AD8295ACPZ-RL Analog Devices Inc, AD8295ACPZ-RL Datasheet - Page 25

• Manufacturer Part Number: AD8295ACPZ-RL
• Description: Dual Precision InAmp
• Manufacturer: Analog Devices Inc

Specifications of AD8295ACPZ-RL

• Amplifier Type: Instrumentation
• Number Of Circuits: 3
• Slew Rate: 2 V/µs
• Gain Bandwidth Product: 1MHz
• -3db Bandwidth: 1.2MHz
• Current - Input Bias: 500pA
• Voltage - Input Offset: 120µV
• Current - Supply: 2mA
• Current - Output / Channel: 18mA
• Voltage - Supply, Single/dual (±): 4.6 V ~ 36 V, ±2.3 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DRIVING DIFFERENTIAL ADCs
Figure 71 shows how to configure the AD8295 to drive a differ-
ential ADC. The circuit shown uses very little board space and
consumes little power. With the AD7690, this configuration
gives excellent dc performance and a THD of 83 dB (10 kHz
input). For applications that need better distortion performance,
a dedicated ADC driver, such as the
is recommended.
The 500 Ω resistors and the 2.2 nF capacitors form a low-pass,
antialiasing filter at 144 kHz. The four elements of the filter also
prevent the switching transients produced by a typical SAR ADC
from destabilizing the AD8295. The capacitors provide charge to
the switched-capacitor front end of the ADC, and the resistors
shield the AD8295 from driving any sharp current changes.
–INPUT
+INPUT
+IN
–IN
R
R
G
G
ADA4941-1
1
2
3
4
+7V
–7V
16
5
AD8295
+V
–V
0.1µF
0.1µF
S
S
IA
15
6
or
REF
OUT
ADA4922-1
Figure 71. Driving a Differential ADC
A1
14
7
A1
OUT
A2
+IN
A2
Rev. A | Page 25 of 28
R1
20kΩ
R2
20kΩ
13
8
A1
R2
A2
–IN
12
11
10
9
A2
OUT
A1
+IN
A1
R1
A1
–IN
+2.5V
If the application requires a lower frequency antialiasing filter
than the one shown, increasing the capacitor values produces
much better distortion results than increasing the resistor values.
The 500 Ω resistors also protect the ADC against overvoltage.
Because the AD8295 runs on wider supply voltages than a typ-
ical ADC, there is a possibility of overdriving some converters.
This is not an issue with a PulSAR® ADC, such as the AD7690,
because its input can handle a 130 mA overdrive, which is much
higher than the short-circuit limit of the AD8295. However,
other converters have less robust inputs and may benefit from
the resistive protection.
–OUT
+OUT
500Ω
500Ω
2.2nF
2.2nF
10kΩ
10kΩ
+5V
ADR435
+7V
IN+
IN– GND
AD7690
0.1µF
0.1µF
VDD
+5V
REF
0.1µF
10µF
+5V
+
AD8295