OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 Low-Noise, 900kHz, RRIO, Precision OPERATIONAL AMPLIFIER Zerø-Drift Series Check for Samples: OPA378 OPA2378 FEATURES DESCRIPTION • The OPA378 and OPA2378 represent a new generation of Zerø-Drift, microPOWER™ operational amplifiers that use a proprietary auto-calibration technique to provide minimal input offset voltage (20μV) and offset voltage drift (0.1μV/°C). The combination of low input voltage noise, high gain bandwidth (900kHz), and low power (150μA max) enable these devices to achieve optimum performance for low-power precision applications. In addition, the excellent PSRR performance, coupled with a wide input supply range of 2.2V to 5.5V and rail-to-rail input and output, makes it an outstanding choice for single-supply applications that run directly from batteries without regulation. 1 23 • • • • • • • LOW NOISE – 0.4μVPP, 0.1Hz to 10Hz – 20nV/√Hz at 1kHz ZERØ-DRIFT SERIES – LOW OFFSET VOLTAGE: 20μV – LOW OFFSET DRIFT: 0.1μV/°C QUIESCENT CURRENT: 125μA GAIN BANDWIDTH: 900kHz RAIL-TO-RAIL INPUT/OUTPUT EMI FILTERING SUPPLY VOLTAGE: 2.2V to 5.5V microSIZE PACKAGES: SC70 and SOT23 APPLICATIONS • • • • • • PORTABLE MEDICAL DEVICES – GLUCOSE METERS – OXYGEN METERING – HEART RATE MONITORS WEIGH SCALES BATTERY-POWERED INSTRUMENTS THERMOPILE MODULES HANDHELD TEST EQUIPMENT SENSOR SIGNAL CONDITIONING The OPA378 (single version) is available in both a microSIZE SC70-5 and a SOT23-5 package. The OPA2378 (dual version) is offered in a SOT23-8 package. All versions are specified for operation from –40°C to +125°C. NOISE SPECTRAL DENSITY vs FREQUENCY 0.1Hz TO 10Hz NOISE 1k 100nV/div Voltage Noise Density (nV/ÖHz) Current Noise (fA/ÖHz) Continues with No 1/f (flicker) Noise Current Noise 100 Voltage Noise 10 1 Time (1s/div) 1 10 100 1k 10k Frequency (Hz) 1 2 3 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. microPOWER is a trademark of Texas Instruments Incorporated. All other 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 © 2008–2009, Texas Instruments Incorporated OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. PACKAGE INFORMATION (1) (1) PRODUCT PACKAGE-LEAD PACKAGE DESIGNATOR PACKAGE MARKING OPA378 SOT23-5 DBV OAZI OPA378 SC70-5 DCK BTS OPA2378 SOT23-8 DCN OCAI For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) Over operating free-air temperature range (unless otherwise noted). OPA378, OPA2378 UNIT +7 V Supply Voltage, VS = (V+) – (V–) Signal Input Terminals Voltage (2) (V–) – 0.3 ≤ VIN ≤ (V+) + 0.3 V Current (2) ±10 mA Output Short-Circuit (3) Continuous Operating Temperature, TA –55 to +150 °C Storage Temperature, TA –65 to +150 °C Junction Temperature, TJ +150 °C Human Body Model (HBM) 4000 V Charged Device Model (CDM) 1000 V Machine Model (MM) 200 V ESD Ratings (1) (2) (3) Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not supported. Input terminals are diode-clamped to the power-supply rails. Input signals that can swing more than 0.3V beyond the supply rails should be current limited to 10mA or less. Short-circuit to ground, one amplifier per package. PIN CONFIGURATIONS OPA378 SC70-5 (TOP VIEW) +In V-In 2 1 5 V+ 2 3 OPA2378 SOT23-8 (TOP VIEW) OPA378 SOT23-5 (TOP VIEW) Out V4 Out Submit Documentation Feedback +In 1 5 Out A V+ -In A 2 3 4 -In 1 2 +In A 3 V- 4 A B 8 V+ 7 Out B 6 -In B 5 +In B Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 ELECTRICAL CHARACTERISTICS: VS = +2.2V to +5.5V Boldface limits apply over the specified temperature range, TA = –40°C to +125°C. At TA = +25°C, RL = 10kΩ connected to VS/2, VCM = VS/2, and VOUT = VS/2, unless otherwise noted. OPA378, OPA2378 PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 20 50 μV 0.1 0.25 μV/°C 20 70 µV -40°C to +125°C 0.25 0.4 µV/°C µV/°C OFFSET VOLTAGE Input Offset Voltage, OPA378 vs Temperature VOS VCM = V– dVOS/dT Input Offset Voltage, OPA2378 vs Temperature vs Power Supply, OPA378 dVOS/dT PSRR over Temperature vs Power Supply, OPA2378 –40°C to +85°C 0.15 0.25 VCM = 0V, VS = +2.2V to +5.5V 1.5 5 μV/V VCM = 0V, VS = +2.2V to +5.5V 3 8 μV/V VCM = 0V, VS = +2.2V to +5.5V over Temperature Channel Separation (Dual Version) VCM = 0V, VS = +2.2V to +5.5V 3 At dc 135 10 μV/V 13 μV/V dB INPUT BIAS CURRENT Input Bias Current, OPA378 IB Input Bias Current, OPA2378 ±150 ±550 ±150 ±670 pA ±2 nA ±0.3 ±1.1 nA ±0.3 ±1.34 nA over Temperature, OPA378 and OPA2378 Input Offset Current, OPA378 IOS Input Offset Current, OPA2378 pA NOISE Input Voltage Noise en f = 0.1Hz to 10Hz, VS = +5.5V 0.4 μVPP Input Voltage Noise Density en f = 1kHz 20 nV/√Hz in f = 10Hz 200 fA/√Hz Input Current Noise INPUT VOLTAGE RANGE Common-Mode Voltage Range VCM Common-Mode Rejection Ratio CMRR over Temperature (V–) – 0.05 (V+) + 0.05 V (V–) – 0.05V < VCM < (V+) + 0.05V, VS = 5.5V 100 112 dB (V–) – 0.05V < VCM < (V+) + 0.05V, VS = 2.2V 94 106 (V–) – 0.05V < VCM < (V+) + 0.05V, VS = 5.5V 96 dB (V–) – 0.05V < VCM < (V+) + 0.05V, VS = 2.2V 90 dB dB INPUT CAPACITANCE Differential CIN Common-Mode 4 pF 5 pF dB OPEN-LOOP GAIN Open-Loop Voltage Gain AOL over Temperature 50mV < VO < (V+) – 50mV, RL = 100kΩ 110 134 100mV < VO < (V+) – 100mV, RL = 10kΩ 110 130 100mV < VO < (V+) – 100mV, RL = 10kΩ 106 dB dB FREQUENCY RESPONSE Gain-Bandwidth Product Slew Rate GBW SR 900 kHz G = +1 0.4 V/μs Settling Time 0.1% tS VS = 5.5V, 2V Step, G = +1 7 μs Settling Time 0.01% tS VS = 5.5V, 2V Step, G = +1 9 μs VIN × Gain > VS 4 μs VS = 5V, VO = 3VPP, G = +1, f = 1kHz 0.003 % Overload Recovery Time THD + Noise THD + N Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 3 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com ELECTRICAL CHARACTERISTICS: VS = +2.2V to +5.5V (continued) Boldface limits apply over the specified temperature range, TA = –40°C to +125°C. At TA = +25°C, RL = 10kΩ connected to VS/2, VCM = VS/2, and VOUT = VS/2, unless otherwise noted. OPA378, OPA2378 PARAMETER TEST CONDITIONS MIN TYP MAX UNIT RL = 10kΩ 6 8 mV RL = 10kΩ 8 13 mV RL = 10kΩ 6 10 mV RL = 10kΩ 8 15 mV RL = 100kΩ 0.7 2 mV 3 mV OUTPUT Voltage Output Swing from Rail, OPA378 VO over Temperature Voltage Output Swing from Rail, OPA2378 VO over Temperature Voltage Output Swing from Rail over Temperature RL = 100kΩ Short-Circuit Current Capacitive Load Drive ±30 mA CLOAD ISC See Figure 18 pF ZO See Figure 23 Ω Open-Loop Output Impedance POWER SUPPLY Specified Voltage Range Quiescent Current (per Amplifier) VS IQ 2.2 IO = 0mA, VS = +5.5V 125 over Temperature 5.5 V 150 μA 165 μA °C TEMPERATURE RANGE Specified Range –40 +125 Operating Range –55 +150 Thermal Resistance 4 θJA °C °C/W SOT23-5 200 °C/W SC70-5 250 °C/W SOT23-8 100 °C/W Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 TYPICAL CHARACTERISTICS At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. INPUT CURRENT AND VOLTAGE NOISE SPECTRAL DENSITY vs FREQUENCY 0.1Hz TO 10Hz NOISE 1k 100nV/div Voltage Noise Density (nV/ÖHz) Current Noise (fA/ÖHz) Continues with No 1/f (flicker) Noise Current Noise 100 Voltage Noise 10 1 Time (1s/div) 1 10 100 1k 10k Frequency (Hz) Figure 1. Figure 2. OFFSET VOLTAGE PRODUCTION DISTRIBUTION OFFSET VOLTAGE DRIFT DISTRIBUTION VS = 5.5V 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 Population Population VS = 5.5V Offset Voltage (mV) |Offset Voltage Drift| (mV/°C) Figure 3. Figure 4. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 5 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. POWER-SUPPLY REJECTION RATIO vs FREQUENCY OFFSET VOLTAGE vs TEMPERATURE 80 120 60 100 Offset Voltage (mV) 40 +PSRR 80 PSRR (dB) 20 0 -20 60 -PSRR 40 -40 20 -60 -80 0 -75 -50 -25 25 0 75 50 100 125 150 10 1 100 Temperature (°C) Figure 5. Figure 6. OPEN-LOOP GAIN AND PHASE vs FREQUENCY OPEN-LOOP GAIN vs TEMPERATURE 140 120 Phase 140 150 120 145 140 100 100 60 60 40 40 Gain AOL (dB) 80 Phase (°) 80 20 100k 1M RL = 100kW 135 Gain (dB) 10k 1k Frequency (Hz) RL = 10kW 130 RL = 5kW 125 120 115 20 110 0 0 -20 1 0.1 10 100 1k 10k 100k 1M 105 -20 10M 100 -75 -50 -25 0 Frequency (Hz) 75 100 125 150 Figure 8. COMMON-MODE REJECTION RATIO vs FREQUENCY COMMON-MODE REJECTION RATIO AND POWER-SUPPLY REJECTION RATIO vs TEMPERATURE 120 140 100 130 PSRR, CMRR (dB) CMRR (dB) 50 Figure 7. 80 60 40 VSCMRR = 5.5V VS = 5.5V 120 PSRR 110 CMRR VS = 2.2V 100 90 20 80 0 10 100 1k 10k 100k 1M -75 -25 -50 Figure 9. Submit Documentation Feedback 0 25 50 75 100 125 150 Temperature (°C) Frequency (Hz) 6 25 Temperature (°C) Figure 10. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. INPUT BIAS CURRENT vs INPUT COMMON-MODE VOLTAGE INPUT BIAS CURRENT vs TEMPERATURE 2000 400 1500 -IB 200 Input Bias Current (pA) Input Bias Current (pA) 300 100 0 -100 -200 +IB 500 0 -500 -1000 -1500 -300 -400 -0.5 0 1000 -2000 -75 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -50 -25 0 75 Figure 12. QUIESCENT CURRENT vs SUPPLY VOLTAGE QUIESCENT CURRENT vs TEMPERATURE 200 200 175 175 Quiescent Current (mA) Quiescent Current (mA) 50 Figure 11. 150 125 100 75 100 125 150 150 125 100 75 2.5 2.0 3.0 3.5 4.0 4.5 5.0 5.5 -75 -50 -25 VS (V) 0 25 50 75 100 125 150 Temperature (°C) Figure 13. Figure 14. OUTPUT VOLTAGE SWING vs OUTPUT CURRENT MAXIMUM OUTPUT VOLTAGE vs FREQUENCY 6 3 V+ = +2.75 +125°C +25°C -40°C 1 0 +125°C VS = ±1.1 +25°C -40°C -1 +125°C -2 VS = 5.5V 5 Output Voltage (V) 2 Output Swing (V) 25 Temperature (°C) Input Common-Mode Voltage (V) 4 3 2 VS = 2.2V +25°C -40°C 1 V- = -2.75 -3 0 0 2 4 6 8 10 12 14 16 18 20 1k 10k 100k 1M 10M Frequency (Hz) Output Current (mA) Figure 15. Figure 16. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 7 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE 1 60 50 40 Overshoot (%) THD+N (%) 0.1 0.01 30 Gain = +1V/V, -1V/V R = 10kW 20 0.001 Gain = -1V/V R = 5kW 10 0.0001 0 10 100 10k 1k 1 10 Frequency (Hz) 100 1k Load Capacitance (pF) Figure 17. Figure 18. POSITIVE OVER-VOLTAGE RECOVERY NEGATIVE OVER-VOLTAGE RECOVERY 10kW +2.5V 2V/div Output 0 +2.5V 1kW 2V/div 10kW 1kW 0 OPA378 Output RL OPA378 -2.5V RL 1V/div 1V/div -2.5V 0 Input Input 0 Time (4ms/div) Time (10ms/div) Figure 19. Figure 20. SMALL-SIGNAL STEP RESPONSE LARGE-SIGNAL STEP RESPONSE VS = ±2.75V Voltage (1V/div) Output Voltage (10mV/div) G = +1 VIN Time (5ms/div) Time (20ms/div) Figure 21. 8 Submit Documentation Feedback VOUT Figure 22. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. INPUT BIAS CURRENT vs INPUT DIFFERENTIAL VOLTAGE OPEN-LOOP OUTPUT IMPEDANCE vs FREQUENCY 50 10k Normal Operating Range (see the Input Differential Voltage section in the Applications Information) 40 Input Bias Current (mA) Output Impedance (W) 1k IO = 0A 100 10 IO = 400mA 1 1 10 100 1k 20 10 0 -10 -20 -30 Over-Driven Condition Over-Driven Condition -40 IO = 2mA 0.1 30 -50 10k 100k -1V -800 -600 -400 -200 1M 0 200 400 600 800 1V Input Differential Voltage (mV) Frequency (Hz) Figure 23. Figure 24. OPA2378 CHANNEL SEPARATION -160 -140 Overshoot (%) -120 -100 -80 -60 -40 -20 0 1k 10k 100k 1M 10M 100M 1G Frequency (Hz) Figure 25. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 9 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com APPLICATIONS INFORMATION OPERATING VOLTAGE The OPA378 and OPA2378 can be used with single or dual supplies from an operating range of VS = +2.2V (±1.1V) and up to VS = +5.5V (±2.75V). This device does not require symmetrical supplies, only a differential supply voltage of 2.2V to 5.5V. A power-supply rejection ratio of 1.5μV/V (typical) ensures that the device functions with an unregulated battery source. Supply voltages higher than +7V can permanently damage the device; see the Absolute Maximum Ratings table. Key parameters are assured over the specified temperature range, TA = –40°C to +125°C. Parameters that vary over the supply voltage or temperature range are shown in the Typical Characteristics section of this data sheet. INPUT VOLTAGE 50 40 VS = ±2.75V 10 Typical Units Shown 30 20 VOS (mV) The OPA378 and OPA2378 are unity-gain stable, precision operational amplifiers that are free from phase reversal. The use of proprietary Zerø-Drift circuitry gives the benefit of low input offset voltage over time and temperature as well as lowering the 1/f noise component. This design provides the optimization of gain, noise, and power, making the OPA378 series one of the best performers in this bandwidth range. As a result of the high PSRR, this device works well in applications that run directly from battery power without regulation. They are optimized for low-voltage, single-supply operation. These miniature, high-precision, low quiescent current amplifiers offer high-impedance inputs that have a common-mode range 100mV beyond the supplies, excellent CMRR, and a rail-to-rail output that swings within 10mV of the supplies. This design results in superior performance for driving analog-to-digital converters (ADCs) without degradation of differential linearity. 10 0 -10 -20 -30 -40 -50 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 VCM (V) Figure 26. Offset Voltage versus Common-Mode Voltage Normally, input bias current is about 150pA; however, input voltages exceeding the power supplies can cause excessive current to flow into or out of the input pins. Momentary voltages greater than the power supply can be tolerated if the input current is limited to 10mA. This limitation is easily accomplished with an input resistor, as Figure 27 shows. Current-limiting resistor required if input voltage exceeds supply rails by ³ 0.5V. +5V IOVERLOAD 10mA max OPA378 VOUT VIN 5kW Figure 27. Input Current Protection The OPA378 and OPA2378 input common-mode voltage range extends 0.05V beyond the supply rails. The OPA378 achieves a common-mode rejection ratio of 112dB (typical) over the common-mode voltage range. Figure 26 shows the variation of offset voltage over the entire specified common-mode range for 10 typical units. 10 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 The typical input bias current of the OPA378 during normal operation is approximately 150pA. In over-driven conditions, the bias current can increase significantly (see Figure 24). The most common cause of an over-driven condition occurs when the op amp is outside of the linear range of operation. When the output of the op amp is driven to one of the supply rails the feedback loop requirements cannot be satisfied and a differential input voltage develops across the input pins. This differential input voltage results in activation of parasitic diodes inside the front end input chopping switches that combine with 1.5kΩ EMI filter resistors to create the equivalent circuit shown in Figure 28. 1.5kW Clamp OPA378 operational amplifier family incorporates an internal input low-pass filter that reduces the amplifier response to EMI. Both common-mode and differential-mode filtering are provided by the input filter. The filter is designed for a cutoff frequency of approximately 25MHz (–3dB), with a roll-off of 20dB per decade. Figure 29 shows the EMI filter. 0 Filter Response (dB) INPUT DIFFERENTIAL VOLTAGE -10 -20 -30 fC = 25MHz with Parasitics Over Temperature -29dB at 800MHz +In CORE -In -40 1k 1.5kW 10k 100k 1M 10M 100M 1G Frequency (Hz) Figure 28. Equivalent Input Circuit Figure 29. EMI Filter INTERNAL OFFSET CORRECTION The OPA378 and OPA2378 family of op amps use an auto-calibration technique with a time-continuous 350kHz op amp in the signal path. This amplifier is zero-corrected every 3μs using a proprietary technique. Upon power-up, the amplifier requires approximately 100μs to achieve specified VOS accuracy. This architecture has no aliasing or flicker noise. NOISE The OPA378 series of op amps have excellent distortion characteristics. Total harmonic distortion + noise is below 0.003% (G = +1, VO = 3VRMS, and f = 1kHz, with a 10kΩ load). Design of low-noise op amp circuits requires careful consideration of a variety of possible noise contributors: noise from the signal source, noise generated in the op amp, and noise from the feedback network resistors. The total noise of the circuit is the root-sum-square combination of all the noise components. EMI SUSCEPTIBILITY AND INPUT FILTERING Operational amplifiers vary in their susceptibility to electromagnetic interference (EMI). If conducted EMI enters the operational amplifier, the dc offset observed at the amplifier output may shift from its nominal value while the EMI is present. This shift is a result of signal rectification associated with the internal semiconductor junctions. While all operational amplifier pin functions can be affected by EMI, the input pins are likely to be the most susceptible. The GENERAL LAYOUT GUIDELINES Attention to good layout practices is always recommended. Keep traces short and, when possible, use a printed circuit board (PCB) ground plane with surface-mount components placed as close to the device pins as possible. Place a 0.1μF capacitor closely across the supply pins. These guidelines should be applied throughout the analog circuit to improve performance. For lowest offset voltage and precision performance, circuit layout and mechanical conditions should be optimized. Avoid temperature gradients that create thermoelectric (Seebeck) effects in the thermocouple junctions formed from connecting dissimilar conductors. These thermally-generated potentials can be made to cancel by assuring they are equal on both input terminals. Other layout and design considerations include: • Use low thermoelectric-coefficient conditions (avoid dissimilar metals). • Thermally isolate components from power supplies or other heat sources. • Shield op amp and input circuitry from air currents, such as cooling fans. Following these guidelines reduces the likelihood of junctions being at different temperatures, which can cause thermoelectric voltages of 0.1μV/°C or higher, depending on materials used. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 11 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com ELECTRICAL OVERSTRESS Designers often ask questions about the capability of an operational amplifier to withstand electrical overstress. These questions tend to focus on the device inputs, but may involve the supply voltage pins or even the output pin. Each of these different pin functions have electrical stress limits determined by the voltage breakdown characteristics of the particular semiconductor fabrication process and specific circuits connected to the pin. Additionally, internal electrostatic discharge (ESD) protection is built into these circuits to protect them from accidental ESD events both before and during product assembly. It is helpful to have a good understanding of this basic ESD circuitry and its relevance to an electrical overstress event. Figure 30 shows the ESD circuits contained in the OPA378 (indicated by the dashed line area). The ESD protection circuitry involves several current-steering diodes connected from the input and output pins and routed back to the internal power-supply lines, where they meet at an absorption device internal to the operational amplifier. This protection circuitry is intended to remain inactive during normal circuit operation. RF +V +VS ESD OPA378 V- ESD RI ESD CurrentSteering Diodes -In Op-Amp Core +In Edge-Triggered ESD Absorption Circuit ID Out RL ESD VIN (1) ESD V+ -V -VS (1) VIN = +VS + 500mV. Figure 30. Equivalent Internal ESD Circuitry and Its Relation to a Typical Circuit Application 12 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 An ESD event produces a short duration, high-voltage pulse that is transformed into a short duration, high-current pulse as it discharges through a semiconductor device. The ESD protection circuits are designed to provide a current path around the operational amplifier core to prevent it from being damaged. The energy absorbed by the protection circuitry is then dissipated as heat. When an ESD voltage develops across two or more of the amplifier device pins, current flows through one or more of the steering diodes. Depending on the path that the current takes, the absorption device may activate. The absorption device has a trigger, or threshold voltage, that is above the normal operating voltage of the OPA378 but below the device breakdown voltage level. Once this threshold is exceeded, the absorption device quickly activates and clamps the voltage across the supply rails to a safe level. When the operational amplifier connects into a circuit such as that illustrated in Figure 30, the ESD protection components are intended to remain inactive and not become involved in the application circuit operation. However, circumstances may arise where an applied voltage exceeds the operating voltage range of a given pin. Should this condition occur, there is a risk that some of the internal ESD protection circuits may be biased on, and conduct current. Any such current flow occurs through steering diode paths and rarely involves the absorption device. Figure 30 depicts a specific example where the input voltage, VIN, exceeds the positive supply voltage (+VS) by 300mV or more. Much of what happens in the circuit depends on the supply characteristics. If +VS can sink the current, one of the upper input steering diodes conducts and directs current to +VS. Excessively high current levels can flow with increasingly higher VIN. As a result, the datasheet specifications recommend that applications limit the input current to 10mA. If the supply is not capable of sinking the current, VIN may begin sourcing current to the operational amplifier, and then take over as the source of positive supply voltage. The danger in this case is that the voltage can rise to levels that exceed the operational amplifier absolute maximum ratings. In extreme but rare cases, the absorption device triggers on while +VS and –VS are applied. If this event happens, a direct current path is established between the +VS and –VS supplies. The power dissipation of the absorption device is quickly exceeded, and the extreme internal heating destroys the operational amplifier. Another common question involves what happens to the amplifier if an input signal is applied to the input while the power supplies +VS and/or –VS are at 0V. Again, it depends on the supply characteristic while at 0V, or at a level below the input signal amplitude. If the supplies appear as high impedance, then the operational amplifier supply current may be supplied by the input source via the current steering diodes. This state is not a normal bias condition; the amplifier most likely will not operate normally. If the supplies are low impedance, then the current through the steering diodes can become quite high. The current level depends on the ability of the input source to deliver current, and any resistance in the input path. APPLICATION IDEAS Figure 31 shows the basic configuration for a bridge amplifier. A low-side current shunt monitor is shown in Figure 32. RN are optional resistors used to isolate the ADS8325 from the noise of the digital two-wire bus. Because the ADS8325 is a 16-bit converter, a precise reference is essential for maximum accuracy. If absolute accuracy is not required, and the 5V power supply is sufficiently stable, the REF3330 may be omitted. Figure 33 shows a high-side current monitor. The load current develops a voltage drop across RSHUNT. The noninverting input monitors this voltage and is duplicated on the inverting input. RG then has the same voltage drop as RSHUNT. RG can be sized to provide whatever current is most convenient to the designer based on design constraints. The current from RG then flows through the MOSFET and to resistor RL, creating a voltage that can be read. Note that RL and RG set the voltage gain of the circuit. The supply voltage for the op amp is derived from the zener diode. For the OPA378 VS must be between 2.2V and 5.5V. Two possible methods to bias the zener are shown in the circuit of Figure 33: the customary resistor bias and the current monitor. The current monitor biasing achieves the lowest possible voltage. Resistor R1 and the diode on the noninverting input provide short-circuit protection. VEX R1 +5V R R R R OPA378 VOUT R1 VREF Figure 31. Single Op Amp Bridge Amplifier Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 13 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com REF3330 +5V 3V Load R1 4.99kW R2 49.9kW ILOAD R6 71.5kW RS 600W V RSHUNT 1W OPA378 C1 1.2nF R4 48.7kW R3 4.99kW ADS1100 R7 1.18kW Stray Ground-Loop Resistance RN 56W RN 56W 2 IC (PGA Gain = 4) FS = 3.0V NOTE: 1% resistors provide adequate common-mode rejection at small ground-loop errors. Figure 32. Low-Side Current Monitor RG RSHUNT zener (1) V+ (2) R1 10kW CBYPASS MOSFET rated to stand-off supply voltage such as BSS84 for up to 50V. OPA378 +5V V+ Two zener biasing methods (3) are shown. Output Load RBIAS RL (1) Zener rated for op amp supply capability (that is, 5.1V for the OPA378). (2) Current-limiting resistor. (3) Choose zener biasing resistor or dual NMOSFETs (2N7002, NTZD511ON, SM6K2T110). Figure 33. High-Side Current Monitor 14 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 REF3333 +5V 0.1mF 3.3V + R1 6.04kW D1 - R2 2.94kW - + + R8 150kW R5 31.6kW +5V 10mF 0.1mF R7 549W R4 6.04kW R3 60.4W VO OPA378 R6 200W K-Type Thermocouple 40.7mV/°C Zero Adj. Figure 34. Temperature Measurement 1MW 60kW 100kW V1 -In INA152 OPA378 3V 1MW NTC Thermistor R2 OPA378 R1 2 5 6 R2 3 Figure 35. Thermistor Measurement VO 1 OPA378 V2 +In VO = (1 + 2R2/R1) (V2 - V1) Figure 36. Precision Instrumentation Amplifier Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 15 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com +VS R1 100kW fLPF = 150Hz C4 1.06nF 1/2 OPA2378 RA +VS R2 100kW R6 100kW 1/2 OPA2378 +VS 3 2 LL 7 INA321 (1) 4 5 R8 100kW +VS dc R3 100kW 1/2 OPA2378 Wilson LA R14 1MW GTOT = 1kV/V R7 100kW ac GINA = 5 R12 5kW 6 +VS 1 C3 1mF VOUT OPA378 R13 318kW GOPA = 200 +VS 1/2 OPA2378 VCENTRAL C1 47pF (RA + LA + LL)/3 fHPF = 0.5Hz (provides ac signal coupling) 1/2 VS R5 390kW R9 20kW +VS R4 100kW 1/2 OPA2378 RL Inverted VCM +VS VS = +2.7V to +5.5V 1/2 OPA2378 BW = 0.5Hz to 150Hz +VS R10 1MW 1/2 VS C2 0.64mF R11 1MW fO = 0.5Hz (1) Other instrumentation amplifiers can be used, such as the INA326, which has lower noise but higher quiescent current. Figure 37. Single-Supply, Very Low Power ECG Circuit 16 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 C7 110pF C4 600pF Digital Stethoscope Microphone Output R5 100kW R3 100kW C2 10mF Electret Microphone Element with Internal FET +5V R2 10kW Out OPA378 C6 470nF C3 1 mF 2.2kW Mic Bias Mic Output +5V R4 10kW OPA378 C1 33pF Gnd C5 10mF VBIAS1 VBIAS2 Figure 38. Digital Stethoscope Circuit Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 17 OPA378 OPA2378 SBOS417D – JANUARY 2008 – REVISED OCTOBER 2009 www.ti.com REVISION HISTORY NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision C (June 2009) to Revision D Page • Changed OPA2378 orderable status to production data; updated references throughout document ................................. 1 • Changed first sentence of Description section ..................................................................................................................... 1 • Deleted footnote 2 from Package Information table ............................................................................................................. 2 • Added OPA2378 parameters to the Offset Voltage section of the Electrical Characteristics table ...................................... 3 • Deleted footnote 1 from Electrical Characteristics table ....................................................................................................... 3 • Added OPA378 to the Offset Voltage, Input Offset Voltage and vs Power Supply parameters of the Electrical Characteristics table ............................................................................................................................................................. 3 • Added typical specification to the OPA378 Offset Voltage, Over Temperature parameter of the Electrical Characteristics table ............................................................................................................................................................. 3 • Added Offset Voltage, Channel Separation parameter to the Electrical Characteristics table ............................................. 3 • Added OPA2378 parameters to the Input Bias Current section of the Electrical Characteristics table ............................... 3 • Added OPA378 to the Input Bias Current, Input Bias Current and Input Offset Current parameters of the Electrical Characteristics table ............................................................................................................................................................. 3 • Added typical specification to the Input Bias Current, Input Offset Current, OPA378 parameter of the Electrical Characteristics table ............................................................................................................................................................. 3 • Added OPA378 to the Output, Voltage Output Swing from Rail parameter of the Electrical Characteristics ...................... 4 • Added typical specification to the OPA378 Output, Over Temperature parameter of the Electrical Characteristics table ...................................................................................................................................................................................... 4 • Added the OPA2378 Output, Voltage Output Swing from Rail and Over Temperature parameters to the Electrical Characteristics table ............................................................................................................................................................. 4 • Updated Figure 18 ................................................................................................................................................................ 8 • Added Figure 25 ................................................................................................................................................................... 9 • Updated Figure 32 .............................................................................................................................................................. 14 • Updated Figure 33 and changed footnote 3 ....................................................................................................................... 14 18 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 PACKAGE OPTION ADDENDUM www.ti.com 31-May-2010 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Qty Eco Plan (2) Lead/ Ball Finish MSL Peak Temp (3) Samples (Requires Login) OPA2378AIDCNR ACTIVE SOT-23 DCN 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Purchase Samples OPA2378AIDCNT ACTIVE SOT-23 DCN 8 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples OPA378AIDBVR ACTIVE SOT-23 DBV 5 3000 Green (RoHS & no Sb/Br) OPA378AIDBVT ACTIVE SOT-23 DBV 5 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples OPA378AIDCKR ACTIVE SC70 DCK 5 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Purchase Samples OPA378AIDCKT ACTIVE SC70 DCK 5 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples Call TI Level-2-260C-1 YEAR Purchase Samples (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. 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 PACKAGE OPTION ADDENDUM www.ti.com 31-May-2010 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 28-Oct-2009 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) OPA2378AIDCNR SOT-23 DCN 8 3000 179.0 8.4 OPA2378AIDCNT SOT-23 DCN 8 250 179.0 OPA378AIDBVR SOT-23 DBV 5 3000 179.0 OPA378AIDBVT SOT-23 DBV 5 250 OPA378AIDCKR SC70 DCK 5 OPA378AIDCKT SC70 DCK 5 3.2 3.2 1.4 4.0 8.0 Q3 8.4 3.2 3.2 1.4 4.0 8.0 Q3 8.4 3.2 3.2 1.4 4.0 8.0 Q3 179.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 3000 179.0 8.4 2.2 2.5 1.2 4.0 8.0 Q3 250 179.0 8.4 2.2 2.5 1.2 4.0 8.0 Q3 Pack Materials-Page 1 W Pin1 (mm) Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 28-Oct-2009 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) OPA2378AIDCNR SOT-23 DCN 8 3000 195.0 200.0 45.0 OPA2378AIDCNT SOT-23 DCN 8 250 195.0 200.0 45.0 OPA378AIDBVR SOT-23 DBV 5 3000 195.0 200.0 45.0 OPA378AIDBVT SOT-23 DBV 5 250 195.0 200.0 45.0 OPA378AIDCKR SC70 DCK 5 3000 195.0 200.0 45.0 OPA378AIDCKT SC70 DCK 5 250 195.0 200.0 45.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. 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