General Description
The MAX1455 is a highly integrated automotive analog-
sensor signal processor for resistive element sensors.
The MAX1455 provides amplification, calibration, and
temperature compensation that enable 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 integrated 16-bit digi-
tal-to-analog converters (DACs). Offset and span are
also calibrated using 16-bit DACs, allowing sensor
products to be truly interchangeable.
The MAX1455 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 MAX1455 provides a unique tem-
perature compensation strategy that was developed to
provide a remarkable degree of flexibility while minimiz-
ing testing costs.
The MAX1455 is available in die form, 16-pin SSOP and
TSSOP packages.
Customization
Maxim can customize the MAX1455 for high-volume
dedicated applications. Using our dedicated cell library
of more than 2000 sensor-specific function blocks,
Maxim can quickly provide a modified MAX1455 solu-
tion. Contact Maxim for further information.
Applications
Pressure Sensors and Transducers
Piezoresistive Silicon Sensors
Strain Gauges
Resistive Element Sensors
Accelerometers
Humidity Sensors
MR and GMR Sensors
Outputs
Ratiometric Voltage Output
Programmable Output Clip Limits
Features
o Provides Amplification, Calibration, and
Temperature Compensation
o Selectable Output Clipping Limits
o Accommodates Sensor Output Sensitivities
from 5mV/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 PRT Bridge Can Be Used for Temperature-
Correction Input
o On-Chip Lookup Table Supports Multipoint
Calibration Temperature Correction
o Fast 3.2kHz Frequency Response
o On-Chip Uncommitted Op Amp
o Secure-LockTM Prevents Data Corruption
MAX1455
Low-Cost Automotive Sensor Signal
Conditioner
________________________________________________________________ Maxim Integrated Products
1
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
TEST1
TEST2
TEST3
TEST4
DIO
UNLOCK
V
DD2
AMP-
AMPOUT
TOP VIEW
MAX1455
SSOP/TSSOP
OUT
INP
V
SS
BDR
INM
V
DD1
AMP+
Pin Configuration
19-2088; Rev 1; 10/01
EVALUATION KIT
AVAILABLE
Ordering Information
*Future product--contact factory for availability.
**Dice are tested at T
A
= +25C, DC parameters only.
A detailed Functional Diagram appears at end of data sheet.
Secure-Lock is a trademark of Maxim Integrated Products, Inc.
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.
PART
TEMP. RANGE
PIN-PACKAGE
MAX1455EUE*
-40C to +85C
16 TSSOP
MAX1455AUE*
-40C to +125C
16 TSSOP
MAX1455EAE
-40C to +85C
16 SSOP
MAX1455AAE
-40C to +125C
16 SSOP
MAX1455C/D
-40C to +85C
Dice**
MAX1455
Low-Cost Automotive 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
V
DD1
- V
DD2
..............................................................-0.3V, +0.6V
All Other Pins..................................(V
SS
- 0.3V) to (V
DD_
+ 0.3V)
Short-Circuit Duration, OUT, BDR, AMPOUT .............Continuous
Continuous Power Dissipation (T
A
= +70C)
16-Pin SSOP (derate 8.00mW/C above +70C) .........640mW
Operating Temperature Ranges (T
MIN
to T
MAX
)
MAX1455EUE ..................................................-40C to +85C
MAX1455AUE ................................................-40C to +125C
MAX1455C/D ...................................................-40C to +85C
MAX1455EAE ..................................................-40C to +85C
MAX1455AAE ................................................-40C to +125C
Storage Temperature Range .............................-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
I
DD1
+ I
DD2
(Note 1)
3.0
6.0
mA
Oscillator Frequency
f
OSC
0.85
1
1.15
MHz
ANALOG INPUT
Input Impedance
R
IN
1
M
Input-Referred Adjustable Offset
Range
Offset TC = 0 (Note 2), minimum gain
150
mV
Input-Referred Offset Tempco
T
A
= T
MIN
to T
MAX
1
V/C
Amplifier Gain Nonlinearity
0.025
%
Common-Mode Rejection Ratio
CMRR
Specified for common-mode voltages
between V
SS
and V
DD
90
dB
Minimum Input-Referred FSO
Range
(Note 3)
7
mV/V
Maximum Input-Referred FSO
Range
(Note 3)
40
mV/V
ANALOG OUTPUT
Minimum Differential Signal-
Gain Range
PGA [3:0] = 0000
39
V/V
Maximum Differential Signal-
Gain Range
PGA [3:0] = 1111
234
V/V
Low
0.10
Clip[1:0] = 00
High
4.90
Low
0.15
Clip[1:0] = 01
High
4.85
Low
0.20
Clip[1:0] = 10
High
4.80
Low
0.25
Output Clip Voltage Settings
V
OUT
No load,
T
A
= T
MIN
to T
MAX
Clip[1:0] = 11
High
4.75
V
Load Current Source
V
OUT
=
+0.5V to +4.5V, T
A
= T
MIN
to T
MAX
,
Clip[1:0] = 00
1
mA
MAX1455
Low-Cost Automotive 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
Load Current Sink
V
OUT
=
+0.5V to +4.5V, T
A
= T
MIN
to T
MAX
,
Clip[1:0] = 00
2
mA
DC Output Impedance
1
Offset DAC Output Ratio
V
OUT
/
ODAC
1.0
V/V
Offset TC DAC Output Ratio
V
OUT
/
OTCDAC
1.0
V/V
Step Response
0% to 63% of final value
300
s
Output Capacitive Load
1000
nF
Output Noise
DC to 1kHz (gain = minimum, source
impedance = 5k
)
2.5
mV
RMS
BRIDGE DRIVE
Bridge Current
I
BDR
V
BDR
3.75V
0.1
0.5
2
mA
Current Mirror Ratio
12
m A/m A
Minimum FSODAC Code
Recommended minimum value
4000
Hex
DIGITAL-TO-ANALOG CONVERTERS
DAC Resolution
16
Bits
ODAC Bit Weight
V
OU T
/
C OD E , D AC r efer ence = V
D D
=
+ 5.0V ( N ote 4)
153
V/Bit
OTCDAC Bit Weight
V
OU T
/
C OD E , D AC r efer ence = V
BD R
=
2.5V ( N ote 4)
76
V/Bit
FSODAC Bit Weight
V
OU T
/
C OD E , D AC r efer ence = V
D D
=
+ 5.0V ( N ote 4)
153
V/Bit
FSOTCDAC Bit Weight
V
OU T
/
C OD E , D AC r efer ence = V
BD R
=
2.5V ( N ote 4)
76
V/Bit
COARSE-OFFSET DAC
IRODAC Resolution
Excluding sign bit
3
Bits
IRODAC Bit Weight
V
OUT
/
C OD E , input referred,
DAC reference = V
DD
= +5.0V (Note 4)
9
m V /Bi t
INTERNAL RESISTORS
Current-Source Reference
R
ISRC
75
k
Ful l - S p an Outp ut ( FS O) Tr i m
Resi stor
R
STC
75
k
Resi stor Tem p er atur e C oeffi ci ent
Applies to R
ISRC
and
R
STC
1333
ppm/C
Minimum Resistance Value
Applies to R
ISRC
and
R
STC
60
k
Maximum Resistance Value
Applies to R
ISRC
and
R
STC
90
k
Resistor Matching
R
ISRC
to
R
STC
1
%
AUXILIARY OP AMP
Open-Loop Gain
90
dB
Input Common-Mode Range
V
CM
V
SS
V
DD
V
Output Swing
No load, T
A
= T
MIN
to T
MAX
V
SS
+
0.01
V
DD
-
0.01
V
MAX1455
Low-Cost Automotive Sensor Signal
Conditioner
4
_______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
DD
= +5V, V
SS
= 0, T
A
= +25C, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Output Current Drive
V
OUT
= (V
SS
+ 0.25) to (V
DD
- 0.25)
-1
+1
mA
C om m on- M od e Rej ecti on Rati o
CMRR
V
CM
= V
SS
to V
DD
70
dB
T
A
= +25C
1
20
Input Offset Voltage
V
OS
V
IN
= 2.5V unity-gain
buffer (Note 5)
T
A
= T
MIN
to T
MAX
25
mV
Unity-Gain Bandwidth
2
MHz
TEMPERATURE-TO-DIGITAL CONVERTER
Temperature ADC Resolution
8
Bits
Offset
3
Bits
Gain
1.45
C/Bit
Nonlinearity
1
LSB
Lowest Digital Output
00
Hex
Highest Digital Output
AF
Hex
EEPROM
Maximum Erase/Write Cycles
(Notes 6, 7)
10k
Cycles
Erase Time
(Note 8)
7.1
ms
Typical Operating Characteristics
(V
DD_
= +5V, V
SS
= 0, T
A
= +25C, unless otherwise noted.)
OFFSET DAC DNL
MAX1455 toc01
DAC CODE
DNL (mV)
0
30k
40k
10k
20k
50k
60k
70k
-2.5
-1.0
-1.5
-2.0
-0.5
0
0.5
1.0
1.5
2.0
2.5
5.0
2.5
0
-2.5
-5.0
AMPLIFIER GAIN NONLINEARITY
MAX1455 toc02
INPUT VOLTAGE [INP - INM] (mV)
OUTPUT ERROR FROM STRAIGHT LINE (mV)
-50
-30
-10
10
30
50
ODAC = +6000HEX
OTCDAC = 0
FSODAC = 6000HEX
FSOTCDAC = 8000HEX
IRO = 2HEX
PGA = 0
OUTPUT NOISE
MAX1455 toc03
400
s/div
OUT
10mV/div
INP - INM SHORTED TOGETHER
PGA = 0HEX
Note 1: Excludes sensor or load current.
Note 2: This is the maximum allowable sensor offset.
Note 3: This is the sensor's sensitivity normalized to its drive voltage, assuming a desired full-span output of 4V and a bridge voltage of 2.5V.
Note 4: Bit weight is ratiometric to V
DD
.
Note 5: All units production tested at T
A
= +25
C. Limits over temperature are guaranteed by design.
Note 6: Programming of the EEPROM at temperatures below +70
C is recommended.
Note 7: For operation above +70
C, limit erase/write cycle to 100.
Note 8: All erase commands require 7.1ms minimum time.
Detailed Description
The MAX1455 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. The MAX1455 includes four selectable high/low
clipping limits set in discrete 50mV steps from
0.1V/4.9V to 0.25V/4.75V. Offset and span can be cali-
brated to within 0.02% of span.
The MAX1455 architecture includes a programmable
sensor excitation, a 16-step PGA, a 768-byte (6144 bits)
internal EEPROM, four 16-bit DACs, an uncommitted op
amp, and an on-chip temperature sensor. The MAX1455
also provides a unique temperature compensation strat-
egy that was developed to provide a remarkable degree
of flexibility while minimizing testing costs.
The customer can select from 1 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
EEPROM locations corrects performance in 1.5C tem-
perature increments over a range of -40C to +125C.
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. The sensor and the MAX1455
should be at the same temperature during calibration
and use. This allows the electronics and sensor errors
to be compensated together and optimizes perfor-
mance. For applications where the sensor and elec-
tronics are at different temperatures, the MAX1455 can
use the sensor bridge as an input to correct for temper-
ature errors.
The single pin, serial 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 MAX1455 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.
MAX1455
Low-Cost Automotive Sensor Signal
Conditioner
_______________________________________________________________________________________
5
Pin Description
PIN
NAME
FUNCTION
1, 15, 16
TEST1,
TEST3,
TEST2
Test Pins. Connect to V
SS
or leave unconnected.
2
OUT
Analog Output. Internal voltage nodes can be accessed in digital mode. OUT can be parallel
connected to DIO. Bypass OUT to ground with a 0.1F capacitor to reduce output noise.
3
INP
Positive Input. Can be swapped to INM by the Configuration register.
4
BDR
Bridge Drive Output
5
INM
Negative Input. Can be swapped to INP by the Configuration register.
6
V
SS
Negative Supply Voltage
7
V
DD1
Positive Supply Voltage 1. Connect a 0.1F capacitor from V
DD
to V
SS
.
8
AMP+
Auxiliary Op Amp Positive Input
9
AMPOUT
Auxiliary Op Amp Output
10
AMP-
Auxiliary Op Amp Negative Input
11
V
DD2
Positive Supply Voltage 2. Connect a 0.47F capacitor from V
DD2
to V
SS
. Connect V
DD2
to V
DD1
or
for improved noise performance, connect a 1k
resistor to V
DD1
.
12
UNLOCK
Secure-Lock Disable. There is a 150A pulldown to V
SS
. Connect to V
DD
to disable Secure-Lock
and enable serial communication.
13
DIO
Digital Input Output. Single-pin serial communication port. There are no internal pullups on DIO.
Connect pullup resistor from DIO to V
DD
when in digital mode.
14
TEST4
Test Pin. Do not connect.
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