MAX1455C/D .................................................. -40°C to +85°C
MAX1455EAE ................................................. -40°C to +85°C
MAX1455AAE ............................................... -40°C to +125°C
MAX1455EUE................................................. -40°C to +85°C
MAX1455AUE............................................... -40°C to +125°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................ +300°C
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
PARAMETER
GENERAL CHARACTERISTICS
Supply Voltage
Supply Current
Oscillator Frequency
ANALOG INPUT
Input Impedance
Input-Referred Adjustable Offset
Range
Input-Referred Offset Tempco
Amplifier Gain Nonlinearity
Common-Mode Rejection Ratio
Minimum Input-Referred FSO
Range
Maximum Input-Referred FSO
Range
ANALOG OUTPUT
Minimum Differential Signal-Gain
Range
Maximum Differential Signal-
Gain Range
(V
DD
= +5V, V
SS
= 0V, T
A
= +25°C, unless otherwise noted.)
SYMBOL
V
DD
I
DD
f
OSC
R
IN
Offset TC = 0 (Note 2), minimum gain
T
A
= T
MIN
to T
MAX
CMRR
Specified for common-mode voltages
between V
SS
and V
DD
(Note 3)
(Note 3)
I
DD1
+ I
DD2
(Note 1)
0.85
CONDITIONS
MIN
4.5
TYP
5.0
3.0
1
1
±150
±1
0.025
90
7
40
MAX
5.5
6.0
1.15
UNITS
V
mA
MHz
MΩ
mV
µV/°C
%
dB
mV/V
mV/V
PGA [3:0] = 0000
PGA [3:0] = 1111
Clip[1:0] = 00
Clip[1:0] = 01
Clip[1:0] = 10
Clip[1:0] = 11
Low
High
Low
High
Low
High
Low
High
39
234
0.10
4.90
0.15
4.85
0.20
4.80
0.25
4.75
1
V/V
V/V
Output Clip Voltage Settings
V
OUT
No load,
T
A
= T
MIN
to T
MAX
V
Load Current Source
V
OUT
= +0.5V to +4.5V, T
A
= T
MIN
to T
MAX
,
Clip[1:0] = 00
mA
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2
MAX1455
Low-Cost Precision Sensor Signal Conditioner
Electrical Characteristics (continued)
(V
DD
= +5V, V
SS
= 0V, T
A
= +25°C, unless otherwise noted.)
PARAMETER
Load Current Sink
DC Output Impedance
Offset DAC Output Ratio
Offset TC DAC Output Ratio
Step Response
Output Capacitive Load
Output Noise
BRIDGE DRIVE
Bridge Current
Current Mirror Ratio
Minimum FSODAC Code
DIGITAL-TO-ANALOG CONVERTERS
DAC Resolution
ODAC Bit Weight
OTCDAC Bit Weight
FSODAC Bit Weight
FSOTCDAC Bit Weight
COARSE-OFFSET DAC
IRODAC Resolution
IRODAC Bit Weight
INTERNAL RESISTORS
Current-Source Reference
Full-Span Output (FSO) Trim
Resistor
Resistor Temperature Coefficient
Minimum Resistance Value
Maximum Resistance Value
Resistor Matching
AUXILIARY OP AMP
Open-Loop Gain
Input Common-Mode Range
Output Swing
V
CM
No load, T
A
= T
MIN
to T
MAX
V
SS
V
SS
+
0.01
90
V
DD
V
DD
-
0.01
dB
V
V
R
ISRC
∆R
STC
Applies to R
ISRC
and
DR
STC
Applies to R
ISRC
and
DR
STC
Applies to R
ISRC
and
DR
STC
R
ISRC
to
DR
STC
75
75
1333
60
90
1
kΩ
kΩ
ppm/°C
kΩ
kΩ
%
Excluding sign bit
DV
OUT
/DCODE, input referred,
DAC reference = V
DD
= +5.0V (Note 4)
3
9
Bits
mV/Bit
DV
OUT
/DCODE, DAC reference = V
DD
=
+5.0V (Note 4)
DV
OUT
/DCODE, DAC reference = V
BDR
=
2.5V (Note 4)
DV
OUT
/DCODE, DAC reference = V
DD
=
+5.0V (Note 4)
DV
OUT
/DCODE, DAC reference = V
BDR
=
2.5V (Note 4)
16
153
76
153
76
Bits
µV/Bit
µV/Bit
µV/Bit
µV/Bit
Recommended minimum value
I
BDR
V
BDR
≤ 3.75V
0.1
0.5
12
4000
2
mA
mA/mA
Hex
DC to 1kHz (gain = minimum, source
impedance = 5kΩ)
2.5
DV
OUT
/DODAC
DV
OUT
/DOTCDAC
0% to 63% of final value
SYMBOL
CONDITIONS
V
OUT
= +0.5V to +4.5V, T
A
= T
MIN
to T
MAX
,
Clip[1:0] = 00
1
1.0
1.0
300
1000
MIN
TYP
MAX
2
UNITS
mA
Ω
V/V
V/V
µs
nF
mV
RMS
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Maxim Integrated
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3
MAX1455
Low-Cost Precision Sensor Signal Conditioner
Electrical Characteristics (continued)
(V
DD
= +5V, V
SS
= 0V, T
A
= +25°C, unless otherwise noted.)
PARAMETER
Output Current Drive
Common-Mode Rejection Ratio
Input Offset Voltage
Unity-Gain Bandwidth
TEMPERATURE-TO-DIGITAL CONVERTER
Temperature ADC Resolution
Offset
Gain
Nonlinearity
Lowest Digital Output
Highest Digital Output
EEPROM
Maximum Erase/Write Cycles
Erase Time
(Notes 6, 7)
(Note 8)
7.1
10k
Cycles
ms
8
±3
1.45
±1
00
AF
Bits
Bits
°C/Bit
LSB
Hex
Hex
CMRR
V
OS
SYMBOL
CONDITIONS
V
OUT
= (V
SS
+ 0.25) to (V
DD
- 0.25)
V
CM
= V
SS
to V
DD
V
IN
= 2.5V unity-gain
buffer (Note 5)
T
A
= +25°C
T
A
= T
MIN
to T
MAX
2
MIN
-1
70
±1
±20
TYP
MAX
+1
UNITS
mA
dB
mV
MHz
±
25
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 volt-
age 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.
Typical Operating Characteristics
OFFSET DAC DNL
MAX1455 toc01
(V
DD_
= +5V, V
SS
= 0V, T
A
= +25°C, unless otherwise noted.)
AMPLIFIER GAIN NONLINEARITY
OUTPUT ERROR FROM STRAIGHT LINE (mV)
MAX1455 toc02
2.0
1.5
1.0
DNL (mV)
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.5
0
10k
20k
30k
40k
50k
60k
2.5
ODAC = +6000HEX
OTCDAC = 0
FSODAC = 6000HEX
FSOTCDAC = 8000HEX
IRO = 2HEX
PGA = 0
INP - INM SHORTED TOGETHER
PGA = 0HEX
0
-2.5
70k
-5.0
-50
-30
-10
10
30
50
400µs/div
DAC CODE
INPUT VOLTAGE [INP - INM] (mV)
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4
MAX1455 toc03
2.5
OUTPUT NOISE
5.0
OUT
10mV/div
MAX1455
Low-Cost Precision Sensor Signal Conditioner
Pin Description
PIN
1, 15, 16
2
3
4
5
6
7
8
9
10
11
12
13
14
NAME
TEST1,
TEST3,
TEST2
OUT
INP
BDR
INM
V
SS
V
DD1
AMP+
AMPOUT
AMP-
V
DD2
UNLOCK
DIO
TEST4
FUNCTION
Test Pins. Connect to V
SS
or leave unconnected.
Analog Output. Internal voltage nodes can be accessed in digital mode. OUT can be parallel
connected to DIO. Bypass OUT to ground with a 0.1µF capacitor to reduce output noise.
Positive Input. Can be swapped to INM by the Configuration register.
Bridge Drive Output
Negative Input. Can be swapped to INP by the Configuration register.
Negative Supply Voltage
Positive Supply Voltage 1. Connect a 0.1µF capacitor from V
DD
to V
SS
.
Auxiliary Op Amp Positive Input
Auxiliary Op Amp Output
Auxiliary Op Amp Negative Input
Positive Supply Voltage 2. Connect a 0.47µF capacitor from V
DD2
to V
SS
. Connect V
DD2
to V
DD1
or
for improved noise performance, connect a 1kΩ resistor to V
DD1
.
Secure-Lock Disable. There is a 150µA pulldown to V
SS
. Connect to V
DD
to disable Secure-Lock
and enable serial communication.
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.
Test Pin. Do not connect.
Detailed Description
The MAX1455 provides amplification, calibration, and tem-
perature 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. The MAX1455
includes four selectable high/low clipping limits set in dis-
crete 50mV steps from 0.1V/4.9V to 0.25V/4.75V. Offset
and span can be calibrated 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
latitude to compensate a sensor with a simple first-
order linear correction or match an unusual tempera-
ture curve. Programming up to 114 independent 16-bit
EEPROM locations corrects performance in 1.5°C tem-
perature 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. The sensor and the MAX1455 should
be at the same temperature during calibration and use.
This allows the electronics and sensor errors to be com-
pensated together and optimizes performance. For appli-
cations where the sensor and electronics are at different
temperatures, the MAX1455 can use the sensor bridge as
an input to correct for temperature 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 sen-
sor 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
