OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 2009 Low-Noise, 900kHz, RRIO, Precision OPERATIONAL AMPLIFIER Zerø-Drift Series FEATURES DESCRIPTION • 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 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 (50µV max) and offset voltage drift (0.25µV/°C max). 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 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. UNLESS OTHERWISE NOTED this document contains PRODUCTION DATA information current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2008–2009, Texas Instruments Incorporated OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 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) PRODUCT PACKAGE-LEAD PACKAGE DESIGNATOR PACKAGE MARKING OPA378 SOT23-5 DBV OAZI OPA378 SC70-5 DCK BTS SOT23-8 DCN OCAI OPA2378 (1) (2) (2) 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. Available 3Q 2009. 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 1 5 V+ 2 3 OPA2378 SOT23-8 (TOP VIEW) OPA378 SOT23-5 (TOP VIEW) Out V- 4 Out +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 NOTE: The OPA2378 will be available 3Q 2009. 2 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 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 (1) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 20 50 µV 0.1 0.25 µV/°C 1.5 5 µV/V 8 µV/V OFFSET VOLTAGE Input Offset Voltage VOS vs Temperature dVOS/dT vs Power Supply PSRR VCM = V– VCM = 0V, VS = +2.2V to +5.5V over Temperature VCM = 0V, VS = +2.2V to +5.5V INPUT BIAS CURRENT Input Bias Current IB ±150 over Temperature Input Offset Current IOS ±550 pA ±2 nA ±1.1 nA 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 % RL = 10kΩ 6 Overload Recovery Time THD + Noise THD + N OUTPUT Voltage Output Swing from Rail VO over Temperature RL = 10kΩ Voltage Output Swing from Rail RL = 100kΩ over Temperature Short-Circuit Current Capacitive Load Drive Open-Loop Output Impedance (1) 0.7 RL = 100kΩ ISC 8 mV 13 mV 2 mV 3 mV ±30 mA CLOAD See Figure 18 pF ZO See Figure 23 Ω Specifications for OPA2378 are preview. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 3 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 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 (1) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 5.5 V POWER SUPPLY Specified Voltage Range VS Quiescent Current (per Amplifier) IQ 2.2 IO = 0mA, VS = +5.5V 125 over Temperature 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 ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 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) 10 1 100 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. OFFSET VOLTAGE vs TEMPERATURE POWER-SUPPLY REJECTION RATIO vs FREQUENCY 80 120 100 40 +PSRR 80 20 PSRR (dB) Offset Voltage (mV) 60 0 -20 60 -PSRR 40 -40 20 -60 -80 0 -75 -50 -25 0 25 50 75 100 125 150 1 10 100 1k Temperature (°C) Frequency (Hz) Figure 5. Figure 6. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 10k 100k Submit Documentation Feedback 1M 5 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 2009 ..................................................................................................................................................... www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. OPEN-LOOP GAIN AND PHASE vs FREQUENCY 150 140 140 140 100 80 80 60 60 40 40 Gain 0.1 1 10 100 1k 10k 100k 1M RL = 5kW 125 120 110 0 -20 RL = 10kW 130 115 20 0 RL = 100kW 135 Phase (°) 100 20 145 120 Phase AOL (dB) 120 Gain (dB) OPEN-LOOP GAIN vs TEMPERATURE 105 -20 10M 100 -75 -25 -50 0 100 125 150 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) 75 Figure 8. 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 -75 1M 25 50 75 Frequency (Hz) Figure 9. Figure 10. INPUT BIAS CURRENT vs INPUT COMMON-MODE VOLTAGE INPUT BIAS CURRENT vs TEMPERATURE 100 125 150 2000 1500 -IB 100 0 -100 -200 +IB Input Bias Current (pA) 300 200 0 -25 -50 Temperature (°C) 400 Input Bias Current (pA) 50 Figure 7. 80 1000 500 0 -500 -1000 -300 -1500 -400 -0.5 0 -2000 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -75 -50 Figure 11. Submit Documentation Feedback -25 0 25 50 75 100 125 150 Temperature (°C) Input Common-Mode Voltage (V) 6 25 Temperature (°C) Frequency (Hz) Figure 12. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 2009 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. QUIESCENT CURRENT vs TEMPERATURE 200 200 175 175 Quiescent Current (mA) Quiescent Current (mA) QUIESCENT CURRENT vs SUPPLY VOLTAGE 150 125 100 75 150 125 100 75 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 -75 -25 -50 0 VS (V) 50 75 100 Figure 13. Figure 14. OUTPUT VOLTAGE SWING vs OUTPUT CURRENT MAXIMUM OUTPUT VOLTAGE vs FREQUENCY 125 150 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) +25°C -40°C 4 3 2 VS = 2.2V 1 V- = -2.75 -3 0 0 2 4 6 8 10 12 14 16 18 1k 20 10k 100k 1M 10M Frequency (Hz) Output Current (mA) Figure 15. Figure 16. TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE 60 1 50 Overshoot (%) THD+N (%) 0.1 0.01 40 30 Gain = ±1V/V R = 10kW 20 0.001 Gain = -1V/V R = 5kW 10 0 0.0001 10 100 1k 10k 1 10 100 1k Load Capacitance (pF) Frequency (Hz) Figure 17. Figure 18. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 7 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 2009 ..................................................................................................................................................... www.ti.com TYPICAL CHARACTERISTICS (continued) At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted. POSITIVE OVER-VOLTAGE RECOVERY NEGATIVE OVER-VOLTAGE RECOVERY 10kW +2.5V 10kW 1kW 2V/div 2V/div Output +2.5V 0 1kW 0 OPA378 Output RL OPA378 -2.5V RL Input 1V/div 1V/div -2.5V 0 Input 0 Time (10ms/div) Time (4ms/div) Figure 19. Figure 20. SMALL-SIGNAL STEP RESPONSE LARGE-SIGNAL STEP RESPONSE VS = ±2.75V VIN Voltage (1V/div) Output Voltage (10mV/div) G = +1 VOUT Time (20ms/div) Time (5ms/div) Figure 21. Figure 22. OPEN-LOOP OUTPUT IMPEDANCE vs FREQUENCY INPUT BIAS CURRENT vs INPUT DIFFERENTIAL VOLTAGE 50 10k Normal Operating Range (see the Input Differential Voltage section in the Applications Information) 40 IO = 0A 100 10 IO = 400mA 1 1 10 100 1k 10k 30 20 10 0 -10 -20 -30 Over-Driven Condition Over-Driven Condition -40 IO = 2mA 0.1 8 Input Bias Current (mA) Output Impedance (W) 1k -50 100k 1M -1V -800 -600 -400 -200 0 200 400 600 800 Frequency (Hz) Input Differential Voltage (mV) Figure 23. Figure 24. Submit Documentation Feedback 1V Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 2009 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 25. 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 26 shows. Current-limiting resistor required if input voltage exceeds supply rails by ³ 0.5V. +5V IOVERLOAD 10mA max OPA378 VOUT VIN 5kW Figure 26. 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 25 shows the variation of offset voltage over the entire specified common-mode range for 10 typical units. Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 9 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 2009 ..................................................................................................................................................... www.ti.com 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 27. 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 28 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 -40 -In 1k 1.5kW 10k 100k 1M 10M 100M 1G Frequency (Hz) Figure 27. Equivalent Input Circuit Figure 28. 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 10 Submit Documentation Feedback 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 OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 2009 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 29 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 29. Equivalent Internal ESD Circuitry and Its Relation to a Typical Circuit Application Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 11 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 2009 ..................................................................................................................................................... www.ti.com 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 29, 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 29 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 30 shows the basic configuration for a bridge amplifier. A low-side current shunt monitor is shown in Figure 31. 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 32 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 32: 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 30. Single Op Amp Bridge Amplifier 12 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 2009 REF3330 +5V 3V Load R1 4.99kW R2 49.9kW ILOAD R6 71.5kW RS 100W V RSHUNT 1W OPA378 R3 4.99kW C1 7nF R4 48.7kW RN 56W ADS8325 R7 1.18kW Stray Ground-Loop Resistance RN 56W 2 IC (PGA Gain = 4) FS = 3.0V NOTE: 1% resistors provide adequate common-mode rejection at small ground-loop errors. Figure 31. 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 (FDG6301N, NTJD4001N, or Si1034). Figure 32. High-Side Current Monitor Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 13 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 2009 ..................................................................................................................................................... www.ti.com 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 33. Temperature Measurement 100kW 1MW 3V 1MW 60kW NTC Thermistor V1 -In INA152 OPA378 2 R2 OPA378 R1 5 6 R2 3 Figure 34. Thermistor Measurement VO 1 OPA378 V2 +In VO = (1 + 2R2/R1) (V2 - V1) Figure 35. Precision Instrumentation Amplifier 14 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 OPA378 OPA2378 www.ti.com ..................................................................................................................................................... SBOS417C – JANUARY 2008 – REVISED JUNE 2009 +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 VOUT OPA378 C3 1m F 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 R4 100kW +VS R9 20kW +VS 1/2 OPA2378 1/2 OPA2378 RL VS = +2.7V to +5.5V Inverted VCM BW = 0.5Hz to 150Hz +VS R10 1MW 1/2 VS R11 1MW C2 0.64mF fO = 0.5Hz (1) Other instrumentation amplifiers can be used, such as the INA326, which has lower noise but higher quiescent current. Figure 36. Single-Supply, Very Low Power, ECG Circuit Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 Submit Documentation Feedback 15 OPA378 OPA2378 SBOS417C – JANUARY 2008 – REVISED JUNE 2009 ..................................................................................................................................................... www.ti.com C7 110pF C4 600pF Digital Stethoscope Microphone Output R5 100kW R3 100kW C2 10mF Electret Microphone Element with Internal FET Out OPA378 C6 470nF C3 1m F 2.2kW Mic Bias Micr Output +5V R4 10kW OPA378 C1 33pF Gnd C5 10mF +5V R2 10kW VBIAS1 VBIAS2 Figure 37. Digital Stethoscope Circuit 16 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): OPA378 OPA2378 PACKAGE OPTION ADDENDUM www.ti.com 26-Jun-2009 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty Lead/Ball Finish MSL Peak Temp (3) OPA2378AID PREVIEW SOIC D 8 75 TBD Call TI Call TI OPA2378AIDCNR PREVIEW SOT-23 DCN 8 3000 TBD Call TI Call TI OPA2378AIDCNT PREVIEW SOT-23 DCN 8 250 TBD Call TI Call TI OPA2378AIDR PREVIEW SOIC D 8 2500 TBD Call TI Call TI OPA378AIDBVR ACTIVE SOT-23 DBV 5 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR OPA378AIDBVT ACTIVE SOT-23 DBV 5 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR OPA378AIDCKR ACTIVE SC70 DCK 5 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR OPA378AIDCKT ACTIVE SC70 DCK 5 250 CU NIPDAU Level-2-260C-1 YEAR Green (RoHS & no Sb/Br) (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. 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 1 PACKAGE MATERIALS INFORMATION www.ti.com 24-Jun-2009 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ OPA378AIDBVR SOT-23 3000 179.0 DBV 5 Reel Reel Diameter Width (mm) W1 (mm) A0 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 8.4 3.2 3.2 1.4 4.0 8.0 Q3 OPA378AIDBVT SOT-23 DBV 5 250 179.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 OPA378AIDCKR SC70 DCK 5 3000 179.0 8.4 2.2 2.5 1.2 4.0 8.0 Q3 OPA378AIDCKT SC70 DCK 5 250 179.0 8.4 2.2 2.5 1.2 4.0 8.0 Q3 Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 24-Jun-2009 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) 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. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Amplifiers Data Converters DLP® Products DSP Clocks and Timers Interface Logic Power Mgmt Microcontrollers RFID RF/IF and ZigBee® Solutions amplifier.ti.com dataconverter.ti.com www.dlp.com dsp.ti.com www.ti.com/clocks interface.ti.com logic.ti.com power.ti.com microcontroller.ti.com www.ti-rfid.com www.ti.com/lprf Applications Audio Automotive Broadband Digital Control Medical Military Optical Networking Security Telephony Video & Imaging Wireless www.ti.com/audio www.ti.com/automotive www.ti.com/broadband www.ti.com/digitalcontrol www.ti.com/medical www.ti.com/military www.ti.com/opticalnetwork www.ti.com/security www.ti.com/telephony www.ti.com/video www.ti.com/wireless Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2009, Texas Instruments Incorporated