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PDF MAX1450 Data sheet ( Hoja de datos )
| Número de pieza | MAX1450 | |
| Descripción | 1%-Accurate Signal Conditioner | |
| Fabricantes | Maxim Integrated | |
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MAX1450
EVALUATION KIT AVAILABLE
Low-Cost, 1%-Accurate Signal Conditioner
for Piezoresistive Sensors
General Description
The MAX1450 sensor signal conditioner is optimized for
piezoresistive sensor calibration and temperature com-
pensation. It includes an adjustable current source for
sensor excitation and a 3-bit programmable-gain amplifier
(PGA). Achieving a total typical error factor within 1% of
the sensor’s inherent repeatability errors, the MAX1450
compensates offset, full-span output (FSO), offset temp-
co, FSO tempco, and FSO nonlinearity of silicon piezore-
sistive sensors via external trimmable resistors, potenti-
ometers, or digital-to-analog converters (DACs).
The MAX1450 is capable of compensating sensors that
display close error distributions with a single temperature
point, making it ideal for low-cost, medium-accuracy appli-
cations. Although optimized for use with popular piezore-
sistive sensors, it may also be used with other resistive
sensor types such as strain gauges.
Customization
Maxim can customize the MAX1450 for unique requirements
including improved power specifications. With a dedicated cell
library consisting of more than 90 sensor-specific functional
blocks, Maxim can quickly provide customized MAX1450
solutions. Contact the factory for additional information.
Applications
●● Piezoresistive Pressure and Acceleration
Transducers and Transmitters
●● Manifold Absolute Pressure (MAP) Sensors
●● Hydraulic Systems
●● Industrial Pressure Sensors
Pin Configuration
TOP VIEW
INP 1
I.C. 2
I.C. 3
SOTC 4
SOFF 5
A1 6
A0 7
OFFTC 8
OFFSET 9
BBUF 10
MAX1450
20 INM
19 VSS
18 BDRIVE
17 ISRC
16 I.C.
15 VDD
14 OUT
13 A2
12 I.C.
11 FSOTRIM
SSOP
Features
●● 1% Sensor Signal Conditioning
●● Corrects Sensor Errors Using Coefficients Stored
in External Trimmable Resistors, Potentiometers, or
DACs
●● Compensates Offset, Offset TC, FSO, FSO TC, and
FSO Linearity
●● Rail-to-Rail Analog Output
●● Programmable Current Source for Sensor Excitation
●● Fast Signal-Path Settling Time (< 1ms)
●● Accepts Sensor Outputs from 10mV/V to 30mV/V
●● Fully Analog Signal Path
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1450CAP
0°C to +70°C
20 SSOP
MAX1450C/D
0°C to +70°C
Dice*
MAX1450AAP
-40°C to +125°C
20 SSOP
*Dice are tested at TA = +25°C, DC parameters only.
Functional Diagram
FSOTRIM VDD
ISRC
CURRENT
SOURCE
VDD
BDRIVE
INP
INM
+
PGA
-
A=1
MAX1450
A2
A1
A0
OUT
SOTC
SOFF
OFFTC
OFFSET
BBUF
VSS
19-1365; Rev 2; 5/14
1 page  
MAX1450
Low-Cost, 1%-Accurate Signal Conditioner
for Piezoresistive Sensors
Summing Junction
The second stage in the analog signal path consists of a
summing junction for offset, offset temperature compen-
sation, and the PGA output. The offset voltage (VOFFSET)
and offset temperature-compensation voltage (VOFFTC)
add or subtract from the PGA output depending on their
respective sign bits, offset sign (SOFF), and offset TC
sign (SOTC). VOFFSET and VOFFTC can range in magni-
tude from VSS to VDD.
Output Buffer
The final stage in the analog signal path consists of a uni-
ty-gain buffer. This buffer is capable of swinging to within
250mV of VSS and VDD while sourcing/sinking up to
1.0mA, or within 50mV of the power supplies with no load.
Bridge Drive
Figure 2 shows the functional diagram of the on-chip cur-
rent source. The voltage at FSOTRIM, in conjunction with
RISRC, sets the nominal current, IISRC which sets the
FSO (refer to Figure 3 for sensor terminology.) IISRC is
additionally modulated by components from the external
resistor RSTC and the optional resistor RLIN. RSTC is
used to feed back a portion of the buffered bridge-excita-
tion voltage (VBBUF), which compensates FSO TC errors
by modulating the bridge-excitation current over tempera-
ture. To correct FSO linearity errors, feed back a portion
of the output voltage to the currentsource reference node
via the optional RLIN resistor.
Applications Information
Compensation Procedure
The following compensation procedure assumes a pres-
sure transducer with a +5V supply and an output voltage
that is ratiometric to the supply voltage (see Ratiometric
Output Configuration section). The desired offset voltage
(VOUT at PMIN) is 0.5V, and the desired FSO voltage
(VOUT(PMAX) - VOUT(PMIN)) is 4V; thus the FS output
voltage (VOUT at PMAX) will be 4.5V. The procedure
requires a minimum of two test pressures (e.g., zero and
full scale) and two temperatures. A typical compensation
procedure is as follows:
1) Perform Coefficient Initialization
2) Perform FSO Calibration
3) Perform FSO TC Compensation
4) Perform OFFSET TC Compensation
5) Perform OFFSET Calibration
6) Perform Linearity Calibration (Optional)
Coefficient Initialization
Select the resistor values and the PGA gain to prevent
gross overload of the PGA and bridge current source.
These values depend on sensor behavior and require
some sensor characterization data. This data may be
available from the sensor manufacturer. If not, it can be
generated by performing a two-temperature, two-pressure
FSOTRIM
VDD
MAX1450
IISRC
IBDRIVE ≈ 13 (IISRC)
VBDRIVE
A=1
BBUF
BBUF
OUT
RSTC
(EXTERNAL)
IISRC
BDRIVE
RLIN (OPTIONAL)
(EXTERNAL)
RISRC
(EXTERNAL)
SENSOR
INP
INM
Figure 2. Bridge Drive Circuit
www.maximintegrated.com
Maxim Integrated │ 5
5 Page 
MAX1450
Low-Cost, 1%-Accurate Signal Conditioner
for Piezoresistive Sensors
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE TYPE
20 SSOP
PACKAGE CODE
A20-1
OUTLINE NO.
21-0056
LAND PATTERN NO.
09-0094
www.maximintegrated.com
Maxim Integrated │ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX1450.PDF ] | |
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