AD8295ACPZ-RL Analog Devices Inc, AD8295ACPZ-RL Datasheet - Page 25
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AD8295ACPZ-RL
Manufacturer Part Number
AD8295ACPZ-RL
Description
Dual Precision InAmp
Manufacturer
Analog Devices Inc
Datasheet
1.AD8295ACPZ-R7.pdf
(28 pages)
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