19-1619; Rev 0; 1/00
2-Wire, 4–20mA
Smart Signal Conditioner
General Description
Features
ꢀ Highly Integrated Sensor Signal Conditioner for
The MAX1459 highly integrated analog-sensor signal
conditioner is optimized for piezoresistive sensor calibra-
tion and compensation with minimal external compo-
nents. It includes a programmable current source for
sensor excitation, a 3-bit programmable-gain amplifier
(PGA), a 128-bit internal EEPROM, and four 12-bit DACs.
Achieving a total error factor within 1% of the sensor’s
repeatability errors, the MAX1459 compensates offset,
offset temperature coefficient (offset TC), full-span output
(FSO), FSO temperature coefficient (FSOTC), and FSO
nonlinearity of silicon piezoresistive sensors.
2-Wire, 4–20mA Transmitters
ꢀ Sensor Errors Trimmed Using Correction
Coefficients Stored in Internal EEPROM—
Eliminates the Need for Laser Trimming and
Potentiometers
ꢀ Compensates Offset, Offset TC, FSO, FSOTC,
FSO Linearity
ꢀ Programmable Current Source (0.1mA to 2.0mA)
for Sensor Excitation
The MAX1459 calibrates and compensates first-order
temperature errors by adjusting the offset and span of
the input signal through digital-to-analog converters
(DACs), thereby eliminating quantization noise.
ꢀ Fast Signal-Path Settling Time (≈1ms)
ꢀ Accepts Sensor Outputs from +1mV/V to +40mV/V
ꢀ Fully Analog Signal Path
The MAX1459 allows temperature compensation via the
external sensor, an internal temperature-dependent
resistor, or a dedicated external temperature transduc-
er. Accuracies better than 0.5% can be achieved with
low-cost external temperature sensors (i.e., silicon tran-
sistor), depending on sensor choice.
ꢀ Internal or External Temperature Reference
Compensation
ꢀ Automated Pilot Production (Calibration/
Compensation) System Available
Built-in testability features on the MAX1459 result in the
integration of three traditional sensor-manufacturing
operations into one automated process:
ꢀ Write Protection for EEPROM Data Security
Ordering Information
• Pretest: Data acquisition of sensor performance
PART
TEMP. RANGE
PIN-PACKAGE
20 SSOP
Dice*
under the control of a host test computer.
MAX1459CAP
MAX1459C/D
MAX1459AAP
0°C to +70°C
• Calibration and compensation: Computation and
storage (in an internal EEPROM) of calibration and
compensation coefficients computed by the test
computer and downloaded to the MAX1459.
0°C to +70°C
-40°C to +125°C
20 SSOP
*Dice are tested at T = +25°C, DC parameters only.
A
Functional Diagram appears at end of data sheet.
• Final test operation: Verification of transducer cali-
bration and compensation without removal from the
pretest socket.
Pin Configuration
Although optimized for use with piezoresistive sensors,
the MAX1459 may also be used with other resistive
sensors (i.e., accelerometers and strain gauges) with
some additional external components.
TOP VIEW
SCLK
CS
1
2
3
4
5
6
7
8
9
20 V
DD
19 NBIAS
18 CK50
17 TEMP2
16 TEMP1
15 INM
DIO
For custom versions of the MAX1459, see the Customization
section at end of data sheet.
WE
MAX1459
FSOTC
AMP+
AMP-
AMPOUT
TEMPIN
________________________Applications
4–20mA Transmitters
14 INP
Piezoresistive Pressure and Acceleration
Industrial Pressure Sensors
13 BDRIVE
12
V
SS
Load Cells/Wheatstone Bridges
Strain Gauges
ISRC 10
11 OUT
Temperature Sensors
SSOP
________________________________________________________________ Maxim Integrated Products
1
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