Set Reference Temperature (e.g., 25°C):
• Initialize each transducer by loading its respective
register with default coefficients (e.g., based on
mean values of offset, FSO, and bridge resistance)
to prevent overload of the MAX1455. The internal
calibration registers are addressed in ICRA[3:0]
and decoded as shown in Table 15.
• Set the initial bridge voltage (with the FSODAC) to
half of the supply voltage. Measure the bridge volt-
age using the BDR or OUT pins, or calculate based
on measurements.
• Calibrate the output offset and FSO of the transduc-
er using the ODAC and FSODAC, respectively.
• Store calibration data in the test computer or
MAX1455 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
MAX1455 EEPROM user memory.
• Calculate the correction coefficients.
MAX1455
Low-Cost Automotive Sensor Signal
Conditioner
______________________________________________________________________________________ 21
MAX1455
V
OUT
V
DD
MODULE 1
DATA DATA
V
SS
V
SS
V
DD
V
DD
V
SS
TEST OVEN
MAX1455
V
OUT
MODULE 2
V
OUT
DIGITAL
MULTIPLEXER
+5V
DIO[1:N]
DIO1
DIO2
DION
MAX1455
V
OUT
MODULE N
DVM
Figure 7. Automated Test System Concept
Table 16. Effects of Compensation
TYPICAL UNCOMPENSATED INPUT (SENSOR) TYPICAL COMPENSATED TRANSDUCER OUTPUT
Offset…………………..…….………………………….±100% FSO
FSO…………………………….………………....1mV/V to 40mV/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..…….………………………………Rati om etr i c to V
DD
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)
