AD8295BCPZ-RL Analog Devices Inc, AD8295BCPZ-RL Datasheet - Page 23

• Manufacturer Part Number: AD8295BCPZ-RL
• Description: Dual Precision InAmp
• Manufacturer: Analog Devices Inc

Specifications of AD8295BCPZ-RL

• Amplifier Type: Instrumentation
• Number Of Circuits: 3
• Slew Rate: 2 V/µs
• Gain Bandwidth Product: 1MHz
• -3db Bandwidth: 1.2MHz
• Current - Input Bias: 200pA
• Voltage - Input Offset: 60µV
• 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-VQFN, CSP Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AD8295BCPZ-RL; AD8295BCPZ-RLTR

APPLICATIONS INFORMATION
CREATING A REFERENCE VOLTAGE AT MIDSCALE
A reference voltage other than ground is often useful, for
example, when driving a single-supply ADC. Creating a
reference voltage derived from a voltage divider is straight-
forward with the AD8295 (see Figure 67). In this configuration,
Op Amp A2 is used to provide a buffered V
in-amp section. This configuration is very similar to the one
described in the Reference Terminal section.
Note that the internal resistors of Op Amp A1 are not used
to provide V
used. Because the negative input of Op Amp A1 is permanently
connected to the junction of internal resistors R1 and R2,
Op Amp A1 operates as a low voltage clamp, preventing the
resistor string from providing a convenient V
Noise at the reference feeds directly to the output, so if the
reference voltage is derived from a noisy source, filtering is
required. In Figure 67, Capacitor C1 has been added to filter
out high frequency noise on the positive power supply line.
The 10 μF capacitor and the 100 kΩ resistors shown in Figure 67
roll off noise starting at 0.3 Hz. The filter frequency is a trade-
off between noise rejection and start-up time.
–INPUT
+INPUT
Figure 67. Single-Supply Connection with Buffered Reference
+IN
–IN
R
R
G
G
+V
S
/2. Instead, external 1% (or better) resistors are
1
2
3
4
S
+V
16
AD8295
S
5
0.1µF
REF
IA
OUTPUT
6
15
OUT
A1
14
7
OUT
+IN
A1
A2
A2
+
V
S
100kΩ
100kΩ
R1
20kΩ
R2
20kΩ
A1
R2
13
8
–IN
A2
12
11
10
S
9
/2 reference for the
S
A2
OUT
A1
+IN
A1
R1
A1
–IN
/2 voltage.
C1
10µF
V
BUFFERED
S
/2
Rev. A | Page 23 of
HIGH ACCURACY G = −1 CONFIGURATION WITH
LOW-PASS FILTER
The circuit in Figure 68 uses Op Amp A1 and the resistor string
to provide a precise G = −1 configuration. Because no external
resistors are used to set the gain, gain accuracy and gain drift
depend only on the internally matched resistors, yielding excel-
lent performance.
Adding a capacitor across Resistor R2 is a simple way to provide
a single-pole low-pass filter that rolls off at 20 dB per decade.
This capacitor is shown as C1 in Figure 68.
If the connections to Pin 10 and Pin 11 in Figure 68 are changed
so that Pin 10 connects to ground and Pin 11 connects to the
in-amp output, the result is a G = 2 circuit, also with excellent
gain accuracy and drift. In the G = 2 configuration, Capacitor C1
lowers the gain from 2 to 1 at higher frequencies.
–INPUT
+INPUT
NOTES
1.
28
Figure 68. Single-Pole Output Filter Using a Single External Capacitor
f
LOW-PASS
+IN
–IN
R
R
G
G
1
2
3
4
= 1/(2π 20kΩ C1).
–V
+V
16
5
AD8295
S
S
V
REF
IA
15
6
INPUT
OUT
A1
14
7
A1
OUT
A2
+IN
A2
R1
20kΩ
R2
20kΩ
13
8
A1
R2
A2
–IN
12
11
10
9
C1
A2
OUT
V
A1
R1
A1
–IN
REF
INPUT
V
BUFFERED
REF
LOW-PASS
FILTERED
OUTPUT
AD8295