Sample & Buy Product Folder Support & Community Tools & Software Technical Documents LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 LMP7721 3-Femtoampere Input Bias Current Precision Amplifier 1 Features 3 Description • The LMP7721 is the industry’s lowest specified input bias current precision amplifier. The ultra-low input bias current is 3 fA, with a specified limit of ±20 fA at 25°C and ±900 fA at 85°C. This is achieved with the latest patent-pending technology of input bias current cancellation amplifier circuitry. This technology also maintains the ultra-low input bias current over the entire input common-mode voltage range of the amplifier. 1 • • • • • • • • • • • • • Unless Otherwise Noted, Typical Values at TA = 25°C, VS = 5 V. Input Bias Current (VCM = 1 V) – Maximum at 25°C ±20 fA – Maximum at 85°C ±900 fA Offset Voltage ±26 µV Offset Voltage Drift −1.5 μV/°C DC Open-Loop Gain 120 dB DC CMRR 100 dB Input Voltage Noise (at f = 1 kHz) 6.5 nV/√Hz THD 0.0007% Supply Current 1.3 mA GBW 17 MHz Slew Rate (Falling Edge) 12.76 V/μs Supply Voltage 1.8 V to 5.5 V Operating Temperature Range −40°C to 125°C 8-Pin SOIC 2 Applications • • • • • • Photodiode Amplifier High Impedance Sensor Amplifier Ion Chamber Amplifier Electrometer Amplifier pH Electrode Amplifier Transimpedance Amplifier Ultra-Low Input Bias Current 5 Other outstanding features, such as low voltage noise (6.5 nV/√Hz), low DC-offset voltage (±150 µV maximum at 25°C) and low-offset voltage temperature coefficient (−1.5 µV/°C), improve system sensitivity and accuracy in high-precision applications. With a supply voltage range of 1.8 V to 5.5 V, the LMP7721 is the ideal choice for batteryoperated, portable applications. The LMP7721 is part of the LMP™ precision amplifier family. As part of Texas Instruments' PowerWise™ products, the LMP7721 provides the remarkably wide-gain bandwidth product (GBW) of 17 MHz while consuming only 1.3 mA of current. This wide GBW along with the high open-loop gain of 120 dB enables accurate signal conditioning. With these specifications, the LMP7721 has the performance to excel in a wide variety of applications such as electrochemical cell amplifiers and sensor interface circuits. The LMP7721 is offered in an 8-pin SOIC package with a special pinout that isolates the amplifier’s input from the power supply and output pins. With proper board layout techniques, the unique pinout of the LMP7721 will prevent PCB leakage current from reaching the input pins. Thus system error will be further reduced. INPUT BIAS (fA) 0 Device Information(1) -5 PART NUMBER LMP7721 PACKAGE BODY SIZE (NOM) SOIC (8) 4.90 mm × 3.90 mm -10 (1) For all available packages, see the orderable addendum at the end of the datasheet. + 5V V -15 - = V = 0V TA = 25°C -20 0 0.5 1 1.5 2 2.5 3 3.5 VCM (V) 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 6.7 4 4 4 4 5 6 8 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics: 2.5 V ................................ Electrical Characteristics: 5 V ................................... Typical Characteristics .............................................. Detailed Description ............................................ 16 7.1 Overview ................................................................. 16 7.2 Functional Block Diagram ....................................... 16 7.3 Feature Description................................................. 16 7.4 Device Functional Modes........................................ 17 8 Application and Implementation ........................ 20 8.1 Application Information............................................ 20 8.2 Typical Application ................................................. 22 9 Power Supply Recommendations...................... 25 10 Layout................................................................... 25 10.1 Layout Guidelines ................................................. 25 10.2 Layout Example .................................................... 25 11 Device and Documentation Support ................. 26 11.1 11.2 11.3 11.4 11.5 Device Support...................................................... Documentation Support ........................................ Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 26 26 26 26 26 12 Mechanical, Packaging, and Orderable Information ........................................................... 26 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision D (March 2013) to Revision E • Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1 Changes from Revision C (March 2013) to Revision D • 2 Page Page Changed layout of National Data Sheet to TI format ........................................................................................................... 25 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 5 Pin Configuration and Functions 8-Pin SOIC Package Top View N/C - V VOUT 1 8 2 7 + IN+ 3 6 4 5 IN- N/C V + N/C Note: Non-standard single pinout. Substitutions may require a new layout. Pin Functions PIN NAME NO. I/O DESCRIPTION IN+ 1 I Non-Inverting Input N/C 2 - No Internal Connection V- 3 P Negative Power Supply VOUT 4 O Output N/C 5 - No Internal Connection V+ 6 P Positive Power Supply N/C 7 - No Internal Connection IN- 8 I Inverting Input (1) (1) (1) Recommeded to connect to system guard trace. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 3 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings (1) (2) MIN MAX UNIT –0.3 0.3 V –0.3 6.0 V V+ + 0.3 V− − 0.3 V 150 °C 235 °C 260 °C 150 °C VIN Differential Supply Voltage (VS = V+ – V−) (3) Voltage on Input/Output Pins Junction Temperature (4) Soldering Information Infrared or Convection (20 sec) Wave Soldering Lead Temp. (10 sec) −65 Storage temperature, Tstg (1) (2) (3) (4) (1)(2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Recommended Operating Conditions indicate conditions for which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test conditions, see the Electrical Characteristics Tables. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. The voltage on any pin should not exceed 6V relative to any other pins. The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly onto a PC Board. 6.2 ESD Ratings VALUE V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) ±2000 Charged-device model (CDM), per JEDEC specification JESD22C101 (2) ±200 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 6.3 Recommended Operating Conditions MIN MAX UNIT –40 125 °C 0°C ≤ TA ≤ 125°C 1.8 5.5 V −40°C ≤ TA ≤ 125°C 2.0 5.5 V Temperature Range (1) + − Supply Voltage (VS = V – V ): (1) The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly onto a PC Board. 6.4 Thermal Information LMP7721 THERMAL METRIC (1) D UNIT 8 PINS RθJA (1) 4 Junction-to-ambient thermal resistance 190 °C/W For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 6.5 Electrical Characteristics: 2.5 V Unless otherwise specified, all limits are specified for TA = 25°C, V+ = 2.5 V, V− = 0 V, VCM = (V+ + V−)/2. PARAMETER VOS TEST CONDITIONS Input Offset Voltage –40°C ≤ TJ ≤ 125°C TC VOS Input Offset Voltage Drift IBIAS Input Bias Current MIN (1) TYP (2) MAX (1) –180 ±50 180 –480 VCM = 1 V (4) (5) 25°C –20 −40°C to 85°C −40°C to 125°C pA ±40 fA VCM = 1 V Common-Mode Rejection Ratio 0 V ≤ VCM ≤ 1.4 V 83 ±6 0 V ≤ VCM ≤ 1.4 V, –40°C ≤ TJ ≤ 125°C 80 1.8 V ≤ V+ ≤ 5.5 V, V− = 0 V, VCM = 0 84 1.8 V ≤ V ≤ 5.5 V, V = 0 V, VCM = 0, –40°C ≤ TJ ≤ 125°C CMVR AVOL VO 100 92 dB 80 CMRR ≥ 80 dB −0.3 1.5 CMRR ≥ 78 dB, –40°C ≤ TJ ≤ 125°C –0.3 1.5 Large Signal Voltage Gain VO = 0.15 V to 2.2 V, RL = 2 kΩ to V+/2 88 VO = 0.15 V to 2.2 V, RL = 2 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 82 VO = 0.15 V to 2.2 V, RL = 10 kΩ to V+/2 92 VO = 0.15 V to 2.2 V, RL = 10 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 88 RL = 2 kΩ to V+/2 70 RL = 2 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 77 RL = 10 kΩ to V+/2 60 RL = 10 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 66 Output Swing Low RL = 2 kΩ to V+/2 25 IS (6) 36 Sourcing to V−, VIN = 200 mV TJ ≤ 125°C (6) 30 Sinking to V+, VIN = −200 mV (6) 7.5 Sinking to V+, VIN = −200 mV TJ ≤ 125°C (6) 5.0 46 Slew Rate GBW Gain Bandwidth Product en Input-Referred Voltage Noise (1) (2) (3) (4) (5) (6) mA 15 1.1 –40°C ≤ TJ ≤ 125°C SR mV 60 62 Sourcing to V−, VIN = 200 mV Supply Current 70 73 RL = 10 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C , –40°C ≤ mV from V+ 20 15 , –40°C ≤ dB 120 30 RL = 10 kΩ to V+/2 Output Short Circuit Current V 107 RL = 2 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C IO dB Input Common-Mode Voltage Range Output Swing High fA 5 Input Offset Current − 20 –5 (5) + μV/°C 900 CMRR Power Supply Rejection Ratio ±3 –4 –900 IOS PSRR μV 480 –1.5 (3) UNIT 1.5 mA 1.75 AV = +1, Rising (10% to 90%) 9.3 AV = +1, Falling (90% to 10%) 10.8 15 f = 400 Hz 8 f = 1 kHz 7 V/μs MHz nV/ Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlations using the Statistical Quality Control (SQC) method. Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not specified on shipped production material. Offset voltage average drift is determined by dividing the change in VOS at the temperature extremes by the total temperature change. Positive current corresponds to current flowing into the device. This parameter is specified by design and/or characterization and is not tested in production. The short circuit test is a momentary open loop test. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 5 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Electrical Characteristics: 2.5 V (continued) Unless otherwise specified, all limits are specified for TA = 25°C, V+ = 2.5 V, V− = 0 V, VCM = (V+ + V−)/2. PARAMETER TEST CONDITIONS MIN (1) TYP (2) In Input-Referred Current Noise f = 1 kHz THD+N Total Harmonic Distortion + Noise f = 1 kHz, AV = 2, RL = 100 kΩ VO = 0.9 VPP 0.003% f = 1 kHz, AV = 2, RL = 600 Ω VO = 0.9 VPP 0.003% MAX (1) 0.01 UNIT pA/ 6.6 Electrical Characteristics: 5 V Unless otherwise specified, all limits are specified for TA = 25°C, V+ = 5 V, V− = 0 V, VCM = (V+ + V−)/2. PARAMETER VOS TEST CONDITIONS Input Offset Voltage –40°C ≤ TJ ≤ 125°C TC VOS Input Offset Average Drift IBIAS Input Bias Current MIN (1) TYP (2) MAX (1) –150 ±26 150 450 –1.5 (3) VCM = 1 V (4) (5) 25°C −40°C to 85°C −40°C to 125°C –20 5 pA ±40 fA Input Offset Current Common-Mode Rejection Ratio 0 V ≤ VCM ≤ 3.7 V 84 0 V ≤ VCM ≤ 3.7 V, –40°C ≤ TJ ≤ 125°C 82 1.8 V ≤ V+ ≤ 5.5 V, V− = 0 V, VCM = 0 84 1.8 V ≤ V+ ≤ 5.5 V, V− = 0 V, VCM = 0, –40°C ≤ TJ ≤ 125°C 80 AVOL VO ±6 100 96 dB CMRR ≥ 80 dB −0.3 4 CMRR ≥ 78 dB, –40°C ≤ TJ ≤ 125°C –0.3 4 Large Signal Voltage Gain VO = 0.3 V to 4.7 V, RL = 2 kΩ to V+/2 88 VO = 0.3 V to 4.7 V, RL = 2 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 82 VO = 0.3 V to 4.7 V, RL = 10 kΩ to V+/2 92 VO = 0.3 V to 4.7 V, RL = 10 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 88 RL = 2 kΩ to V+/2 70 RL = 2 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 77 RL = 10 kΩ to V+/2 60 RL = 10 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C 66 Output Swing Low RL = 2 kΩ to V+/2 + RL = 10 kΩ to V /2 RL = 10 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C (2) (3) (4) (5) 6 V 111 dB 120 30 mV from V+ 20 31 RL = 2 kΩ to V+/2, –40°C ≤ TJ ≤ 125°C (1) dB Input Common-Mode Voltage Range Output Swing High fA –5 CMRR CMVR 20 μV/°C 900 IOS Power Supply Rejection Ratio ±3 –4 μV –900 (5) PSRR 450 UNIT 70 73 20 60 mV 62 Limits are 100% production tested at 25°C. Limits over the operating temperature range are specified through correlations using the Statistical Quality Control (SQC) method. Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not specified on shipped production material. Offset voltage average drift is determined by dividing the change in VOS at the temperature extremes by the total temperature change. Positive current corresponds to current flowing into the device. This parameter is specified by design and/or characterization and is not tested in production. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Electrical Characteristics: 5 V (continued) Unless otherwise specified, all limits are specified for TA = 25°C, V+ = 5 V, V− = 0 V, VCM = (V+ + V−)/2. MIN (1) TYP (2) Sourcing to V , VIN = 200 mV (6) 46 60 Sourcing to V−, VIN = 200 mV TJ ≤ 125°C (6) 38 Sinking to V+, VIN = −200 mV (6) 10.5 Sinking to V+, VIN = −200 mV TJ ≤ 125°C (6) 6.5 PARAMETER IO Output Short Circuit Current IS TEST CONDITIONS − , –40°C ≤ , –40°C ≤ Supply Current Slew Rate GBW Gain Bandwidth Product en Input-Referred Voltage Noise 1.3 mA 1.7 mA 1.95 AV = +1, Rising (10% to 90%) 10.43 AV = +1, Falling (90% to 10%) 12.76 17 f = 400 Hz 7.5 f = 1 kHz 6.5 0.01 In Input-Referred Current Noise f = 1 kHz THD+N Total Harmonic Distortion + Noise f = 1 kHz, AV = 2, RL = 100 kΩ VO = 4 VPP 0.0007% f = 1 kHz, AV = 2, RL = 600Ω VO = 4 VPP 0.0007% (6) UNIT 22 –40°C ≤ TJ ≤ 125°C SR MAX (1) V/μs MHz nV/ pA/ The short circuit test is a momentary open loop test. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 7 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com 6.7 Typical Characteristics Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 5 10 0 INPUT BIAS (fA) INPUT BIAS (fA) 0 -5 -10 -10 -20 -30 + + V = 5V V = 0V -15 V = 5V V = 0V -40 TA = 25°C -20 0 TA = 25°C 1 0.5 2 1.5 3 2.5 -50 3.5 0 1 2 VCM (V) 400 0.4 + V = 0V TA = 85°C 100 0 -100 -200 - V = 0V TA = 85°C 0 -0.2 -0.4 -0.6 -0.8 -300 -400 + V = +5V 0.2 - INPUT BIAS CURRENT (pA) INPUT BIAS CURRENT (fA) Figure 2. Input Bias Current vs. VCM V = +5V 200 -1 0 0.5 1 1.5 2 2.5 3 -1.2 3.5 0 0.5 1 VCM (V) + 2.5 3 3.5 4 + V = 2.5V - - V = 0V 4 2 Figure 4. Input Bias Current vs. VCM 25 V = +5V 6 1.5 VCM (V) Figure 3. Input Bias Current vs. VCM 8 20 TA = 125°C PERCENTAGE (%) INPUT BIAS CURRENT (pA) 4 VCM (V) Figure 1. Input Bias Current vs. VCM 300 3 2 0 -2 -4 V = 0V 15 10 -6 5 -8 -10 0 0.5 1 1.5 2 2.5 3 3.5 4 VCM (V) -100 0 100 200 OFFSET VOLTAGE (PV) Figure 5. Input Bias Current vs. VCM 8 0 -200 Submit Documentation Feedback Figure 6. Offset Voltage Distribution Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 25 25 + V = 5.0V 20 PERCENTAGE (%) PERCENTAGE (%) - V = 0V 20 + V = 2.5V - 15 10 V = 0V 15 10 5 5 0 -200 -100 0 100 0 -4 200 -3 Figure 7. Offset Voltage Distribution 25 -2 -1 Figure 8. TCVOS Distribution 400 + + V = 1.8V V- = 0V V = 5.0V 300 - V = 0V OFFSET VOLTAGE (PV) PERCENTAGE (%) 20 0 TCVOS DISTRIBUTION (PV/qC) OFFSET VOLTAGE (PV) 15 10 5 -40°C 200 100 25°C 0 -100 125°C -200 -300 0 -4 -3 -2 -1 -400 -0.3 0 0 0.3 TCVOS DISTRIBUTION (PV/qC) 0.9 0.6 1.5 VCM (V) Figure 9. TCVOS Distribution Figure 10. Offset Voltage vs. VCM 400 400 + + V = +2.5V 300 V = 0V -40°C 200 100 25°C 0 -100 -200 125°C -300 V = +5V 300 - OFFSET VOLTAGE (PV) OFFSET VOLTAGE (PV) 1.2 - V = 0V -40°C 200 100 0 25°C -100 -200 125°C -300 -400 -0.3 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 -400 -0.3 VCM (V) 0.7 1.7 2.7 3.7 4.7 VCM (V) Figure 11. Offset Voltage vs. VCM Figure 12. Offset Voltage vs. VCM Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 9 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 200 400 150 300 + OFFSET VOLTAGE (PV) 200 100 25°C 0 -100 -200 125°C V = +2.5V 100 - V = 0V 50 0 + -50 V = +5V - V = 0V -100 -300 -150 -400 1.5 2.5 3.5 4.5 5.5 -200 -40 -20 6 VS (V) 0 20 40 60 Figure 14. Offset Voltage vs. Temperature 140 2 SUPPLY CURRENT (mA) 125°C - V = -2.5V 135 RL = 10 M: 113 100 25°C 80 GAIN (dB) 1.2 0.8 -40°C 90 60 20 pF 100 pF 40 68 45 50 pF 20 23 0.4 0 0 1.5 2.5 3.5 4.5 50 pF 100 pF -20 5.5 1k VS (V) 135 40 CL = 20 pF 113 35 V = -2.5V PHASE 100 90 80 60 68 40 45 GAIN 20 23 0 0 PHASE MARGIN (°) 45 - 120 10k 100k 1M 1M 10M -23 100M 10M VS = 2.5V RL = 600: 30 RL = 10 k: 25 20 RL = 10 M: 15 10 5 RL = 100 k:, 10 k:, 10 M:, 600: -20 1k 100k Figure 16. Open-Loop Frequency Response Gain and Phase 158 V+ = +2.5V PHASE (°) 140 10k 0 FREQUENCY (Hz) Figure 15. Supply Current vs. Supply Voltage GAIN (dB) 158 + V = +2.5V 120 0 20 -23 100M 200 CAPACITIVE LOAD (pF) FREQUENCY (Hz) Figure 17. Open-Loop Frequency Response Gain and Phase 10 125 TEMPERATURE (°C) Figure 13. Offset Voltage vs. Supply Voltage 1.6 80 100 PHASE (°) OFFSET VOLTAGE (PV) -40°C Figure 18. Phase Margin vs. Capacitive Load Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 45 100 VS = 5V 40 90 PHASE MARGIN (°) 35 RL = 600: RL = 10 k: 25 20 80 CMRR (dB) 30 RL = 10 M: 70 15 60 10 50 5 + V = +2.5V - 0 20 V = -2.5V 40 10 100 200 Figure 19. Phase Margin vs. Capacitive Load 100k 1M Figure 20. CMRR vs. Frequency 1000 120 100 VS = 5V VOLTAGE NOISE (nV/ Hz) -PSRR 80 PSRR (dB) 10k FREQUENCY (Hz) CAPACITIVE LOAD (pF) 60 +PSRR 40 20 1k + 100 VS = 2.7V 10 V = +2.5V - V = -2.5V 0 10 1k 100 10k 1 0.1 10M 1M 100k 10 1 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz) Figure 21. PSRR vs. Frequency Figure 22. Input-Referred Voltage Noise vs. Frequency + f = 1 MHz - AV = +1 + V = +2.5V - V = -2.5V V = +2.5V V = -2.5V CL = 10 pF RL = 1 M: 1 PV/DIV 10 mV/DIV VIN = 20 mVPP 1s/DIV 200 ns/DIV Figure 23. Time Domain Voltage Noise Figure 24. Small Signal Step Response Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 11 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. + + f = 1 MHz V = +2.5V - V = -1.25V AV = +1 V = -2.5V VIN = 20 mVPP CL = 10 pF V = +1.25V CL = 10 pF VIN = 1 VPP f = 200 kHz - RL = 1 M: AV = +1 10 mV/DIV 200 mV/DIV RL = 1 M: 1 Ps/DIV 200 ns/DIV Figure 26. Large Signal Step Response Figure 25. Small Signal Step Response + VIN = 1 VPP f = 200 kHz V = +1.25V - - RL = 1 M: AV = +1 200 mV/DIV + V = +1.2V THD+N (dB) V = -1.25V -40 CL = 10 pF -50 V = -0.6V f = 1 kHz -60 AV = +2 VCM = 0V -70 RL = 600: -80 -90 RL = 100 k: -100 0.01 0.1 1 Ps/DIV 10 OUTPUT AMPLITUDE (VPP) Figure 27. Large Signal Step Response Figure 28. THD+N vs. Output Voltage 0.006 0 + + V = +1.2V V = +2.5V - - -20 V = -2.5V f = 1 kHz 0.005 V = -0.6V VCM = 0V -40 AV = +2 0.004 VO = 0.9 VPP AV = +2 THD+N (%) THD+N (dB) 1 -60 RL = 600: RL = 600: 0.003 RL = 100 k: -80 0.002 -100 0.001 RL = 100 k: -120 0.001 0.01 0.1 1 10 100 1k 10k 100k FREQUENCY (Hz) OUTPUT AMPLITUDE (VPP) Figure 29. THD+N vs. Output Voltage 12 0 10 Submit Documentation Feedback Figure 30. THD+N vs. Frequency Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 0.008 80 + V = +2.5V 0.007 V- = -2.5V 70 125°C 60 ISOURCE (mA) THD+N (%) 0.006 VO = 4 VPP AV = +2 0.005 0.004 0.003 50 25°C 40 -40°C 30 RL = 600: 0.002 20 0.001 10 RL = 100 k: 0 10 100 1k 0 1.5 100k 10k 2.5 3.5 FREQUENCY (Hz) 4.5 5.5 VS (V) Figure 31. THD+N vs. Frequency Figure 32. Sourcing Current vs. Supply Voltage 35 70 30 60 + V = +2.5V - V = 0V 25°C 50 25°C 125°C 20 15 -40°C 10 125°C ISOURCE (mA) ISINK (mA) 25 40 30 -40°C 20 10 5 0 1.5 0 2.5 3.5 4.5 5.5 0 0.5 1 1.5 2 2.5 VS (V) VOUT (V) Figure 33. Sinking Current vs. Supply Voltage Figure 34. Sourcing Current vs. Output Voltage 70 35 + V = +2.5V 25°C 60 - 30 V = 0V 125°C 25 ISINK (mA) ISOURCE (mA) 50 40 -40°C 30 20 25°C 125°C 20 15 10 -40°C + 10 5 V = +5V - V = 0V 0 0 0 1 2 3 4 5 0 0.5 1 1.5 2 2.5 VOUT (V) VOUT (V) Figure 35. Sourcing Current vs. Output Voltage Figure 36. Sinking Current vs. Output Voltage Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 13 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 35 50 + RL = 10 k: V = +5V - V = 0V 125°C VOUT FROM RAIL (mV) 30 ISINK (mA) 25 20 15 25°C -40°C 10 40 125°C 30 25°C 20 10 -40°C 5 0 0 1 2 3 4 0 1.5 5 2.5 VOUT (V) Figure 37. Sinking Current vs. Output Voltage 4.5 5.5 Figure 38. Output Swing High vs. Supply Voltage 50 50 RL = 10 k: 40 30 25°C -40°C 20 125°C 10 0 1.5 2.5 3.5 RL = 2 k: VOUT FROM RAIL (mV) VOUT FROM RAIL (mV) 3.5 VS (V) 40 25°C 125°C 30 20 -40°C 10 4.5 0 1.5 5.5 2.5 3.5 4.5 5.5 VS (V) VS (V) Figure 39. Output Swing Low vs. Supply Voltage Figure 40. Output Swing High vs. Supply Voltage 50 70 40 25°C -40°C VOUT FROM RAIL (mV) VOUT FROM RAIL (mV) RL = 600: 125°C 60 30 125°C 20 50 40 -40°C 25°C 30 20 10 10 RL = 2 k: 0 1.5 2.5 3.5 4.5 0 1.5 5.5 VS (V) 3.5 4.5 5.5 VS (V) Figure 41. Output Swing Low vs. Supply Voltage 14 2.5 Figure 42. Output Swing High vs. Supply Voltage Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Typical Characteristics (continued) Unless otherwise specified: TA = 25°C, VCM = (V+ + V−)/2. 140 RL = 600: VOUT FROM RAIL (mV) 120 25°C 100 125°C 80 60 -40°C 40 20 0 1.5 2.5 3.5 4.5 5.5 VS (V) Figure 43. Output Swing Low vs. Supply Voltage Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 15 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com 7 Detailed Description 7.1 Overview The LMP7721 combines a patented input bias current cancelling circuitry along with an optimized pinout to provide and ultra-low maximum specified bias current of ±20 fA. 7.2 Functional Block Diagram 7.3 Feature Description 7.3.1 Ultra-Low Input Bias Current The LMP7721 has the industry’s lowest specified input bias current. The ultra-low input bias current is typically 3 fA, with a specified limit of ±20 fA at 25°C, ±900 fA at 85°C and ±5 pA at 125°C when VCM = 1 V with a 5-V or a 2.5-V power supply. 7.3.2 Wide Bandwidth at Low-Supply Current The LMP7721 is a high-performance amplifier that provides a 17-MHz unity gain bandwidth while drawing only 1.3 mA of current. This makes the LMP7721 ideal for wideband amplification in portable applications. 7.3.3 Low Input Referred Noise The LMP7721 has a low input-referred voltage noise density (6.5 nV at 1 kHz with 5-V supply). Its MOS input stage ensures a very low input-referred current noise density (0.01 pA/ ). The low input-referred noise and the ultra-low input bias current make the LMP7721 stand out in maintaining signal fidelity. This quality makes the LMP7721 a suitable candidate for sensor-based applications. 7.3.4 Low-Supply Voltage The LMP7721 has performance specified at 2.5-V and 5-V power supplies. The LMP7721 is ensured to be functional at all supply voltages between 2 V to 5.5 V, for ambient temperatures ranging from −40°C to 125°C. This means that the LMP7721 has a long operational span over the battery's lifetime. The LMP7721 is also specified to be functional at 1.8-V supply voltage, for ambient temperatures ranging from 0°C to 125°C. This makes the LMP7721 ideal for use in low-voltage commercial applications. 7.3.5 Rail-to-Rail Output and Ground Sensing Rail-to-rail output swing provides the maximum possible output dynamic range. This is particularly important when operating at low-supply voltages. An innovative positive feedback scheme is created to boost the LMP7721’s output current drive capability. This allows the LMP7721 to source 30 mA to 40 mA of current at 1.8V power supply. The LMP7721’s input common-mode range includes the negative supply rail which makes direct sensing at ground possible in single-supply operation. 16 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Feature Description (continued) 7.3.6 Unique Pinout The LMP7721 has been designed with the IN+ and IN−, V+ and V− pins on opposite sides of the package. There are isolation pins between IN+ and V−, IN− and V+. This unique pinout makes it easy to guard the LMP7721’s input. This pinout design reduces the input bias current’s dependence on common mode or supply bias. The SOIC package features low leakage and it has large pin spacing. This lowers the probability of dust particles settling down between two pins thus reducing the resistance between the pins which can be a problem. The two No Connect (N/C) isolation pins are not internally connected and may be tied to the guard trace to provide down-into-the-package level guarding of the inputs. 7.3.7 Input Protection The LMP7721 input stage is protected from seeing excessive differential input voltage by a pair of back-to-back diodes attached between the inputs. This limits the differential voltage and hence prevents phase inversion as well as any performance drift. These diodes can conduct current when the input signal has a really fast edge, and, if necessary, should be isolated (using a resistor or a current follower) in such cases. Under normal feedback operation, the average differential voltage is less than 1 mV and these diodes do not affect the normal operation of the device. This clamp also limits the use as a comparator, which is not a recommended function for operational amplifiers. + + V V D1 ESD IN R1 ESD R2 + IN ESD ESD D2 - V - - V Figure 44. Input Protection Diodes 7.4 Device Functional Modes 7.4.1 Compensating Input Capacitance The high-input resistance of the LMP7721 allows the use of large feedback and source resistor values without losing gain accuracy due to loading. However, the circuit will be especially sensitive to its layout when these large-value resistors are used. Figure 45. General Operational Amplifier Circuit Every amplifier has some capacitance between each input and AC ground, and also some differential capacitance between the inputs. When the feedback network around an amplifier is resistive, this input capacitance (along with any additional capacitance due to circuit board traces, the socket, etc.) and the feedback resistors create a pole in the feedback path. This pole can cause gain "peaking" or outright oscillations. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 17 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Device Functional Modes (continued) In the General Operational Amplifier circuit, Figure 45 the frequency of this pole is: (1) where: • CS is the total capacitance at the inverting input, including amplifier input capacitance and any stray capacitance from the circuit board traces. • RP is the parallel combination of RF and RIN The typical input capacitance of the LMP7721 is about 11pF. This formula, as well as all formulas derived below, apply to inverting and non-inverting op amp configurations. When the feedback resistors are smaller than a few kΩ, the frequency of the feedback pole will be quite high, since CS is generally less than 15 pF. If the frequency of the feedback pole is much higher than the “ideal” closed-loop bandwidth (the nominal closed-loop bandwidth in the absence of CS), the pole will have a negligible effect on stability, as it will add only a small amount of phase shift. However, if the feedback pole is less than approximately 6 to 10 times the “ideal” −3 dB frequency, a feedback capacitor, CF, should be connected between the output and the inverting input of the op amp. This condition can also be stated in terms of the amplifier’s low-frequency noise gain: To maintain stability a feedback capacitor will probably be needed if (2) where (3) is the amplifier’s low-frequency noise gain and GBW is the amplifier’s gain bandwidth product. An amplifier’s lowfrequency noise gain is represented by the formula (4) regardless of whether the amplifier is being used in inverting or noninverting mode. Note that a feedback capacitor is more likely to be needed when the noise gain is low and/or the feedback resistor is large. If the above condition is met (indicating a feedback capacitor will probably be needed), and the noise gain is large enough that: (5) the following value of feedback capacitor is recommended: (6) If 18 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Device Functional Modes (continued) (7) the feedback capacitor should be: (8) Note that these capacitor values are usually significant smaller than those given by the older, more conservative formula: (9) NOTE CS consists of the amplifier’s input capacitance plus any stray capacitance from the circuit board. CF compensates for the pole caused by CS and the feedback resistors. Using the smaller capacitors will give much higher bandwidth with little degradation of transient response. It may be necessary in any of the above cases to use a somewhat larger feedback capacitor to allow for unexpected stray capacitance, or to tolerate additional phase shifts in the loop, or excessive capacitive load, or to decrease the noise or bandwidth, or simply because the particular circuit implementation needs more feedback capacitance to be sufficiently stable. For example, a printed circuit board’s stray capacitance may be larger or smaller than the breadboard’s, so the actual optimum value for CF may be different from the one estimated using the breadboard. In most cases, the values of CF should be checked on the actual circuit, starting with the computed value. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 19 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information The LMP7721 is specified for operation from 1.8 V to 5.5 V. Many of the specifications apply from –40°C to 125°C. Parameters that can exhibit significant variance with regard to operating voltage or temperature are presented in the Typical Characteristics section. 8.1.1 Using a Guard In order to take full advantage of the LMP7721’s ultra-low input bias current, a "Guard" trace is recommended when designing sub-nanoamp systems. High Impedance Input Amplifer Input Guard Ground 2.5V Rleak Leakage Path ûV = 0V! Cstray Rleak Leakage Path ûV = 2.5V! Cstray Vcm 2.5V Guard Driver 0V Figure 46. Guarding Theory A "Guard" is a driven trace or shield that physically surrounds the input trace and feedback circuitry that is held at a potential equal to the average input signal potential. Since the input circuitry and the guard are kept at the same potential, the leakage current between the two nodes is practically zero. The guard is a low-impedance node, so any external leakages will "leak" into the guard and not into the protected input. One benefit of using a guard is it cancels the effect of the added stray and cable capacitance at low frequencies (but cannot cancel the sensor or amplifier input capacitance). The guard potential may be taken from the inverting input (summing node) in noninverting and buffer applications. An example of this is shown in Figure 47 If the guarding needs to extend beyond the immediate local area around the IC, then a buffer should be used to drive the guard to prevent adding additional capacitance to the inverting node. VREF + - +1 - OUT + IN Guard Figure 47. Guarding the Noninverting Configuration The guard potential may be taken from the noninverting input or reference voltage in inverting or transimpedance applications. An example of this is shown in Figure 48 20 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Application Information (continued) Guard IN - Guard Driver OUT + +1 VREF + - Figure 48. Guarding the Inverting or Transimpedance Configuration The gain of the buffer should be slightly less than one to prevent oscillations and should be current limited to protect against short circuits. The buffer amplifier should also be capable of driving large capacitive loads. To satisfy these two requirements, a small series output resistor is usually placed on the buffer output in the range of 100 Ω to 1 kΩ. For optimum results, the guard should completely enclose the input circuitry within a conductive "cocoon", including above and below the circuitry. A cover or shield connected to the guard should protect the circuitry above (or below) the PC board. Do not forget about thru-hole devices (like leaded photodiodes or connectors) that may expose high-impedance nodes to the opposite side of the board. The guard trace should not be relied upon as the only method of shielding. A ground plane or shield should surround and protect the guard from large external leakages and noise, as the guard trace has the potential to couple noise back into the input. For more information on guarding, please see the articles referenced in Related Documentation. 8.1.2 Use Triaxial Cable A triaxial cable or connector is similar to a coaxial cable or connector and is often referred to as “triax”. The triaxial cable extends the guard protection through the length of the cable by adding a second internal guard "shield" around the center conductor in addition to the outer ground shield. Figure 49 shows the structure of the triax connector. OUTER SHIELD/GROUND GUARD 1 SIGNAL CONDUCTOR Figure 49. The Structure of a Triax 8.1.3 Properly Clean the Assembly Proper cleaning of the board is very critical to providing the expected sub-picoamp performance. Properly cleaning the board and components takes a few extra steps over conventional board cleaning methods. Leftover flux residue, moisture and cleaning solvent residues will severely degrade the low-current performance. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 21 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Application Information (continued) If using "water soluble" or "no clean" flux, a second cleaning step is needed. These fluxes still leave a film behind that can attract contaminates and dust. The board should be washed with fresh isopropyl alcohol or methanol and baked to make sure all remaining traces of moisture are removed from the board. Areas between the component leads should be scrubbed and areas under surface mount devices thoroughly flushed. The board should be re-cleaned after any rework to components within the guarded areas. Boards should be handled by the edges and stored in sealed containers with desiccant. 8.2 Typical Application The following application examples highlight only a few of the circuits where the LMP7721 can be used. A CMOS input stage with ultra-low input bias current, negligible input current noise, and low input voltage noise allows the LMP7721 to provide high fidelity amplification. In addition, the LMP7721 has a 17 MHz gain bandwidth product, which enables high gain at wide bandwidth. A rail-to-rail output swing at 5.5-V power supply allows detection and amplification of a wide range of input currents. These properties make the LMP7721 ideal for transimpedance amplification. RF + V 0.1 µF RG LMP7721 TRIAX Vout + - 0.1 µF V 0.1 µF 100: + LMP7715 0.1 µF pH ELECTRODE Figure 50. LMP7721 as pH Electrode Amplifier 8.2.1 Design Requirements The output of a pH electrode is typically 59.16 mV per pH unit at 25°C, for an output range of 414 mV to −414 mV as the pH changes from 0 to 14 at 25°C. 22 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 Typical Application (continued) mV 600 100°C (74.04 mV/pH) 500 400 25°C (59.16 mV/pH) 300 200 100 2 4 12 10 8 14 pH 0 -100 1 3 5 7 9 11 13 -200 -300 -400 -500 0°C (54.20 mV/pH) -600 Figure 51. pH Electrode Transfer Function The output impedance of a pH electrode is extremely high, ranging from 10 MΩ to 1000 MΩ. The ultra low input bias current of the LMP7721 allows the voltage error produced by the input bias current and electrode resistance to be minimal. For example, the output impedance of the pH electrode used is 10 MΩ, if an op amp with 3 nA of Ibias is used, the error caused due to this amplifier’s input bias current and the source resistance of the pH electrode is 30 mV! This error can be greatly reduced to 30 nV by using the LMP7721. + RS V Ibias VS Vin + LMP7721 - + - - Vin = VS ± (Ibias x RS) V Error Figure 52. Error Caused by Amplifier’s Input Bias Current and Sensor Source Impedance 8.2.2 Detailed Design Procedure The output voltage of the pH electrode will range from 54.2 mV/pH at 0°C, to 74.04 mV/pH at 100°C. The maximum input voltage will then be ±74.04 mV * 7 = ±518.3 mV. Allowing for output swing and offset headroom, the maximum output swing should be limited to ±2.4V. The amplifier gain would then be 2.4 V / 0.5183 V = 4.6 V/V. With RF = 3.57 kΩ and RG = 1 kΩ, the gain would be 4.57 V/V. The output voltage from the pH electrode is fed to the signal conductor of the triax and then sent to the noninverting input of the LMP7721. In this application, the inverting input is a low impedance node and hence is used to drive the LMP7715 which acts as a guard driver. The output of the guard driver is connected to the guard of the triax through a 100-Ω isolation resistor. Figure 50 is an example of the LMP7721 used as a pH sensor amplifier. Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 23 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com Typical Application (continued) 8.2.3 Application Curve 2.5 OUTPUT VOLTAGE (V) 2.0 GAIN = 4.6 V/V 1.5 1.0 0.5 0.0 -0.5 -1.0 0°C -1.5 25°C -2.0 100°C -2.5 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 pH LEVEL C002 Figure 53. Output Voltage vs. pH Level 24 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 LMP7721 www.ti.com SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 9 Power Supply Recommendations For high-sensitivity applications, the power supply rails should be as clean as possible. Noise on the power supply lines can modulate the tiny capacitance (about 0.5 pF) of the ESD structure on each input. While this is not a major concern for most applications, charge-sensitive or high-gain, high-impedance applications can be affected. Common results are power line "hum" or high-frequency switcher "hash" imposed on the signal. TI recommends using a very low noise linear regulator and add a dedicated filter network to the LMP7721 power supply pins consisting of a series resistor of about 100 Ω, and a bypass capacitor of 100 uF or larger. Series inductors or ferrite beads may be required if high frequency switcher noise is present. 10 Layout 10.1 Layout Guidelines In order to capitalize on the LMP7721’s ultra-low input bias current, careful circuit layout and assembly are required. Guarding techniques are highly recommended to reduce parasitic leakage current by isolating the LMP7721’s input from large voltage gradients across the PC board. A guard is a low-impedance conductor that surrounds an input line and its potential is raised to the input line’s voltage. The input pins should be fully guarded as shown in Figure 54. The guard traces should completely encircle the input connections. In addition, they should be located on both sides of the PCB and be connected together. To further guard the inputs from the supply pins, the two N/C pins may be connected to the guard trace which will provide guarding down to the leadframe level. Solder mask should not cover the input and the guard area including guard traces on either side of the PCB. Keep switching power supplies and other noise-producing devices away from the input area. 10.2 Layout Example GUARD + V IN- N/C IN+ N/C - V N/C VOUT GUARD Figure 54. Layout Example Showing Guard Trace Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 25 LMP7721 SNOSAW6E – JANUARY 2008 – REVISED DECEMBER 2014 www.ti.com 11 Device and Documentation Support 11.1 Device Support 11.1.1 Development Support • LMP7721 PSPICE Model, SNOM096 • TINA-TI SPICE Based Circuit Simulation Software (free download), http://www.ti.com/tool/tina-ti • TI FilterPro Filter Design software, http://www.ti.com/tool/filterpro 11.2 Documentation Support 11.2.1 Related Documentation For related documentation, see the following: • LMP7721 Multi-Function Evaluation Board (current evaluation board), SNOU004 • AN-1796 LMP7721 Evaluation Board (obsolete evaluation board - for reference only), SNOA513 • AN-1798 Designing with Electro-Chemical Sensors, SNOA514 • AN-1803 Design Considerations for a Transimpedance Amplifier, SNOA515 • AN-1852 Designing With pH Electrodes, SNOA529 • Compensate Transimpedance Amplifiers Intuitively, SBOA055 • Transimpedance Considerations for High-Speed Operational Amplifiers, SBOA112 • Noise Analysis of FET Transimpedance Amplifiers, SBOA060 • Circuit Board Layout Techniques - SLOA089 • Handbook of Operational Amplifier Applications - SBOA092 • Low Level Measurements Handbook, Keithley Instruments, Inc., Latest Edition. Available: www.keithley.com • Grohe, P., "Design femtoampere circuits with low leakage, Part 1", EDN Magazine, November 7, 2011. Available: www.edn.com • Grohe, P., "Design femtoampere circuits with low leakage, Part 2", EDN Magazine, June 15, 2012. Available: www.edn.com • Grohe, P., "Design femtoampere circuits with low leakage, Part 3", EDN Magazine, September 7, 2012. Available: www.edn.com 11.3 Trademarks LMP, PowerWise are trademarks of Texas Instruments. All other trademarks are the property of their respective owners. 11.4 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 11.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 26 Submit Documentation Feedback Copyright © 2008–2014, Texas Instruments Incorporated Product Folder Links: LMP7721 PACKAGE OPTION ADDENDUM www.ti.com 21-Oct-2014 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LMP7721MA/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LMP77 21MA LMP7721MAX/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 125 LMP77 21MA (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 21-Oct-2014 In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 21-Oct-2014 TAPE AND REEL INFORMATION *All dimensions are nominal Device LMP7721MAX/NOPB Package Package Pins Type Drawing SOIC D 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 12.4 Pack Materials-Page 1 6.5 B0 (mm) K0 (mm) P1 (mm) 5.4 2.0 8.0 W Pin1 (mm) Quadrant 12.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 21-Oct-2014 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMP7721MAX/NOPB SOIC D 8 2500 367.0 367.0 35.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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