LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 LPV531 Programmable Micropower CMOS Input, Rail-to-Rail Output Operational Amplifier Check for Samples: LPV531 FEATURES 1 • • • • 2 • • • • • (Typical 5V Supply, unless otherwise Noted.) Supply Voltage 2.7V to 5.5V Dynamic Power Mode Setting Continuously Programmable Supply Current – Range 5 μA to 425 μA Continuously Programmable Bandwidth – Range 73 kHz to 4.6 MHz Input Common Mode Voltage Range −0.3V to 3.8V CMRR 95 dB Rail-to-Rail Output Voltage Swing Input Offset Voltage 1 mV APPLICATIONS • • • AC Coupled Circuits Portable Instrumentation Active Filters R1 R2 VIN R3 VOUT + +V The LPV531 is an extremely versatile operational amplifier. A single external resistor gives the system designer the ability to define the quiescent current, gain bandwidth product and output short circuit current. This innovative feature gives the system designer a method to dynamically switch the power level to optimize the performance of the op amp and meet the system design requirements. The LPV531 can be tailored to a wide variety of applications. It offers the system designer the ability to dynamically trade off supply current for bandwidth by adjusting the current drawn from the ISEL pin using a DAC or switching in different value resistors in series with the ISEL pin. The LPV531 is capable of operating from 73 kHz, consuming only 5 μA, to as fast as 4.6 MHz, consuming only 425 μA. The input offset voltage is relatively independent and therefore is not significantly affected by the chosen power level. Utilizing a CMOS input stage, the LPV531 achieves an input bias current of 50 fA and a common mode input voltage which extends from the negative rail to within 1.2V of the positive supply. The LPV531's railto-rail class AB output stage enables this op amp to offer maximum dynamic range at low supply voltage. Typical Application C1 DESCRIPTION C2 ISEL Offered in the space saving 6-pin SOT package, the LPV531 is ideal for use in handheld electronics and portable applications. The LPV531 is manufactured using TI’s advanced VIP50 process. A fixed supply current/gain bandwidth is available upon request. R4 REXT Figure 1. AC Coupled Application 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2006–2013, Texas Instruments Incorporated LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com 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. Absolute Maximum Ratings ESD Tolerance (1) (2) (3) Human Body Model 2000V Machine Model 200V VIN Differential ±2V Supply Voltage (V+ - V−) 6V −65°C to +150°C Storage Temperature Range Junction Temperature (4) +150°C Soldering Information (1) (2) (3) (4) Infrared or Convection (20 sec) 235°C Wave Soldering Lead Temp. (10 sec) 260°C Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings 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. Human Body Model is 1.5 kΩ in series with 100 pF. Machine Model is 0Ω in series with 200 pF. Typical values represent the most likely parametric norm. Operating Ratings (1) −40°C to +85°C Operating Temperature Range + − Supply Voltage (V – V ) Package Thermal Resistance (θJA ) 2.7V to 5.5V (2) 6-Pin SOT (1) (2) 2 171°C/W Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings 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. The maximum power dissipation is a function of TJ(MAX), θJA, and TA. 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. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 5V Full Power Mode Electrical Characteristics Unless otherwise specified, all limits are ensured for TJ = 25°C, V+ = 5V, V− = 0V, VCM = VO = V+/2, ISEL pin connected to V−, RL = 100 kΩ. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (1) Typ (2) VOS Input Offset Voltage ΔVOS Input Offset Voltage Difference TC VOS Input Offset Average Drift (3) ±2 IB Input Bias Current (4) .05 CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 3.5V 72 68 95 PSRR Power Supply Rejection Ratio V+ = 2.7V to 5.5V VCM = 1V 74 70 90 CMVR Input Common Mode Voltage Range CMRR ≥ 50 dB AVOL Large Signal Voltage Gain VO = 0.5V to 4.5V RL = 1 kΩ to V+/2 87 84 96 VO = 0.5V to 4.5V RL = 10 kΩ to V+/2 104 100 114 VO = 0.5V to 4.5V RL = 100 kΩ, to V+/2 108 104 128 VO Output Swing High Output Swing Low (VOS in Full Power Mode) − (VOS in Low Power Mode) Output Short Circuit Current (5) ±4.5 ±5 ±0.1 ±2 3.8 80 85 RL = 100 kΩ to V+/2 30 50 60 RL = 1 kΩ to V+/2 160 210 230 RL = 10 kΩ to V+/2 105 120 135 RL = 100 kΩ to V /2 95 120 135 Sourcing, VO = 2.5V VID = 100 mV −15 −8 −3 SR Slew Rate GBW Gain Bandwidth Product CL = 20 pF 4.6 en Input-Referred Voltage Noise f = 100 kHz 20 f = 1 kHz 28 f = 1 kHz 6 (1) (2) (3) (4) (5) (6) mV from V+ mV mA 24 Supply Current Input-Referred Current Noise V dB 55 IS in pA dB RL = 10 kΩ to V+/2 425 1.55 1 mV dB 180 195 AV = +1, VIN = 0.5V to 3.5V CL = 15 pF mV ±10 ±100 120 13 10 Units μV/°C RL = 1 kΩ to V+/2 Sinking, VO = 2.5V VID = −100 mV (6) (1) ±1 −0.3 + ISC Max 2.5 530 650 μA V/μs MHz nV/√Hz fA/√Hz All limits are specified by testing or statistical analysis. Typical values represent the most likely parametric norm. Offset voltage average drift is determined by dividing the change in VOS at temperature extremes into the total temperature change. Specified by design. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150°C. Slew rate is the slower of the rising or falling slew rates. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 3 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com 5V Mid-Power Mode Electrical Characteristics Unless otherwise specified, all limits are ensured for TJ = 25°C, V+ = 5V, V− = 0V, VCM = VO = V+/2, ISEL pin connected to V− through 100 kΩ resistor, RL = 100 kΩ. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (1) Typ (2) VOS Input Offset Voltage ΔVOS Input Offset Voltage Difference TC VOS Input Offset Average Drift (3) ±2 IB Input Bias Current (4) .05 CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 3.5V 72 68 92 PSRR Power Supply Rejection Ratio V+ = 2.7V to 5.5V 72 68 88 CMVR Input Common Mode Voltage Range CMRR ≥ 50 dB AVOL Large Signal Voltage Gain VO = 0.5V to 4.5V RL = 10 kΩ to V+/2 86 82 96 VO = 0.5V to 4.5V RL = 100 kΩ to V+/2 100 98 114 VO Output Swing High Output Swing Low ISC Output Short Circuit Current (5) (VOS in Full Power Mode) − (VOS in Low Power Mode) ±1 ±4.5 ±5 ±0.1 ±2 −0.3 110 120 RL = 10 kΩ to V+/2 150 165 180 RL = 100 kΩ to V+/2 105 120 135 Sourcing, VO = 2.5V VID = 100 mV −4 −1.5 −1 4 Slew Rate GBW Gain Bandwidth Product CL = 20 pF 625 en Input-Referred Voltage Noise f = 100 kHz 55 f = 1 kHz 60 f = 1 kHz 6 (1) (2) (3) (4) (5) (6) 4 AV = +1, VIN = 0.5V to 3.5V 180 100 250 pA V dB 65 SR mV dB RL = 100 kΩ to V+/2 42 mV dB 160 175 Supply Current Input-Referred Current Noise ±10 ±100 115 1.5 1 Units μV/°C 3.8 IS in (1) RL = 10 kΩ to V+/2 Sinking, VO = 2.5V VID = −100 mV (6) Max 55 62 mV from V+ mV mA μA V/ms kHz nV/√Hz fA/√Hz All limits are specified by testing or statistical analysis. Typical values represent the most likely parametric norm. Offset voltage average drift is determined by dividing the change in VOS at temperature extremes into the total temperature change. Specified by design. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150°C. Slew rate is the slower of the rising or falling slew rates. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 5V Low Power Mode Electrical Characteristics Unless otherwise specified, all limits are ensured for TJ = 25°C, V+ = 5V, V− = 0V, VCM = VO = V+/2, ISEL connected to V− through 1 MΩ resistor, RL = 100 kΩ. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (1) Typ (2) VOS Input Offset Voltage ΔVOS Input Offset Voltage Difference TC VOS Input Offset Average Drift (3) ±2 IB Input Bias Current (4) .05 CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 3.5V 72 68 90 PSRR Power Supply Rejection Ratio V+ = 2.7V to 5.5V 72 68 85 CMVR Input Common-Mode Voltage Range CMRR ≥ 50 dB AVOL Large Signal Voltage Gain VO = 0.5V to 4.5V RL = 10 kΩ to V+/2 (VOS in Full Power Mode) − (VOS in Low Power Mode) VO = 0.5V to 4.5V RL = 100 kΩ to V+/2 VO Output Swing High Output Swing Low ISC Output Short Circuit Current (5) Max (1) ±1 ±4.5 ±5 ±0.1 ±2 −0.3 mV mV μV/°C ±10 ±100 pA dB dB 3.8 V 90 80 78 dB 100 RL = 10 kΩ to V+/2 175 400 1600 RL = 100 kΩ to V+/2 115 200 230 RL = 10 kΩ to V+/2 250 1200 1800 RL = 100 kΩ to V+/2 150 165 180 Sourcing, VO = 2.5V VID = 100 mV −400 −100 −35 Sinking, VO = 2.5V VID = −100 mV Units 80 35 mV from V+ mV µA 300 IS Supply Current SR Slew Rate GBW Gain Bandwidth Product CL = 20 pF 73 kHz en Input-Referred Voltage Noise f = 1 kHz 200 nV/√Hz in Input-Referred Current Noise f = 1 kHz 60 fA/√Hz (1) (2) (3) (4) (5) (6) (6) 5 AV = +1, VIN = 0.5V to 3.5V 10 8 28 7 8 μA V/ms All limits are specified by testing or statistical analysis. Typical values represent the most likely parametric norm. Offset voltage average drift is determined by dividing the change in VOS at temperature extremes into the total temperature change. Specified by design. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150°C. Slew rate is the slower of the rising or falling slew rates. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 5 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com Power Select Electrical Characteristics Unless otherwise specified, all limits are ensured for TJ = 25°C, V+ = 5V, V− = 0V, VCM = VO = V+/2, RL = 100 kΩ. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (1) Typ (2) Max (1) Units tLF Time from Low Power Mode to Full Power Mode 210 ns tFL Time from Full Power Mode to Low Power Mode 500 ns VREXT Voltage @ ISEL Pin ISEL Pin Left Open RINT (1) (2) 100 110 125 mV 9 11 14.5 kΩ All limits are specified by testing or statistical analysis. Typical values represent the most likely parametric norm. Connection Diagram 1 6 - + V OUT 2 5 ISEL V + 3 4 IN- IN+ Figure 2. 6-Pin SOT – Top View See Package Number DDC 6 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 Typical Performance Characteristics Unless otherwise specified, V = 5V, TJ = 25°C. For Full Power Mode the ISEL pin is connected to V−; for Mid-Power Mode the ISEL pin is connected to V− through a 100 kΩ resistor; for Low Power Mode the ISEL pin is connected to V− through a 1 MΩ resistor. + Supply Current vs. ISEL Supply Current vs. ISEL 1000 600 SUPPLY CURRENT (PA) 500 SUPPLY CURRENT (PA) 25°C 85°C 400 -40°C 300 200 100 85°C 10 -40°C 25°C 100 0 -12 -8 -10 -4 -6 -2 1 -0.1 0 -1 -10 ISEL (PA) ISEL (PA) Figure 3. Figure 4. Supply Current vs. Supply Voltage (Full Power Mode) Supply Current vs. Supply Voltage (Mid Power Mode) 55 550 85°C 50 450 SUPPLY CURRENT (PA) 25°C 400 350 -40°C 45 25°C 40 35 -40°C 30 300 250 2.5 3.5 4.5 5.5 25 2.5 6.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) Figure 5. Figure 6. Supply Current vs. Supply Voltage (Low Power Mode) Gain and Phase vs. Frequency (Full Power Mode) 7 120 6.5 RL = 100 k: CL = 20 pF 100 85°C 135 113 + V = 5V 6 80 GAIN (dB) SUPPLY CURRENT (PA) 85°C 25°C 5 -40°C 90 PHASE 60 68 GAIN 40 45 20 23 0 0 PHASE (°) SUPPLY CURRENT (PA) 500 4 3 2.5 3.5 4.5 5.5 -20 100 6.5 SUPPLY VOLTAGE (V) 1k 10k 100k 1M 10M -23 100M FREQUENCY (Hz) Figure 7. Figure 8. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 7 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified, V = 5V, TJ = 25°C. For Full Power Mode the ISEL pin is connected to V−; for Mid-Power Mode the ISEL pin is connected to V− through a 100 kΩ resistor; for Low Power Mode the ISEL pin is connected to V− through a 1 MΩ resistor. + 120 Gain and Phase vs. Frequency (Low Power Mode) RL = 100 k: CL = 20 pF 100 120 135 113 + RL = 100 k: 100 PHASE V = 5V 60 68 40 45 GAIN 20 GAIN (dB) 90 PHASE PHASE (°) GAIN (dB) 80 23 -20 100 1k 10k 100k -23 10M 1M 113 + V = 5V 90 60 68 40 45 GAIN 20 23 0 0 -20 100 1k FREQUENCY (Hz) 10k -23 1M 100k FREQUENCY (Hz) Figure 9. Figure 10. Input Offset Voltage vs. Common Mode Voltage (Full Power Mode) Input Offset Voltage vs. Common Mode Voltage (Mid Power Mode) 1.5 1.5 DEVICE A @ 85°C DEVICE A @ 85°C 1 1 0.5 VOS (mV) 0.5 VOS (mV) 135 80 0 0 CL = 20 pF PHASE (°) Gain and Phase vs. Frequency (Mid Power Mode) DEVICE B @ 85°C DEVICE B @ 25°C 0 DEVICE A @ 25°C -0.5 DEVICE B @ 85°C DEVICE B @ 25°C 0 DEVICE A @ 25°C -0.5 DEVICE B @ -40°C DEVICE B @ -40°C -1 -1 DEVICE A @ -40°C DEVICE A @ -40°C -1.5 -1.5 0 2 1 3 0 4 2 1 3 VCM (V) VCM (V) Figure 11. Figure 12. Input Offset Voltage vs. Common Mode Voltage (Low Power Mode) CMRR vs. Frequency 1.5 4 100 DEVICE A @ 85°C 90 FULL POWER MODE 1 80 70 DEVICE B @ 85°C CMRR (dB) VOS (mV) 0.5 DEVICE B @ 25°C 0 DEVICE A @ 25°C -0.5 DEVICE B @ -40°C 50 40 MID POWER MODE 30 DEVICE A @ -40°C -1 60 20 -1.5 0 8 1 2 3 10 10 4 LOW POWER MODE 100 1k 10k VCM (V) FREQUENCY (Hz) Figure 13. Figure 14. Submit Documentation Feedback 100k 1M Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Unless otherwise specified, V = 5V, TJ = 25°C. For Full Power Mode the ISEL pin is connected to V−; for Mid-Power Mode the ISEL pin is connected to V− through a 100 kΩ resistor; for Low Power Mode the ISEL pin is connected to V− through a 1 MΩ resistor. + PSRR vs. Frequency (Full Power Mode) PSRR vs. Frequency (Mid Power Mode) 100 100 90 90 80 80 -PSRR 70 60 PSRR (dB) PSRR (dB) 60 +PSRR 50 +PSRR 70 40 50 -PSRR 40 30 30 20 20 10 10 0 0 10 1k 100 10k 100k 1M 10 100 1k 10k 100k 1M FREQUENCY (Hz) FREQUENCY (Hz) Figure 15. Figure 16. PSRR vs. Frequency (Low Power Mode) Small Signal Non-Inverting Response (Full Power Mode) 100 INPUT 90 80 +PSRR (50 mV/DIV) 70 PSRR (dB) 60 50 40 -PSRR OUTPUT 30 20 10 0 10 100 1k 10k 100k TIME (10 Ps/DIV) 1M FREQUENCY (Hz) Small Signal Non-Inverting Response (Mid Power Mode) Small Signal Non-Inverting Response (Low Power Mode) (50 mV/DIV) OUTPUT OUTPUT (50 mV/DIV) INPUT Figure 18. INPUT Figure 17. TIME (10 Ps/DIV) TIME (100 Ps/DIV) Figure 19. Figure 20. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 9 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified, V = 5V, TJ = 25°C. For Full Power Mode the ISEL pin is connected to V−; for Mid-Power Mode the ISEL pin is connected to V− through a 100 kΩ resistor; for Low Power Mode the ISEL pin is connected to V− through a 1 MΩ resistor. + Large Signal Non-Inverting Response (Mid Power Mode) OUTPUT OUTPUT (2 V/DIV) (2 V/DIV) INPUT INPUT Large Signal Non-Inverting Response (Full Power Mode) TIME (10 Ps/DIV) Figure 21. Figure 22. Large Signal Non-Inverting Response (Low Power Mode) Small Signal Inverting Pulse Response (Full Power Mode) OUTPUT OUTPUT (2 V/DIV) (50 mV/DIV) INPUT INPUT TIME (10 Ps/DIV) TIME (100 Ps/DIV) TIME (10 Ps/DIV) Figure 24. Small Signal Inverting Pulse Response (Mid Power Mode) Small Signal Inverting Pulse Response (Low Power Mode) OUTPUT OUTPUT (50 mV/DIV) (50 mV/DIV) INPUT INPUT Figure 23. TIME (100 Ps/DIV) TIME (10 Ps/DIV) Figure 25. 10 Figure 26. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Unless otherwise specified, V = 5V, TJ = 25°C. For Full Power Mode the ISEL pin is connected to V−; for Mid-Power Mode the ISEL pin is connected to V− through a 100 kΩ resistor; for Low Power Mode the ISEL pin is connected to V− through a 1 MΩ resistor. + (2 V/DIV) OUTPUT OUTPUT (2 V/DIV) INPUT Large Signal Inverting Response (Mid Power Mode) INPUT Large Signal Inverting Response (Full Power Mode) TIME (10 Ps/DIV) TIME (10 Ps/DIV) Figure 27. Figure 28. Large Signal Inverting Response (Low Power Mode) ISINK vs. Supply Current INPUT 100 ISINK (mA) (2 V/DIV) 10 85°C OUTPUT 1 -40°C 25°C 0.1 TIME (100 Ps/DIV) 1 10 100 1000 SUPPLY CURRENT (PA) Figure 29. Figure 30. ISOURCE vs. Supply Current Gain Bandwidth Product vs. ISEL 5000 GAIN BANDWIDTH PRODUCT (kHz) ISOURCE (mA) 100 10 85°C 1 -40°C 25°C 0.1 4500 4000 3500 3000 2500 2000 1500 1000 500 0 1 10 100 1000 SUPPLY CURRENT (PA) -10 -8 -6 -4 -2 0 ISEL CURRENT (PA) Figure 31. Figure 32. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 11 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics (continued) Unless otherwise specified, V = 5V, TJ = 25°C. For Full Power Mode the ISEL pin is connected to V−; for Mid-Power Mode the ISEL pin is connected to V− through a 100 kΩ resistor; for Low Power Mode the ISEL pin is connected to V− through a 1 MΩ resistor. + Input Referred Voltage Noise vs. Frequency Phase Margin vs. Capacitive Load 70 1000 LOW POWER MODE LOW POWER MODE PHASE MARGIN (°) VOLTAGE NOISE (nV/ Hz) RL=100 k: 60 MID POWER MODE 100 50 40 FULL POWER MODE 30 20 10 FULL POWER MODE MID POWER MODE 10 1 10 100 1k 10k 100k 100 1000 CAPACITIVE LOAD (pF) FREQUENCY (Hz) Figure 33. 12 0 10 Figure 34. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 APPLICATION INFORMATION The LPV531 is an extremely versatile operational amplifier because performance and power consumption can be adjusted during operation. This provides a method to dynamically optimize the supply current, the bandwidth and the output short circuit current in the application. The power level can be set by the current drawn from the ISEL pin according to the application performance requirements. CIRCUIT TOPOLOGY As shown in Figure 35, the LPV531 contains two internal bias reference generators that deliver a reference current (IREF) to the amplifier core. The programmable bias generator generates a 110 mV reference voltage (VINT). This reference voltage is converted into a programmable reference current (IPROG) through the internal resistor (RINT) and the external resistor (REXT) connected to the ISEL pin. Internally, IPROG is added to the output current from the low power bias generator (ISTDB). When the ISEL pin is left floating, IPROG equals zero and the IREF equals ISTDB. The value of ISTDB is such that in this mode the power supply current is below 1 µA. In this 1 µA power mode, the LPV531 is functional but performance over the full temperature range is not ensured. The 1 µA power mode operation is only recommended for applications with a temperature range between 0 and 70°C. VCC IPROG ISTDB PROGRAMMABLE BIAS GENERATOR LOW POWER BIAS GERERATOR IREF +IN OUT VINT RINT BIAS -IN VEE ISEL Figure 35. Simplified Schematic POWER MODE CONTROL To illustrate typical configurations three possible solutions to control the power mode(s) of the LPV531 will be described. Single Power Mode If the application requires one single power mode for the LPV531, then the easiest way to achieve this is to connect a resistor (REXT) from the ISEL pin to V−. Together with the internal circuitry, REXT will determine the current drawn from the ISEL pin. Internally the ISEL pin is connected to an 11 kΩ internal series resistor (RINT) which is biased at VINT = 110 mV. This set up is illustrated in Figure 36. For a desired supply current, bandwidth, short circuit current, or load resistance, the required value of REXT can be calculated using the equations in the section “DETERMINING THE ISEL LEVELS”. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 13 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 IN www.ti.com 4 + + + 6 V VINT = 110 mV RINT = 11 k: IN 3 - 1 2 V OUT - 5 ISEL REXT Figure 36. Single Power Mode Switched Discrete Power Modes In this typical application, the LPV531 can operate at two (or more) power modes in order to fulfill the demands of the design. One of the modes is used to save power. It is a low power mode which is set by using a large resistor. The others are the higher power modes which are set by one or more smaller resistors. The larger resistor that sets the low power mode can be permanently connected while the smaller resistor(s) can be switched in parallel to set the high power mode(s). This configuration allows the designer to get the required performance from the LPV531 when needed. + IN - LPV531 + REXT = 1 M: LOW POWER MODE VOUT ISEL REXT = 100 k: MID POWER MODE REXT = 0: HIGH POWER MODE Figure 37. Power Modes Set by Resistors and Switches The switches shown in Figure 37 can be easily implemented with an open drain I/O port of an ASIC or any other simple pull down switch. DAC Controlled Power Modes For voltage controlled filter applications, where control of the gain bandwidth is essential, a DAC and a resistive voltage divider can be used. In this application the current drawn from the ISEL pin is controlled by the DAC. The DAC’s total output range is divided to match the V− to VINT voltage which has the range of 0-110 mV. 14 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 - + LPV531 IN - DAC + VOUT ISEL VCONTROL REXT2 REXT1 Figure 38. DAC Controlled Power Mode Configurations The output of the resistive voltage divider should have an impedance that is small compared to the value of RINT to allow a linear control of the power level. Therefore, REXT2 needs to have a value in the order of RINT/10 and REXT1 = 125 mV * REXT2 /VCONTROL,MAX. For 1 µA power mode operation, these resistor values will divide the maximum voltage of VCONTROL to 125 mV. DETERMINING THE REXT VALUES AND ISEL LEVELS To determine the value of REXT that is needed for a certain supply current or bandwidth, the following equations can be used: 110 mV PSI = 1 PA + 40 x REXT + 11k (1) or REXT = 40 x 110 mV PSI ± 1 PA GBW = 11 kHz + -11 k: (2) 50[GHz · :] REXT + 11 k: or REXT = 50[GHz · :] GBW - 11 kHz -11 k: (3) For the power modes characterized in this datasheet, these formulas lead to the values in Table 1. These values deviate slightly from the typical values presented in the Electrical Characteristics tables. The values in Table 1 are calculated using approximated linear equations while the values in the Electrical Characteristics tables are the result of characterization measurement procedures. Table 1. Values for Characterized Power Modes REXT ISEL Supply Current Gain Bandwidth Product 1Ω 9 µA 400 µA 4.6 MHz 100 kΩ 0.9 µA 40 µA 460 kHz 1 MΩ 99 nA 5.3 µA 60 kHz To calculate the REXT which will allow the LPV531 to deliver a minimum output current at all times and over all temperatures, use the following equations: ISC = 35V REXT + 11 k: or REXT = 35V -11 k: ISC (4) + If the output has to be kept at V /2 for a known load resistance, the required REXT can be calculated with the following equations: Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 15 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 RLOAD,MIN = 0.07 REXT + 11 k: or REXT = www.ti.com 0.07 RLOAD,MIN -11 k: (5) For the characterized power modes these equations lead to the minimum values in Table 2 below. Table 2. Minimum Values for Characterized Power Modes REXT ISEL ISC RLOAD 1Ω 9 µA 3 mA 770Ω 100 kΩ 0.9 µA 300 µA 7.8 kΩ 1 MΩ 99 nA 55 µA 70.8 kΩ The smallest load resistor that the LPV531 can drive when in low power mode is 70.8 kΩ, as shown in Table 2. When driving smaller loads, such as the 10 kΩ load resistor used in the Electrical Characteristics tables specification, the output swing in the low power mode is limited. If the application requires a 10 kΩ load then it is not recommended to use the LPV531 in low power mode. ISEL SENSITIVITY The ISEL pin is a current reference that directly affects the entire internal bias condition. Therefore, the ISEL pin is very sensitive to parasitic signal coupling. In order to protect the ISEL pin from unwanted distortion, it is important to route the PCB layout such that there is as little coupling between the ISEL pin and the output or other signal traces as possible. Typical Application AC COUPLED CIRCUITS The programmable power mode makes the LPV531 ideal for AC coupled circuits where the circuit needs to be kept active to maintain a quiescent charge on the coupling capacitors with minimal power consumption. Figure 39 shows the schematic of an inverting AC coupled amplifier using the LPV531 with the ISEL pin controlled by I/O ports of a microcontroller. The advantage of the low power active mode for AC coupled amplifiers is the elimination of the time needed to re-establish a quiescent operating point when the amplifier is switched to full power mode. When an amplifier without a low power active mode is used in low power applications, there are two ways to minimize power consumption. The first method turns off the amplifier by switching off power to the op amp using a transistor switch. The second method uses an amplifier with a shutdown pin. Both of these methods have the problem of allowing the coupling capacitors, C1 and C2 to discharge the quiescent DC voltage stored on them when in the shutdown state. When the amplifier is turned on again, the quiescent DC voltages must reestablish themselves. During this time, the amplifier’s output is not usable because the output signal is a mixture of the amplified input signal and the charging voltage on the coupling capacitors. The settling time can range from a several milliseconds to several seconds depending on the resistor and capacitor values. When the LPV531 is placed into the low power mode, the power consumption is minimal but the amplifier is active to maintain the quiescent DC voltage on the coupling capacitors. The transition back to the operational high power mode is fast, within a few hundred nanoseconds. The active low power mode of the LPV531 separates two critical aspects of a low power AC amplifier design. The values of the gain resistors, bias resistors, and coupling capacitors can be chosen independently of the turn-on and stabilization time. 16 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 C1 R2 R1 VIN - R3 VOUT + +V C2 ISEL R4 REXT I/O PIN MICROCONTROLLER Figure 39. Inverting AC Coupled Application PROGRAMMABLE POWER LEVELS AND THE EFFECTS OF STABILITY COMPENSATION METHODS USING EXTERNAL COMPONENTS In some op amp application circuits, external capacitors are used to improve the stability of the feedback loop around the amplifier. When using the programmable power level feature of the LPV531 such stability improvement methods may not work. This is related to the internal frequency compensation method applied inside the LPV531. Figure 40 shows the bode plot of the frequency response of the LPV531. The gain-bandwidth product is determined by the transconductance of the input stage (gm,in) and the internal Miller compensation capacitor (Cm). The non-dominant pole is formed by the transconductance of the output stage (gm,out) and the load capacitance connected to the output of the LPV531 (Cl). The frequency response crosses the frequency axis with a single-pole slope (20 dB/decade). This ensures the stability of feedback loops formed around the LPV531. GAIN 20 dB/decade gm,in/Cm FREQUENCY (Hz) gm,out/CI 40 dB/decade Figure 40. Bode Plot of the Frequency Response When the load capacitance is increased, the pole at the output will shift to lower frequencies. Eventually, the output pole will shift below the unity gain frequency. This will cause the frequency characteristic to move through the 0 dB axis with a slope of 40 dB/decade and a feedback loop formed around the LPV531 may oscillate. The LPV531 is internally compensated in such a manner that it will be stable for load capacitances up to 100 pF. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 17 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 www.ti.com When the power setting of the LPV531 is reduced, both the transconductance of the input stage and the transconductance of the output stage will scale lineary with the power level to lower levels. This means that both the unity gain frequency and the pole to the transconductance of the output stage and the load capacitance will move down. Because both the unity gain frequency and the output pole move down in similar amounts, the stability of the LPV531 is still the same. This is shown in Figure 41 which gives the phase margin as a function of the load capacitance in the low power mode (5 µA), mid-power mode (40 µA) and high power mode (400 µA). Though the power level and unity gain frequency move with about two decades, the phase margin as a function of the capacitive load is hardly affected. This means that when the LPV531 is stable in an application circuit with a given load capacitance in the high power mode, the circuit will remain stable with the same capacitive load connected when the power level is reduced. 70 RL=100 k: 60 PHASE MARGIN (°) LOW POWER MODE 50 40 30 FULL POWER MODE 20 10 MID POWER MODE 0 10 100 1000 CAPACITIVE LOAD (pF) Figure 41. Phase Margin vs. Capacitive Load Figure 42 shows a method that is sometimes used to allow an op amp to drive larger capacitors than it was originally designed to do. The capacitive load is isolated from the output of the op amp with an isolation resistor (RISO). This moves the output pole, that was originally located at gm,out/Cl, to a higher frequency. This method requires that the value of RISO is in the same order of magnitude as 1/gm,out. For the LPV531, this method will not be effective when used across a broad range of power levels. This is because the high power mode will require a relatively small value for RISO, while such a small RISO will be ineffective at low power levels. In most applications this should not be a problem as the LPV531 can drive sufficient capacitive loads without the need for an external isolation resistor. 1 M: 1 M: VIN RISO + ISEL VOUT CL Figure 42. Compensation by Isolation Resistor 18 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 INPUT CAPACITANCE AND FEEDBACK CIRCUIT ELEMENTS The LPV531 has a very low input bias current (50 fA). To obtain this performance a large CMOS input stage is used, which adds to the input capacitance of the op amp, CIN. Though this does not affect the DC and low frequency performance, at higher frequencies the input capacitance interacts with the input and the feedback impedances to create a pole, which results in lower phase margin and gain peaking. The gain peaking can be reduced by carefully choosing the appropriate feedback resistor, as well as, by using a feedback capacitance, CF. For example, in the inverting amplifier shown in Figure 43, if CIN and CF are ignored and the open loop gain of the op amp is considered infinite then the gain of the circuit is −R2/R1. An op amp, however, usually has a dominant pole, which causes its gain to drop with frequency. Hence, this gain is only valid for DC and low frequency. To understand the effect of the input capacitance coupled with the non-ideal gain of the op amp, the circuit needs to be analyzed in the frequency domain using a Laplace transform. CF R2 R1 - + CIN VIN + + - - AV = - VOUT VIN =- VOUT R2 R1 Figure 43. Inverting Amplifier For simplicity, the op amp is modeled as an ideal integrator with a unity gain frequency of A0 . Hence, its transfer function (or gain) in the frequency domain is A0/s. Solving the circuit equations in the frequency domain, ignoring CF for the moment, results in the following equation for the gain: VOUT -R2/R1 (s) = VIN s2 s + 1+ § A0 R 1 § A0 ¨ ¨C R + R R 2 © 1 © IN 2 § ¨ © § ¨ © (6) It can be inferred from the denominator of the transfer function that it has two poles, whose expressions can be obtained by solving for the roots of the denominator: 1 1 + r R1 R2 §1 1 + ¨ R2 © R1 § ¨ © -1 P1,2 = 2CIN 2 - 4 A0CIN R2 (7) Equation 7 shows that as the values of R1 and R2 are increased, the magnitude of the poles is reduced, and hence the bandwidth of the amplifier is decreased. Furthermore, R1 and R2 are related by the gain of the amplifier. AV = −R2/R1, or alternatively R2 = −AVR1 It is the presence of pairs of poles in Equation 7 that causes gain peaking. In order to eliminate this effect, the poles should be placed in Butterworth position, since poles in Butterworth position do not cause gain peaking. To achieve a Butterworth pair, the quantity under the square root in Equation 7 should be set to equal −1. Using this fact and the relation between R1 and R2, the optimum value for R1 can be found. This is shown in Equation 8. If R1 is chosen to be larger than this optimum value, gain peaking will occur. Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 19 LPV531 SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 R1 < (1 - AV) www.ti.com 2 2A0AVCIN (8) In Figure 43, CF is added to compensate for input capacitance and to increase stability. In addition, CF reduce or eliminates the gain peaking that can be caused by having a larger feedback resistor. 20 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 LPV531 www.ti.com SNOSAK5B – MARCH 2006 – REVISED MARCH 2013 REVISION HISTORY Changes from Revision A (March 2013) to Revision B • Page Changed layout of National Data Sheet to TI format .......................................................................................................... 20 Submit Documentation Feedback Copyright © 2006–2013, Texas Instruments Incorporated Product Folder Links: LPV531 21 PACKAGE OPTION ADDENDUM www.ti.com 7-Oct-2013 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish (2) MSL Peak Temp Op Temp (°C) Device Marking (3) (4/5) LPV531MK/NOPB ACTIVE SOT DDC 6 1000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 AV2A LPV531MKX/NOPB ACTIVE SOT DDC 6 3000 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 AV2A (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. 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Addendum-Page 1 Samples PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LPV531MK/NOPB SOT DDC 6 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 LPV531MKX/NOPB SOT DDC 6 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LPV531MK/NOPB SOT DDC 6 1000 210.0 185.0 35.0 LPV531MKX/NOPB SOT DDC 6 3000 210.0 185.0 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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