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LMP90100/LMP90099/
LMP90098/LMP90097
July 25, 2011
Sensor AFE System: Multi-Channel, Low Power 24-Bit
Sensor AFE with True Continuous Background Calibration
1.0 General Description
The LMP90100/LMP90099/LMP90098/LMP90097 are highly
integrated, multi-channel, low power 24-bit Sensor AFEs. The
devices features a precision, 24-bit Sigma Delta Analog-to-
Digital Converter (ADC) with a low-noise programmable gain
amplifier and a fully differential high impedance analog input
multiplexer. A true continuous background calibration feature
allows calibration at all gains and output data rates without
interrupting the signal path. The background calibration fea-
ture essentially eliminates gain and offset errors across tem-
perature and time, providing measurement accuracy without
sacrificing speed and power consumption.
Another feature of the LMP90100/LMP90099/LMP90098/
LMP90097 is continuous background sensor diagnostics, al-
lowing the detection of open and short circuit conditions and
out-of-range signals, without requiring user intervention, re-
sulting in enhanced system reliability.
Two sets of independent external reference voltage pins allow
multiple ratiometric measurements. In addition, two matched
programmable current sources are available in the
LMP90100/LMP90098 to excite external sensors such as re-
sistive temperature detectors and bridge sensors. Further-
more, seven GPIO pins are provided for interfacing to external
LEDs and switches to simplify control across an isolation bar-
rier.
Collectively, these features make the LMP90100/LMP90099/
LMP90098/LMP90097 complete analog front-ends for low
power, precision sensor applications such as temperature,
pressure, strain gauge, and industrial process control. The
LMP90100/LMP90099/LMP90098/LMP90097 are guaran-
teed over the extended temperature range of -40°C to +125°
C and are available in a 28-pin TSSOP package.
2.0 Features
■ 24-Bit Low Power Sigma Delta ADC
■ True Continuous Background Calibration at all gains
■ In-Place System Calibration using Expected Value
programming
■ Low-Noise programmable gain (1x - 128x)
■ Continuous background open/short and out of range
sensor diagnostics
■ 8 output data rates (ODR) with single-cycle settling
■ 2 matched excitation current sources from 100 µA to
1000 µA (LMP90100/LMP90098)
■ 4-DIFF / 7-SE inputs (LMP90100/LMP90099)
■ 2-DIFF / 4-SE inputs (LMP90098/LMP90097)
■ 7 General Purpose Input/Output pins
■ Chopper-stabilized buffer for low offset
■ SPI 4/3-wire with CRC data link error detection
■ 50 Hz to 60 Hz line rejection at ODR ≤13.42 SPS
■ Independent gain and ODR selection per channel
■ Supported by Webench Sensor AFE Designer
■ Automatic Channel Sequencer
3.0 Key Specifications
■ ENOB/NFR
Up to 21.5/19 bits
■ Offset Error (typ)
8.4 nV
■ Gain Error (typ)
7 ppm
■ Total Noise
< 10 µV-rms
■ Integral Non-Linearity (INL max)
±15 ppm of FSR
■ Output Data Rates (ODR) 1.6775 SPS - 214.65 SPS
■ Analog Voltage, VA
+2.85V to +5.5V
■ Operating Temp Range
-40°C to 125°C
■ Package
28-Pin TSSOP
4.0 Applications
■ Temperature and Pressure Transmitters
■ Strain Gauge Interface
■ Industrial Process Control
5.0 Typical Application
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© 2011 National Semiconductor Corporation 301395
30139574
www.national.com
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