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LMP7312
Precision SPI-Programmable AFE with Differential/SingleEnded Input/Output
General Description
Features
The LMP7312 is a digitally programmable variable gain amplifier/attenuator. Its wide input voltage range and superior
precision make it a prime choice for applications requiring
high accuracy such as data acquisition systems for IO modules in programmable logic control (PLC). The LMP7312
provides a differential output to maximize dynamic range and
signal to noise ratio, thereby reducing the overall system error. It can also be configured to handle single ended input data
converters by means of the VOCM pin (see application section
for details). The inputs of LMP7312 can be configured in attenuation mode to handle large input signals of up to +/- 15V,
as well as in amplification mode to handle current loops of
0-20mA and 4-20mA.The LMP7312 is equipped with a null
switch to evaluate the offset of the internal amplifier. A guaranteed 0.035% maximum gain error (for all gains) and a
maximum gain drift of 5ppm over the extended industrial temperature range (-40° to 125°C) make the LMP7312 very
attractive for high precision systems even under harsh conditions. A low input offset voltage of 100µV and low voltage
noise of 3µVpp give the LMP7312 a superior performance.
The LMP7312 is fully specified from -40° to 125°C and is
available in SOIC-14 package.
Typical Values, TA = 25°C, V+=5V, V-=0V.
1 MHz
■ Gain bandwidth
-15V to +15V
■ Input voltage range (G= 0.096 V/V)
100 µV (max)
■ Core op-amp input offset voltage
2 mA (max)
■ Supply current
0.096 V/V, 0.192 V/V
■ Gain (Attenuation Mode)
0.384 V/V, 0.768 V/V
1 V/V, 2 V/V
■ Gain (AmplificationMode)
0.035% (max)
■ Gain Error
90 dB (min)
■ Core op-amp PSRR
80 dB (min)
■ CMRR
1V to 4V
■ Adjustable output common mode
−40 to 125°C
■ Temperature range
14-Pin SOIC
■ Package
Applications
■ Signal conditioning AFE
■
■
■
■
■
±10V; ±5V; 0-5V; 0-10V; 0-20mA; 4-20mA
Data Acquisition systems
Motor control
Instrument and process control
Remote sensing
Programmable automation control
Typical Application
30075513
LMP™ is a trademark of National Semiconductor Corporation.
© 2010 National Semiconductor Corporation
300755
www.national.com
LMP7312 Precision SPI-Programmable AFE with Differential/Single-Ended Input/Output
June 18, 2010
LMP7312
For soldering specification:
see product folder at www.national.com and
www.national.com/ms/MS/MS-SOLDERING.pdf
Junction Temperature
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Rating (Note 2)
Human Body Model
Machine Body Model
Charge device Model
Analog Supply Voltage (VS = V+ - V-)
DigitaI Supply Voltage (VDIO=VIO-V-)
Attenuation pins -VIN, +VIN referred to VAmplification pins -IN, +IN referred to VVoltage at all other pins referred to VStorage Temperature Range
Operating Ratings
2000V
150V
1000V
6V
6V
±17.5V
±10V
6V
-65°C to 150°C
5V Electrical Characteristics
150°C
(Note 1)
V+
Analog Supply Voltage (VS =
– V-), V=0V
Digital Supply Voltage (VDIO = VIO– V-),
V-=0V
Attenuation pins -VIN, +VIN referred to VAmplification pins -IN, +IN referred to VTemperature Range (Note 3)
Package Thermal Resistance (Note 3)
SOIC-14
4.5V to 5.5V
2.7V to 5.5V
-15V to 15V
-2.35V to 7.35V
−40°C to 125°C
145°C/W
(Note 4)
Unless otherwise specified, all limits guaranteed for TA = 25°C, V+ = 5V, VIO = 5V, V− = 0V, G = 0.192 V/V,
VCM_ATT=(+VIN+(-VIN))/2, VCM_AMP=(+IN+(-IN))/2. Differential output configuration. SE = Single Ended Output,
DE = Differential Output. Boldface limits apply at the temperature extremes.
Symbol
VOS
TCVOS
Av
en
Parameter
Core op-amp Input
Offset Voltage
Core op-amp Input
Offset Voltage
(Note 7)
Conditions
Min
(Note 6)
–100
–250
100
250
Nulling Switch Mode, DE, VOCM = 4V;
Nulling Switch Mode, SE, -VOUT/VR = 4V
–100
–250
100
250
Nulling Switch Mode, DE, VOCM = 1V;
Nulling Switch Mode, SE, -VOUT/VR = 1V
-3
±1.5
3
Nulling Switch Mode, DE, VOCM = 4V;
Nulling Switch Mode, SE, -VOUT/VR = 4V
-3
±1.5
3
Gain Error
All gains, RL = 10 kΩ, CL = 50pF, SE / DE
Gain Drift
SE / DE
–0.035
–0.045
-5
Core op-amp Voltage RTI, Nulling Switch Mode, f = 10 kHz
Noise Density
IVA
Analog Supply Current +VIN = −VIN = VOCM
IVIO
Digital Supply Current Without any load connected to SDO pin
RIN_CM
CM Input Resistance
±1
µV/°C
5
ppm/°C
nV/
µVPP
2
120
62.08
µV
%
3
G= 0.192 V/V
Units
0.035
0.045
7.25
G= 1 V/V
Differential Input
Resistance
Max
(Note 6)
Nulling Switch Mode, DE, VOCM = 1V;
Nulling switch Mode, SE, -VOUT/VR = 1V
Core op-amp Peak to RTI, Nulling Switch Mode, f= 0.1Hz to 10Hz
Peak Voltage Noise
RIN_DIFF
Typ
(Note 5)
mA
μA
kΩ
40
G= 0.192 V/V
248.3
G= 1 V/V
kΩ
160
G= 0.096V/V, -15V < VCM_ATT < 15V, SE / DE
G= 0.192V/V, -11.4V < VCM_ATT < 15V, SE / DE
CMRR
DC Common Mode
Rejection Ratio
G= 0.384V/V, -6V < VCM_ATT < 11V, SE / DE
G= 0.768V/V, -3V < VCM_ATT < 8V, SE / DE
80
77
dB
90
dB
G= 1V/V, -2.3V < VCM_AMP < 7.3V, SE / DE
G= 2V/V, -1.15V < VCM_AMP < 6.15V, SE / DE.
PSRR
Core op-amp DC
Power Supply
Rejection Ratio
www.national.com
Nulling Switch Mode, 4.5V
