MAX1452AAE ,Low-Cost Precision Sensor Signal Conditionerblock diagram appears at the end of data sheet.Transducers and Transmitters Strain GaugesPin Config ..
MAX1452AAE+ ,Low-Cost Precision Sensor Signal ConditionerBlock Diagram and Pin Configurations appear at ● Accelerometersthe end of data sheet.● Humidity Sen ..
MAX1452AAE+T ,Low-Cost Precision Sensor Signal ConditionerElectrical Characteristics(V = V = +5V, V = 0V, T = +25°C, unless otherwise noted.)DD DDF SS APARAM ..
MAX1452ATG+ ,Low-Cost Precision Sensor Signal ConditionerFeaturesThe MAX1452 is a highly integrated analog-sensor sig- ● Single-Chip, Integrated Analog Sign ..
MAX1452ATG+T ,Low-Cost Precision Sensor Signal Conditionerapplications utilizing resistive element sensors. The Precision Sensor SolutionMAX1452 provides amp ..
MAX1452CAE ,Low-Cost Precision Sensor Signal Conditionerapplications utilizing resistive element sensors. Accommodates Sensor Output Sensitivities The MAX ..
MAX4051ACSE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4051ACSE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesFeaturesThe MAX4051/MAX4052/MAX4053 and MAX4051A/' Pin Compatible with Industry-Standard MAX4052A/M ..
MAX4051ACSE+ ,Low-Voltage, CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4051ACSE+T ,Low-Voltage, CMOS Analog Multiplexers/SwitchesApplications♦ Low Distortion: < 0.04% (600Ω)Battery-Operated Equipment♦ Low Crosstalk: < -90dB (50Ω ..
MAX4051AEEE ,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 ..
MAX4051AEEE+ ,Low-Voltage, CMOS Analog Multiplexers/SwitchesFeaturesThe MAX4051/MAX4052/MAX4053 and MAX4051A/ ♦ Pin Compatible with Industry-Standard MAX4052A/ ..
MAX1452AAE-MAX1452CAE
Low-Cost Precision Sensor Signal Conditioner
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
General DescriptionThe MAX1452 is a highly integrated analog-sensor sig-
nal processor optimized for industrial and process con-
trol applications utilizing resistive element sensors.
The MAX1452 provides amplification, calibration, and
temperature compensation that enables an overall per-
formance approaching the inherent repeatability of the
sensor. The fully analog signal path introduces no
quantization noise in the output signal while enabling
digitally controlled trimming with the integrated 16-bit
DACs. Offset and span are calibrated using 16-bit
DACs, allowing sensor products to be truly inter-
changeable.
The MAX1452 architecture includes a programmable
sensor excitation, a 16-step programmable-gain ampli-
fier (PGA), a 768-byte (6144 bits) internal EEPROM,
four 16-bit DACs, an uncommitted op amp, and an on-
chip temperature sensor. In addition to offset and span
compensation. The MAX1452 provides a unique tem-
perature compensation strategy for offset TC and
FSOTC that was developed to provide a remarkable
degree of flexibility while minimizing testing costs.
The MAX1452 is packaged for the commercial, industri-
al, and automotive temperature ranges in 16-pin SSOP
packages.
CustomizationMaxim can customize the MAX1452 for high-volume
dedicated applications. Using our dedicated cell library
of more than 2000 sensor-specific functional blocks,
Maxim can quickly provide a modified MAX1452 solu-
tion. Contact Maxim for further information.
ApplicationsPressure Sensors
Transducers and Transmitters
Strain Gauges
Pressure Calibrators and Controllers
Resistive Elements Sensors
Accelerometers
Humidity Sensors
Outputs Supported4–20mA
0 to +5V (Rail-to-Rail®)
+0.5V to +4.5V Ratiometric
+2.5V to ±2.5V
FeaturesProvides Amplification, Calibration, and
Temperature CompensationAccommodates Sensor Output Sensitivities
from 1mV/V to 40mV/VSingle Pin Digital ProgrammingNo External Trim Components Required16-Bit Offset and Span Calibration ResolutionFully Analog Signal Path On-Chip Lookup Table Supports Multipoint
Calibration Temperature CorrectionSupports Both Current and Voltage Bridge
Excitation Fast 3.2kHz Frequency ResponseOn-Chip Uncommitted Op AmpSecure-Lock™Prevents Data CorruptionLow 2mA Current Consumption Rail-to-Rail is a trademark of Nippon Motorola Ltd.
Secure-Lock is a trademark of Maxim Integrated Products.
Pin Configuration
Ordering Information*Dice are tested at TA= +25°C, DC parameters only.
A detailed block diagram appears at the end of data sheet.
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICSStresses 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, +6V
All Other Pins...................................(VSS- 0.3V) to (VDD+ 0.3V)
Short-Circuit Duration, FSOTC, OUT, BDR,
AMPOUT.................................................................Continuous
Continuous Power Dissipation (TA= +70°C)
16-Pin SSOP (derate 8.00mW/°C above +70°C)..........640mW
Operating Temperature:
MAX1452CAE/MAX1452C/D...............................0°C to +70°C
MAX1452EAE...................................................-40°C to +85°C
MAX1452AAE.................................................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature.........................................-65°C to +150°C
Lead Temperature (soldering, 10s)................................+300°C
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
ELECTRICAL CHARACTERISTICS (continued)
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Note 2:All electronics temperature errors are compensated together with sensors errors.
Note 3:The sensor and the MAX1452 must be at the same temperature during calibration and use.
Note 4:This is the maximum allowable sensor offset.
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-
ageof +2.5V.
Note 6:Bit weight is ratiometric to VDD.
Note 7:Programming of the EEPROM at room temperature is recommended.
Note 8:Allow a minimum of 6ms elapsed time before sending any command.
ELECTRICAL CHARACTERISTICS (continued)(VDD= +5V, VSS= 0, TA = +25°C, unless otherwise noted.)
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Typical Operating Characteristics(VDD= +5V, TA = +25°C, unless otherwise noted.)
MAX1452
Detailed DescriptionThe MAX1452 provides amplification, calibration, and
temperature compensation to enable an overall perfor-
mance approaching the inherent repeatability of the
sensor. The fully analog signal-path introduces no
quantization noise in the output signal while enabling
digitally controlled trimming with the integrated 16-bit
DACs. Offset and span can be calibrated to within
±0.02% of span.
The MAX1452 architecture includes a programmable
sensor excitation, a 16-step programmable-gain ampli-
fier (PGA), a 768-byte (6144 bits) internal EEPROM, four
16-bit DACs, an uncommitted op amp, and an on-chip
temperature sensor.The MAX1452 also provides a
unique temperature compensation strategy for offset
TC and FSOTC that was developed to provide a
remarkable degree of flexibility while minimizing testing
costs.
The customer can select from one to 114 temperature
points to compensate their sensor. This allows the lati-
tude to compensate a sensor with a simple first order
linear correction or match an unusual temperature
curve. Programming up to 114 independent 16-bit EEP-
ROM locations corrects performance in 1.5°C tempera-
ture increments over a range of -40°C to +125°C. For
sensors that exhibit a characteristic temperature perfor-
mance, a select number of calibration points can be
used with a number of preset values that define the
temperature curve. In cases where the sensor is at a
different temperature than the ASIC, the MAX1452 uses
the sensor bridge itself to provide additional tempera-
ture correction.
The single pin, serial Digital Input-Output (DIO) commu-
nication architecture and the ability to timeshare its
activity with the sensor’s output signal enables output
sensing and calibration programming on a single line
by parallel connecting OUT and DIO. The MAX1452
provides a Secure-Lock feature that allows the cus-
tomer to prevent modification of sensor coefficients and
the 52-byte user definable EEPROM data after the sen-
sor has been calibrated. The Secure-Lock feature also
provides a hardware override to enable factory rework
and recalibration by assertion of logic high on the
UNLOCK pin.
The MAX1452 allows complete calibration and sensor
verification to be performed at a single test station.
Once calibration coefficients have been stored in the
ASIC, the customer can choose to retest in order to ver-
ify performance as part of a regular QA audit or to gen-
erate final test data on individual sensors.
The MAX1452’s low current consumption and the inte-
grated uncommitted op amp enables a 4–20mA output
signal format in a sensor that is completely powered
from a 2-wire current loop. Frequency response can be
user-adjusted to values lower than the 3.2kHz band-
width by using the uncommitted op amp and simple
passive components.
The MAX1452 (Figure 1) provides an analog amplifica-
tion path for the sensor signal. It also uses an analog
architecture for first-order temperature correction. A
digitally controlled analog path is then used for nonlin-
ear temperature correction. Calibration and correction
is achieved by varying the offset and gain of a pro-
grammable-gain-amplifier (PGA) and by varying the
sensor bridge excitation current or voltage. The PGA
Low-Cost Precision Sensor
Signal Conditioner
utilizes a switched capacitor CMOS technology, with an
input referred offset trimming range of more than
±150mV with an approximate 3µV resolution (16 bits).
The PGA provides gain values from 39V/V to 240V/V in
16 steps.
The MAX1452 uses four 16-bit DACs with calibration
coefficients stored by the user in an internal 768 x 8
EEPROM (6144 bits). This memory contains the follow-
ing information, as 16-bit wide words:Configuration RegisterOffset Calibration Coefficient TableOffset Temperature Coefficient RegisterFSO (Full-Span Output) Calibration TableFSO Temperature Error Correction Coefficient
Register52 bytes (416 bits) uncommitted for customer pro-
gramming of manufacturing data (e.g., serial num-
ber and date)
Offset CorrectionInitial offset correction is accomplished at the input
stage of the signal gain amplifiers by a coarse offset
setting. Final offset correction occurs through the use of
a temperature indexed lookup table with 176 16-bit
entries. The on-chip temperature sensor provides a
unique 16-bit offset trim value from the table with an
indexing resolution of approximately 1.5°C from -40°C
to +125°C. Every millisecond, the on-chip temperature
sensor provides indexing into the offset lookup table in
EEPROM and the resulting value transferred to the off-
set DAC register. The resulting voltage is fed into a
summing junction at the PGA output, compensating the
sensor offset with a resolution of ±76µV (±0.0019%
FSO). If the offset TC DAC is set to zero then the maxi-
mum temperature error is equivalent to one degree of
temperature drift of the sensor, given the Offset DAC
has corrected the sensor at every 1.5°C. The tempera-
ture indexing boundaries are outside of the specified
Absolute MaximumRatings. The minimum indexing
value is 00hex corresponding to approximately -69°C.
All temperatures below this value will output the coeffi-
cient value at index 00hex. The maximum indexing
value is AFhex, which is the highest lookup table entry.
All temperatures higher than approximately 184°C will
output the highest lookup table index value. No index-
ing wrap-around errors are produced.
FSO CorrectionTwo functional blocks control the FSO gain calibration.
First, a coarse gain is set by digitally selecting the gain
of the PGA. Second, FSO DAC sets the sensor bridge
current or voltage with the digital input obtained from a
temperature-indexed reference to the FSO lookup table
in EEPROM. FSO correction occurs through the use of
a temperature indexed lookup table with 176 16-bit
entries. The on-chip temperature sensor provides a
unique FSO trim from the table with an indexing resolu-
tion approaching one 16-bit value at every 1.5°C from
-40°C to +125°C. The temperature indexing boundaries
are outside of the specified Absolute Maximum
Ratings. The minimum indexing value is 00hex corre-
sponding to approximately -69°C. All temperatures
below this value will output the coefficient value at
index 00hex. The maximum indexing value is AFhex,
which is the highest lookup table entry. All tempera-
tures higher than approximately 184°C will output the
highest lookup table index value. No indexing wrap-
around errors are produced.
Linear and Nonlinear Temperature
CompensationWriting 16-bit calibration coefficients into the offset TC
and FSOTC registers compensates first-order tempera-
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
MAX1452ture errors. The piezoresistive sensor is powered by a
current source resulting in a temperature-dependent
bridge voltage due to the sensor's temperature resis-
tance coefficient (TCR). The reference inputs of the off-
set TC DAC and FSOTC DAC are connected to the
bridge voltage. The DAC output voltages will track the
bridge voltage as it varies with temperature, and by
varying the offset TC and FSOTC digital code a portion
of the bridge voltage, which is temperature dependent,
is used to compensate the first order temperature
errors.
The internal feedback resistors (RISRCand RSTC) for
FSO temperature compensation are optimized to 75kΩ
for silicon piezoresistive sensors. However, since the
required feedback resistor values are sensor depen-
dent, external resistors may also be used. The internal
resistors selection bit in the configuration register
selects between internal and external feedback resis-
tors.
To calculate the required offset TC and FSOTC com-
pensation coefficients, two test-temperatures are need-
ed. After taking at least two measurements at each
temperature, calibration software (in a host computer)
calculates the correction coefficients and writes them to
the internal EEPROM.
With coefficients ranging from 0000hex to FFFFhex and
a +5V reference, each DAC has a resolution of 76µV.
Two of the DACs (offset TC and FSOTC) utilize the sen-
sor bridge voltage as a reference. Since the sensor
bridge voltage is approximately set to +2.5V the FSOTC
and offset TC exhibit a step size of less than 38µV.
For high accuracy applications (errors less than
0.25%), the first-order offset and FSOTC should be
compensated with the offset TC and FSOTC DACs, and
the residual higher order terms with the lookup table.
The offset and FSO compensation DACs provide
unique compensation values for approximately 1.5°C of
temperature change as the temperature indexes the
address pointer through the coefficient lookup table.
Changing the offset does not effect the FSO, however
changing the FSO will affect the offset due to nature of
the bridge. The temperature is measured on both the
MAX1452 die and at the bridge sensor. It is recom-
mended to compensate the first-order temperature
errors using the bridge sensor temperature.
ypical Ratiometric
Operating CircuitRatiometric output configuration provides an output that
is proportional to the power supply voltage. This output
can then be applied to a ratiometric ADC to produce a
digital value independent of supply voltage.
Ratiometricity is an important consideration for battery-
operated instruments, automotive, and some industrial
applications.
The MAX1452 provides a high-performance ratiometric
output with a minimum number of external components
(Figure 2). These external components include the fol-
lowing:One supply bypass capacitor.One optional output EMI suppression capacitor.Two optional resistors, RISRC and RSTC, for special
sensor bridge types.
Low-Cost Precision Sensor
Signal Conditioner
ypical Nonratiometric Operating Circuit
(12VDC < VPWR < 40VDC)Nonratiometric output configuration enables the sensor
power to vary over a wide range. A high performance
voltage reference, such as the MAX6105, is incorporat-
ed in the circuit to provide a stable supply and refer-
ence for MAX1452 operation. A typical example is
shown in Figure 3. Nonratiometric operation is valuable
when wide ranges of input voltage are to be expected
and the system A/D or readout device does not enable
ratiometric operation.
Typical 2-Wire, Loop Powered,
4–20mA Operating CircuitProcess Control systems benefit from a 4–20mA current
loop output format for noise immunity, long cable runs,
and 2-wire sensor operation. The loop voltages can
range from 12VDC to 40VDC and are inherently nonra-
tiometric. The low current consumption of the MAX1452
allows it to operate from loop power with a simple
4–20mA drive circuit efficiently generated using the
integrated uncommitted op amp (Figure 4).
Internal Calibration Registers (ICRs)The MAX1452 has five 16-bit internal calibration regis-
ters that are loaded from EEPROM, or loaded from the
serial digital interface.
Data can be loaded into the internal calibration regis-
ters under three different circumstances.
Normal Operation, Power-On Initialization SequenceThe MAX1452 has been calibrated, the Secure-
Lock byte is set (CL[7:0] = FFhex) and UNLOCK is
low.Power is applied to the device.The power-on reset functions have completed.Registers CONFIG, OTCDAC, and FSOTCDAC are
refreshed from EEPROM. Registers ODAC, and FSODAC are refreshed from
the temperature indexed EEPROM locations.
Normal Operation, Continuous RefreshThe MAX1452 has been calibrated, the Secure-
Lock byte has been set (CL[7:0] = FFhex) and
UNLOCK is low.Power is applied to the device.The power-on reset functions have completed.The temperature index timer reaches a 1ms time
period.
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
MAX1452Registers CONFIG, OTCDAC, and FSOTCDAC are
refreshed from EEPROM.Registers ODAC and FSODAC are refreshed from
the temperature indexed EEPROM locations.
Calibration Operation, Registers Updated by Serial
CommunicationsThe MAX1452 has not had the Secure-Lock byte
set (CL[7:0] = 00hex) or UNLOCK is high.Power is applied to the device.The power-on reset functions have completed.The registers can then be loaded from the serial
digital interface by use of serial commands. See the
section on Serial I/O and Commands.
Internal EEPROMThe internal EEPROM is organized as a 768 by 8-bit
memory. It is divided into 12 pages, with 64 bytes per
page. Each page can be individually erased. The mem-
ory structure is arranged as shown in Table 1. The look-
up tables for ODAC and FSODAC are also shown, with
the respective temp-index pointer. Note that the ODAC
table occupies a continuous segment, from address
000hex to address 15Fhex, whereas the FSODAC table
is divided in two parts, from 200hex to 2FFhex, and
from 1A0hex to 1FFhex. With the exception of the gen-
eral purpose user bytes, all values are 16-bit wide
words formed by two adjacent byte locations (high byte
and low byte).
The MAX1452 compensates for sensor offset, FSO, and
temperature errors by loading the internal calibration
registers with the compensation values. These com-
pensation values can be loaded to registers directly via
Low-Cost Precision Sensor
Signal Conditioner
the serial digital interface during calibration or loaded
automatically from EEPROM at power-on. In this way
the device can be tested and configured during cali-
bration and test and the appropriate compensation val-
ues stored in internal EEPROM. The device will
auto-load the registers from EEPROM and be ready for
use without further configuration after each power-up.
The EEPROM is configured as an 8-bit wide array so
each of the 16-bit registers is stored as two 8-bit quan-
tities. The configuration register, FSOTCDAC and OTC-
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
MAX1452DAC registers are loaded from the pre-assigned loca-
tions in the EEPROM.
The ODAC and FSODAC are loaded from the EEPROM
lookup tables using an index pointer that is a function
of temperature. An ADC converts the integrated tem-
perature sensor to an 8-bit value every 1ms. This digi-
tized value is then transferred into the temp-index
register.
The typical transfer function for the temp-index is as fol-
lows:
temp-index = 0.69 ✕Temperature (°C) + 47.58
where temp-index is truncated to an 8-bit integer value.
Typical values for the temp-index register are given in
Table 6.
Note that the EEPROM is byte wide and the registers
that are loaded from EEPROM are 16 bits wide. Thus
each index value points to two bytes in the EEPROM.
Maxim programs all EEPROM locations to FFhex with
the exception of the oscillator frequency setting and
Secure-Lock byte. OSC[2:0] is in the Configuration
Register (Table 3). These bits should be maintained at
the factory preset values. Programming 00hex in the
Secure-Lock byte (CL[7:0] = 00hex), configures the
DIO as an asynchronous serial input for calibration and
test purposes.
Communication ProtocolThe DIO serial interface is used for asynchronous serial
data communications between the MAX1452 and a
host calibration test system or computer. The MAX1452
will automatically detect the baud rate of the host com-
puter when the host transmits the initialization
sequence. Baud rates between 4800bps and
38,400bps can be detected and used regardless of the
internal oscillator frequency setting. Data format is
always 1 start bit, 8 data bits, 1 stop bit and no parity.
Communications are only allowed when Secure-Lock is
disabled (i.e., CL[7:0] = 00hex) or the UNLOCK pin is
held high.
Initialization Sequence Sending the initialization sequence shown below
enables the MAX1452 to establish the baud rate that
initializes the serial port. The initialization sequence is
one byte transmission of 01hex, as follows.
The first start bit 0initiates the baud rate synchronization
sequence. The 8 data bits 01hex (LSB first) follow this
and then the stop bit, which is indicated above as a 1,
terminates the baud rate synchronization sequence.
This initialization sequence on DIOshould occur after a
period of 1ms after stable power is applied to the
device. This allows time for the power-on reset function
to complete and the DIO pin to be configured by
Secure-Lock or the UNLOCK pin.
Reinitialization Sequence The MAX1452 allows for relearning the baud rate. The
reinitialization sequence is one byte transmission of
FFhex, as follows.
When a serial reinitialization sequence is received, the
receive logic resets itself to its power-up state and
waits for the initialization sequence. The initialization
sequence must follow the reinitialization sequence in
order to re-establish the baud rate.
Serial Interface Command FormatAll communication commands into the MAX1452 follow
a defined format utilizing an interface register set (IRS).
The IRS is an 8-bit command that contains both an
interface register set data (IRSD) nibble (4-bit) and an
interface register set address (IRSA) nibble (4-bit). All
internal calibration registers and EEPROM locations are
accessed for read and write through this interface reg-
ister set. The IRS byte command is structured as fol-
lows:
IRS[7:0] = IRSD[3:0], IRSA[3:0]
Where:IRSA[3:0] is the 4-bit interface register set address
and indicates which register receives the data nib-
ble IRSD[3:0].IRSA[0] is the first bit on the serial interface after the
start bit.IRSD[3:0] is the 4-bit interface register set data.IRSD[0] is the fifth bit received on the serial inter-
face after the start bit.
The IRS address decoding is shown in Table 9.
Special Command Sequences A special command register to internal logic
(CRIL[3:0]) causes execution of special command
sequences within the MAX1452. These command
sequences are listed as CRIL command codes as
shown in Table 10.
Write ExamplesA 16-bit write to any of the internal calibration registers
is performed as follows:
Low-Cost Precision Sensor
Signal Conditioner
