OPA2378AIDCNR [TI]
Low-Noise, 900kHz, RRIO, Precision OPERATIONAL AMPLIFIER Zerø-Drift Series; 低噪声， 900kHz的， RRIO ，精密运算放大器零漂移系列
| 型号： | OPA2378AIDCNR |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | Low-Noise, 900kHz, RRIO, Precision OPERATIONAL AMPLIFIER Zerø-Drift Series |
| 文件： | 总24页 (文件大小：959K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
OPA378
OPA2378
www.ti.com ..................................................................................................................................................... SBOS417C–JANUARY 2008–REVISED JUNE 2009
Low-Noise, 900kHz, RRIO,
Precision OPERATIONAL AMPLIFIER
Zerø-Drift Series
1
FEATURES
DESCRIPTION
23
•
LOW NOISE
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.
–
–
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 (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.
APPLICATIONS
•
PORTABLE MEDICAL DEVICES
–
–
–
GLUCOSE METERS
OXYGEN METERING
HEART RATE MONITORS
•
•
•
•
•
WEIGH SCALES
BATTERY-POWERED INSTRUMENTS
THERMOPILE MODULES
HANDHELD TEST EQUIPMENT
SENSOR SIGNAL CONDITIONING
NOISE SPECTRAL DENSITY vs FREQUENCY
0.1Hz TO 10Hz NOISE
1k
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
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.
2
3
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
OPA378
PACKAGE-LEAD
SOT23-5
PACKAGE DESIGNATOR
PACKAGE MARKING
DBV
DCK
DCN
OAZI
BTS
OPA378
OPA2378(2)
SC70-5
SOT23-8
OCAI
(1) 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.
(2) Available 3Q 2009.
ABSOLUTE MAXIMUM RATINGS(1)
Over operating free-air temperature range (unless otherwise noted).
OPA378, OPA2378
UNIT
V
Supply Voltage, VS = (V+) – (V–)
Signal Input Terminals
+7
Voltage(2)
Current(2)
(V–) – 0.3 ≤ VIN ≤ (V+) + 0.3
V
±10
Continuous
–55 to +150
–65 to +150
+150
mA
Output Short-Circuit(3)
Operating Temperature, TA
Storage Temperature, TA
Junction Temperature, TJ
°C
°C
°C
V
Human Body Model (HBM)
Charged Device Model (CDM)
Machine Model (MM)
4000
ESD Ratings
1000
V
200
V
(1) 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.
(2) 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.
(3) Short-circuit to ground, one amplifier per package.
PIN CONFIGURATIONS
OPA2378
SOT23-8
(TOP VIEW)
OPA378
SC70-5
(TOP VIEW)
OPA378
SOT23-5
(TOP VIEW)
Out A
-In A
+In A
V-
1
2
3
4
8
7
6
5
V+
+In
V-
1
2
3
5
4
V+
V+
Out
V-
1
2
3
5
4
A
Out B
-In B
+In B
B
-In
Out
+In
-In
NOTE: The OPA2378 will be available 3Q 2009.
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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
OFFSET VOLTAGE
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Input Offset Voltage
vs Temperature
VOS
dVOS/dT
PSRR
VCM = V–
20
0.1
1.5
50
0.25
5
µV
µV/°C
µV/V
µV/V
vs Power Supply
VCM = 0V, VS = +2.2V to +5.5V
over Temperature
VCM = 0V, VS = +2.2V to +5.5V
8
INPUT BIAS CURRENT
Input Bias Current
IB
±150
±550
±2
pA
nA
nA
over Temperature
Input Offset Current
NOISE
IOS
±1.1
Input Voltage Noise
Input Voltage Noise Density
Input Current Noise
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
en
en
in
f = 0.1Hz to 10Hz, VS = +5.5V
f = 1kHz
0.4
20
µVPP
nV/√Hz
fA/√Hz
f = 10Hz
200
VCM
(V–) – 0.05
(V+) + 0.05
V
CMRR (V–) – 0.05V < VCM < (V+) + 0.05V, VS = 5.5V
(V–) – 0.05V < VCM < (V+) + 0.05V, VS = 2.2V
(V–) – 0.05V < VCM < (V+) + 0.05V, VS = 5.5V
(V–) – 0.05V < VCM < (V+) + 0.05V, VS = 2.2V
100
94
112
106
dB
dB
dB
dB
over Temperature
96
90
INPUT CAPACITANCE
Differential
CIN
4
5
pF
pF
Common-Mode
OPEN-LOOP GAIN
Open-Loop Voltage Gain
AOL
50mV < VO < (V+) – 50mV, RL = 100kΩ
100mV < VO < (V+) – 100mV, RL = 10kΩ
100mV < VO < (V+) – 100mV, RL = 10kΩ
110
110
106
134
130
dB
dB
dB
over Temperature
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
GBW
SR
tS
900
0.4
7
kHz
V/µs
µs
G = +1
Settling Time 0.1%
VS = 5.5V, 2V Step, G = +1
VS = 5.5V, 2V Step, G = +1
VIN × Gain > VS
Settling Time 0.01%
Overload Recovery Time
THD + Noise
tS
9
µs
4
µs
THD + N
VO
VS = 5V, VO = 3VPP, G = +1, f = 1kHz
0.003
%
OUTPUT
Voltage Output Swing from Rail
over Temperature
RL = 10kΩ
RL = 10kΩ
RL = 100kΩ
RL = 100kΩ
6
8
13
2
mV
mV
mV
mV
mA
pF
Voltage Output Swing from Rail
over Temperature
0.7
3
Short-Circuit Current
Capacitive Load Drive
Open-Loop Output Impedance
ISC
CLOAD
ZO
±30
See Figure 18
See Figure 23
Ω
(1) Specifications for OPA2378 are preview.
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OPA2378
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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
POWER SUPPLY
Specified Voltage Range
Quiescent Current (per Amplifier)
over Temperature
TEMPERATURE RANGE
Specified Range
VS
IQ
2.2
5.5
150
165
V
IO = 0mA, VS = +5.5V
125
µA
µA
–40
–55
+125
+150
°C
Operating Range
Thermal Resistance
SOT23-5
°C
θJA
°C/W
°C/W
°C/W
°C/W
200
250
100
SC70-5
SOT23-8
4
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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
100
10
Continues with No 1/f (flicker) Noise
Current Noise
Voltage Noise
1
Time (1s/div)
1
10
100
1k
10k
Frequency (Hz)
Figure 2.
Figure 1.
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
OFFSET VOLTAGE DRIFT DISTRIBUTION
VS = 5.5V
VS = 5.5V
Offset Voltage (mV)
|Offset Voltage Drift| (mV/°C)
Figure 3.
Figure 4.
POWER-SUPPLY REJECTION RATIO
vs FREQUENCY
OFFSET VOLTAGE vs TEMPERATURE
80
60
120
100
80
60
40
20
0
40
+PSRR
20
0
-PSRR
-20
-40
-60
-80
-75 -50 -25
0
25
50
75
100 125 150
1
10
100
1k
10k
100k
1M
Temperature (°C)
Frequency (Hz)
Figure 6.
Figure 5.
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OPA2378
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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
OPEN-LOOP GAIN
vs TEMPERATURE
150
145
140
135
130
125
120
115
110
105
100
140
120
100
80
140
120
100
80
Phase
RL = 100kW
RL = 10kW
RL = 5kW
60
60
40
40
Gain
20
20
0
0
-20
-20
-75 -50 -25
0
25
50
75
100 125 150
0.1
1
10
100
1k
10k 100k
1M
10M
Temperature (°C)
Frequency (Hz)
Figure 7.
Figure 8.
COMMON-MODE REJECTION RATIO
vs FREQUENCY
COMMON-MODE REJECTION RATIO AND
POWER-SUPPLY REJECTION RATIO vs TEMPERATURE
140
120
100
80
60
40
20
0
130
CMRR
VS = 5.5V
120
PSRR
110
CMRR
VS = 2.2V
100
90
80
-75 -50 -25
0
25
50
75
100 125 150
10
100
1k
10k
100k
1M
Temperature (°C)
Frequency (Hz)
Figure 9.
Figure 10.
INPUT BIAS CURRENT
vs INPUT COMMON-MODE VOLTAGE
INPUT BIAS CURRENT
vs TEMPERATURE
2000
400
300
1500
1000
500
-IB
200
100
0
0
-500
-1000
-1500
-2000
-100
-200
-300
-400
+IB
-75 -50 -25
0
25
50
75
100 125 150
-0.5
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
Input Common-Mode Voltage (V)
Figure 11.
Temperature (°C)
Figure 12.
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OPA2378
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, RL = 10kΩ, VS = +5.5V and VOUT = VS/2, unless otherwise noted.
QUIESCENT CURRENT
vs SUPPLY VOLTAGE
QUIESCENT CURRENT
vs TEMPERATURE
200
175
150
125
100
75
200
175
150
125
100
75
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
-75 -50 -25
0
25
50
75
100 125 150
VS (V)
Temperature (°C)
Figure 13.
Figure 14.
OUTPUT VOLTAGE SWING
vs OUTPUT CURRENT
MAXIMUM OUTPUT VOLTAGE
vs FREQUENCY
3
2
6
5
4
3
2
1
0
V+ = +2.75
VS = 5.5V
-40°C
+25°C
+125°C
1
+125°C
+25°C
0
VS = ±1.1
-40°C
-1
-2
-3
VS = 2.2V
-40°C
+25°C
+125°C
V- = -2.75
0
2
4
6
8
10
12
14
16
18
20
1k
10k
100k
1M
10M
Output Current (mA)
Frequency (Hz)
Figure 16.
Figure 15.
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
SMALL-SIGNAL OVERSHOOT
vs LOAD CAPACITANCE
1
60
50
40
30
20
10
0
0.1
0.01
Gain = ±1V/V
R = 10kW
0.001
0.0001
Gain = -1V/V
R = 5kW
10
100
1k
10k
1
10
100
1k
Frequency (Hz)
Load Capacitance (pF)
Figure 17.
Figure 18.
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OPA2378
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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
Output
+2.5V
OPA378
0
0
1kW
RL
Output
OPA378
-2.5V
RL
-2.5V
Input
0
0
Input
Time (10ms/div)
Time (4ms/div)
Figure 19.
Figure 20.
SMALL-SIGNAL STEP RESPONSE
LARGE-SIGNAL STEP RESPONSE
VS = ±2.75V
G = +1
VIN
VOUT
Time (20ms/div)
Time (5ms/div)
Figure 21.
Figure 22.
INPUT BIAS CURRENT vs
INPUT DIFFERENTIAL VOLTAGE
OPEN-LOOP OUTPUT IMPEDANCE vs FREQUENCY
10k
50
40
Normal Operating Range
(see the Input Differential
Voltage section in the
Applications Information)
1k
30
20
IO = 0A
100
10
10
0
-10
-20
-30
-40
-50
IO = 400mA
1
Over-Driven Condition
Over-Driven Condition
IO = 2mA
10k
0.1
1
10
100
1k
100k
1M
-1V -800 -600 -400 -200
0
200 400 600 800 1V
Frequency (Hz)
Input Differential Voltage (mV)
Figure 23.
Figure 24.
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OPA2378
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APPLICATIONS INFORMATION
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
50
VS = ±2.75V
40
10 Typical Units Shown
30
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.
20
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.
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
Current-limiting resistor
required if input voltage
exceeds supply rails by
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.
³ 0.5V.
+5V
IOVERLOAD
10mA max
VOUT
OPA378
VIN
5kW
INPUT VOLTAGE
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.
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INPUT DIFFERENTIAL VOLTAGE
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.
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.
0
-10
-20
1.5kW
-30
Clamp
fC = 25MHz with Parasitics
+In
Over Temperature
-29dB at 800MHz
CORE
-In
-40
1k
10k
100k
1M
10M 100M 1G
1.5kW
Frequency (Hz)
Figure 27. Equivalent Input Circuit
Figure 28. EMI Filter
INTERNAL OFFSET CORRECTION
GENERAL LAYOUT GUIDELINES
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
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.
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
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:
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.
•
•
•
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.
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
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.
10
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ELECTRICAL OVERSTRESS
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.
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.
RF
+VS
+V
ESD
OPA378
V-
ESD
RI
ESD Current-
Steering Diodes
-In
Out
Op-Amp
Core
+In
Edge-Triggered ESD
Absorption Circuit
RL
ID
ESD
(1)
VIN
ESD
V+
-V
-VS
(1) VIN = +VS + 500mV.
Figure 29. Equivalent Internal ESD Circuitry and Its Relation to a Typical Circuit Application
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An ESD event produces
a
short duration,
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.
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.
APPLICATION IDEAS
Figure 30 shows the basic configuration for a bridge
amplifier.
A
low-side current shunt monitor is shown in
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 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.
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.
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.
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.
VEX
R1
+5V
R
R
R
R
VOUT
OPA378
R1
VREF
Figure 30. Single Op Amp Bridge Amplifier
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3V
REF3330
+5V
Load
R1
4.99kW
R2
49.9kW
R6
71.5kW
RS
RN
56W
V
100W
RSHUNT
1W
ILOAD
OPA378
C1
I2C
R3
4.99kW
R4
48.7kW
RN
56W
7nF
ADS8325
R7
1.18kW
(PGA Gain = 4)
FS = 3.0V
Stray Ground-Loop Resistance
NOTE: 1% resistors provide adequate common-mode rejection at small ground-loop errors.
Figure 31. Low-Side Current Monitor
RG
zener(1)
V+
OPA378
CBYPASS
RSHUNT
(2)
R1
10kW
MOSFET rated to
stand-off supply voltage
such as BSS84 for
up to 50V.
+5V
V+
Two zener
biasing methods
are shown.(3)
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
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3.3V
REF3333
+5V
0.1mF
+
R8
150kW
R1
6.04kW
R5
+5V
31.6kW
10mF
D1
0.1mF
R2
R7
2.94kW
549W
-
-
+
+
VO
OPA378
R6
200W
K-Type
Thermocouple
R4
6.04kW
R3
Zero Adj.
40.7mV/°C
60.4W
Figure 33. Temperature Measurement
100kW
V1
-In
1MW
1MW
60kW
INA152
OPA378
2
5
6
3V
R2
NTC
OPA378
Thermistor
VO
R1
R2
3
1
Figure 34. Thermistor Measurement
OPA378
V2
+In
VO = (1 + 2R2/R1) (V2 - V1)
Figure 35. Precision Instrumentation Amplifier
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OPA2378
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+VS
fLPF = 150Hz
C4
R1
1/2
1.06nF
100kW
OPA2378
RA
R14
GTOT = 1kV/V
1MW
R7
+VS
100kW
+VS
GINA = 5
R12
R6
+VS
3
2
7
5kW
100kW
R2
1/2
6
1
INA321(1)
100kW
OPA2378
VOUT
GOPA = 200
OPA378
LL
4
5
C3
1mF
R13
R8
318kW
100kW
+VS
+VS
dc
ac
R3
1/2
100kW
1/2
OPA2378
Wilson
OPA2378
LA
VCENTRAL
C1
(RA + LA + LL)/3
47pF
fHPF = 0.5Hz
(provides ac signal coupling)
1/2 VS
R5
390kW
+VS
VS = +2.7V to +5.5V
BW = 0.5Hz to 150Hz
R9
+VS
20kW
R4
1/2
100kW
OPA2378
1/2
RL
OPA2378
Inverted
VCM
+VS
R10
1MW
1/2 VS
R11
C2
1MW
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
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C7
110pF
C4
600pF
Digital Stethoscope
Microphone Output
R5
R3
100kW
100kW
+5V
C5
R4
+5V
C2
10mF
R2
10kW
10mF
10kW
OPA378
C1
OPA378
33pF
Out
Electret
Microphone
Element
C6
Gnd
C3
470nF
2.2kW
1mF
with
Internal FET
VBIAS1
VBIAS2
Mic
Bias
Micr
Output
Figure 37. Digital Stethoscope Circuit
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PACKAGE OPTION ADDENDUM
www.ti.com
26-Jun-2009
PACKAGING INFORMATION
Orderable Device
Status (1)
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
OPA2378AID
OPA2378AIDCNR
OPA2378AIDCNT
OPA2378AIDR
PREVIEW
PREVIEW
PREVIEW
PREVIEW
ACTIVE
SOIC
D
8
8
8
8
5
75
TBD
TBD
TBD
TBD
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
Call TI
SOT-23
SOT-23
SOIC
DCN
DCN
D
3000
250
2500
OPA378AIDBVR
SOT-23
DBV
3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
OPA378AIDBVT
OPA378AIDCKR
OPA378AIDCKT
ACTIVE
ACTIVE
ACTIVE
SOT-23
SC70
DBV
DCK
DCK
5
5
5
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
3000 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
SC70
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
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
Reel
Reel
A0 (mm)
B0 (mm)
K0 (mm)
P1
W
Pin1
Diameter Width
(mm) W1 (mm)
(mm) (mm) Quadrant
OPA378AIDBVR
OPA378AIDBVT
OPA378AIDCKR
OPA378AIDCKT
SOT-23
SOT-23
SC70
DBV
DBV
DCK
DCK
5
5
5
5
3000
250
179.0
179.0
179.0
179.0
8.4
8.4
8.4
8.4
3.2
3.2
2.2
2.2
3.2
3.2
2.5
2.5
1.4
1.4
1.2
1.2
4.0
4.0
4.0
4.0
8.0
8.0
8.0
8.0
Q3
Q3
Q3
Q3
3000
250
SC70
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
OPA378AIDBVT
OPA378AIDCKR
OPA378AIDCKT
SOT-23
SOT-23
SC70
DBV
DBV
DCK
DCK
5
5
5
5
3000
250
195.0
195.0
195.0
195.0
200.0
200.0
200.0
200.0
45.0
45.0
45.0
45.0
3000
250
SC70
Pack Materials-Page 2
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