AD8223ARM Analog Devices Inc, AD8223ARM Datasheet - Page 18

• Manufacturer Part Number: AD8223ARM
• Description: Single Supply Low Cost Intrumentation Am
• Manufacturer: Analog Devices Inc

Specifications of AD8223ARM

• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 0.3 V/µs
• -3db Bandwidth: 200kHz
• Current - Input Bias: 12nA
• Voltage - Input Offset: 250µV
• Current - Supply: 650µA
• Voltage - Supply, Single/dual (±): 3 V ~ 24 V, ±2 V ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Peak Reflow Compatible (260 C): No
• Rohs Compliant: No
• Input Offset Voltage: 250µV
• Bandwidth: 200kHz
• Amplifier Output: Rail To Rail
• Cmrr: 90dB
• Supply Current: 350µA
• Amplifier Case Style: MSOP
• No. Of Pins: 8
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output / Channel: -
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant, Contains lead / RoHS non-compliant

AD8223
Driving a Cable
All cables have a certain capacitance per unit length, which
varies widely with cable type. The capacitive load from the
cable may cause peaking in the output response of the AD8223.
To reduce the peaking, use a resistor between the AD8223 and
the cable. Because cable capacitance and desired output response
vary widely, this resistor is best determined empirically. A good
starting point is 75 Ω.
The AD8232 operates at a low enough frequency that transmission
line effects are rarely an issue; therefore, the resistor need not
match the characteristic impedance of the cable.
A SINGLE-SUPPLY DATA ACQUISITION SYSTEM
Interfacing bipolar signals to single-supply analog-to-digital
converters (ADCs) presents a challenge. The bipolar signal
must be mapped into the input range of the ADC. Figure 41
shows how this translation can be achieved.
5V
Figure 41. A Single-Supply Data Acquisition System
(SINGLE OUT)
AD8223
AD8223
(DIFF OUT)
±10mV
Figure 40. Driving a Cable
1.02kΩ
R
G
+
–
AD8223
5V
0.1µF
REF
A
REFOUT
REFIN
AD7776
IN
5V
0.1µF
Rev. 0 | Page 18 of 20
The bridge circuit is excited by a +5 V supply. The full-scale output
voltage from the bridge (±10 mV), therefore, has a common-
mode level of 2.5 V. The AD8223 removes the common-mode
component and amplifies the input signal by a factor of 100
(R
prevent this signal from running into the AD8223 ground rail, the
voltage on the REF pin must be raised to at least 1 V. In this
example, the 2 V reference voltage from the
used to bias the AD8223 output voltage to 2 V ± 1 V, which
corresponds to the input range of the ADC.
AMPLIFYING SIGNALS WITH LOW COMMON-
MODE VOLTAGE
Because the common-mode input range of the AD8223 extends
0.15 V below ground, it is possible to measure small differential
signals that have low, or no, common-mode components. Figure 42
shows a thermocouple application in which one side of the J-type
thermocouple is grounded.
Over a temperature range of −200°C to +200°C, the J-type
thermocouple delivers a voltage ranging from −7.890 mV
to +10.777 mV. A programmed gain on the AD8223 of 100
(R
in the AD8223 output voltage ranging from 1.110 V to 3.077 V
relative to ground.
G
Figure 42. Amplifying Bipolar Signals with Low Common-Mode Voltage
G
THERMOCOUPLE
= 1.02 kΩ). This results in an output signal of ±1 V. To
= 845) and a voltage on the AD8223 REF pin of 2 V results
J-TYPE
1.02kΩ
R
G
+
–
AD8223
5V
0.1µF
AD7776
REF
ADC is
V
2V
OUT