Datasheet

2
AD7714
REV. C
–35–
CLOCK
GENERATION
AUTO-ZEROED
SD
MODULATOR
CHARGE BALANCING A/D
CONVERTER
DIGITAL
FILTER
AV
DD
1mA
BUFFER
AV
DD
SERIAL INTERFACE
REGISTER BANK
STANDBY
SYNC
MCLK IN
MCLK OUT
1mA
REF IN (+)
REF IN (–)
AGND
DGND
BUFFER
DOUT
DIN
CS
SCLK
POL
DRDY
RESET
DV
DD
AD7714
DV
DD
GND
+5V
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
C
C
V
OUT
AD780
THERMOCOUPLE
JUNCTION
+5V
+V
IN
A = 1–128
AGND
R
R
SWITCHING
MATRIX
PGA
Figure 13. Thermocouple Measurement Using the AD7714
Temperature Measurement
Another application area for the AD7714 is in temperature
measurement. Figure 13 outlines a connection from a thermo-
couple to the AD7714. In this application, the AD7714 is oper-
ated in its buffered mode to allow large decoupling capacitors
on the front end to eliminate any noise pickup which there may
have been in the thermocouple leads. When the AD7714 is
operated in buffered mode, it has a reduced common-mode
range. In order to place the differential voltage from the thermo-
couple on a suitable common-mode voltage, the AIN2 input of
the AD7714 is biased up at the reference voltage, +2.5␣ V.