MAX1457CWI ,0.1%-Accurate Signal Conditioner for Piezoresistive Sensor CompensationFeaturesThe MAX1457 is a highly integrated analog-sensor sig- ' High Accuracy (within ±0.1% of sens ..
MAX1458AAE ,1%-Accurate / Digitally Trimmed Sensor Signal Conditionerfeatures on the MAX1458 result in the integration of' Fully Analog Signal Paththree traditional sen ..
MAX1458CAE ,1%-Accurate / Digitally Trimmed Sensor Signal ConditionerApplicationsI.C. 3 14 INPPiezoresistive Pressure and AccelerationTEMP 4 MAX1458 13 BDRIVETransducer ..
MAX1459AAP ,2-Wire, 4-20mA Smart Signal ConditionerFeaturesThe MAX1459 highly integrated analog-sensor signal Highly Integrated Sensor Signal Conditi ..
MAX1459AAP+ ,2-Wire, 4-20mA Smart Signal ConditionerFeaturesThe MAX1459 highly integrated analog-sensor signal♦ Highly Integrated Sensor Signal Conditi ..
MAX145ACUA ,+2.7V, Low-Power, 2-Channel, 108ksps, Serial 12-Bit ADCs in 8-Pin レMAXApplications MAX144ACPA 0°C to +70°C 8 Plastic DIP ±0.5MAX144BCPA 0°C to +70°C 8 Plastic DI ..
MAX4052ACEE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4052ACEE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesELECTRICAL CHARACTERISTICS—Dual Supplies(V+ = +4.5V to +5.5V, V- = -4.5V to -5.5V, T = T to T , unl ..
MAX4052ACEE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4052ACEE+ ,Low-Voltage, CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4052ACPE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesMAX4051/A, MAX4052/A, MAX4053/A19-0463; Rev 0; 1/96Low-Voltage, CMOS AnalogMultiplexers/Switches___ ..
MAX4052ACSE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesMAX4051/A, MAX4052/A, MAX4053/A19-0463; Rev 0; 1/96Low-Voltage, CMOS AnalogMultiplexers/Switches___ ..
MAX1457CWI
0.1%-Accurate Signal Conditioner for Piezoresistive Sensor Compensation
________________General DescriptionThe MAX1457 is a highly integrated analog-sensor sig-
nal processor optimized for piezoresistive sensor cali-
bration and compensation. It includes a programmable
current source for sensor excitation, a 3-bit program-
mable-gain amplifier (PGA), a 12-bit ADC, five 16-bit
DACs, and an uncommitted op amp. Achieving a total
error factor within 0.1% of the sensor’s repeatability
errors, the MAX1457 compensates offset, full-span out-
put (FSO), offset TC, FSO TC, and full-span output non-
linearity of silicon piezoresistive sensors.
The MAX1457 calibrates and compensates first-order
temperature errors by adjusting the offset and span of
the input signal via digital-to-analog converters (DACs),
thereby eliminating quantization noise. If needed, resid-
ual higher-order errors are then compensated using lin-
ear interpolation of the first-order coefficients stored in
a look-up table (in external EEPROM).
The MAX1457 integrates three traditional sensor-
manufacturing operations into one automated process:Pretest: Data acquisition of sensor performance under
the control of a host test computer.Calibration and Compensation: Computation and storage
(in an external EEPROM) of calibration and compensation
coefficients determined from transducer pretest data.Final Test: Verification of transducer calibration and
compensation, without removal from a pretest socket.
Analog outputs are provided for both pressure and tem-
perature. A general-purpose, uncommitted op amp is also
included on-chip to increase the overall circuit gain, or to
facilitate the implementation of a 2-wire, 4–20mA transmit-
ter. The serial interface is compatible with MicroWire™
and SPI™, and directly connects to an external EEPROM.
Additionally, built-in testability features of the MAX1457
facilitate manufacturing and calibration of multiple sensor
modules, thus lowering manufacturing cost.
Although optimized for use with piezoresistive sensors,
the MAX1457 may also be used with other resistive
sensor types (i.e., accelerometers and strain gauges)
with the addition of a few external components.
_______________________CustomizationMaxim can customize the MAX1457 for unique require-
ments. With a dedicated cell library of more than 90
sensor-specific functional blocks, Maxim can quickly pro-
vide customized MAX1457 solutions. Contact Maxim for
additional information.
____________________________FeaturesHigh Accuracy (within ±0.1% of sensor’s
repeatable errors)Compensates Offset, Offset TC, FSO, FSO TC,
Temperature/Pressure NonlinearityRail-to-Rail®Analog Output for Calibrated,
Temperature-Compensated Pressure
MeasurementsProgrammable Sensor Excitation Current SPI/MicroWire-Compatible Serial InterfaceFast Signal-Path Settling Time (<1ms)Accepts Sensor Outputs from 5mV/V to 30mV/VPin-Compatible with MCA7707
MAX1457
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
_______________Ordering Information
Ordering Information continued at end of data sheet.
Note: Contact the factory for customized solutions.*Dice are tested at TA= +25°C.
Pin Configurations appear at end of data sheet.Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
SPI is a trademark of Motorola, Inc.
MicroWire is a trademark of National Semiconductor Corp.
Functional Diagram
MAX1457
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD= +5V, VSS= 0V, TA= +25°C, unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Supply Voltage, VDDto VSS......................................-0.3V to +6V
All other pins....................................(VSS- 0.3V) to (VDD+ 0.3V)
Continuous Power Dissipation (TA= +70°C)
28-Pin Wide SO (derate 12.50mW/°C above +70°C)..........1W
32-Pin TQFP (derate 11.1mW/°C above +70°C)...........889mW
Operating Temperature Ranges
MAX1457C_ _......................................................0°C to +70°C
MAX1457A_ _.................................................-40°C to +125°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec).............................+300°C
MAX1457
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
Note 1:Circuit of Figure 5 with current source turned off. This value is adjustable through a bias resistor and represents the IC cur-
rent consumption. This excludes the 93C66 EEPROM average current, which is approximately 13µA at a refresh rate of 3Hz
(fCLK= 100kHz).
Note 2:Temperature errors for the entire range are compensated together with the sensor errors.
Note 3:The sensor and the MAX1457 must always be at the same temperature during calibration and use.
Note 4:This is the maximum allowable sensor offset at minimum gain (54V/V).
Note 5:This is the sensor’s sensitivity normalized to its drive voltage, assuming a desired full-span output of 4V and a bridge volt-
age of 2.5V. Lower sensitivities can be accommodated by using the auxiliary op amp. Higher sensitivities can be accommo-
dated by operating at lower bridge voltages.
ELECTRICAL CHARACTERISTICS (continued)(VDD= +5V, VSS= 0V, TA= +25°C, unless otherwise noted.)
MAX1457
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
______________________________________________________________Pin Description
MAX1457
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
_______________Detailed DescriptionThe MAX1457 provides an analog amplification path for
the sensor signal and a digital path for calibration and
temperature correction. Calibration and correction are
achieved by varying the offset and gain of a program-
mable-gain amplifier (PGA) and by varying the sensor
bridge current. The PGA utilizes a switched-capacitor
CMOS technology, with an input-referred offset trim-
ming range of ±100mV (20mV/V) and an approximate
3µV (input referred, at minimum gain of 54V/V) resolu-
tion (16 bits). The PGA provides eight gain values from
54V/V to 306V/V. The bridge current source is program-
mable from 0.1mA to 2mA, with a 15nA step size.
The MAX1457 uses five 16-bit DACs with calibration
coefficients stored in a low-cost external EEPROM. This
memory (an external 4096-bit EEPROM) contains the
following calibration coefficients as 16-bit words:FSO (full-span output)FSO TC (including nonlinearities)OffsetOffset TC (including nonlinearities)Pressure nonlinearity
Figure 1 shows a typical pressure-sensor output and
defines the offset, full-scale, and full-span output values
as a function of voltage.
Offset CorrectionInitial offset calibration is accomplished by reading a
16-bit word (coefficient) from the EEPROM and writing it
to the OFFSET DAC. The resulting voltage (OFSTDAC)
is fed into a summing junction at the PGA output for
compensating the sensor offset with a resolution of
±0.2mV (±0.005% FSO).
Figure 2. Simplified Diagram of Temperature Error Correction
MAX1457
FSO CalibrationTwo adjustments are required for FSO calibration. First
set the coarse gain by digitally selecting the PGA gain.
Then calibrate the bridge current by writing a 16-bit
calibration coefficient word to the FSO DAC. These two
adjustments result in a calibration resolution of ±0.2mV
(±0.005% FSO).
Linear Temperature CompensationTemperature errors are compensated by writing 16-bit
calibration coefficients into the OFFSET TC DAC and
the FSO TC DAC (changing the current-source value
through resistive feedback from the FSOTCDAC pin to
the ISRC pin). The piezoresistive sensor is powered by
a current source resulting in a temperature-dependent
bridge voltage. The reference inputs of the OFFSET TC
DAC and FSO TC DAC are connected to the bridge
voltage. For a fixed digital word, the DAC output volt-
ages track the bridge voltage as it varies with tempera-
ture (quasi-linearly).
Multislope Temperature CompensationThe MAX1457 utilizes multislope temperature compen-
sation, allowing for compensation of arbitrary error
curves restricted only by the available adjustment
range and the shape of the temperature signal.
The MAX1457 offers a maximum of 120 calibration
points (each consisting of one OFFSET TC coefficient
and one FSO TC coefficient) over the operating temper-
ature range. Each 16-bit calibration coefficient provides
compensation of the output (either offset or FSO) with
±0.2mV (0.005% FSO) resolution. A 12-bit ADC mea-
sures the temperature-dependent bridge voltage
(BDRIVE) and selects (by addressing the EEPROM) the
corresponding offset and FSO calibration data within a
specific narrow temperature span (e.g., @1°C). The
120-segment compensation enables the MAX1457 to
compensate temperature errors for a broad range of
sensors (Figure 2).
Calculate the correction coefficients by curve-fitting to
sensor-error test data. More test points allow for better
curve-fit accuracy but result in increased test over-
head. The remaining error is further affected by the
slope of the temperature errors. For example, correct-
ing a 6% nonlinearity over temperature with 60 seg-
ments (half of the available calibration points) with
perfect curve fitting yields an error on the order of 0.1%
(6%/60). Figure 3 illustrates this compensation.
0.1%-Accurate Signal Conditioner
for Piezoresistive Sensor Compensation
