MAX1458 Datasheet, PDF (16/20 Pages) Maxim Integrated Products – 1%-Accurate, Digitally Trimmed Sensor Signal Conditioner

1%-Accurate, Digitally Trimmed
Sensor Signal Conditioner
Ratiometric Output Configuration
Ratiometric output configuration provides an output that
is proportional to the power-supply voltage. When used
with ratiometric A/D converters, this output provides
digital pressure values independent of supply voltage.
Most automotive and some industrial applications
require ratiometric outputs.
The MAX1458 provides a high-performance ratiometric
output with a minimum number of external components
(Figure 10). These external components include the fol-
lowing:
• One power-supply bypass capacitor (C1)
• Two optional resistors, one from FSOTC to ISRC, and
another from ISRC to V_SS, depending on the sensor
type
• One optional capacitor C2 from BDRIVE to V_SS
Test System Configuration
The MAX1458 is designed to support an automated
production pressure-temperature test system with inte-
grated calibration and temperature compensation.
Figure 11 shows the implementation concept for a low-
cost test system capable of testing up to 12 transducer
modules connected in parallel. Three-state outputs on
the MAX1458 allow for parallel connection of transduc-
ers. The test system shown in Figure 11 includes a
dedicated test bus consisting of five wires:
• Two power-supply lines
• One analog output voltage line from the transducers
to a system digital voltmeter
• Two serial-interface lines: DIO (input/output) and
SCLK (clock)
For simultaneous testing of more than 12 sensor mod-
ules, use buffers to prevent overloading the data bus. A
digital multiplexer controls the chip-select signal for
each transducer.
+5V
C2
0.1µF
BDRIVE
INP
INM
V_DD
MAX1458
Σ
PGA
C1
0.1µF
LIMIT
OUT
SENSOR
ISRC
V_DD
R_ISRC
R_FTC
R_FTC
R_ISRC
128-BIT
V_SS
EEPROM
FSOTC
A=1
CS
WE
SCLK
DIO
DIGITAL
INTERFACE
TEMP
TEMP
V_SS
Figure 10. Basic Ratiometric Output Configuration
16 ______________________________________________________________________________________