EVALUATION KIT AVAILABLE
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
General Description
Benefits and Features
The MAX1452 architecture includes a programmable
sensor excitation, a 16-step programmable-gain amplifier (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 temperature
compensation strategy for offset TC and FSOTC that was
developed to provide a remarkable degree of flexibility
while minimizing testing costs.
●● On-Chip Lookup Table Supports Multipoint
Calibration Temperature Correction Improving
System Performance
The MAX1452 is a highly integrated analog-sensor signal processor optimized for industrial and process control applications utilizing resistive element sensors. The
MAX1452 provides amplification, calibration, and temperature compensation that enables an overall performance
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 interchangeable.
The MAX1452 is packaged for the commercial, industrial,
and automotive temperature ranges in 16-pin SSOP/
TSSOP and 24-pin TQFN packages.
Customization
Maxim 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 solution.
Contact Maxim for further information.
Applications
●●
●●
●●
●●
●●
●●
●●
Pressure Sensors
Transducers and Transmitters
Strain Gauges
Pressure Calibrators and Controllers
Resistive Elements Sensors
Accelerometers
Humidity Sensors
●● Single-Chip, Integrated Analog Signal Path Reduces
Design Time and Saves Space in a Complete
Precision Sensor Solution
• Provides Amplification, Calibration, and
Temperature Compensation
• Fully Analog Signal Path
• Accommodates Sensor Output Sensitivities from
4mV/V to 60mV/V
• Single-Pin Digital Programming
• No External Trim Components Required
• 16-Bit Offset and Span Calibration Resolution
• Supports Both Current and Voltage Bridge Excitation
• Fast 150μs Step Response
• On-Chip Uncommitted Op Amp
●● Secure-Lock™ Prevents Data Corruption
●● Low 2mA Current Consumption Simplifies PowerSupply Design in 4–20mA Applications
Ordering Information
PART
TEMP RANGE
MAX1452CAE+
0°C to +70°C
16 SSOP
MAX1452EAE+
-40°C to +85°C
16 SSOP
MAX1452AAE+
-40°C to +125°C
16 SSOP
MAX1452AUE+
-40°C to +125°C
16 TSSOP
MAX1452ATG+
-40°C to +125°C
24 TQFN-EP*
MAX1452C/D
0°C to +70°C
PIN-PACKAGE
Dice**
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
**Dice are tested at TA = +25°C, DC parameters only.
Detailed Block Diagram and Pin Configurations appear at
the end of data sheet.
Outputs Supported
●●
●●
●●
●●
4–20mA
0 to +5V (Rail-to-Rail)
+0.5V to +4.5V Ratiometric
+2.5V to ±2.5V
19-1829; Rev 5; 4/15
Secure-Lock is a trademark of Maxim Integrated Products, Inc.
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Absolute Maximum Ratings
Supply Voltage, VDD to VSS.........................................-0.3V, +6V
Supply Voltage, VDD to VDDF................................-0.5V to +0.5V
All Other Pins...................................(VSS - 0.3V) to (VDD + 0.3V)
Short-Circuit Duration, FSOTC, OUT, BDR,
AMPOUT................................................................Continuous
Continuous Power Dissipation (TA = +70°C)
Operating Temperature:
MAX1452CAE+/MAX1452C/D.............................0°C to +70°C
MAX1452EAE+.................................................-40°C to +85°C
MAX1452AAE+...............................................-40°C to +125°C
MAX1452AUE+..............................................-40°C to +125°C
MAX1452ATG+...............................................-40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) ................................ +300°C
16-Pin SSOP/TSSOP (derate 8.00mW/°C above +70°C)..640mW
24-Pin TQFN (derate 20.8mW/°C above +70°C).................1.67W
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.
Electrical Characteristics
(VDD = VDDF = +5V, VSS = 0V, TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4.5
5.0
5.5
V
4.5
5.0
5.5
V
2.0
2.5
mA
GENERAL CHARACTERISTICS
Supply Voltage
VDD
EEPROM Supply Voltage
VDDF
Supply Current
IDD
(Note 1)
Maximum EEPROM Erase/
Write Current
IDDFW
30
mA
Maximum EEPROM Read
Current
IDDFR
12
mA
Oscillator Frequency
fOSC
0.85
1
1.15
MHz
ANALOG INPUT
Input Impedance
RIN
1
MI
P1
µV/°C
Input-Referred Offset Tempco
(Notes 2, 3)
Input-Referred Adjustable
Offset Range
Offset TC = 0 at minimum gain (Note 4)
P150
mV
Amplifier Gain Nonlinearity
Percent of +4V span, VOUT = +0.5V to
4.5V
0.01
%
Specified for common-mode voltages
between VSS and VDD (Note 2)
90
dB
(Note 5)
4 to
60
mV/V
Common-Mode Rejection Ratio
Input Referred Adjustable
FSO Range
CMRR
ANALOG OUTPUT
Differential Signal-Gain Range
Differential Signal Gain
Maximum Output-Voltage Swing
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Selectable in 16 steps
39 to 234
V/V
Configuration [5:2] 0000bin
34
39
46
Configuration [5:2] 0001bin
47
52
59
Configuration [5:2] 0010bin
58
65
74
Configuration [5:2] 0100bin
82
91
102
Configuration [5:2] 1000bin
133
143
157
No load from each supply
0.02
V/V
V
Maxim Integrated │ 2
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Electrical Characteristics (continued)
(VDD = VDDF = +5V, VSS = 0V, TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
Output-Voltage Low
IOUT = 1mA sinking, TA = TMIN to TMAX
Output-Voltage High
IOUT = 1mA sourcing, TA = TMIN to TMAX
MIN
4.75
Output Impedance at DC
Output Offset Ratio
Output Offset TC Ratio
TYP
MAX
UNITS
0.100
0.20
V
4.87
V
0.1
Ω
ΔVOUT/
ΔOffset
0.90
1.05
1.20
V/V
ΔVOUT/
ΔOffset TC
0.9
1
1.2
V/V
Step Response and IC
(63% Final Value)
Maximum Capacitive Load
DC to 1kHz (gain = minimum, source
impedance = 5kΩ VDDF filter)
Output Noise
150
µs
1
µF
0.5
mVRMS
BRIDGE DRIVE
Bridge Current
Current Mirror Ratio
IBDR
AA
VSPAN Range (Span Code)
RL = 1.7kΩ
RISOURCE = internal
TA = TMIN to TMAX
0.1
0.5
10
12
4000
2
mA
14
A/A
C000
hex
DIGITAL-TO-ANALOG CONVERTERS
DAC Resolution
16
Bits
DAC reference = VDD = +5.0V
76
µV/bit
ΔVOUT/
ΔCode
DAC reference = VBDR = +2.5V
38
µV/bit
FSODAC Bit Weight
ΔVOUT/
ΔCode
DAC reference = VDD = +5.0V
76
µV/bit
FSOTCDAC Bit Weight
ΔVOUT/
ΔCode
DAC reference = VBDR = +2.5V
38
µV/bit
Including sign
4
Bits
Input referred, DAC reference =
VDD = +5.0V (Note 6)
9
mV/bit
ODAC Bit Weight
ΔVOUT/
ΔCode
OTCDAC Bit Weight
COARSE OFFSET DAC
IRODAC Resolution
IRODAC Bit Weight
ΔVOUT/
ΔCode
FSOTC BUFFER
Minimum Output-Voltage Swing
No load
Maximum Output-Voltage
Swing
No load
Current Drive
VFSOTC = +2.5V
VSS
+ 0.1
VDD - 1.0
V
V
-40
+40
µA
INTERNAL RESISTORS
Current-Source Reference
Resistor
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RISRC
75
kΩ
Maxim Integrated │ 3
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Electrical Characteristics (continued)
(VDD = VDDF = +5V, VSS = 0V, TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
Current-Source Reference
Resistor Temperature Coefficient
ΔRISRC
1300
ppm/°C
RFTC
75
kΩ
ΔRFTC
1300
ppm/°C
8
Bits
FSOTC Resistor
FSOTC Resistor Temperature
Coefficient
CONDITIONS
MIN
TYP
MAX
UNITS
TEMPERATURE-TO-DIGITAL CONVERTER
Temperature ADC Resolution
Offset
P3
LSB
Gain
1.45
°C/bit
Nonlinearity
P0.5
LSB
Lowest Digital Output
00
hex
Highest Digital Output
AF
hex
90
dB
UNCOMMITTED OP AMP
Open-Loop Gain
RL = 100kΩ
Input Common-Mode Range
Output Swing
No load, TA = TMIN to TMAX
Output-Voltage High
1mA source, TA = TMIN to TMAX
Output-Voltage Low
1mA sink, TA = TMIN to TMAX
Offset
VIN+ = +2.5V, unity-gain buffer
Unity-Gain Bandwidth
VSS
VDD
V
VSS +
0.02
VDD 0.02
V
4.85
4.90
0.05
-20
V
0.15
V
+20
mV
2
MHz
10k
Cycles
6
ms
100
µs
EEPROM
Maximum Erase/Write Cycles
(Note 7)
Minimum Erase Time
(Note 8)
Minimum Write Time
Note
Note
Note
Note
Note
1: Excludes sensor or load current.
2: All electronics temperature errors are compensated together with sensors errors.
3: The sensor and the MAX1452 must be at the same temperature during calibration and use.
4: This is the maximum allowable sensor offset.
5: This is the sensor’s sensitivity normalized to its drive voltage, assuming a desired full span output of +4V and a bridge voltage range of +1.7V to +4.25V.
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.
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Maxim Integrated │ 4
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Typical Operating Characteristics
(VDD = +5V, TA = +25°C, unless otherwise noted.)
MAX1452 toc01
OUTPUT ERROR FROM STRAIGHT LINE (mV)
DNL (mV)
2.5
0
-2.5
-5.0
0
10k
20k
30k
40k
50k
60k
70k
5.0
MAX1452 toc02
AMPLIFIER GAIN NONLINEARITY
OFFSET DAC DNL
5.0
ODAC = 6250hex
OTCDAC = 0
FSODAC = 4000hex
FSOTCDAC = 8000hex
PGA INDEX = 0
IRO = 2
2.5
0
-2.5
-5.0
-50 -40 -30 -20 -10
DAC CODE
0
10 20 30 40
50
INPUT VOLTAGE [INP - INM] (mV)
MAX1452 toc03
OUTPUT NOISE
OUT
10mV/div
400µs/div
C = 4.7µF, RLOAD = 1kΩ
Pin Description
PIN
NAME
FUNCTION
SSOP/TSSOP
TQFN-EP
1
1
ISRC
Bridge Drive Current Mode Setting
2
2
OUT
High ESD and Scan Path Output Signal. May need a 0.1µF capacitor, in
noisy environments. OUT may be parallel connected to DIO.
3
3
VSS
Negative Supply Voltage
4
4
INM
Bridge Negative Input. Can be swapped to INP by configuration register.
5
5
BDR
Bridge Drive
6
6
INP
Bridge Positive Input. Can be swapped to INM by configuration register.
7
7
VDD
Positive Supply Voltage. Connect a 0.1µF capacitor from VDD to VSS.
—
8, 9, 13, 16, 20, 22,
23, 24
N.C.
No Connection. Not internally connected; leave unconnected (TQFN
package only).
8
10
TEST
Internally Connected. Connect to VSS.
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Maxim Integrated │ 5
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Pin Description (continued)
PIN
NAME
FUNCTION
SSOP/TSSOP
TQFN-EP
9
11
VDDF
10
12
UNLOCK
11
14
DIO
12
15
CLK1M
13
17
AMPOUT
14
18
AMP-
Uncommitted Amplifier Negative Input
15
19
AMP+
Uncommitted Amplifier Positive Input
16
21
FSOTC
—
—
EP
Positive Supply Voltage for EEPROM. Connect a 1µF capacitor from
VDDF to VSS. Connect VDDF to VDD or for improved noise performance
connect a 30Ω resistor to VDD.
Secure-Lock Disable. Allows communication to the device.
Digital Input Output. DIO allows communication with the device.
1MHz Clock Output. The output can be controlled by a configuration bit.
Uncommitted Amplifier Output
Full Span TC Buffered Output
Exposed Pad (TQFN Only). Internally connected; connect to VSS.
Detailed Description
The MAX1452 provides amplification, calibration, and
temperature compensation to enable an overall performance 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 amplifier (PGA), a 768-byte (6144 bits) internal EEPROM,
four 16-bit DACs, an uncommitted op amp, and an onchip 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
latitude to compensate a sensor with a simple first order
linear correction or match an unusual temperature curve.
Programming up to 114 independent 16-bit EEPROM
locations corrects performance in 1.5°C temperature
increments over a range of -40°C to +125°C. For sensors
that exhibit a characteristic temperature performance,
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 MAX1452, the MAX1452 uses the sensor
bridge itself to provide additional temperature correction.
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The single pin, serial Digital Input-Output (DIO) communication 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 customer to prevent
modification of sensor coefficients and the 52-byte user
definable EEPROM data after the sensor 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 MAX1452,
the customer can choose to retest in order to verify performance as part of a regular QA audit or to generate final
test data on individual sensors.
The MAX1452’s low current consumption and the integrated 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 bandwidth by using the
uncommitted op amp and simple passive components.
The MAX1452 (Figure 1) provides an analog amplification
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 nonlinear temperature
correction. Calibration and correction is achieved by varying the offset and gain of a programmable-gain-amplifier
(PGA) and by varying the sensor bridge excitation current
Maxim Integrated │ 6
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Offset Correction
VDD
VDD
IRO
DAC
BIAS
GENERATOR
MAX1452
OSCILLATOR
CLK1M
TEST
INP
∑
PGA
OUT
INM
BDR
CURRENT
SOURCE
TEMP
SENSOR
8-BIT ADC
VDDF
DIO
UNLOCK
INTERNAL
EEPROM
6144 BITS
ANAMUX
16 BIT DAC - FSO (176) POINT
16 BIT DAC - OFFSET (176)
16 BIT DAC - OFFSET TC
16 BIT DAC - FSO TC
ISRC
416 BITS
FOR USER VDD
A=1
176
TEMPERATURE
LOOK UP
POINTS FOR
OFFSET AND
SPAN.
BDR
AMP+
FSOTC
OP-AMP
AMPOUT
AMPVSS
Figure 1. Functional Diagram
or voltage. The PGA 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
234V/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 following
information, as 16-bit wide words:
● Configuration Register
● Offset Calibration Coefficient Table
● Offset Temperature Coefficient Register
● FSO (Full-Span Output) Calibration Table
● FSO Temperature Error Correction Coefficient Register
● 52 bytes (416 bits) uncommitted for customer programming of manufacturing data (e.g., serial number
and date)
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Initial 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 offset 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 maximum 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 temperature indexing boundaries
are outside of the specified Absolute Maximum Ratings.
The minimum indexing value is 00hex corresponding to
approximately -69°C. All temperatures below this value
output the coefficient value at index 00hex. The maximum
indexing value is AFhex, which is the highest lookup table
entry. All temperatures higher than approximately 184°C
output the highest lookup table index value. No indexing
wraparound errors are produced.
FSO Correction
Two 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 resolution 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 corresponding to approximately
-69°C. All temperatures below this value output the coefficient value at index 00hex. The maximum indexing
value is AFhex, which is the highest lookup table entry.
All temperatures higher than approximately 184°C output
the highest lookup table index value. No indexing wraparound errors are produced.
Maxim Integrated │ 7
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Linear and Nonlinear
Temperature Compensation
For high-accuracy applications (errors less than 0.25%),
the first-order offset and FSO TC error 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 affects the offset due to nature of the bridge. The
temperature is measured on both the MAX1452 die and
at the bridge sensor. It is recommended to compensate
the first-order temperature errors using the bridge sensor
temperature.
The internal feedback resistors (RISRC and RSTC) for
FSO temperature compensation are optimized to 75kΩ
for silicon piezoresistive sensors. However, since the
required feedback resistor values are sensor dependent,
external resistors may also be used. The internal resistors
selection bit in the configuration register selects between
internal and external feedback resistors.
Typical Ratiometric Operating Circuit
Writing 16-bit calibration coefficients into the offset TC
and FSOTC registers compensates first-order temperature errors. The piezoresistive sensor is powered by a
current source resulting in a temperature-dependent
bridge voltage due to the sensor’s temperature resistance
coefficient (TCR). The reference inputs of the offset TC
DAC and FSOTC DAC are connected to the bridge voltage. The DAC output voltages 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.
Ratiometric 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
and some industrial applications.
To calculate the required offset TC and FSOTC compensation coefficients, two test-temperatures are needed.
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.
The MAX1452 provides a high-performance ratiometric
output with a minimum number of external components
(Figure 2). These external components include the following:
● One supply bypass capacitor.
● One optional output EMI suppression capacitor.
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 sensor
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.
● Two optional resistors, RISRC and RSTC, for special
sensor bridge types.
+5V VDD
7
5
6
BDR
VDD
INP
VDDF
9
OUT 2
OUT
MAX1452
FSOTC
SENSOR
4
16
INM
RSTC
ISRC
TEST VSS
8
3
1
RISRC
0.1µF
0.1µF
GND
Figure 2. Basic Ratiometric Output Configuration
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Maxim Integrated │ 8
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
G 2N4392
IN
1
S
D
VPWR
+12V TO +40V
MAX15006B
8
7
5
6
BDR
VDD
INP
OUT
5
30Ω
VDDF
GND
9
OUT 2
OUT
MAX1452
FSOTC
SENSOR
4
16
INM
RSTC
ISRC
TEST VSS
8
1
RISRC
1.0µF
2.2µF
0.1µF
0.1µF
3
GND
Figure 3. Basic Nonratiometric Output Configuration
Typical 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 MAX15006B, is incorporated
in the circuit to provide a stable supply and reference 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 Circuit
Process 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 nonratiometric.
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 registers
that are loaded from EEPROM, or loaded from the serial
digital interface.
Data can be loaded into the internal calibration registers
under three different circumstances.
Normal Operation, Power-On Initialization Sequence
● The 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 Refresh
● The 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.
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Maxim Integrated │ 9
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
2N4392
G
VIN+
+12V TO +40V
D 100Ω
S
IN
1
Z1
MAX15006B
8
7
5
6
BDR
VDDF
FSOTC
9
16
MAX1452
SENSOR
4
1.0µF
RSTC
ISRC
GND
5
30Ω
VDD
INP
OUT
1
INM
2.2µF
0.1µF
RISRC 4.99MΩ
OUT
AMPOUT
AMPAMP+
TEST VSS
8
2
499kΩ
0.1µF
13
14
15
2N2222A
4.99kΩ
0.1µF
100kΩ
3
100kΩ
47Ω
VIN-
Figure 4. Basic 4–20mA Output, Loop-Powered Configuration
● Registers 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
Communications
● The 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 Interface Command Format.
Internal EEPROM
The internal EEPROM is organized as a 768 by 8-bit
memory. It is divided into 12 pages, with 64 bytes per
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page. Each page can be individually erased. The memory
structure is arranged as shown in Table 1. The lookup
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 general-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 compensation values can be loaded to registers directly through
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 calibration
and test and the appropriate compensation values stored
Maxim Integrated │ 10
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 1. EEPROM Memory Address Map
PAGE
0
1
2
3
4
5
6
7
8
9
A
B
LOW-BYTE
ADDRESS (hex)
HIGH-BYTE ADDRESS
(hex)
TEMP-INDEX[7:0]
(hex)
000
001
00
03E
03F
1F
040
041
20
07E
07F
3F
080
081
40
0BE
0BF
5F
0C0
0C1
60
0FE
0FF
7F
100
101
80
13E
13F
9F
140
141
A0
15E
15F
AF to FF
160
161
Configuration
162
163
Reserved
164
165
OTCDAC
166
167
Reserved
168
169
FSOTCDAC
Control Location
16A
16B
16C
16D
17E
17F
180
181
19E
19F
ODAC
Lookup Table
52 General-Purpose
User Bytes
1A0
1A1
80
1BE
1BF
8F
1C0
1C1
90
1FE
1FF
AF to FF
200
201
00
23E
23F
1F
240
241
20
27E
27F
3F
280
281
40
2BE
2BF
5F
2C0
2C1
60
2FE
2FF
7F
in internal EEPROM. The device auto-loads 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
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CONTENTS
FSODAC
Lookup Table
is stored as two 8-bit quantities. The configuration register,
FSOTCDAC and OTCDAC registers are loaded from the
pre-assigned locations in the EEPROM.
Maxim Integrated │ 11
MAX1452
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 temperature
sensor output to an 8-bit value every 1ms. This digitized
value is then transferred into the temp-index register.
The typical transfer function for the temp-index is as follows:
temp-index = 0.6879 Temperature (°C) + 44.0
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 SecureLock 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 Protocol
The DIO serial interface is used for asynchronous serial
data communications between the MAX1452 and a host
calibration test system or computer. The MAX1452 automatically detects the baud rate of the host computer 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 SecureLock 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:
1111111101000000011111111
The first start bit 0 initiates 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 DIO should 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
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Low-Cost Precision Sensor
Signal Conditioner
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:
11111111011111111111111111
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 reestablish the baud rate.
Serial Interface Command Format
All 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 register set. The IRS
byte command is structured as follows:
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 nibble
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 interface
after the start bit.
The IRS address decoding is shown in Table 10.
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 11.
Write Examples
A 16-bit write to any of the internal calibration registers is
performed as follows:
1) Write the 16 data bits to DHR[15:0] using four byte
accesses into the interface register set.
2) Write the address of the target internal calibration register to ICRA[3:0].
Maxim Integrated │ 12
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
THREE-STATE
NEED WEAK
PULLUP
DRIVEN BY TESTER
DIO
11111 0 1 0 0 11 0 1 0 11 1
THREE-STATE
NEED WEAK
PULLUP
DRIVEN BY MAX1452
1 1 1 1 1 1
1 0 0 0 0 0 1 0 0 0 111111
1 1 1
11
STOP-BIT
MSB
LSB
START-BIT
STOP-BIT
MSB
LSB
START-BIT
Figure 5. DIO Output Data Format
3) Write the load internal calibration register (LdICR) command to CRIL[3:0].
When a LdICR command is issued to the CRIL register,
the calibration register loaded depends on the address in
the internal calibration register address (ICRA). Table 12
specifies which calibration register is decoded.
Erasing and Writing the EEPROM
The internal EEPROM needs to be erased (bytes set
to FFhex) prior to programming the desired contents.
Remember to save the 3 MSBs of byte 161 hex (high byte
of the configuration register) and restore it when programming its contents to prevent modification of the trimmed
oscillator frequency.
The internal EEPROM can be entirely erased with the
ERASE command, or partially erased with the PageErase
command (see Table 11, CRIL command). It is necessary
to wait 6ms after issuing the ERASE or PageErase command.
After the EEPROM bytes have been erased (value of
every byte = FFhex), the user can program its contents,
following the procedure below:
1) Write the 8 data bits to DHR[7:0] using two byte
accesses into the interface register set.
2) Write the address of the target internal EEPROM location to IEEA[9:0] using three byte accesses into the
interface register set.
3) Write the EEPROM write command (EEPW) to
CRIL[3:0].
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Serial Digital Output
When a RdIRS command is written to CRIL[3:0], DIO
is configured as a digital output and the contents of the
register designated by IRSP[3:0] are sent out as a byte
framed by a start bit and a stop bit.
Once the tester finishes sending the RdIRS command,
it must three-state its connection to DIO to allow the
MAX1452 to drive the DIO line. The MAX1452 threestates DIO high for 1 byte time and then drive with the
start bit in the next bit period followed by the data byte and
stop bit. The sequence is shown in Figure 5.
The data returned on a RdIRS command depends on the
address in IRSP. Table 13 defines what is returned for the
various addresses.
Multiplexed Analog Output
When a RdAlg command is written to CRIL[3:0] the analog signal designated by ALOC[3:0] is asserted on the
OUT pin. The duration of the analog signal is determined
by ATIM[3:0] after which the pin reverts to three-state.
While the analog signal is asserted in the OUT pin, DIO
is simultaneously three-stated, enabling a parallel wiring
of DIO and OUT. When DIO and OUT are connected in
parallel, the host computer or calibration system must
three-state its connection to DIO after asserting the stop
bit. Do not load the OUT line when reading internal
signals, such as BDR, FSOTC...etc.
The analog output sequence with DIO and OUT is shown
in Figure 6.
The duration of the analog signal is controlled by ATIM[3:0]
as given in Table 14.
Maxim Integrated │ 13
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
THREE-STATE
NEED WEAK
PULLUP
DRIVEN BY TESTER
DIO
11111 0 1 0 0 11 0 1 0 11 1
THREE-STATE
2ATIM +1 BYTE
TIMES
THREE-STATE
NEED WEAK
PULLUP
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
11
STOP-BIT
MSB
LSB
START-BIT
HIGH IMPEDANCE
OUT
VALID OUT
Figure 6. Analog Output Timing
The analog signal driven onto the OUT pin is determined
by the value in the ALOC register. The signals are specified in Table 15.
Test System Configuration
The MAX1452 is designed to support an automated
production test system with integrated calibration and
temperature compensation. Figure 7 shows the implementation concept for a low-cost test system capable of
testing many transducer modules connected in parallel.
The MAX1452 allows for a high degree of flexibility in
system calibration design. This is achieved by use of
single-wire digital communication and three-state output
nodes. Depending upon specific calibration requirements
one may connect all the OUTs in parallel or connect DIO
and OUT on each individual module.
Sensor Compensation Overview
Compensation requires an examination of the sensor performance over the operating pressure and temperature
range. Use a minimum of two test pressures (e.g., zero
and full-span) and two temperatures. More test pressures
and temperatures result in greater accuracy. A typical
compensation procedure can be summarized as follows:
Set reference temperature (e.g., +25°C):
● Initialize each transducer by loading their respective
registers with default coefficients (e.g., based on mean
values of offset, FSO and bridge resistance) to prevent
overload of the MAX1452.
● Set the initial bridge voltage (with the FSODAC) to
half of the supply voltage. Measure the bridge voltage
using the BDR or OUT pins, or calculate based on
measurements.
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● Calibrate the output offset and FSO of the transducer
using the ODAC and FSODAC, respectively.
● Store calibration data in the test computer or MAX1452
EEPROM user memory.
Set next test temperature:
● Calibrate offset and FSO using the ODAC and
FSODAC, respectively.
● Store calibration data in the test computer or MAX1452
EEPROM user memory.
● Calculate the correction coefficients.
● Download correction coefficients to EEPROM.
● Perform a final test.
Sensor Calibration and
Compensation Example
The MAX1452 temperature compensation design corrects
both sensor and IC temperature errors. This enables the
MAX1452 to provide temperature compensation approaching the inherent repeatability of the sensor. An example of
the MAX1452’s capabilities is shown in Figure 8.
A repeatable piezoresistive sensor with an initial offset of
16.4mV and a span of 55.8mV was converted into a compensated transducer (utilizing the piezoresistive sensor
with the MAX1452) with an offset of 0.5000V and a span
of 4.0000V. Nonlinear sensor offset and FSO temperature
errors, which were on the order of 20% to 30% FSO, were
reduced to under ±0.1% FSO. The following graphs show
the output of the uncompensated sensor and the output of
the compensated transducer. Six temperature points were
used to obtain this result.
Maxim Integrated │ 14
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
DIO[1:N]
DATA
DATA
VOUT
+5V
DVM
VDD
MODULE N
MAX1452
MODULE 2
MAX1452
MODULE 1
DION
DIO2
DIO1
MAX1452
DIGITAL
MULTIPLEXER
VSS
VOUT
VDD
VSS
VOUT
VDD
VSS
VOUT
TEST OVEN
Figure 7. Automated Test System Concept
MAX1452 Evaluation Kit
To expedite the development of MAX1452-based transducers and test systems, Maxim has produced the
MAX1452 evaluation kit (EV kit). First-time users of the
MAX1452 are strongly encouraged to use this kit.
The EV kit is designed to facilitate manual programming
of the MAX1452 with a sensor. It includes the following:
1) Evaluation Board with or without a silicon pressure
sensor, ready for customer evaluation.
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2) Design/Applications Manual, which describes
in detail the architecture and functionality of the
MAX1452. This manual was developed for test engineers familiar with data acquisition of sensor data and
provides sensor compensation algorithms and test
procedures.
3) MAX1452 Communication Software, which enables
programming of the MAX1452 from a computer keyboard (IBM compatible), one module at a time.
4) Interface Adapter, which allows the connection of the
evaluation board to a PC serial port.
Maxim Integrated │ 15
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
RAW SENSOR OUTPUT
TA = +25ºC
30.0
ERROR (% FSO)
VOUT (mV)
80
60
40
6
0
0
20
40
60
UNCOMPENSATED SENSOR
TEMPERATURE ERROR
80
100
FSO
20.0
OFFSET
10.0
0.0
-10.0
-20.0
-50
0
-0.1
-0.15
FSO
100
150
COMPENSATED TRANSDUCER
TA = +25ºC
5.0
OFFSET
4.0
VOUT (V)
ERROR (% FSO)
COMPENSATED TRANSDUCER ERROR
0.15
0.1
0.05
0
-0.05
50
TEMPERATURE (ºC)
PRESSURE (kPs)
3.0
2.0
1.0
-50
0
50
100
TEMPERATURE (ºC)
150
0
0
20
40
60
PRESSURE (kPs)
80
100
Figure 8. Comparison of an Uncalibrated Sensor and a Calibrated Transducer
Table 2. Registers
REGISTER
CONFIG
ODAC
DESCRIPTION
Configuration Register
Offset DAC Register
OTCDAC
Offset Temperature Coefficient DAC Register
FSODAC
Full Span Output DAC Register
FSOTCDAC
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Full Span Output Temperature Coefficient DAC Register
Maxim Integrated │ 16
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 3. Configuration Register (CONFIG[15:0])
FIELD
NAME
15:13
OSC[2:0]
12
REXT
DESCRIPTION
Oscillator frequency setting. Factory preset, do not change.
Logic ‘1’ selects external RISRC and RSTC.
11
CLK1M EN
Logic ‘1’ enables CLK1M output driver.
10
PGA Sign
Logic ‘1’ inverts INM and INP polarity.
9
IRO Sign
Logic ‘1’ for positive input-referred offset (IRO). Logic ‘0’ for negative input-referred offset (IRO).
8:6
IRO[2:0]
Input-referred coarse offset adjustment.
5:2
PGA[3:0]
Programmable gain amplifier setting.
1
ODAC Sign
0
OTCDAC Sign
Logic ‘1’ for positive offset DAC output. Logic ‘0’ for negative offset DAC output.
Logic ‘1’ for positive offset TC DAC output. Logic ‘0’ for negative offset TC DAC output.
Table 4. Input Referred Offset (IRO[2:0])
IRO SIGN, IRO[2:0]
INPUT-REFERRED OFFSET
CORRECTION AS % OF VDD
INPUT-REFERRED OFFSET, CORRECTION
AT VDD = 5VDC IN mV
1,111
+1.25
+63
1,110
+1.08
+54
1,101
+0.90
+45
1,100
+0.72
+36
1,011
+0.54
+27
1,010
+0.36
+18
1,001
+0.18
+9
1,000
0
0
0,000
0
0
0,001
-0.18
-9
0,010
-0.36
-18
0,011
-0.54
-27
0,100
-0.72
-36
0,101
-0.90
-45
0,110
-1.08
-54
0,111
-1.25
-63
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Maxim Integrated │ 17
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 5. PGA Gain Setting (PGA[3:0])
PGA[3:0]
PGA GAIN (V/V)
0000
0001
Table 6. Temp-Index Typical Values
TEMP-INDEX[7:0]
39
TEMPERATURE
(°C)
DECIMAL
HEXADECIMAL
52
-40
20
14
0010
65
25
65
41
0011
78
85
106
6A
0100
91
125
134
86
0101
104
0110
117
Table 7. Oscillator Frequency Setting
0111
130
OSC[2:0]
OSCILLATOR FREQUENCY
1000
143
100
-37.5%
1001
156
101
-28.1%
1010
169
110
-18.8%
1011
182
111
-9.4%
1100
195
000
1MHz (nominal)
1101
208
001
+9.4%
1110
221
010
+18.8%
234
011
+28.1%
1111
Table 8. EEPROM ODAC and FSODAC Lookup Table Memory Map
TEMP-INDEX[7:0]
EEPROM ADDRESS ODAC
LOW BYTE AND HIGH BYTE
EEPROM ADDRESS FSODAC
LOW BYTE AND HIGH BYTE
00hex
to
7Fhex
000hex and 001hex
to
0FEhex and 0FFhex
200hex and 201hex
to
2FEhex and 2FFhex
80hex
to
AFhex
100hex and 101hex
to
15Ehex and 15Fhex
1A0hex and 1A1hex
to
1FEhex and 1FFhex
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Maxim Integrated │ 18
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 9. Control Location (CL[15:0])
FIELD
NAME
DESCRIPTION
15:8
CL[15:8]
Reserved
7:0
CL[7:0]
Control Location. Secure-Lock is activated by setting this to FFhex which disables DIO serial
communications and connects OUT to PGA output.
Table 10. IRSA Decoding
IRSA[3:0]
DESCRIPTION
0000
Write IRSD[3:0] to DHR[3:0] (data hold register)
0001
Write IRSD[3:0] to DHR[7:4] (data hold register)
0010
Write IRSD[3:0] to DHR[11:8] (data hold register)
0011
Write IRSD[3:0] to DHR[15:12] (data hold register)
0100
Reserved
0101
Reserved
0110
Write IRSD[3:0] to ICRA[3:0] or IEEA[3:0], (internal calibration register address or internal EEPROM address
nibble 0)
0111
Write IRSD[3:0] to IEEA[7:4] (internal EEPROM address, nibble 1)
1000
Write IRSD[3:0] to IRSP[3:0] or IEEA[9:8], (interface register set pointer where IRSP[1:0] is IEEA[9:8])
1001
Write IRSD[3:0] to CRIL[3:0] (command register to internal logic)
1010
Write IRSD[3:0] to ATIM[3:0] (analog timeout value on read)
1011
Write IRSD[3:0] to ALOC[3:0] (analog location)
1100 to 1110
1111
Reserved
Write IRSD[3:0] = 1111bin to relearn the baud rate
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Maxim Integrated │ 19
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 11. CRIL Command Codes
CRIL[3:0]
NAME
DESCRIPTION
0000
LdICR
Load internal calibration register at address given in ICRA with data from DHR[15:0].
0001
EEPW
EEPROM write of 8 data bits from DHR[7:0] to address location pointed by IEEA[9:0].
0010
ERASE
Erase all of EEPROM (all bytes equal FFhex).
0011
RdICR
Read internal calibration register as pointed to by ICRA and load data into DHR[15:0].
0100
RdEEP
Read internal EEPROM location and load data into DHR[7:0] pointed by IEEA[9:0].
0101
RdIRS
Read interface register set pointer IRSP[3:0]. See Table 13.
0110
RdAlg
Output the multiplexed analog signal onto OUT. The analog location is specified in ALOC[3:0] (Table
15) and the duration (in byte times) that the signal is asserted onto the pin is specified in ATIM[3:0]
(Table 14).
0111
PageErase
Erases the page of the EEPROM as pointed by IEEA[9:6]. There are 64 bytes per page and thus 12
pages in the EEPROM.
1000 to
1111
Reserved
Reserved.
Table 12. ICRA[3:0] Decode
ICRA[3:0]
NAME
0000
CONFIG
0001
ODAC
0010
OTCDAC
Offset Temperature Coefficient DAC Register
0011
FSODAC
Full Scale Output DAC Register
0100
FSOTCDAC
0101
0110 to
1111
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DESCRIPTION
Configuration Register
Offset DAC Register
Full Scale Output Temperature Coefficient DAC Register
Reserved. Do not write to this location (EEPROM test).
Reserved. Do not write to this location.
Maxim Integrated │ 20
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 13. IRSP Decode
IRSP[3:0]
RETURNED VALUE
0000
DHR[7:0]
0001
DHR[15:8]
0010
IEEA[7:4], ICRA[3:0] concatenated
0011
CRIL[3:0], IRSP[3:0] concatenated
0100
ALOC[3:0], ATIM[3:0] concatenated
0101
IEEA[7:0] EEPROM address byte
0110
IEED[7:0] EEPROM data byte
0111
TEMP-Index[7:0]
1000
BitClock[7:0]
1001
Reserved. Internal flash test data.
1010-1111
11001010 (CAhex). This can be used to test communication.
Table 14. ATIM Definition
ATIM[3:0]
DURATION OF ANALOG SIGNAL SPECIFIED IN BYTE TIMES (8-BIT TIME)
0000
20 + 1 = 2 byte times i.e. (2 x 8)/baud rate
0001
21 + 1 = 3 byte times
0010
22 + 1 = 5 byte times
0011
23 + 1 = 9 byte times
0100
24 + 1 = 17 byte times
0101
25 + 1 = 33 byte times
0110
26 + 1 = 65 byte times
0111
27 + 1 = 129 byte times
1000
28 + 1 = 257 byte times
1001
29 + 1 = 513 byte times
1010
210 + 1 = 1025 byte times
1011
211 + 1 = 2049 byte times
1100
212 + 1 = 4097 byte times
1101
213 + 1 = 8193 byte times
1110
214 + 1 = 16,385 byte times
1111
In this mode OUT is continuous, however DIO accepts commands after 32,769 byte times. Do not parallel
connect DIO to OUT.
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Maxim Integrated │ 21
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Table 15. ALOC Definition
ALOC[3:0]
ANALOG SIGNAL
DESCRIPTION
0000
OUT
PGA Output
0001
BDR
Bridge Drive
0010
ISRC
Bridge Drive Current Setting
0011
VDD
Internal Positive Supply
0100
VSS
Internal Ground
0101
BIAS5U
0110
AGND
0111
FSODAC
1000
FSOTCDAC
1001
ODAC
1010
OTCDAC
1011
VREF
Internal Test Node
Internal Analog Ground. Approximately half of VDD.
Full Scale Output DAC
Full Scale Output TC DAC
Offset DAC
Offset TC DAC
Bandgap Reference Voltage (nominally 1.25V)
1100
VPTATP
Internal Test Node
1101
VPTATM
Internal Test Node
1110
INP
Sensor’s Positive Input
1111
INM
Sensor’s Negative Input
Table 16. Effects of Compensation
TYPICAL UNCOMPENSATED INPUT (SENSOR)
TYPICAL COMPENSATED TRANSDUCER OUTPUT
Offset........................................................................ ±100% FSO
FSO................................................................. 4mV/V to 60mV/V
Offset TC...................................................................... 20% FSO
Offset TC Nonlinearity.................................................... 4% FSO
FSOTC........................................................................ -20% FSO
FSOTC Nonlinearity....................................................... 5% FSO
Temperature Range........................................... -40°C to +125°C
OUT................................................... Ratiometric to VDD at 5.0V
Offset at +25°C.................................................... 0.500V ±200μV
FSO at +25°C...................................................... 4.000V ±200μV
Offset accuracy over temp. range.................±4mV (±0.1% FSO)
FSO accuracy over temp. range...................±4mV (±0.1% FSO)
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Maxim Integrated │ 22
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Detailed Block Diagram
EEPROM
(LOOKUP PLUS CONFIGURATION DATA)
VDD
EEPROM ADDRESS USAGE
000H + 001H
VDD
16-BIT
FSO
DAC
ISRC
:
15EH + 15FH
160H + 161H
162H + 163H
164H + 165H
VSS
VDD
RISRC
75kΩ
16-BIT
OFFSET
DAC
RSTC
75kΩ
166H + 167H
168H + 169H
16AH + 16BH
16CH + 16DH
:
INP
16-BIT
FSOTC
DAC
PHASE
REVERSAL
MUX
VSS
∑
VSS
TEST
CLK1M
VDDF
FSO DAC LOOKUP TABLE
(176 x 16-BITS)
BANDGAP
TEMP
SENSOR
8-BIT
LOOKUP
ADDRESS
∑∆
DIGITAL
INTERFACE
VSS
FSOTC REGISTER
MUX
USER STORAGE (52 BYTES)
VDD
2FEH + 2FFH
VDD
FSOTC
FSOTC REGISTER SHADOW
CONTROL LOCATION REGISTER
19EH + 19FH
1A0H + 1A1H
VSS
BDR
CONFIGURATION REGISTER SHADOW
RESERVED
OFFSET TC REGISTER SHADOW
RESERVED
:
VSS
±1
OFFSET DAC LOOKUP TABLE
(176 x 16-BITS)
UNLOCK
DIO
PGA BANDWIDTH
3kHz 10%
x 26
∑
PGA
MUX
OUT
INM
VSS
INPUT REFERRED OFFSET
(COARSE OFFSET)
IRO (3, 2:0)
OFFSET mV
1,111
1,110
1,101
63
54
45
1,100
1,011
1,010
36
27
18
1,001
1,000
0,000
9
0
0
0,001
0,010
0,011
-9
-18
-27
0,100
0,101
0,110
-36
-45
-54
0,111
-63
AMP-
PROGRAMMABLE GAIN STAGE
±1
16-BIT
OFFSET
TC DAC
OTC REGISTER
VSS
* INPUT REFERRED
OFFSET VALUE IS
PROPORTIONAL TO VDD.
VALUES GIVEN ARE FOR
VDD = 5V.
PGA (3:0)
PGA GAIN
TOTAL GAIN
0000
0001
0010
1.5
2.0
2.5
39
52
65
0011
0100
0101
3.0
3.5
4.0
78
91
104
0110
0111
1000
4.5
5.0
5.5
117
130
143
1001
1010
1011
6.0
156
6.5
7.0
7.5
169
182
195
8.0
8.5
9.0
208
221
234
1100
1101
1110
1111
AMPOUT
AMP+
UNCOMMITTED OP AMP
PARAMETER
I/P RANGE
I/P OFFSET
VALUE
VSS TO VDD
±20mV
O/P RANGE
NO LOAD
1mA LOAD
VSS, VDD ±0.01V
VSS, VDD ±0.25V
UNITY GBW
10MHz TYPICAL
PGA BANDWIDTH 3kHz ± 10%
www.maximintegrated.com
Maxim Integrated │ 23
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
OUT
2
INM 4
BDR 5
MAX1452
13 AMPOUT
VSS
3
INM
4
BDR
5
INP
6
12 CLK1M
INP 6
11 DIO
VDD 7
10 UNLOCK
TEST 8
9
SSOP/TSSOP
VDDF
N.C.
FSOTC
N.C.
AMP+
21
20
19
+
MAX1452
7
8
9
10
11
12
UNLOCK
14 AMP-
VSS 3
22
VDDF
1
15 AMP+
23
TEST
ISRC
OUT 2
24
N.C.
16 FSOTC
N.C.
+
N.C.
ISRC 1
VDD
TOP VIEW
N.C.
Pin Configurations
TQFN
Chip Information
SUBSTRATE CONNECTED TO: VSS
www.maximintegrated.com
18
AMP-
17
AMPOUT
16
N.C.
15
CLK1M
14
DIO
13
N.C.
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
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 SSOP
A16+2
21-0056
90-0106
16 TSSOP
U16+2
21-0066
90-0117
24 TQFN-EP
T2444+4
21-0139
90-0022
Maxim Integrated │ 24
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
4/09
Added TQFN and TSSOP package information, changed packages to lead free,
changed all occurrences of ASIC to MAX1452, changed VDDF RC filter values,
recommended a more suitable voltage reference for non-ratiometric application
circuits, corrected MAX1452 input range, and added typical EEPROM current
requirements to EC table, and added gain nonlinearity graph.
3
11/13
Updated Package Information section
24
4
10/14
Deleted automotive reference
8
5
4/15
Updated Benefits and Features section
1
2
1–7, 9, 10, 12,
18, 22, 24
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. │ 25
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