LMV358TP-VR [3PEAK]
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps;
| 型号： | LMV358TP-VR |
| 厂家： | 
3PEAK |
| 描述： | 40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps |
| 文件： | 总18页 (文件大小：1765K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Features
Description
Upgrade to LMV321/LMV358/LMV324 Family
LMV321TP/358TP/324TP are CMOS single, dual,
Stable 1.27MHz GBWP with Low IQ of Only 40μA
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.
Typical per Amplifier
0.9V/μs Slew Rate
Unity Gain Stable for ANY CAPACITIVE Load
Offset Voltage: 3.5mV Maximum
Offset Voltage Temperature Drift: 0.6uV/°C
Input Bias Current: 1pA Typical
The LMV321TP/358TP/324TP are unity gain stable
with Any Capacitive Load with a Constant 1.27MHz
gain-bandwidth product, 0.9V/μs slew rate while
consuming only 40μA of supply current per amplifier.
Analog trim and calibration routine reduces input
offset voltage to below 3.5mV. Adaptive biasing and
dynamic compensation enables the LMV321TP
/358TP/324TP 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.
THD+Noise: -105dB at 1kHz, -90dB at 10kHz
CMRR/PSRR: 110dB/102dB
Beyond the Rails Input Common-Mode Range
Outputs Swing to within 5mV Typical 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
This combination of features makes the LMV321TP
/358TP/324TP superior among rail-to-rail input
/output CMOS op amps in its power class. The
LMV321TP/358TP/324TP are ideal choices for
ESD Rating:
Robust 8KV – HBM, 2KV – CDM and 500V – MM
battery-powered
applications
because
they
Green, Popular Type Package
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
The LMV321TP/358TP/324TP 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.
Smoke/Gas/Environment Sensors
Portable Instruments and Mobile Device
Audio Output
3PEAK and the 3PEAK logo are registered trademarks of
3PEAK INCORPORATED. All other trademarks are the property
of their respective owners.
PCMCIA Cards
Battery or Solar Powered Systems
Medical Equipment
Piezo Electrical Transducer Amplifier
Pin Configuration(Top View)
LMV321TP
5-Pin SOT23/SC70
(-T and -C Suffixes)
LMV358TP
8-Pin SOIC/MSOP
(-S and -V Suffixes)
LMV324TP
14-Pin SOIC/TSSOP
(-S and -T Suffixes)
1
2
3
5
4
1
2
3
4
8
7
6
5
1
2
3
4
5
6
7
14
13
12
11
10
9
+In
-VS
-In
+VS
Out
Out A
-In A
+In A
-VS
+VS
Out A
-In A
Out D
-In D
+In D
-VS
Out B
-In B
+In B
A
A
B
D
C
+In A
B
+VS
+In B
+In C
-In C
Out C
LMV358TP
8-Pin DFN
(-F Suffixes)
-In B
8
Out B
8
1
2
3
4
﹢Vs
Out A
7
6
5
﹣In A
﹢In A
﹣Vs
Out B
﹣In B
﹢In B
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REV A.02
1
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Note 1
Absolute Maximum Ratings
Supply Voltage: V+ – V–....................................6.0V
Input Voltage............................. V– – 0.2 to V+ + 0.2
Input Current: +IN, –IN, SHDN Note 2.............. ±10mA
Output Current: OUT.................................... ±45mA
Output Short-Circuit Duration Note 3…......... Indefinite
Operating Temperature Range.......–40°C to 125°C
Maximum Junction Temperature................... 150°C
Storage Temperature Range.......... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) ......... 260°C
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 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 3: 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
HBM
Parameter
Human Body Model ESD
Machine Model ESD
Condition
Minimum Level
Unit
kV
MIL-STD-883H Method 3015.8
JEDEC-EIA/JESD22-A115
JEDEC-EIA/JESD22-C101E
8
MM
500
2
V
CDM
Charged Device Model ESD
kV
Order and MSL Information
Model
Name
Transport Media,
Quantity
Marking
Information
AC4YW (1)
AT4YW (1)
A42S
MSL
Level
Order Number
Package
5-Pin SC70
LMV321TP-CR
LMV321TP-TR
LMV358TP-SR
LMV358TP-VR
LMV358TP-FR
LMV324TP-SR
Tape and Reel, 3000
Tape and Reel, 3000
Tape and Reel, 4000
Tape and Reel, 3000
Tape and Reel, 3000
Tape and Reel, 2500
MSL 3
MSL 3
MSL 3
MSL 3
MSL 3
MSL 3
LMV321TP
5-Pin SOT23
8-Pin SOIC
8-Pin MSOP
8-Pin DFN
LMV358TP
LMV324TP
A42V
A42
14-Pin SOIC
A44S
14-Pin
TSSOP
LMV324TP-TR
Tape and Reel, 3000
A44T
MSL 3
Note (1): ‘YW’ is date coding scheme. 'Y' stands for calendar year, and 'W' stands for single workweek coding scheme.
REV A.02
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
5V Electrical Characteristics
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 27° C.
VSUPPLY = 5V, VCM = VOUT = VSUPPLY/2, RL = 100KΩ, CL =100pF
SYMBOL
VOS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
mV
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Input Offset Current
Input Voltage Noise
VCM = VSUPPLY/2
●
-3.5
± 0.1 +3.5
VOS TC
IB
0.6
1.0
1.0
5.6
μV/° C
pA
IOS
pA
Vn
f = 0.1Hz to 10Hz
μVP-P
f = 1kHz
f = 10kHz
39
23
en
Input Voltage Noise Density
Input Resistance
nV/√Hz
GΩ
RIN
CIN
>100
Differential
Common Mode
VCM = 0.1V to 4.9V
1.5
3.0
110
Input Capacitance
pF
dB
V
CMRR
VCM
Common Mode Rejection Ratio
Common-mode Input Voltage
Range
●
●
80
-0.1
5.1
PSRR
AVOL
Power Supply Rejection Ratio
●
●
●
80
80
72
102
102
102
5
45
40
dB
dB
VOUT = 2.5V, RLOAD = 100kΩ
VOUT = 0.1V to 4.9V, RLOAD = 100kΩ
RLOAD = 100kΩ
Open-Loop Large Signal Gain
VOL
ISC
IQ
PM
GM
GBWP
Output Swing from Supply Rail
Output Short-Circuit Current
Quiescent Current per Amplifier
Phase Margin
mV
mA
μA
0
Sink or source current
●
51
RLOAD = 100kΩ, CLOAD = 100pF
RLOAD = 100kΩ, CLOAD = 100pF
f = 1kHz
0.1%
0.01%
0.1%
0.01%
66
Gain Margin
-15
1.27
2.3
2.8
0.33
0.38
dB
MHz
Gain-Bandwidth Product
Settling Time, 1.5V to 3.5V,
Unity Gain
Settling Time, 2.45V to 2.55V,
Unity Gain
μs
μs
tS
AV = 1, VOUT = 1.5V to 3.5V, CLOAD
100pF, RLOAD = 100kΩ
2VP-P
f=1kHz, AV=1, RL=100kΩ, VOUT = 2VPP
f=10kHz, AV=1, RL=100kΩ, VOUT = 2VPP
=
SR
Slew Rate
0.9
V/μs
kHz
dB
FPBW
THD+N
Full Power Bandwidth
Total Harmonic Distortion and
Noise
140
-105
-90
Note: 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.
A heat sink may be required to keep the junction
temperature below the absolute maximum rating when
the output is shorted indefinitely.
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.
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.
Full power bandwidth is calculated from the slew rate
FPBW = SR/π • VP-P.
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REV A.02
3
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
Small-Signal Step Response, 100mV Step
Large-Signal Step Response, 2V Step
Open-Loop Gain and Phase
Phase Margin vs. CLOAD (Stable for Any CLOAD)
Input Voltage Noise Spectral Density
Common-Mode Rejection Ratio
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
Over-Shoot Voltage, CLOAD = 40nF, Gain = +1
Over-Shoot Voltage, CLOAD=40nF, Gain= -1, RFB=100kΩ
Power-Supply Rejection Ratio
Over-Shoot % vs. CLOAD, Gain = -1, RFB = 20kΩ
Small-Signal Over-Shoot % vs. CLOAD, Gain = +1
VIN = -0.2V to 5.7V, No Phase Reversal
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REV A.02
5
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
Quiescent Supply Current vs. Temperature
Open-Loop Gain vs. Temperature
Quiescent Supply Current vs. Supply Voltage
Short-Circuit Current vs. Supply Voltage
Input Offset Voltage Distribution
Closed-Loop Output Impedance vs. Frequency
REV A.02
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Typical Performance Characteristics
THD+Noise, Gain = +1, VIN = 1kHz, VPP = 2V
THD+Noise, Gain = +1, VIN = 20kHz, VPP = 2V
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REV A.02
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Pin Functions
–IN: Inverting Input of the Amplifier. Voltage range
of this pin can go from V– – 0.1V to V+ + 0.1V.
–VS: Negative Power Supply. It is normally tied to
ground. It can also be tied to a voltage other than
ground as long as the voltage between V+ and V– is
from 2.1V to 5.25V. If it is not connected to ground,
bypass it with a capacitor of 0.1μF as close to the
part as possible.
+IN: Non-Inverting Input of Amplifier. This pin has
the same voltage range as –IN.
+VS: Positive Power Supply. Typically the voltage is
from 2.1V to 5.25V. Split supplies are possible as
long as the voltage between V+ and V– is between
2.1V and 5.25V. A bypass capacitor of 0.1μF as
close to the part as possible should be used
between power supply pins or between supply pins
and ground.
OUT: Amplifier Output. The voltage range extends
to within millivolts of each supply rail.
The exposed thermal pad of DFN package should
be left floated.
Operation
The LMV321TP/358TP/324TP 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 LMV321TP/358TP/324TP of operational amplifiers can operate with power supply voltages from 2.1V to 6.0V.
Each amplifier draws only 40μA 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 LMV321TP/358TP/324TP 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 LMV321TP/358TP/324TP provides a low input referred noise density of 39nV/√Hz at 1kHz. The voltage
noise will grow slowly with the frequency in wideband range, and the input voltage noise is typically 5.6μVP-P at the
frequency of 0.1Hz to 10Hz.
Low Input Offset Voltage
The LMV321TP/358TP/324TP has a low offset voltage of 3.5mV 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 LMV321TP/358TP/324TP 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.
REV A.02
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
PCB Surface Leakage
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 conditions, a typical resistance between nearby traces is 1012Ω. A 5V difference would cause 5pA of
current to flow, which is greater than the LMV321TP/358TP/324TP 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 LMV321TP/358TP/324TP has excellent output drive capability, delivering over 10mA 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 LMV321TP/358TP/324TP 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
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
5pF
10kΩ
VOUT
VIN
CPAR
10kΩ
Figure 2
Driving Large Capacitive Load
The LMV321TP/358TP/324TP 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 LMV321TP/358TP/324TP (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 LMV321TP/358TP/324TP 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.
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
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 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 LMV321TP/358TP/324TP OPA is well suited for conditioning sensor signals in battery-powered applications.
Figure 4 shows a two op-amp instrumentation amplifier, using the LMV321TP/358TP/324TP 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
R2
VREF
R2
R1
VOUT
V2
V1
R
2R
1 ) VREF
1
VOUT =(V V2 )(1
1
R2 RG
Figure 4
Gain-of-100 Amplifier Circuit
Figure 5 shows a Gain-of-100 amplifier circuit using two LMV321TP/358TP/324TP 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
90.9k
10k
10k
Figure 5: 100kHz, 74μA Gain-of-100 Amplifier
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REV A.02
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, 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 LMV321TP/358TP/324TP 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
LMV321TP/358TP/324TP 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)
GENERAL PURPOSE
COMBINATION
pH PROBE
COAX
(CORNING 476540)
R1
10M
pH
PROBE
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:
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LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
C1
400pF
VIN
VOUT
C2
R1
R2
400pF
1MΩ
1MΩ
R1= R2 = R = 1M
C1= C2 = C = 400pF
R4
2MΩ
Q = Filter Peaking Factor = 1
f-3dB = 1/(2 RC) = 400Hz
R3
2MΩ
R3 = R4 /(2-1/Q) ; with Q = 1, R3 =R4
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 37μA 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
100 kΩ
1%
VOUT 1Vin Air ( 21% O2 )
IDD 0.7uA
100 Ω
1%
I
O2
Figure 9
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REV A.02
13
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
SC70-5 /SOT-353
Dimensions
In Millimeters In Inches
Min Max Min Max
Dimensions
Symbol
A
0.900 1.100 0.035 0.043
0.000 0.100 0.000 0.004
0.900 1.000 0.035 0.039
0.150 0.350 0.006 0.014
0.080 0.150 0.003 0.006
2.000 2.200 0.079 0.087
1.150 1.350 0.045 0.053
2.150 2.450 0.085 0.096
A1
A2
b
C
D
E
E1
e
0.650TYP
1.200 1.400 0.047 0.055
0.525REF 0.021REF
0.260 0.460 0.010 0.018
0° 8° 0° 8°
0.026TYP
e1
L
L1
θ
SOT23-5
Dimensions
Symbol In Millimeters In Inches
Min Max Min Max
Dimensions
A
1.050 1.250 0.041 0.049
0.000 0.100 0.000 0.004
1.050 1.150 0.041 0.045
0.300 0.400 0.012 0.016
0.100 0.200 0.004 0.008
2.820 3.020 0.111 0.119
1.500 1.700 0.059 0.067
2.650 2.950 0.104 0.116
A1
A2
b
C
D
E
E1
e
0.950TYP
1.800 2.000 0.071 0.079
0.700REF 0.028REF
0.300 0.460 0.012 0.024
0° 8° 0° 8°
0.037TYP
e1
L
L1
θ
REV A.02
www.3peakic.com.cn
14
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
SOIC-8
Dimensions
Dimensions In
Inches
In Millimeters
Symbol
Min
Max
Min
Max
A
1.350
0.100
1.350
0.330
0.190
4.780
3.800
5.800
1.270TYP
0.400
0°
1.750
0.250
1.550
0.510
0.250
5.000
4.000
6.300
0.053
0.004
0.053
0.013
0.007
0.188
0.150
0.228
0.050TYP
0.016
0°
0.069
0.010
0.061
0.020
0.010
0.197
0.157
0.248
A1
A2
B
C
D
E
E1
e
L1
θ
1.270
8°
0.050
8°
MSOP-8
Dimensions
Dimensions In
Inches
In Millimeters
Symbol
Min
Max
Min
Max
A
0.800
0.000
0.760
0.30 TYP
0.15 TYP
2.900
0.65 TYP
2.900
4.700
0.410
0°
1.200
0.200
0.970
0.031
0.000
0.030
0.012 TYP
0.006 TYP
0.114
0.026
0.114
0.185
0.016
0°
0.047
0.008
0.038
A1
A2
b
C
D
3.100
0.122
e
E
3.100
5.100
0.650
6°
0.122
0.201
0.026
6°
E1
L1
θ
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REV A.02
15
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
DFN-8
Dimensions
Dimensions In Inches
In Millimeters
Symbol
Min
0.80
0.00
Nom
0.85
0.02
Max
0.9
Min
Nom
0.033
0.001
0.008
0.009
0.079
0.079
0.024
0.047
0.20
Max
A
0.031
0.000
0.035
0.002
0.010
0.012
0.083
0.083
0.028
0.051
A1
A2
b
0.05
0.153 0.203
0.253 0.006
0.18
1.9
1.9
0.5
1.1
0.24
2.0
0.30
2.1
2.1
0.7
1.3
0.007
0.075
0.075
0.020
0.043
D
E
2.0
D1
E1
e
0.6
1.2
0.50
k
0.2
0.008
0.010
L
0.25
0.35
0.45
0.014
0.018
REV A.02
www.3peakic.com.cn
16
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
SOIC-14
Dimensions
In Millimeters
Symbol
MIN
NOM
1.60
0.15
1.45
0.65
MAX
A
1.35
0.10
1.25
0.55
0.36
0.35
0.16
0.15
8.53
5.80
3.80
1.75
0.25
1.65
0.75
0.49
0.45
0.25
0.25
8.73
6.20
4.00
A1
A2
A3
b
b1
c
0.40
c1
D
0.20
8.63
E
6.00
E1
e
3.90
1.27 BSC
0.60
L
0.45
0.80
L1
L2
R
1.04 REF
0.25 BSC
0.07
0.07
0.30
0°
R1
h
0.40
0.50
8°
θ
θ1
θ2
θ3
θ4
6°
8°
8°
7°
7°
10°
10°
9°
6°
5°
5°
9°
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REV A.02
17
LMV321TP/LMV358TP/LMV324TP
40μA, 1.27MHz, Micro-Power Rail-to-Rail I/O Op Amps
Package Outline Dimensions
TSSOP-14
Dimensions
Symbol
In Millimeters
MIN
NOM
MAX
A
-
-
-
1.20
0.15
1.05
0.54
0.28
0.24
0.19
0.15
5.06
6.60
4.50
A1
A2
A3
b
0.05
0.90
0.34
0.20
0.20
0.10
0.10
4.86
6.20
4.30
1.00
0.44
-
b1
c
0.22
-
c1
D
0.13
4.96
6.40
4.40
0.65 BSC
0.60
E
E1
e
L
0.45
0.75
L1
L2
R
1.00 REF
0.25 BSC
0.09
-
-
-
R1
s
0.09
-
0.20
-
θ1
θ2
θ3
0°
-
8°
10°
12°
12°
14°
14°
10°
REV A.02
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18
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