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Datasheet: AN753 (Maxim Integrated Products)

Low-cost Precision Sensor Signal Conditioner

 

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Maxim Integrated Products
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
________________________________________________________________ Maxim Integrated Products
1
19-1829; Rev 1; 6/01
EVALUATION KIT
AVAILABLE
General Description
The 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.
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 solu-
tion. Contact Maxim for further information.
Applications
Pressure Sensors
Transducers and Transmitters
Strain Gauges
Pressure Calibrators and Controllers
Resistive Elements Sensors
Accelerometers
Humidity Sensors
Outputs Supported
420mA
0 to +5V (Rail-to-Rail
)
+0.5V to +4.5V Ratiometric
+2.5V to 2.5V
Features
o Provides Amplification, Calibration, and
Temperature Compensation
o Accommodates Sensor Output Sensitivities
from 1mV/V to 40mV/V
o Single Pin Digital Programming
o No External Trim Components Required
o 16-Bit Offset and Span Calibration Resolution
o Fully Analog Signal Path
o On-Chip Lookup Table Supports Multipoint
Calibration Temperature Correction
o Supports Both Current and Voltage Bridge
Excitation
o Fast 3.2kHz Frequency Response
o On-Chip Uncommitted Op Amp
o Secure-LockTM Prevents Data Corruption
o Low 2mA Current Consumption
Rail-to-Rail is a trademark of Nippon Motorola Ltd.
Secure-Lock is a trademark of Maxim Integrated Products.
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
ISRC
FSOTC
AMP+
AMP-
AMPOUT
CLK1M
DIO
UNLOCK
V
DDF
TOP VIEW
MAX1452
(NOT TO SCALE)
SSOP
OUT
V
SS
INP
INM
BDR
V
DD
TEST
Pin Configuration
Ordering Information
16 SSOP
PIN-PACKAGE
TEMP. RANGE
0C to +70C
MAX1452CAE
PART
16 SSOP
-40C to +85C
MAX1452EAE
16 SSOP
-40C to +125C
MAX1452AAE
Dice*
0C to +70C
MAX1452C/D
*Dice are tested at T
A
= +25C, DC parameters only.
A detailed block diagram appears at the end of data sheet.
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
DD
= +5V, V
SS
= 0, T
A
= +25C, 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, V
DD
to V
SS
.........................................-0.3V, +6V
All Other Pins ...................................(V
SS
- 0.3V) to (V
DD
+ 0.3V)
Short-Circuit Duration, FSOTC, OUT, BDR,
AMPOUT .................................................................Continuous
Continuous Power Dissipation (T
A
= +70C)
16-Pin SSOP (derate 8.00mW/C above +70C) ..........640mW
Operating Temperature:
MAX1452CAE/MAX1452C/D ...............................0C to +70C
MAX1452EAE ...................................................-40C to +85C
MAX1452AAE .................................................-40C to +125C
Junction Temperature ......................................................+150C
Storage Temperature.........................................-65C to +150C
Lead Temperature (soldering, 10s) ................................ +300C
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL CHARACTERISTICS
Supply Voltage
V
DD
4.5
5.0
5.5
V
Supply Current
I
DD
(Note 1)
2.0
2.5
mA
Oscillator Frequency
f
OSC
0.85
1
1.15
MHz
ANALOG INPUT
Input Impedance
R
IN
1
M
Input Referred Offset Tempco
(Notes 2, 3)
1
V/C
Input Referred Adjustable
Offset Range
Offset TC = 0 at minimum gain (Note 4)
150
mV
Amplifier Gain Nonlinearity
P er cent of + 4V sp an, V
OU T
= + 0.5V to 4.5V
0.01
%
Common-Mode Rejection Ratio
CMRR
Specified for common-mode voltages
between V
SS
and V
DD
(Note 2)
90
dB
Input Referred Adjustable FSO
Range
(Note 5)
1-40
mV/V
ANALOG OUTPUT
Differential Signal-Gain Range
Selectable in 16 steps
39-
240
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
Differential Signal Gain
Configuration [5:2] 1000bin
133
143
157
V/V
Maximum Output Voltage Swing
No load from each supply
0.02
V
Output Voltage Low
I
OUT
= 1mA sinking, T
A
= T
MIN
to T
MAX
0.100
0.20
V
Output Voltage High
I
OUT
= 1mA sourcing, T
A
= T
MIN
to T
MAX
4.75
4.87
V
Output Impedance at DC
0.1
Output Offset Ratio
V
OUT
/
Offset
0.90
1.05
1.20
V/V
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +5V, V
SS
= 0, T
A
= +25C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Output Offset TC Ratio
V
OU T
/
Offset TC
0.9
1
1.2
V/V
Step Response and IC
(63% Final Value)
150
s
Maximum Capacitive Load
1
F
Output Noise
DC to 1kHz (gain = minimum, source
impedance = 5k
V
DDF
filter)
0.5
m V
RMS
BRIDGE DRIVE
Bridge Current
I
BDR
R
L
= 1.7k
0.1
0.5
2
mA
Current Mirror Ratio
AA
R
ISOURCE
= internal
10
12
14
A/A
V
SPAN
Range (Span Code)
T
A
= T
MIN
to T
MAX
4000
C000
hex
DIGITALTOANALOG CONVERTERS
DAC Resolution
16
bits
ODAC Bit Weight
V
OUT
/
Code
DAC reference = V
DD
= +5.0V
76
V/bit
OTCDAC Bit Weight
V
OUT
/
Code
DAC reference = V
BDR
= +2.5V
38
V/bit
FSODAC Bit Weight
V
OUT
/
Code
DAC reference = V
DD
= +5.0V
76
V/bit
FSOTCDAC Bit Weight
V
OUT
/
Code
DAC reference = V
BDR
= +2.5V
38
V/bit
COARSE OFFSET DAC
IRODAC Resolution
Including sign
4
bits
IRODAC Bit Weight
V
OUT
/
Code
Input referred, DAC reference =
V
DD
= +5.0V (Note 6)
9
mV/bit
FSOTC BUFFER
Minimum Output Voltage Swing
No load
V
SS
+
0.1
V
Maximum Output Voltage Swing
No load
V
D D
- 1.0
V
Current Drive
V
FSOTC
= +2.5V
-40
+40
A
INTERNAL RESISTORS
Current-Source Reference
Resistor
R
ISRC
75
k
C ur r ent- S our ce Refer ence
Resi stor Tem p er atur e C oeffi ci ent
R
IS RC
1300
p p m/C
FSOTC Resistor
R
FTC
75
k
FSOTC Resistor Tem p er atur e
C oeffi ci ent
R
FTC
1300
p p m/C
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
4
_______________________________________________________________________________________
Note 1: Excludes sensor or load current.
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-
age of +2.5V.
Note 6: Bit weight is ratiometric to V
DD
.
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)
(V
DD
= +5V, V
SS
= 0, T
A
= +25C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TEMPERATURE-TO-DIGITAL CONVERTER
Temperature ADC Resolution
8
bits
Offset
3
LSB
Gain
1.45
C/bit
Nonlinearity
0.5
LSB
Lowest Digital Output
00
hex
Highest Digital Output
AF
hex
UNCOMMITTED OP AMP
Open Loop Gain
R
L
= 100k
90
dB
Input Common-Mode Range
V
SS
V
DD
V
Output Swing
No load, T
A
= T
MIN
to T
MAX
V
SS
+
0.02
V
DD
-
0.02
V
Output Voltage High
1mA source, T
A
= T
MIN
to T
MAX
4.85
4.90
V
Output Voltage Low
1mA sink, T
A
= T
MIN
to T
MAX
0.05
0.15
V
Offset
V
IN+
= +2.5V, unity gain buffer
-20
+20
mV
Unity Gain Bandwidth
2
MHz
EEPROM
Maximum Erase/Write Cycles
(Note 7)
10k
Cycles
Minimum Erase Time
(Note 8)
6
ms
MAX1452
Low-Cost Precision Sensor
Signal Conditioner
_______________________________________________________________________________________
5
Typical Operating Characteristics
(V
DD
= +5V, T
A
= +25C, unless otherwise noted.)
PIN
NAME
FUNCTION
1
ISRC
Bridge Drive Current Mode Setting
2
OUT
High ESD and Scan Path Output Signal. May need a 0.1
F capacitor, in noisy environments.
OUT may be parallel connected to DIO.
3
V
SS
Negative Supply Voltage
4
INM
Bridge Negative Input. Can be swapped to INP by configuration register.
5
BDR
Bridge Drive
6
INP
Bridge Positive Input. Can be swapped to INM by configuration register.
7
V
DD
Positive Supply Voltage. Connect a 0.1
F capacitor from V
DD
to V
SS
.
8
TEST
Internally Connected. Connect to V
SS
.
Pin Description
OFFSET DAC DNL
MAX1452 toc01
DAC CODE
DNL (mV)
0
30k
40k
10k
20k
50k
60k
70k
5.0
2.5
0
-2.5
-5.0
5.0
2.5
0
-2.5
-5.0
AMPLIFIER GAIN NONLINEARITY
MAX1452 toc02
INPUT VOLTAGE [INP-INM] (mV)
OUTPUT ERROR FROM STRAIGHT LINE (mV)
-50
0
-25
25
50
ODAC = 6800hex
OTCDAC = 0
FSODAC = 4000hex
FSOTCDAC = 8000hex
IRO = 2hex
PGA = 0
OUTPUT NOISE
MAX1452 toc03
400
s/div
C = 4.7
F, R
LOAD
= 1k
OUT
10mV/div
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