Datasheet

Typical Nonratiometric
Operating Circuit
(12VDC < VPWR < 40VDC)
Nonratiometric output configuration enables the sensor
power to vary over a wide range. A high performance volt-
age 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 uncom-
mitted 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.
Figure 3. Basic Nonratiometric Output Configuration
MAX1452
VPWR
+12V TO +40V
OUT
GND
R
STC
R
ISRC
1.0µF
2.2µF
0.1µF
0.1µF
INM
TEST V
SS
INP
7
9
2
16
1
8
3
BDR
V
DDF
OUT
5
6
4
FSOTC
ISRC
SENSOR
MAX15006B
OUT
GND
1
5
IN
8
30Ω
V
DD
G
S
D
2N4392
MAX1452 Low-Cost Precision Sensor
Signal Conditioner
www.maximintegrated.com
Maxim Integrated │ 9