AD627ARZ Analog Devices Inc, AD627ARZ Datasheet - Page 14

• Manufacturer Part Number: AD627ARZ
• Description: IC AMP INST R-R 25MA 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Rail-to-Railr

Specifications of AD627ARZ

• Slew Rate: 0.06 V/µs
• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• -3db Bandwidth: 80kHz
• Current - Input Bias: 2nA
• Voltage - Input Offset: 25µV
• Current - Supply: 60µA
• Current - Output / Channel: 25mA
• Voltage - Supply, Single/dual (±): 2.2 V ~ 36 V, ±1.1 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• No. Of Amplifiers: 1
• Input Offset Voltage: 200µV
• Gain Db Min: 5dB
• Gain Db Max: 1000dB
• Bandwidth: 40MHz
• Amplifier Output: Rail To Rail
• Cmrr: 77dB
• Supply Voltage Range: ± 1.1V To ±
• Common Mode Rejection Ratio: 90
• Current, Input Bias: 3 nA (Single), 2 nA (Dual)
• Current, Input Offset: 0.3 nA
• Current, Supply: 60 μA
• Impedance, Thermal: 155 °C/W
• Package Type: SOIC-8
• Power Dissipation: 0.8 W
• Resistance, Input: 20 Gigaohms (Differential), 20 Gigaohms (Common-Mode)
• Temperature, Operating, Range: -40 to +85 °C
• Voltage, Gain: 1000 V/V
• Voltage, Input: -35.9 to +35 V (Single), -17.9 to +17 V (Dual)
• Voltage, Input Offset: 50 μV (Single), 25 μV (Dual)
• Voltage, Noise: 38 nV/sqrt Hz
• Voltage, Supply: 2.2 to ±18 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Gain Bandwidth Product: -
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

AD627
In dc-coupled resistive bridge applications, providing this path
is generally not necessary as the bias current simply flows from
the bridge supply, through the bridge and into the amplifier.
However, if the impedance that the two inputs see are large, and
differ by a large amount (>10 kΩ), the offset current of the
input stage will cause dc errors compatible with the input offset
voltage of the amplifier.
100k
–INPUT
+INPUT
–INPUT
+INPUT
100k
–INPUT
+INPUT
R
R
G
G
R
G
AD627
AD627
–V
–V
+V
AD627
+V
S
S
–V
S
S
+V
S
REFERENCE
REFERENCE
S
REFERENCE
LOAD
LOAD
AD627
LOAD
0.1 F
V
TO POWER
SUPPLY
GROUND
TO POWER
SUPPLY
GROUND
V
OUT
OUT
0.1 F
TO POWER
SUPPLY
GROUND
V
OUT
ANALOG POWER SUPPLY
+5V
–5V
V
V
IN1
IN2
GND
V
Layout and Grounding
The use of ground planes is recommended to minimize the
impedance of ground returns (and hence the size of dc errors).
In order to isolate low level analog signals from a noisy digital
environment, many data-acquisition components have separate
analog and digital ground returns (Figure 12). All ground pins
from mixed signal components such as analog-to-digital converters
should be returned through the “high quality” analog ground
plane. Digital ground lines of mixed signal components should
also be returned through the analog ground plane. This may
seem to break the rule of keeping analog and digital grounds
separate. However, in general, there is also a requirement to keep
the voltage difference between digital and analog grounds on
a converter as small as possible (typically <0.3 V). The increased
noise, caused by the converter’s digital return currents flowing
through the analog ground plane, will generally be negligible.
Maximum isolation between analog and digital is achieved by
connecting the ground planes back at the supplies.
If there is only a single power supply available, it must be shared
by both digital and analog circuitry. Figure 13 shows the how
to minimize interference between the digital and analog cir-
cuitry. As in the previous case, separate analog and digital
ground planes should be used (reasonably thick traces can be
used as an alternative to a digital ground plane). These ground
planes should be connected at the power supply’s ground pin.
Separate traces (or power planes) should be run from the power
supply to the supply pins of the digital and analog circuits. Ideally
each device should have its own power supply trace, but these
can be shared by a number of devices as long as a single trace is
not used to route current to both digital and analog circuitry.
INPUT PROTECTION
As shown in the simplified schematic (Figure 2), both the inverting
and noninverting inputs are clamped to the positive and nega-
tive supplies by ESD diodes. In addition to this a 2 kΩ series
resistor on each input provides current limiting in the event of
an overvoltage. These ESD diodes can tolerate a maximum
continuous current of 10 mA. So an overvoltage, (that is the
amount by which input voltage exceeds the supply voltage), of
± 20 V can be tolerated. This is true for all gains, and for power
on and off. This last case is particularly important since the
signal source and amplifier may be powered separately.
If the overvoltage is expected to exceed 20 V, additional external
series resistors current limiting resistors should be used to keep
the diode current to below 10 mA.
DD
ADC
0.1 F
AGND DGND
AD7892-2
12
DIGITAL POWER SUPPLY
AGND
GND
PROCESSOR
0.1 F
+5V
V
DD