3PEAK
LMV321A/LMV358A/LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Features
Description
Upgrade to LMV321/LMV358/LMV324 Family
Stable 1.0MHz GBWP with Low IQ of Only 80μA
Typical per Amplifier
0.7V/μs Slew Rate
Excellent EMIRR performance: 80dB(1GHz)
Offset Voltage Tolerance: 400μV Max.
Offset Voltage Temperature Drift: 1uV/°C
Input Bias Current: 1pA Typical
High Output Current: 50mA (1.0V Drop)
CMRR/PSRR: 95dB/90dB
Beyond the Rails Input Common-Mode Range
Outputs Swing to within 6mV Max of each Rail
No Phase Reversal for Overdriven Inputs
No Crossover Distortion
Drives 2kΩ Resistive Loads
Single +2.1V to +6.0V Supply Voltage Range
–40°C to 125°C Operation Range
ESD Rating:
Robust 8KV – HBM, 2KV – CDM
Green, Popular Type Package
LMV321A/358A/324A are CMOS single, dual, and
quad op-amps with low offset, stable high frequency
response, low power, low supply voltage, and
rail-to-rail inputs and outputs. They incorporate
3PEAK‟s proprietary and patented design
techniques to achieve best in-class performance
among all micro-power CMOS amplifiers.
The LMV321A/358A/324A are unity gain stable with
Any Capacitive Load with a Constant 1.0MHz
gain-bandwidth product, 0.7V/μs slew rate while
consuming only 80μA of supply current per amplifier.
Analog trim and calibration routine reduces input
offset voltage tolerance to below 400μV. Adaptive
biasing and dynamic compensation enables the
LMV321A /358A/324A to achieve „THD+NOISE‟ for
1kHz and 10kHz 2VPP signal at -105dB and -90dB,
respectively. Beyond the rails input and rail-to-rail
output characteristics allow the full power-supply
voltage to be used for signal range.
This combination of features makes the LMV321A
/358A/324A superior among rail-to-rail input /output
CMOS op amps in its power class. The
LMV321A/358A/324A are ideal choices for
battery-powered
applications
because
they
minimize errors due to power supply voltage
variations over the lifetime of the battery and
maintain high CMRR even for a rail-to-rail input
op-amp.
Applications
Active Filters, ASIC Input or Output Amplifier
Sensor Interface
Smoke/Gas/Environment Sensors
Portable Instruments and Mobile Device
Audio Output
PCMCIA Cards
Battery or Solar Powered Systems
Medical Equipment
Piezo Electrical Transducer Amplifier
The LMV321A/358A/324A can be used as
cost-effective plug-in replacements for many
commercially available op amps to reduce power
and improve input/output range and performance.
3PEAK and the 3PEAK logo are registered trademarks of
3PEAK INCORPORATED. All other trademarks are the property of
their respective owners.
Pin Configuration (Top View)
LMV321A
5-Pin SOT23/SC70
(-T and -C Suffixes)
+In
1
-VS
2
-In
3
LMV358A
8-Pin SOIC/MSOP
(-S and -V Suffixes)
5
+VS
4
Out
Out A
1
-In A
2
+In A
3
-VS
4
A
LMV324A
14-Pin SOIC/TSSOP
(-S and -T Suffixes)
8
+VS
7
Out A
1
Out B
-In A
2
13
-In D
-In B
+In A
3
12
+In D
5
+In B
+VS
4
11
-VS
+In B
5
10
+In C
B
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Out D
6
A
B
14
D
C
-In B
6
9
-In C
Out B
7
8
Out C
Rev. A.02
1
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Order Information
Model Name
Order Number
LMV321A
LMV358A
LMV324A
Package
Marking
Information
Transport Media, Quantity
LMV321A -TR
5-Pin SOT23
Tape and Reel, 3,000
321
LMV321A -CR
5-Pin SC70
Tape and Reel, 3,000
321
LMV358A -SR
8-Pin SOP
Tape and Reel, 4,000
LMV358A
LMV358A -VR
8-Pin MSOP
Tape and Reel, 3,000
LMV358A
LMV324A -SR
14-Pin SOP
Tape and Reel, 2,500
LMV324A
LMV324A -TR
14-Pin TSSOP
Tape and Reel, 3,000
LMV324A
Absolute Maximum Ratings Note 1
+
Supply Voltage: V – V
– Note 2
..............................7.0V
–
Operating Temperature Range........–40°C to 125°C
+
Input Voltage............................. V – 0.3 to V + 0.3
Input Current: +IN, –IN
Maximum Junction Temperature................... 150°C
Note 3..........................
±20mA
Storage Temperature Range.......... –65°C to 150°C
Note 4….............
Infinite
Lead Temperature (Soldering, 10 sec) ......... 260°C
Output Short-Circuit Duration
Current at Supply Pins……………............... ±60mA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum
Rating condition for extended periods may affect device reliability and lifetime.
Note 2: The op amp supplies must be established simultaneously, with, or before, the application of any input signals.
Note 3: The inputs are protected by ESD protection diodes to each power supply. If the input extends more than 500mV beyond the power supply, the input
current should be limited to less than 10mA.
Note 4: A heat sink may be required to keep the junction temperature below the absolute maximum. This depends on the power supply voltage and how many
amplifiers are shorted. Thermal resistance varies with the amount of PC board metal connected to the package. The specified values are for short traces
connected to the leads.
ESD, Electrostatic Discharge Protection
Symbol
Parameter
Condition
Minimum Level
Unit
HBM
Human Body Model ESD
MIL-STD-883H Method 3015.8
8
kV
CDM
Charged Device Model ESD
JEDEC-EIA/JESD22-C101E
2
kV
Thermal Resistance
2
Package Type
θJA
θJC
Unit
5-Pin SOT23
250
81
° C/W
5-Pin SC70
395
165
° C/W
8-Pin SOP
158
43
° C/W
8-Pin MSOP
210
45
° C/W
14-Pin SOP
120
36
° C/W
14-Pin TSSOP
180
35
° C/W
Rev. A.02
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Electrical Characteristics
The specifications are at TA = 27° C. VS = +2.1 V to +6.0 V, or ± 1.05 V to ± 3.0 V, RL = 2kΩ, CL =100pF.Unless otherwise noted.
SYMBOL
VOS
VOS TC
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
0.6
1
1.4
mV
Input Offset Voltage
VCM = Vss+0.1V
Input Offset Voltage Drift
-40° C to 125° C
1
TA = 27 ° C
1
TA = 85 ° C
25
pA
0.001
pA
μV/° C
10
pA
IB
Input Bias Current
IOS
Input Offset Current
Vn
Input Voltage Noise
f = 0.1Hz to 10Hz
7
μVPP
en
in
Input Voltage Noise Density
Input Current Noise
27
nV/√Hz
fA/√Hz
CIN
Input Capacitance
f = 1kHz
f = 1kHz
Differential
Common Mode
VCM = 0V to 2.5V
CMRR
PSRR
Common Mode Rejection Ratio
Common-mode Input Voltage
Range
Power Supply Rejection Ratio
AVOL
VCM
85
2
8
7
95
V– -0.3
pF
dB
V++0.3
V
VCM = 0V, VS = 3V to 5V
77
90
dB
Open-Loop Large Signal Gain
RLOAD = 10kΩ
98
120
dB
VOL, VOH
Output Swing from Supply Rail
RLOAD = 10kΩ
ROUT
Closed-Loop Output Impedance
G = 1, f =1kHz, IOUT = 0
RO
Open-Loop Output Impedance
ISC
3
6
mV
0.002
Ω
f = 1kHz, IOUT = 0
125
Ω
Output Short-Circuit Current
Sink or source current
100
IO
Output Current
Sink or source current, Output 1V Drop
50
VDD
Supply Voltage
IQ
2.1
120
mA
mA
6.0
V
120
μA
Quiescent Current per Amplifier
VS = 5V
80
PM
Phase Margin
RLOAD = 1kΩ, CLOAD = 60pF
65
°
GM
Gain Margin
RLOAD = 1kΩ, CLOAD = 60pF
15
dB
Gain-Bandwidth Product
f = 1kHz
AV = 1, VOUT = 1.5V to 3.5V, CLOAD =
60pF, RLOAD = 1kΩ
1.0
MHz
0.7
V/μs
58.6
3.7
4.9
kHz
0.003
%
110
dB
GBWP
SR
FPBW
tS
THD+N
Xtalk
Slew Rate
Full Power Bandwidth Note 1
Settling Time, 0.1%
Settling Time, 0.01%
Total Harmonic Distortion and
Noise
Channel Separation
AV = –1, 1V Step
f = 1kHz, AV =1, RL = 2kΩ, VOUT = 1Vp-p
f = 1kHz, RL = 2kΩ
μs
Note 1: Full power bandwidth is calculated from the slew rate FPBW = SR/π • VP-P
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Rev. A.02
3
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
VS = ±2.75V, VCM = 0V, RL = Open, unless otherwise specified.
Offset Voltage Production Distribution
Unity Gain Bandwidth vs. Temperature
2.0
4000
Number = 20000 pcs
1.8
3000
1.5
2500
1.3
GBW(MHz)
Population
3500
2000
1500
1.0
0.8
0.5
1000
0.3
500
0.0
-50
其他
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
0
0
100
150
Temperature(℃)
Offset Voltage(uV)
Open-Loop Gain and Phase
Input Voltage Noise Spectral Density
140
1000
200
120
Phase
60
50
40
Gain
0
20
0
Phase (°)
100
80
Noise(nV/√Hz)
150
100
Gain(dB)
50
100
10
-50
-20
-100
-40
-60
0.1
10
1k
100k
1
-150
1000M
10M
1
10
Input Bias Current vs. Temperature
10k
100k
1M
0
40
-5
Input Bias Current(pA)
Input Bias Current(pA)
1k
Input Bias Current vs. Input Common Mode Voltage
50
30
20
10
-10
-15
-20
0
-10
-40
-20
0
20
40
60
Temperature(℃)
4
100
Frequency(Hz)
Frequency (Hz)
Rev. A.02
80
100
120
-25
0
1
2
3
4
5
Common Mode Voltage(V)
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
VS = ±2.75V, VCM = 0V, RL = Open, unless otherwise specified. (Continued)
Common Mode Rejection Ratio
CMRR vs. Frequency
160
140
140
120
120
CMRR(dB)
CMRR(dB)
100
80
60
40
100
80
60
40
20
20
0
0
0
1
2
3
4
5
1
10
100
Common-mode Voltage(V)
10k
100k
1M
Frequency(Hz)
Quiescent Current vs. Temperature
Short Circuit Current vs. Temperature
120
140
VCM= 2.5V
120
Current(mA)
100
Supply current(μA)
1k
VCM= 5.0V
80
60
VCM= 0V
ISOURCE
100
ISINK
80
60
40
40
20
20
0
0
-50
-50
0
50
100
0
100
150
Temperature(℃)
Temperature(℃)
Power-Supply Rejection Ratio
Quiescent Current vs. Supply Voltage
120
120
PSRR+
100
Supply current (uA)
100
PSRR-
80
PSRR(dB)
50
150
60
40
20
80
60
40
20
0
0
-20
1.5
0.1
10
1k
Frequency(Hz)
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100k
2
2.5
3
3.5
4
4.5
5
Supply Voltage (V)
Rev. A.02
5
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
VS = ±2.75V, VCM = 0V, RL = Open, unless otherwise specified. (Continued)
PSRR vs. Temperature
CMRR vs. Temperature
140
120
120
CMRR(-dB)
PSRR(-dB)
100
80
60
100
80
60
40
40
20
20
0
0
-50
0
50
100
-50
150
0
50
100
150
Temperature(℃)
Temperature(℃)
EMIRR IN+ vs. Frequency
Large-Scale Step Response
90
Gain = 1
RL = 10kΩ
2V/div
80
EMIRR IN+ (dB)
70
60
50
40
30
2V/div
20
10
0
1
10
100
1000
Time (50μs/div)
Frequency (MHz)
Gain = +10
±V = ±2.5V
1V/div
Time (50μs/div)
6
Positive Over-Voltage Recovery
2V/div
Gain = +10
±V = ±2.5V
1V/div
2V/div
Negative Over-Voltage Recovery
Rev. A.02
Time (50μs/div)
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
VS = ±2.75V, VCM = 0V, RL = Open, unless otherwise specified. (Continued)
0.1 Hz TO 10 Hz Input Voltage Noise
Offset Voltage vs Common-Mode Voltage
1500
5μV/div
Offset voltage Change(μV)
1000
500
0
-500
-1000
-1500
0
1
Time (1s/div)
3
4
5
Common-mode voltage(V)
Positive Output Swing vs. Load Current
Negative Output Swing vs. Load Current
120
0
100
-20
25℃
-40℃
125℃
-40
80
-60
Iout(mA)
Iout(mA)
2
60
-80
40
25℃
-100
-40℃
20
-120
125℃
0
-140
0
1
2
3
4
5
0
1
2
3
4
5
Vout Dropout (V)
Vout Dropout (V)
Offset Voltage vs. Temperature
Offset voltage Change(μV)
80
70
60
50
40
30
20
10
0
-50
0
50
100
150
Temperature(℃)
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Rev. A.02
7
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Pin Functions
-IN: Inverting Input of the Amplifier.
possible should be used between power supply pins or
+IN: Non-Inverting Input of Amplifier.
between supply pins and ground.
OUT: Amplifier Output. The voltage range extends to
V- or -Vs: Negative Power Supply. It is normally tied to
within mV of each supply rail.
ground. It can also be tied to a voltage other than
V+ or +Vs: Positive Power Supply. Typically the voltage
ground as long as the voltage between V+ and V– is from
is from 2.1V to 6.0V. Split supplies are possible as long
2.1V to 6.0V. If it is not connected to ground, bypass it
as the voltage between V+ and V– is between 2.1V and
with a capacitor of 0.1μF as close to the part as
possible.
6.0V. A bypass capacitor of 0.1μF as close to the part as
Operation
The LMV321A/358A/324A input signal range extends beyond the negative and positive power supplies. The output can
even extend all the way to the negative supply. The input stage is comprised of two CMOS differential amplifiers, a
PMOS stage and NMOS stage that are active over different ranges of common mode input voltage. The Class-AB
control buffer and output bias stage uses a proprietary compensation technique to take full advantage of the process
technology to drive very high capacitive loads. This is evident from the transient over shoot measurement plots in the
Typical Performance Characteristics.
Applications Information
Low Supply Voltage and Low Power Consumption
The LMV321A/358A/324A of operational amplifiers can operate with power supply voltages from 2.1V to 6.0V. Each
amplifier draws only 80μA quiescent current. The low supply voltage capability and low supply current are ideal for
portable applications demanding HIGH CAPACITIVE LOAD DRIVING CAPABILITY and WIDE BANDWIDTH. The
LMV321A/358A/324A is optimized for wide bandwidth low power applications. They have an industry leading high
GBWP to power ratio and are unity gain stable for ANY CAPACITIVE load. When the load capacitance increases, the
increased capacitance at the output pushed the non-dominant pole to lower frequency in the open loop frequency
response, lowering the phase and gain margin. Higher gain configurations tend to have better capacitive drive
capability than lower gain configurations due to lower closed loop bandwidth and hence higher phase margin.
Low Input Referred Noise
The LMV321A/358A/324A provides a low input referred noise density of 27nV/√Hz at 1kHz. The voltage noise will
grow slowly with the frequency in wideband range, and the input voltage noise is typically 7μVP-P at the frequency of
0.1Hz to 10Hz.
Low Input Offset Voltage
The LMV321A/358A/324A has a low offset voltage tolerance of 400μV maximum which is essential for precision
applications. The offset voltage is trimmed with a proprietary trim algorithm to ensure low offset voltage for precision
signal processing requirement.
Low Input Bias Current
The LMV321A/358A/324A is a CMOS OPA family and features very low input bias current in pA range. The low input
bias current allows the amplifiers to be used in applications with high resistance sources. Care must be taken to
minimize PCB Surface Leakage. See below section on “PCB Surface Leakage” for more details.
PCB Surface Leakage
8
Rev. A.02
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
In applications where low input bias current is critical, Printed Circuit Board (PCB) surface leakage effects need to be
considered. Surface leakage is caused by humidity, dust or other contamination on the board. Under low humidity
12
conditions, a typical resistance between nearby traces is 10 Ω. A 5V difference would cause 5pA of current to flow,
which is greater than the LMV321A/358A/324A OPA‟s input bias current at +27°C (±1pA, typical). It is recommended
to use multi-layer PCB layout and route the OPA‟s -IN and +IN signal under the PCB surface.
The effective way to reduce surface leakage is to use a guard ring around sensitive pins (or traces). The guard
ring is biased at the same voltage as the sensitive pin. An example of this type of layout is shown in Figure 1 for
Inverting Gain application.
1. For Non-Inverting Gain and Unity-Gain Buffer:
a) Connect the non-inverting pin (VIN+) to the input with a wire that does not touch the PCB surface.
b) Connect the guard ring to the inverting input pin (VIN–). This biases the guard ring to the Common Mode input voltage.
2. For Inverting Gain and Trans-impedance Gain Amplifiers (convert current to voltage, such as photo detectors):
a) Connect the guard ring to the non-inverting input pin (VIN+). This biases the guard ring to the same reference voltage as
the op-amp (e.g., VDD/2 or ground).
b) Connect the inverting pin (VIN–) to the input with a wire that does not touch the PCB surface.
Guard Ring
VIN+
VIN-
+VS
Figure 1
Ground Sensing and Rail to Rail Output
The LMV321A/358A/324A has excellent output drive capability, delivering over 100mA of output drive current. The
output stage is a rail-to-rail topology that is capable of swinging to within 5mV of either rail. Since the inputs can go
100mV beyond either rail, the op-amp can easily perform „True Ground Sensing‟.
The maximum output current is a function of total supply voltage. As the supply voltage to the amplifier increases, the
output current capability also increases. Attention must be paid to keep the junction temperature of the IC below 150°C
when the output is in continuous short-circuit. The output of the amplifier has reverse-biased ESD diodes connected to
each supply. The output should not be forced more than 0.5V beyond either supply, otherwise current will flow through
these diodes.
ESD
The LMV321A/358A/324A has reverse-biased ESD protection diodes on all inputs and output. Input and out pins
cannot be biased more than 200mV beyond either supply rail.
Feedback Components and Suppression of Ringing
Care should be taken to ensure that the pole formed by the feedback resistors and the parasitic capacitance at the
inverting input does not degrade stability. For example, in a gain of +2 configuration with gain and feedback resistors of
10k, a poorly designed circuit board layout with parasitic capacitance of 5pF (part +PC board) at the amplifier‟s
inverting input will cause the amplifier to ring due to a pole formed at 3.2MHz. An additional capacitor of 5pF across the
feedback resistor as shown in Figure 2 will eliminate any ringing.
Careful layout is extremely important because low power signal conditioning applications demand high-impedance
circuits. The layout should also minimize stray capacitance at the OPA‟s inputs. However some stray capacitance may
be unavoidable and it may be necessary to add a 2pF to 10pF capacitor across the feedback resistor. Select the
smallest capacitor value that ensures stability.
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Rev. A.02
9
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
5pF
10kΩ
VOUT
10kΩ
CPAR
VIN
Figure 2
Driving Large Capacitive Load
The LMV321A/358A/324A of OPA is designed to drive large capacitive loads. Refer to Typical Performance
Characteristics for “Phase Margin vs. Load Capacitance”. As always, larger load capacitance decreases overall
phase margin in a feedback system where internal frequency compensation is utilized. As the load capacitance
increases, the feedback loop‟s phase margin decreases, and the closed-loop bandwidth is reduced. This produces
gain peaking in the frequency response, with overshoot and ringing in output step response. The unity-gain buffer (G =
+1V/V) is the most sensitive to large capacitive loads.
When driving large capacitive loads with the LMV321A/358A/324A (e.g., > 200 pF when G = +1V/V), a small series
resistor at the output (RISO in Figure 3) improves the feedback loop‟s phase margin and stability by making the output
load resistive at higher frequencies.
RISO
VOUT
VIN
CLOAD
Figure 3
Power Supply Layout and Bypass
The LMV321A/358A/324A OPA‟s power supply pin (VDD for single-supply) should have a local bypass capacitor (i.e.,
0.01μF to 0.1μF) within 2mm for good high frequency performance. It can also use a bulk capacitor (i.e., 1μF or larger)
within 100mm to provide large, slow currents. This bulk capacitor can be shared with other analog parts.
Ground layout improves performance by decreasing the amount of stray capacitance and noise at the OPA‟s inputs
and outputs. To decrease stray capacitance, minimize PC board lengths and resistor leads, and place external
components as close to the op amps‟ pins as possible.
Proper Board Layout
To ensure optimum performance at the PCB level, care must be taken in the design of the board layout. To avoid
leakage currents, the surface of the board should be kept clean and free of moisture. Coating the surface creates a
barrier to moisture accumulation and helps reduce parasitic resistance on the board.
Keeping supply traces short and properly bypassing the power supplies minimizes power supply disturbances due to
output current variation, such as when driving an ac signal into a heavy load. Bypass capacitors should be connected
as closely as possible to the device supply pins. Stray capacitances are a concern at the outputs and the inputs of the
amplifier. It is recommended that signal traces be kept at least 5mm from supply lines to minimize coupling.
A variation in temperature across the PCB can cause a mismatch in the Seebeck voltages at solder joints and other
points where dissimilar metals are in contact, resulting in thermal voltage errors. To minimize these thermocouple
effects, orient resistors so heat sources warm both ends equally. Input signal paths should contain matching numbers
10
Rev. A.02
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
and types of components, where possible to match the number and type of thermocouple junctions. For example,
dummy components such as zero value resistors can be used to match real resistors in the opposite input path.
Matching components should be located in close proximity and should be oriented in the same manner. Ensure leads
are of equal length so that thermal conduction is in equilibrium. Keep heat sources on the PCB as far away from
amplifier input circuitry as is practical.
The use of a ground plane is highly recommended. A ground plane reduces EMI noise and also helps to maintain a
constant temperature across the circuit board.
Instrumentation Amplifier
The LMV321A/358A/324A OPA is well suited for conditioning sensor signals in battery-powered applications. Figure 4
shows a two op-amp instrumentation amplifier, using the LMV321A/358A/324A OPA.
The circuit works well for applications requiring rejection of Common Mode noise at higher gains. The reference
voltage (VREF) is supplied by a low-impedance source. In single voltage supply applications, VREF is typically VDD/2.
RG
R1
VREF
R2
R2
R1
VOUT
V2
V1
VOUT =(V1 V2 )(1
R1 2 R1
) VREF
R2 RG
Figure 4
Gain-of-100 Amplifier Circuit
Figure 5 shows a Gain-of-100 amplifier circuit using two LMV321A/358A/324A OPAs. It draws 74uA total current
from supply rail, and has a -3dB frequency at 100kHz. Figure 6 shows the small signal frequency response of the
circuit.
+0.9V
VIN
VOUT
-0.9V
90.9k
10k
90.9k
10k
Figure 5: 100kHz, 74μA Gain-of-100 Amplifier
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Rev. A.02
11
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Figure 6: Frequency response of 100kHz, 74uA Gain-of-100 Amplifier
Buffered Chemical Sensor (pH) Probe
The LMV321A/358A/324A OPA has input bias current in the pA range. This is ideal in buffering high impedance
chemical sensors such as pH probe. As an example, the circuit in Figure 7 eliminates expansive low-leakage cables
that that is required to connect pH probe to metering ICs such as ADC, AFE and/or MCU. A LMV321A/358A/324A
OPA and a lithium battery are housed in the probe assembly. A conventional low-cost coaxial cable can be used to
carry OPA‟s output signal to subsequent ICs for pH reading.
BATTERY
3V
(DURACELL
DL1620)
R1
10M
GENERAL PURPOSE
COMBINATION
pH PROBE
(CORNING 476540)
pH
PROBE
COAX
To
ADC/AFE/MCU
R2
10M
ALL COMPONENTS CONTAJNED WITHIN THE pH PROBE
Figure 7: Buffer pH Probe
Two-Pole Micro-power Sallen-Key Low-Pass Filter
Figure 8 shows a micro-power two-pole Sallen-Key Low-Pass Filter with 400Hz cut-off frequency. For best results,
the filter‟s cut-off frequency should be 8 to 10 times lower than the OPA‟s crossover frequency. Additional OPA‟s
phase margin shift can be avoided if the OPA‟s bandwidth-to-signal ratio is greater than 8. The design equations for
the 2-pole Sallen-Key low-pass filter are given below with component values selected to set a 400Hz low-pass filter
cutoff frequency:
12
Rev. A.02
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
C1
400pF
VIN
VOUT
R1
1MΩ
C2
400pF
R2
1MΩ
R1 = R 2 = R = 1M
C1 = C2 = C = 400pF
Q = Filter Peaking Factor = 1
R4
2MΩ
R3
2MΩ
f -3dB = 1/(2 RC ) = 400Hz
R 3 = R 4 /(2-1/Q) ; with Q = 1, R 3 =R 4
Figure 8
Portable Gas Sensor Amplifier
Gas sensors are used in many different industrial and medical applications. Gas sensors generate a current that is
proportional to the percentage of a particular gas concentration sensed in an air sample. This output current flows
through a load resistor and the resultant voltage drop is amplified. Depending on the sensed gas and sensitivity of the
sensor, the output current can be in the range of tens of microamperes to a few milli-amperes. Gas sensor datasheets
often specify a recommended load resistor value or a range of load resistors from which to choose.
There are two main applications for oxygen sensors – applications which sense oxygen when it is abundantly present
(that is, in air or near an oxygen tank) and those which detect traces of oxygen in parts-per-million concentration. In
medical applications, oxygen sensors are used when air quality or oxygen delivered to a patient needs to be monitored.
In fresh air, the concentration of oxygen is 20.9% and air samples containing less than 18% oxygen are considered
dangerous. In industrial applications, oxygen sensors are used to detect the absence of oxygen; for example,
vacuum-packaging of food products.
The circuit in Figure 9 illustrates a typical implementation used to amplify the output of an oxygen detector. With the
components shown in the figure, the circuit consumes less than 100μA of supply current ensuring that small
form-factor single- or button-cell batteries (exhibiting low mAh charge ratings) could last beyond the operating life of
the oxygen sensor. The precision specifications of these amplifiers, such as their low offset voltage, low TC-VOS, low
input bias current, high CMRR, and high PSRR are other factors which make these amplifiers excellent choices for this
application.
10 MΩ
1%
100 kΩ
1%
VOUT
Oxygen Sensor
City Technology
4OX2
I O2
100 kΩ
1%
100 Ω
1%
VOUT 1Vin Air ( 21% O 2 )
I DD 0.7uA
Figure 9
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Rev. A.02
13
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Revision History
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted.
Please go to web to make sure you have the latest revision.
Revision
Rev. A
14
Rev. A.02
Change
Initial Release
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
SC70-5 /SOT-353
Dimensions
Dimensions
In Millimeters
In Inches
Min
Max
Min
Max
A
0.900
1.100
0.035
0.043
A1
0.000
0.100
0.000
0.004
A2
0.900
1.000
0.035
0.039
b
0.150
0.350
0.006
0.014
C
0.080
0.150
0.003
0.006
D
2.000
2.200
0.079
0.087
E
1.150
1.350
0.045
0.053
E1
2.150
2.450
0.085
0.096
e
0.650TYP
0.026TYP
e1
1.200
0.047
L
0.525REF
0.021REF
L1
0.260
0.460
0.010
0.018
θ
0°
8°
0°
8°
Symbol
1.400
0.055
SOT23-5
Dimensions
Dimensions
In Millimeters
In Inches
Min
Max
Min
Max
A
1.050
1.250
0.041
0.049
A1
0.000
0.100
0.000
0.004
A2
1.050
1.150
0.041
0.045
b
0.300
0.400
0.012
0.016
C
0.100
0.200
0.004
0.008
D
2.820
3.020
0.111
0.119
E
1.500
1.700
0.059
0.067
E1
2.650
2.950
0.104
0.116
e
0.950TYP
0.037TYP
e1
1.800
0.071
L
0.700REF
0.028REF
L1
0.300
0.460
0.012
0.024
θ
0°
8°
0°
8°
Symbol
www.3peakic.com.cn
2.000
Rev. A.02
0.079
15
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
SOP-8
A2
C
θ
L1
A1
e
E
D
Symbol
E1
b
16
Rev. A.02
Dimensions
Dimensions In
In Millimeters
Inches
Min
Max
Min
Max
A1
0.100
0.250
0.004
0.010
A2
1.350
1.550
0.053
0.061
b
0.330
0.510
0.013
0.020
C
0.190
0.250
0.007
0.010
D
4.780
5.000
0.188
0.197
E
3.800
4.000
0.150
0.157
E1
5.800
6.300
0.228
0.248
e
1.270 TYP
0.050 TYP
L1
0.400
1.270
0.016
0.050
θ
0°
8°
0°
8°
www.3peakic.com.cn
LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
MSOP-8
Dimensions
Dimensions In
In Millimeters
Inches
Min
Max
Min
Max
A
0.800
1.200
0.031
0.047
A1
0.000
0.200
0.000
0.008
A2
0.760
0.970
0.030
0.038
b
0.30 TYP
0.012 TYP
C
0.15 TYP
0.006 TYP
D
2.900
e
0.65 TYP
E
2.900
3.100
0.114
0.122
E1
4.700
5.100
0.185
0.201
L1
0.410
0.650
0.016
0.026
θ
0°
6°
0°
6°
Symbol
E
E1
A
A2
e
b
D
3.100
0.114
0.122
0.026
A1
R1
R
θ
L1
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L
L2
Rev. A.02
17
LMV321A / LMV358A / LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
TSSOP-14
Dimensions
E1
E
A
A2
e
c
D
Symbol
In Millimeters
MIN
TYP
MAX
A
-
-
1.20
A1
0.05
-
0.15
A2
0.90
1.00
1.05
b
0.20
-
0.28
c
0.10
-
0.19
D
4.86
4.96
5.06
E
6.20
6.40
6.60
E1
4.30
4.40
4.50
e
L
A1
R1
R
0.65 BSC
0.45
0.60
0.75
L1
1.00 REF
L2
0.25 BSC
R
0.09
-
-
θ
0°
-
8°
θ
L1
18
Rev. A.02
L
L2
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LMV321A/LMV358A/ LMV324A
80μA, 1.0MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
SOP-14
D
E1
Dimensions
E
In Millimeters
Symbol
e
b
A A2
A1
MIN
TYP
MAX
A
1.35
1.60
1.75
A1
0.10
0.15
0.25
A2
1.25
1.45
1.65
b
0.36
D
8.53
8.63
8.73
E
5.80
6.00
6.20
E1
3.80
3.90
4.00
e
L
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1.27 BSC
0.45
0.60
0.80
L1
1.04 REF
L2
0.25 BSC
θ
L
L1
0.49
0°
8°
θ
L2
Rev. A.02
19
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