EVAL-AD7706EB Analog Devices Inc, EVAL-AD7706EB Datasheet - Page 30

• Manufacturer Part Number: EVAL-AD7706EB
• Description: BOARD EVAL FOR AD7706
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD7706EB

• Number Of Adc's: 1
• Number Of Bits: 16
• Sampling Rate (per Second): 500
• Data Interface: Serial
• Inputs Per Adc: 3 Differential
• Input Range: 0 ~ 5.25 V
• Power (typ) @ Conditions: 6.5mW @ 500SPS
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD7706
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD7705/AD7706
Figure 24. RTD Measurement Using the AD7705
RTD
SENSORS
6.25k
R
R
R
R
L1
L2
L3
L4
RTD
mV
TC
400 A
REF IN(+)
REF IN(–)
AIN1(+)
AIN1(–)
GND
V
DD
AD7705
DOUT DIN
+5V
GND
ISOLATED GROUND
REF IN
AD7705
ISOLATED SUPPLY
V
DD
CS
MCLK OUT
MCLK IN
4.7 F
SCLK
Figure 25. Smart Transmitter Using the AD7705
100k
MCLK OUT
MCLK IN
RESET
DRDY
ISOLATION
BARRIER
MICROCONTROLLER UNIT
•PID
•RANGE SETTING
•CALIBRATION
•LINEARIZATION
•OUTPUT CONTROL
•SERIAL COMMUNICATION
•HART PROTOCOL
V
–30–
CC
COM
Smart Transmitters
Another area where the low power, single supply, three-wire
interface capabilities is of benefit is in smart transmitters. Here,
the entire smart transmitter must operate from the 4 mA to
20 mA loop. Tolerances in the loop mean that the amount of
current available to power the transmitter is as low as 3.5 mA.
The AD7705 consumes only 320 A, leaving at least 3 mA
available for the rest of the transmitter. Figure 25 shows a block
diagram of a smart transmitter which includes the AD7705. The
AD7705 with its dual input channel is ideally suited to systems
requiring an auxiliary channel whose measured variable is used
to correct that of the primary channel.
MAIN TRANSMITTER ASSEMBLY
4.7 F
0.01 F
V
REF OUT1
REF OUT2
REF IN
C1 C2 C3
CC
2.2 F
0.01 F
AD421
0.1 F
0.0033 F
BOOST
COMP
DRIVE
LOOP
COM
RTN
DN25D
1000pF
0.01 F
1k
4mA
TO
20mA
REV. A