MAX1401 Datasheet, PDF (33/36 Pages) Maxim Integrated Products – +3V, 18-Bit, Low-Power, Multichannel, Oversampling Sigma-Delta ADC

+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
Strain-Gauge Operation
Connect the differential inputs of the MAX1401 to the
bridge network of the strain gauge. In Figure 14, the
analog positive supply voltage powers the bridge net-
work and the MAX1401 along with its reference voltage.
The on-chip PGA allows the MAX1401 to handle an
analog input voltage range as low as 10mV full scale.
The differential inputs of the part allow this analog input
range to have an absolute value anywhere between
AGND and V+.
Temperature Measurement
Figure 15 shows a connection from a thermocouple to
the MAX1401. In this application, the MAX1401 is oper-
ated in its buffered mode to allow large decoupling
capacitors on the front end. These decoupling capaci-
tors eliminate any noise pickup from the thermocouple
leads. When the MAX1401 is operated in buffered mode,
it has a reduced common-mode range. In order to place
the differential voltage from the thermocouple on a suit-
able common-mode voltage, the AIN2 input of the
MAX1401 is biased at the reference voltage, +1.25V.
ANALOG SUPPLY
R_REF
ACTIVE
GAUGE
R
DUMMY
R
GAUGE
REFIN+
REFIN-
AIN1
AIN2
ADDITIONAL
ANALOG
AND
CALIBRATION
CHANNELS
MUXOUT+
V+
ADCIN+
V+
V_DD
MAX1401
DIVIDER
CLOCK
GEN
SWITCHING
NETWORK
BUFFER
PGA
MODULATOR
DIGITAL
FILTER
BUFFER
DAC
AGND
INTERFACE
AND
CONTROL
CLKIN
CLKOUT
SCLK
DIN
DOUT
INT
CS
RESET
MUXOUT- ADCIN-
AGND
DGND
Figure 14. Strain-Gauge Application with MAX1401
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