filter Frequency Response To get the maximum signal bandwidth, select POWER DISSIPATION C2 = C1 2πR 2 f U Although the AD8616/AD8618 are capable of providing load currents to 150 mA, the usable output load current drive capability is limited to the maximum power dissipation allowed by the device package used. In any application, the absolute maximum junction temperature for the AD8616/AD8618 is 150°C; this should never be exceeded because the device could suffer premature failure. Accurately measuring power dissipation of an integrated circuit is not always a straightforward exercise; Figure 49 has been provided as a design aid for setting a safe output current drive level or selecting a heat sink for the package options available on the AD8616. where fU is the unity gain bandwidth of the amplifier. C2 R2 +2.5V RSH CD CIN + V– V+ 04648-0-044 – ID –2.5V –VBIAS 1.5 The low input bias current and high unity gain bandwidth of the AD8616 make it an excellent choice for precision filter design. Figure 47 shows the implementation of a second-order low-pass filter. The Butterworth response has a corner frequency of 100 kHz and a phase shift of 90°. The frequency response is shown in Figure 48. 1.0 SOIC MSOP 0.5 0 2nF 0 20 40 60 80 100 TEMPERATURE (°C) 120 140 VCC Figure 49. Maximum Power Dissipation vs. Ambient Temperature V– VIN 1.1kΩ V+ 1nF VEE 04648-0-045 1.1kΩ Figure 47. Second-Order Low-Pass Filter Rev. A | Page 14 of 16 04648-0-047 ACTIVE FILTERS POWER DISSIPATION (W) Figure 46. High Speed Photodiode Preamplifier AD8616/AD8618 Calculating Power by Measuring Ambient and Case Temperature These thermal resistance curves were determined using the AD8616 thermal resistance data for each package and a maximum junction temperature of 150°C. The following formula can be used to calculate the internal junction temperature of the AD8616/AD8618 for any application: Given the two equations for calculating junction temperature: TJ = TA + P θJA where: TJ = PDISS × θJA + TA TJ = junction temperature; TA = ambient temperature. θJA = the junction-to-ambient thermal resistance. where: TJ = junction temperature; PDISS = power dissipation; θJA = package thermal resistance, junction-to-case; and TA = ambient temperature of the circuit. TJ = TC + P θJC To calculate the power dissipated by the AD8616/AD8618, use the following equation: where TC is case temperature and θJA and θJC are given in the data sheet. The two equations can be solved for P (power): PDISS = ILOAD × (VS – VOUT) TA + P θJA = TC + P θJC where: P = (TA – TC)/(θJC – θJA) ILOAD = output load current; VS = supply voltage; and VOUT = output voltage. Once power has been determined, it is necessary to go back and calculate the junction temperature to assure that it has not been exceeded. The quantity within the parentheses is the maximum voltage developed across either output transistor. The temperature measurements should be directly on the package and on a spot on the board that is near the package but not touching it. Measuring the package could be difficult. A very small bimetallic junction glued to the package could be used; an infrared sensing device could be used if the spot size is small enough. POWER CALCULATIONS FOR VARYING OR UNKNOWN LOADS Often, calculating power dissipated by an integrated circuit to determine if the device is being operated in a safe range is not as simple as it might seem. In many cases, power cannot be directly measured. This may be the result of irregular output waveforms or varying loads; indirect methods of measuring power are required. There are two methods to calculate power dissipated by an integrated circuit. The first can be done by measuring the package temperature and the board temperature. The other is to directly measure the circuit’s supply current. Calculating Power by Measuring Supply Current Power can be calculated directly if the supply voltage and current are known. However, supply current may have a dc component with a pulse into a capacitive load. This could make rms current very difficult to calculate. This can be overcome by lifting the supply pin and inserting an rms current meter into the circuit. For this to work, the user must be sure that all of the current is being delivered by the supply pin being measured. This is usually a good method in a single-supply system; however, if the system uses dual supplies, both supplies may need to be monitored. Rev. A | Page 15 of 16 AD8616/AD8618 OUTLINE DIMENSIONS 3.00 BSC 8 8.75 (0.3445) 8.55 (0.3366) 5 4.00 (0.1575) 3.80 (0.1496) 4.90 BSC 3.00 BSC 14 8 1 7 6.20 (0.2441) 5.80 (0.2283) 4 PIN 1 0.65 BSC 1.10 MAX 0.15 0.00 0.38 0.22 COPLANARITY 0.10 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) 0.80 0.60 0.40 8° 0° 0.23 0.08 0.51 (0.0201) 0.31 (0.0122) COPLANARITY 0.10 0.50 (0.0197) × 45° 0.25 (0.0098) 1.75 (0.0689) 1.35 (0.0531) SEATING PLANE 8° 0.25 (0.0098) 0° 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) COMPLIANT TO JEDEC STANDARDS MS-012AB CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-187AA Figure 52. 14-Lead Standard Small Outline Package [SOIC] (R-14) Dimensions shown in millimeters and (inches) Figure 50. 8-Lead Micro Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters 5.10 5.00 4.90 5.00 (0.1968) 4.80 (0.1890) 8 5 4.00 (0.1574) 3.80 (0.1497) 1 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 6.20 (0.2440) 5.80 (0.2284) 14 8 4.50 4.40 4.30 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE 0.50 (0.0196) × 45° 0.25 (0.0099) 6.40 BSC 1 7 PIN 1 1.05 1.00 0.80 8° 0.25 (0.0098) 0° 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) COMPLIANT TO JEDEC STANDARDS MS-012AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN 0.65 BSC 1.20 MAX 0.15 0.05 0.30 0.19 0.20 0.09 SEATING COPLANARITY PLANE 0.10 8° 0° COMPLIANT TO JEDEC STANDARDS MO-153AB-1 Figure 53. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters Figure 51. 8-Lead Standard Small Outline Package [SOIC] (R-8) Dimensions shown in millimeters and (inches) ORDERING GUIDE Model AD8616ARM-R2 AD8616ARM-REEL AD8616AR AD8616AR-REEL AD8616AR-REEL7 AD8618AR AD8618AR-REEL AD8618AR-REEL7 AD8618ARU AR8618ARU-REEL Temperature Range –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C Package Description 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead SOIC 14-Lead TSSOP 14-Lead TSSOP © 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04648–0–4/04(A) Rev. A | Page 16 of 16 Package Outline RM-8 RM-8 R-8 R-8 R-8 R-14 R-14 R-14 RU-14 RU-14 Branding Code BLA BLA 0.75 0.60 0.45