Precision, Ultralow Noise, RRIO, Zero-Drift Op Amp ADA4528-1 PIN CONFIGURATION Low offset: 2.5 μV maximum Low offset voltage drift: 0.015 μV/°C maximum Low noise 5.6 nV/√Hz at f = 1 kHz, AV = +100 97 nV p-p at f = 0.1 Hz to 10 Hz, AV = +100 Open-loop voltage gain: 130 dB minimum CMRR: 135 dB minimum PSRR: 130 dB minimum Gain bandwidth product: 4 MHz Single-supply operation: 2.2 V to 5.5 V Dual-supply operation: ±1.1 V to ±2.75 V Rail-to-rail input and output Unity-gain stable NC 1 –IN 2 +IN 3 ADA4528-1 TOP VIEW (Not to Scale) V– 4 8 NC 7 V+ 6 OUT 5 NC NC = NO CONNECT. DO NOT CONNECT TO THIS PIN. 09437-001 FEATURES Figure 1. 8-Lead MSOP APPLICATIONS Thermocouple/thermopile Load cell and bridge transducer Precision instrumentation Electronic scales Medical instrumentation Handheld test equipment GENERAL DESCRIPTION The ADA4528-1 is an ultralow noise, zero-drift operational amplifier featuring rail-to-rail input and output swing. With an offset voltage of 2.5 μV, offset voltage drift of 0.015 μV/°C, and noise of 97 nV p-p (0.1 Hz to 10 Hz, AV = +100), the ADA4528-1 is well suited for applications in which error sources cannot be tolerated. TheADA4528-1 has a wide operating supply range of 2.2 V to 5.5 V, high gain, and excellent CMRR and PSRR specifications that make it ideal for precision amplification of low level signals, such as position and pressure sensors, strain gages, and medical instrumentation. Table 1. Analog Devices, Inc., Zero-Drift Op Amp Portfolio 1 Type Single Dual Quad 1 Ultralow Noise ADA4528-1 Micropower (<20 μA) ADA4051-1 ADA4051-2 Low Power (<1 mA) AD8628 AD8538 AD8629 AD8539 AD8630 16 V Operating Voltage AD8638 AD8639 See www.analog.com for a selection of zero-drift operational amplifiers. The ADA4528-1 is specified over the extended industrial temperature range (−40°C to +125°C) and is available in an 8-lead MSOP package. Rev. 0 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: 781.461.3113 ©2011 Analog Devices, Inc. All rights reserved. ADA4528-1 TABLE OF CONTENTS Features .............................................................................................. 1 ESD Caution...................................................................................5 Applications....................................................................................... 1 Typical Performance Characteristics ..............................................6 Pin Configuration............................................................................. 1 Applications Information .............................................................. 15 General Description ......................................................................... 1 Input Protection ......................................................................... 15 Revision History ............................................................................... 2 Rail-to-Rail Input and Output.................................................. 15 Specifications..................................................................................... 3 Noise Considerations................................................................. 15 Electrical Characteristics—2.5 V Operation ............................ 3 Printed Circuit Board Layout ................................................... 17 Electrical Characteristics—5 V Operation................................ 4 Outline Dimensions ....................................................................... 18 Absolute Maximum Ratings............................................................ 5 Ordering Guide .......................................................................... 18 Thermal Resistance ...................................................................... 5 REVISION HISTORY 1/11—Revision 0: Initial Version Rev. 0 | Page 2 of 20 ADA4528-1 SPECIFICATIONS ELECTRICAL CHARACTERISTICS—2.5 V OPERATION VS = 2.5 V, VCM = VSY/2 V, TA = 25°C, unless otherwise specified. Table 2. Parameter INPUT CHARACTERISTICS Offset Voltage Symbol Test Conditions/Comments VOS Offset Voltage Drift Input Bias Current ΔVOS/ΔT IB VCM = 0 V to 2.5 V −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C Input Offset Current IOS Min Typ Max Unit 0.3 2.5 4 0.015 400 600 800 1 2.5 μV μV μV/°C pA pA pA nA V dB dB dB dB dB dB kΩ GΩ pF pF 0.002 220 −40°C ≤ TA ≤ +125°C 440 −40°C ≤ TA ≤ +125°C Input Voltage Range Common-Mode Rejection Ratio CMRR Open-Loop Gain AVO Input Resistance, Differential Mode Input Resistance, Common Mode Input Capacitance, Differential Mode Input Capacitance, Common Mode OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time to 0.1% Gain Bandwidth Product Phase Margin Overload Recovery Time NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Current Noise Density VCM = 0 V to 2.5 V −40°C ≤ TA ≤ +125°C RL = 10 kΩ, VO = 0.1 V to 2.4 V −40°C ≤ TA ≤ +125°C RL = 2 kΩ, VO = 0.1 V to 2.4 V −40°C ≤ TA ≤ +125°C 0 135 116 130 126 125 121 RINDM RINCM CINDM CINCM VOH VOL ISC ZOUT PSRR ISY 158 140 132 225 1 15 30 RL = 10 kΩ to VCM −40°C ≤ TA ≤ +125°C RL = 2 kΩ to VCM −40°C ≤ TA ≤ +125°C RL = 10 kΩ to VCM −40°C ≤ TA ≤ +125°C RL = 2 kΩ to VCM −40°C ≤ TA ≤ +125°C 2.49 2.485 2.46 2.44 2.48 5 20 10 15 40 60 ±30 0.1 f = 1 kHz, AV = +10 VS = 2.2 V to 5.5 V −40°C ≤ TA ≤ +125°C IO = 0 mA −40°C ≤ TA ≤ +125°C 2.495 130 127 150 1.4 1.7 2.1 V V V V mV mV mV mV mA Ω dB dB mA mA SR ts GBP ΦM RL = 10 kΩ, CL = 100 pF, AV = +1 VIN = 1.5 V step, RL = 10 kΩ, CL = 100 pF RL = 10 kΩ, CL = 100 pF, AV = +1 RL = 10 kΩ, CL = 100 pF, AV = +1 RL = 10 kΩ, CL = 100 pF, AV = −10 0.45 7 4 57 50 V/μs μs MHz Degrees μs en p-p en f = 0.1 Hz to 10 Hz, AV = +100 f = 1 kHz, AV = +100 f = 1 kHz, AV = +100, VCM = 2.0 V f = 0.1 Hz to 10 Hz, AV = +100 f = 1 kHz, AV = +100 97 5.6 5.5 2.6 0.7 nV p-p nV/√Hz nV/√Hz pA p-p pA/√Hz in p-p in Rev. 0 | Page 3 of 20 ADA4528-1 ELECTRICAL CHARACTERISTICS—5 V OPERATION VS = 5 V, VCM = VSY/2 V, TA = +25°C, unless otherwise specified. Table 3. Parameter INPUT CHARACTERISTICS Offset Voltage Symbol Test Conditions/Comments VOS Offset Voltage Drift Input Bias Current ΔVOS/ΔT IB VCM = 0 V to 5 V −40°C ≤ TA ≤ +125°C −40°C ≤ TA ≤ +125°C Input Offset Current IOS Min Typ Max Unit 0.3 2.5 4 0.015 200 300 400 500 5 μV μV μV/°C pA pA pA pA V dB dB dB dB dB dB kΩ GΩ pF pF 0.002 90 −40°C ≤ TA ≤ +125°C 180 −40°C ≤ TA ≤ +125°C Input Voltage Range Common-Mode Rejection Ratio CMRR Open-Loop Gain AVO Input Resistance, Differential Mode Input Resistance, Common Mode Input Capacitance, Differential Mode Input Capacitance, Common Mode OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Short-Circuit Current Closed-Loop Output Impedance POWER SUPPLY Power Supply Rejection Ratio Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time to 0.1% Gain Bandwidth Product Phase Margin Overload Recovery Time NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Current Noise Density VCM = 0 V to 5 V −40°C ≤ TA ≤ +125°C RL = 10 kΩ, VO = 0.1 V to 4.9 V −40°C ≤ TA ≤ +125°C RL = 2 kΩ, VO = 0.1 V to 4.9 V −40°C ≤ TA ≤ +125°C 0 137 122 127 125 121 120 RINDM RINCM CINDM CINCM VOH VOL ISC ZOUT PSRR ISY 160 139 131 190 1 16.5 33 RL = 10 kΩ to VCM −40°C ≤ TA ≤ +125°C RL = 2 kΩ to VCM −40°C ≤ TA ≤ +125°C RL = 10 kΩ to VCM −40°C ≤ TA ≤ +125°C RL = 2 kΩ to VCM −40°C ≤ TA ≤ +125°C 4.99 4.98 4.96 4.94 4.98 5 20 10 20 40 60 ±40 0.1 f = 1 kHz, AV = +10 VSY = 2.2 V to 5.5 V −40°C ≤ TA ≤ +125°C IO = 0 mA −40°C ≤ TA ≤ +125°C 4.995 130 127 150 1.5 1.8 2.2 V V V V mV mV mV mV mA Ω dB dB mA mA SR ts GBP ΦM RL = 10 kΩ, CL = 100 pF, AV = +1 VIN = 4 V step, RL = 10 kΩ, CL = 100 pF RL = 10 kΩ, CL = 100 pF, AV = +1 RL = 10 kΩ, CL = 100 pF, AV = +1 RL = 10 kΩ, CL = 100 pF, AV = −10 0.5 10 4 57 50 V/μs μs MHz Degrees μs en p-p en f = 0.1 Hz to 10 Hz, AV = +100 f = 1 kHz, AV = +100 f = 1 kHz, AV = +100, VCM = 4.5 V f = 0.1 Hz to 10 Hz, AV = +100 f = 1 kHz, AV = +100 99 5.9 5.3 2.6 0.5 nV p-p nV/√Hz nV/√Hz pA p-p pA/√Hz in p-p in Rev. 0 | Page 4 of 20 ADA4528-1 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 4. Parameter Supply Voltage Input Voltage Input Current1 Differential Input Voltage Output Short-Circuit Duration to GND Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature (Soldering, 60 sec) 1 Rating 6V ±VSY ± 0.3 V ±10 mA ±VSY Indefinite −65°C to +150°C −40°C to +125°C −65°C to +150°C 300°C θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. This was measured using a standard 4-layer board. Table 5. Thermal Resistance Package Type 8-Lead MSOP (RM-8) ESD CAUTION The input pins have clamp diodes to the power supply pins. Limit the input current to 10 mA or less whenever input signals exceed the power supply rail by 0.5 V. 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. Rev. 0 | Page 5 of 20 θJA 142 θJC 45 Unit °C/W ADA4528-1 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. 100 100 VSY = 2.5V VCM = VSY/2 90 80 NUMBER OF AMPLIFIERS 80 60 50 40 30 70 60 50 40 30 20 20 10 10 –0.8 –0.6 –0.4 –0.2 0 0.2 VOS (µV) 0.4 0.6 0.8 1.0 0 –1.0 09437-002 0 –1.0 Figure 2. Input Offset Voltage Distribution VSY = 2.5V VCM = VSY/2 NUMBER OF AMPLIFIERS 30 20 0 0.2 VOS (µV) 0.4 0.6 0.8 1.0 VSY = 5V VCM = VSY/2 40 30 20 09437-003 0 3 6 9 12 0 15 09437-006 10 10 0 3 TCVOS (nV/°C) 6 9 12 15 TCVOS (nV/°C) Figure 6. Input Offset Voltage Drift Distribution Figure 3. Input Offset Voltage Drift Distribution 1.0 1.0 VSY = 2.5V 0.8 0.6 0.4 0.4 0.2 0.2 VOS (µV) 0.6 0 –0.2 0 –0.2 –0.4 –0.4 –0.6 –0.6 –0.8 –0.8 0 0.5 VSY = 5V 0.8 1.5 1.0 2.0 VCM (V) 2.5 09437-004 VOS (µV) –0.2 50 40 –1.0 –0.4 60 50 NUMBER OF AMPLIFIERS –0.6 Figure 5. Input Offset Voltage Distribution 60 0 –0.8 09437-005 70 –1.0 0 1 3 2 4 VCM (V) Figure 7. Input Offset Voltage vs. Common-Mode Voltage Figure 4. Input Offset Voltage vs. Common-Mode Voltage Rev. 0 | Page 6 of 20 5 09437-007 NUMBER OF AMPLIFIERS VSY = 5V VCM = VSY/2 90 ADA4528-1 400 400 VSY = 2.5V VCM = VSY/2 300 IB+ 200 200 IB+ 100 IB (pA) 100 IB (pA) VSY = 5V VCM = VSY/2 300 0 –100 0 IB– –100 –200 –300 –300 –25 0 25 50 75 100 125 TEMPERATURE (°C) –400 –50 09437-008 –400 –50 0 25 50 75 125 Figure 11. Input Bias Current vs. Temperature 600 600 400 +85°C 400 +85°C –40°C 200 200 IB (pA) +25°C +125°C 0 –40°C 0 +25°C –200 +125°C –200 –400 –400 –600 –800 0.5 1.0 1.5 2.0 2.5 VCM (V) 0 3 4 5 Figure 12. Input Bias Current vs. Common-Mode Voltage 10 OUTPUT VOLTAGE (VOL) TO SUPPLY RAIL (V) 10 VSY = 2.5V 1 100m –40°C +25°C +85°C +125°C 0.01 0.1 1 LOAD CURRENT (mA) 10 100 09437-014 1m 0.1m 0.001 2 VCM (V) Figure 9. Input Bias Current vs. Common-Mode Voltage 10m 1 VS = 5V 1 100m 10m –40°C +25°C +85°C +125°C 1m 0.1m 0.001 0.01 0.1 1 LOAD CURRENT (mA) 10 100 Figure 13. Output Voltage (VOL) to Supply Rail vs. Load Current Figure 10. Output Voltage (VOL) to Supply Rail vs. Load Current Rev. 0 | Page 7 of 20 09437-017 0 09437-009 –600 09437-012 VSY = 5V VSY = 2.5V OUTPUT VOLTAGE (VOL) TO SUPPLY RAIL (V) 100 TEMPERATURE (°C) Figure 8. Input Bias Current vs. Temperature IB (pA) –25 09437-110 IB– –200 ADA4528-1 1 100m –40°C +25°C +85°C +125°C 1m 0.01 10 0.1 1 LOAD CURRENT (mA) 100m 100 Figure 14. Output Voltage (VOH) to Supply Rail vs. Load Current OUTPUT VOLTAGE (VOL) TO SUPPLY RAIL (mV) RL = 2kΩ 15 10 RL = 10kΩ 0 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 125 09437-016 OUTPUT VOLTAGE (VOL) TO SUPPLY RAIL (mV) VSY = 2.5V 5 OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (mV) 15 10 RL = 10kΩ 5 0 25 50 75 100 125 TEMPERATURE (°C) 0.01 10 0.1 1 LOAD CURRENT (mA) 100 45 VSY = 5V 40 RL = 2kΩ 35 30 25 20 15 RL = 10kΩ 10 5 0 –50 –25 0 25 50 75 100 125 25 VSY = 5V RL = 2kΩ 20 15 10 RL = 10kΩ 5 0 –50 09437-015 OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (mV) RL = 2kΩ 20 –25 0.1m 0.001 Figure 18. Output Voltage (VOL) to Supply Rail vs. Temperature 25 0 –50 1m TEMPERATURE (°C) Figure 15. Output Voltage (VOL) to Supply Rail vs. Temperature VSY = 2.5V 10m Figure 17. Output Voltage (VOH) to Supply Rail vs. Load Current 25 20 –40°C +25°C +85°C +125°C 09437-019 0.1m 0.001 1 –25 0 25 50 75 100 125 TEMPERATURE (°C) Figure 16. Output Voltage (VOH) to Supply Rail vs. Temperature Figure 19. Output Voltage (VOH) to Supply Rail vs. Temperature Rev. 0 | Page 8 of 20 09437-117 10m VSY = 5V 09437-013 OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (V) 10 VSY = 2.5V 09437-010 OUTPUT VOLTAGE (VOH) TO SUPPLY RAIL (V) 10 ADA4528-1 2.00 2.0 +125°C 1.8 +85°C 1.50 ISY PER AMPLIFIER (mA) ISY PER AMPLIFIER (mA) 1.75 +25°C 1.25 –40°C 1.00 0.75 0.50 VSY = 5.0V 1.6 VSY = 2.5V 1.4 1.2 1.5 2.0 2.5 3.0 VSY (V) 3.5 4.0 4.5 5.0 5.5 1.0 –50 –25 0 25 Figure 20. Supply Current vs. Supply Voltage 75 100 125 Figure 23. Supply Current vs. Temperature 120 135 120 90 90 90 90 60 45 60 45 135 PHASE 0 VSY = 2.5V RL = 10kΩ CL = 100pF –30 1k GAIN –45 10k 100k VSY = 5V RL = 10kΩ CL = 100pF 0 –90 10M 1M 0 30 –30 1k 09437-022 0 PHASE (Degrees) GAIN 30 OPEN-LOOP GAIN (dB) PHASE FREQUENCY (Hz) –45 10k 100k Figure 24. Open-Loop Gain and Phase vs. Frequency 60 60 VSY = 2.5V VSY = 5V 50 50 AV = 100 AV = 100 CLOSED-LOOP GAIN (dB) 40 30 AV = 10 20 10 AV = 1 0 –10 40 30 AV = 10 20 10 AV = 1 0 –10 100 1k 10k 100k 1M FREQUENCY (Hz) 10M –20 10 09437-026 –20 10 –90 10M 1M FREQUENCY (Hz) Figure 21. Open-Loop Gain and Phase vs. Frequency CLOSED-LOOP GAIN (dB) OPEN-LOOP GAIN (dB) 50 TEMPERATURE (°C) PHASE (Degrees) 1.0 09437-025 0.5 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 25. Closed-Loop Gain vs. Frequency Figure 22. Closed-Loop Gain vs. Frequency Rev. 0 | Page 9 of 20 10M 09437-029 0 09437-021 0 09437-024 0.25 ADA4528-1 140 160 VSY = 2.5V 140 100 100 CMRR (dB) 80 60 60 40 40 VCM = VSY/2 VCM = 1.1V 10k 100k 1M 10M FREQUENCY (Hz) 0 100 09437-126 1k 1k 10k 100k Figure 26. CMRR vs. Frequency 120 VSY = 5V 100 100 80 80 PSRR (dB) 60 PSRR+ 40 60 PSRR+ 40 PSRR– PSRR– 20 20 0 0 10k 100k 1M 10M FREQUENCY (Hz) –20 100 09437-032 1k 10k 100k 1M 10M FREQUENCY (Hz) Figure 27. PSRR vs. Frequency Figure 30. PSRR vs. Frequency 1k 1k VSY = 2.5V VSY = 5V 100 100 10 1 ZOUT (Ω) 10 AV = 100 AV = 10 AV = 1 AV = 100 AV = 1 0.1 0.01 0.01 1k 10k 100k 1M FREQUENCY (Hz) 10M Figure 28. Output Impedance vs. Frequency AV = 10 1 0.1 09437-027 ZOUT (Ω) 1k 09437-035 PSRR (dB) VSY = 2.5V 0.001 100 10M Figure 29. CMRR vs. Frequency 120 –20 100 1M FREQUENCY (Hz) 09437-031 20 0 100 80 0.001 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 31. Output Impedance vs. Frequency Rev. 0 | Page 10 of 20 10M 09437-030 CMRR (dB) 120 20 VSY = 5V VCM = VSY/2 120 VOLTAGE (1V/DIV) TIME (20µs/DIV) TIME (20µs/DIV) Figure 35. Large Signal Transient Response VOLTAGE (50mV/DIV) VSY = ±2.5V VIN = 100mV p-p AV = 1 RL = 10kΩ CL = 100pF 09437-038 VSY = ±1.25V VIN = 100mV p-p AV = 1 RL = 10kΩ CL = 100pF TIME (1µs/DIV) TIME (1µs/DIV) Figure 33. Small Signal Transient Response 12 16 12 8 OVERSHOOT (%) OS+ 10 OS– 6 10 6 4 2 2 0 10 100 1000 LOAD CAPACITANCE (pF) OS+ 8 4 1 VSY = 5V VIN = 100mV p-p AV = 1 RL = 10kΩ 14 OS– 0 09437-033 OVERSHOOT (%) Figure 36. Small Signal Transient Response VSY = 2.5V VIN = 100mV p-p AV = 1 RL = 10kΩ 14 09437-041 VOLTAGE (50mV/DIV) Figure 32. Large Signal Transient Response 16 09437-037 VSY = ±2.5V VIN = 4V p-p AV = 1 RL = 10kΩ CL = 100pF 09437-034 VSY = ±1.25V VIN = 2V p-p AV = 1 RL = 10kΩ CL = 100pF 1 10 100 1000 LOAD CAPACITANCE (pF) Figure 34. Small Signal Overshoot vs. Load Capacitance Figure 37. Small Signal Overshoot vs. Load Capacitance Rev. 0 | Page 11 of 20 09437-036 VOLTAGE (0.5V/DIV) ADA4528-1 VSY = ±1.25V AV = –10 VIN = 187.5mV RL = 10kΩ CL = 100pF OUTPUT 1 0 –1 TIME (10µs/DIV) –0.5 2 0 –1 TIME (10µs/DIV) Figure 41. Positive Overload Recovery VSY = ±1.25V VIN = 187.5mV AV = –10 RL = 10kΩ CL = 100pF 0 INPUT 1 –0.5 OUTPUT 1 0 –1 0 OUTPUT VOLTAGE (V) OUTPUT –2 TIME (10µs/DIV) –1 VSY = ±2.5V AV = –10 VIN = 375mV RL = 10kΩ CL = 100pF –2 OUTPUT VOLTAGE (V) INPUT 0 0.5 09437-042 INPUT VOLTAGE (V) 0.5 –3 TIME (10µs/DIV) Figure 39. Negative Overload Recovery Figure 42. Negative Overload Recovery INPUT INPUT VOLTAGE (2V/DIV) VSY = 2.5V RL = 10kΩ CL = 100pF +7.5mV ERROR BAND 0 –7.5mV +20mV OUTPUT ERROR BAND 0 –20mV 09437-047 OUTPUT VSY = 5V RL = 10kΩ CL = 100pF 09437-044 VOLTAGE (1V/DIV) 3 1 09437-039 INPUT VOLTAGE (V) VSY = ±2.5V AV = –10 VIN = 375mV RL = 10kΩ CL = 100pF OUTPUT Figure 38. Positive Overload Recovery –0.5 INPUT 2 OUTPUT VOLTAGE (V) –0.5 0 OUTPUT VOLTAGE (V) INPUT 0 0.5 09437-043 INPUT VOLTAGE (V) 0.5 09437-040 INPUT VOLTAGE (V) ADA4528-1 TIME (10µs/DIV) TIME (10µs/DIV) Figure 40. Positive Settling Time to 0.1% Figure 43. Positive Settling Time to 0.1% Rev. 0 | Page 12 of 20 ADA4528-1 VSY = 2.5V RL = 10kΩ CL = 100pF VSY = 5V RL = 10kΩ CL = 100pF +7.5mV OUTPUT 0 ERROR BAND INPUT VOLTAGE (2V/DIV) VOLTAGE (1V/DIV) INPUT +20mV ERROR BAND OUTPUT –7.5mV 0 TIME (10µs/DIV) TIME (10µs/DIV) Figure 44. Negative Settling Time to 0.1% Figure 47. Negative Settling Time to 0.1% 100 10 1 10 100 1k 10k FREQUENCY (Hz) VSY = 5V AV = 100 VCM = VSY/2 10 1 1 1k 10k Figure 48. Voltage Noise Density vs. Frequency 10 10 1 1 10 100 1k 10k FREQUENCY (Hz) 100k Figure 46. Current Noise Density vs. Frequency VSY = 5V AV = 100 VCM = VSY/2 1 0.1 1 10 100 1k 10k FREQUENCY (Hz) Figure 49. Current Noise Density vs. Frequency Rev. 0 | Page 13 of 20 100k 09437-153 CURRENT NOISE DENSITY (pA/√Hz) VSY = 2.5V AV = 100 VCM = VSY/2 09437-150 CURRENT NOISE DENSITY (pA/√Hz) 100 FREQUENCY (Hz) Figure 45. Voltage Noise Density vs. Frequency 0.1 10 09437-049 VOLTAGE NOISE DENSITY (nV/√Hz) VSY = 2.5V AV = 100 VCM = VSY/2 09437-046 VOLTAGE NOISE DENSITY (nV/√Hz) 100 1 09437-048 09437-045 –20mV ADA4528-1 VSY = 5V AV = 100 VCM = VSY/2 TIME (1s/DIV) TIME (1s/DIV) Figure 53. 0.1 Hz to 10 Hz Noise 10 1 1 0.1 0.001 0.001 0.1 0.01 VSY = 2.5V AV = 1 f = 1kHz RL = 10kΩ 0.01 0.1 1 10 AMPLITUDE (V p-p) 0.001 0.001 VSY = 5V AV = 1 f = 1kHz RL = 10kΩ 0.01 0.1 1 10 AMPLITUDE (V p-p) 09437-155 THD + N (%) 10 09437-152 Figure 54. THD + Noise vs. Amplitude Figure 51. THD + Noise vs. Amplitude 1 1 VSY = 5V RL = 10kΩ AV = 1 80kHz LOW-PASS FILTER VIN = 2V p-p VSY = 2.5V RL = 10kΩ AV = 1 80kHz LOW-PASS FILTER VIN = 2V p-p 0.1 THD + N (%) THD + N (%) 0.1 0.01 0.001 10 100 1k 10k FREQUENCY (Hz) 100k 09437-056 0.01 Figure 52. THD + Noise vs. Frequency 0.001 10 100 1k 10k FREQUENCY (Hz) Figure 55. THD + Noise vs. Frequency Rev. 0 | Page 14 of 20 100k 09437-057 THD + N (%) Figure 50. 0.1 Hz to 10 Hz Noise 0.01 09437-053 09437-050 INPUT VOLTAGE (20nV/DIV) INPUT VOLTAGE (20nV/DIV) VSY = 2.5V AV = 100 VCM = VSY/2 ADA4528-1 3 APPLICATIONS INFORMATION VIN VOUT 2 The ADA4528-1 is a precision, ultralow noise, zero-drift operational amplifier that features a patented chopping technique. This chopping technique offers ultralow input offset voltage of 0.3 μV typical and input offset voltage drift of 0.002 μV/oC typical. VOLTAGE (V) 1 Offset voltage errors due to common-mode voltage swings and power supply variations are also corrected by the chopping technique, resulting in a typical CMRR figure of 158 dB and a PSRR figure of 150 dB at 2.5 V supply voltage. The ADA4528-1 has low broadband noise of 5.6 nV/√Hz (at f = 1 kHz, AV = +100, VSY = 2.5 V) and no 1/f noise component. These features are ideal for amplification of low level signals in dc or subhertz high precision applications. 0 –1 VSY = ±2.5V AV = 1 RL = 10kΩ –3 TIME (200µs/DIV) Figure 56. Rail-to Rail Input and Output INPUT PROTECTION NOISE CONSIDERATIONS The ADA4528-1 has internal ESD protection diodes that are connected between the inputs and each supply rail. These diodes protect the input transistors in the event of electrostatic discharge and are reverse-biased during normal operation. This protection scheme allows voltages as high as approximately 300 mV beyond the rails to be applied at the input of either terminal without causing permanent damage. Refer to Table 4 in the Absolute Maximum Ratings section. 1/f noise When either input exceeds one of the supply rails by more than 300 mV, these ESD diodes become forward-biased and large amounts of current begin to flow through them. Without current limiting, this excessive fault current causes permanent damage to the device. If the inputs are expected to be subject to overvoltage conditions, insert a resistor in series with each input to limit the input current to 10 mA maximum. However, consider the resistor thermal noise effect on the entire circuit. At a 5 V supply voltage, the broadband voltage noise of the ADA4528-1 is approximately 6 nV/√Hz (at unity gain), and a 1 kΩ resistor has thermal noise of 4 nV/√Hz. Adding a 1 kΩ resistor increases the total noise by 30% root sum square (rss). RAIL-TO-RAIL INPUT AND OUTPUT The ADA4528-1 features rail-to-rail input and output with a supply voltage from 2.2 V to 5.5 V. Figure 56 shows the input and output waveforms of the ADA4528-1 configured as a unitygain buffer with a supply voltage of ±2.5 V and a resistive load of 10 kΩ. With an input voltage of ±2.5 V, the ADA4528-1 allows the output to swing very close to both rails. Additionally, it does not exhibit phase reversal. 09437-059 –2 1/f noise, also known as pink noise or flicker noise, is inherent in semiconductor devices and increases as frequency decreases. At low frequency, 1/f noise is a major noise contributor and causes a significant output voltage offset when amplified by the noise gain of the circuit. However, the ADA4528-1 eliminates the 1/f noise internally, thus making it an excellent choice for dc or subhertz high precision applications. The 0.1 Hz to 10 Hz amplifier voltage noise is only 97 nV p-p (AV = +100) at 2.5 V of supply voltage. The low frequency 1/f noise appears as a slow varying offset to the ADA4528-1 and is greatly reduced by the chopping technique. This allows the ADA4528-1 to have a much lower noise at dc and low frequency in comparison to standard low noise amplifiers that are susceptible to 1/f noise. Figure 45 and Figure 48 show the voltage noise density of the amplifier with no 1/f noise. Source Resistance The ADA4528-1 is one of the lowest noise zero drift amplifiers with 5.6 nV/√Hz of broadband noise at 1 kHz (VSY = 2.5 V and AV = +100) currently available in the industry. Therefore, it is important to consider the input source resistance of choice to maintain a total low noise. The total input referred broadband noise (eN total) from any amplifier is primarily a function of three types of noise: input voltage noise, input current noise, and thermal (Johnson) noise from the external resistors. These uncorrelated noise sources can be summed up in a root sum squared (rss) manner by using the following equation: eN total = [en2 + 4 kTRS + (in × RS)2]1/2 where: en is the input voltage noise of the amplifier (V/√Hz). In is the input current noise of the amplifier (A/√Hz). RS is the total input source resistance (Ω). k is the Boltzmann’s constant (1.38 × 10−23 J/K). T is the temperature in Kelvin (K). Rev. 0 | Page 15 of 20 ADA4528-1 100 The total equivalent rms noise over a specific bandwidth is expressed as This analysis is valid for broadband noise calculation. If the bandwidth of concern includes the chopping frequency, more complicated calculations must be made to include the effect of the noise spike at the chopping frequency (see Figure 59). With a low source resistance of RS < 1 kΩ, the voltage noise of the amplifier dominates. As source resistance increases, the thermal noise of RS dominates. As the source resistance further increases, where RS > 100 kΩ, the current noise becomes the main contributor of the total input noise. A good selection table for low noise op amps can be found in the AN-940 Application Note, Low Noise Amplifier Selection Guide for Optimal Noise Performance. Voltage Noise Density with Different Gain Configurations Figure 57 shows the voltage noise density vs. closed-loop gain of a zero-drift amplifier from Competitor A. The voltage noise density of the amplifier increases from 11 nV/√Hz to 21 nV/√Hz as closedloop gain decreases from 1000 to 1. Figure 58 shows the voltage noise density vs. frequency of the ADA4528-1 for three different gain configurations. The ADA4528-1 offers lower input voltage noise density of 6 nV/√Hz to 7 nV/√Hz regardless of gain configurations. 20 1 16 12 8 100 1k 10k Figure 58. Voltage Noise Density vs. Frequency Residual Ripple Although the ACFB suppresses the chopping related ripples, there exists higher noise spectrum at the chopping frequency and its harmonics due to the remaining ripples. Figure 59 shows the voltage noise density of the ADA4528-1 configured in unity gain. A noise spike of 50 nV/√Hz can be seen at the chopping frequency of 200 kHz. This noise spike is significant when the op amp has a closed-loop frequency that is higher than the chopping frequency. To further suppress the noise to a desired level, it is recommended to have a post filter at the output of the amplifier. 100 4 0 10 FREQUENCY (Hz) VOLTAGE NOISE DENSITY (nV/√Hz) VSY = 5V f = 100Hz COMPETITOR A AV = 1 AV = 10 AV = 100 1 VSY = 5V AV = 1 VCM = VSY/2 10 1 09437-061 VOLTAGE NOISE DENSITY (nV/√Hz) 24 10 1 10 100 09437-062 where BW is the bandwidth in hertz. 1 10 100 1k 10k 100k FREQUENCY (Hz) 1000 Figure 59. Voltage Noise Density CLOSED-LOOP GAIN (V/V) Figure 57. Competitor A: Voltage Noise Density vs. Closed-Loop Gain Rev. 0 | Page 16 of 20 1M 10M 09437-063 eN,RMS = eN total √BW VOLTAGE NOISE DENSITY (nV/√Hz) VSY = 5V VCM = VSY/2 ADA4528-1 COMPONENT LEAD The ADA4528-1 is a high precision device with ultralow offset voltage and noise. Therefore, care must be taken in the design of the printed circuit board (PCB) layout to achieve optimum performance of the ADA4528-1 at board level. To avoid leakage currents, keep the surface of the board clean and free of moisture. Coating the board surface creates a barrier to moisture accumulation and reduces parasitic resistance on the board. Properly bypassing the power supplies and keeping the supply traces short minimizes power supply disturbances caused by output current variation. Connect bypass capacitors as close as possible to the device supply pins. Stray capacitances are a concern at the outputs and the inputs of the amplifier. It is recommended that signal traces be kept at a distance of at least 5 mm from supply lines to minimize coupling. A potential source of offset error is the Seebeck voltage on the circuit board. The Seebeck voltage occurs at the junction of two dissimilar metals and is a function of the temperature of the junction. The most common metallic junctions on a circuit board are solder-to-board trace and solder-to-component lead. Figure 60 shows a cross section of a surface-mount component soldered to a PCB. A variation in temperature across the board (where TA1 ≠ TA2) causes a mismatch in the Seebeck voltages at the solder joints, thereby resulting in thermal voltage errors that degrade the performance of the ultralow offset voltage of the ADA4528-1. VSC1 + SURFACE-MOUNT COMPONENT VTS1 + + VSC2 SOLDER + VTS2 PC BOARD TA1 COPPER TRACE TA2 IF TA1 ≠ TA2, THEN VTS1 + VSC1 ≠ VTS2 + VSC2 09437-154 PRINTED CIRCUIT BOARD LAYOUT Figure 60. Mismatch in Seebeck Voltages Causes Seebeck Voltage Error To minimize these thermocouple effects, orient resistors so that heat sources warm both ends equally. Where possible, the input signal paths should contain matching numbers and types of components to match the number and type of thermocouple junctions. For example, dummy components, such as zero value resistors, can be used to match the thermoelectric error source (real resistors in the opposite input path). Place matching components in close proximity and orient them in the same manner to ensure equal Seebeck voltages, thus cancelling thermal errors. Additionally, use leads that are of equal length to keep thermal conduction in equilibrium. Keep heat sources on the PCB as far away from amplifier input circuitry as is practical. It is highly recommended to use a ground plane. A ground plane helps distribute heat throughout the board, maintains a constant temperature across the board, and reduces EMI noise pick up. Rev. 0 | Page 17 of 20 ADA4528-1 OUTLINE DIMENSIONS 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15° MAX 1.10 MAX 0.40 0.25 6° 0° 0.23 0.09 0.80 0.55 0.40 COMPLIANT TO JEDEC STANDARDS MO-187-AA 10-07-2009-B 0.15 0.05 COPLANARITY 0.10 Figure 61. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model 1 ADA4528-1ARMZ ADA4528-1ARMZ-R7 ADA4528-1ARMZ-RL 1 Temperature Range −40°C to +125°C −40°C to +125°C −40°C to +125°C Package Description 8-Lead Mini Small Outline Package [MSOP] 8-Lead Mini Small Outline Package [MSOP] 8-Lead Mini Small Outline Package [MSOP] Z = RoHS Compliant Part. Rev. 0 | Page 18 of 20 Package Option RM-8 RM-8 RM-8 Branding A2R A2R A2R ADA4528-1 NOTES Rev. 0 | Page 19 of 20 ADA4528-1 NOTES ©2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D09437-0-1/11(0) Rev. 0 | Page 20 of 20