AD7766-1 AD [Analog Devices], AD7766-1 Datasheet - Page 20

• Manufacturer Part Number: AD7766-1
• Description: 24-Bit, 8.5 mW, 109 dB, 128/64/32 kSPS ADCs
• Manufacturer: AD [Analog Devices]

AD7767
DRIVING THE AD7767
The AD7767 must be driven with fully differential inputs. The
common-mode voltage of the differential inputs to the AD7767
device and thus the limits on the differential inputs are set by
the reference voltage V
mode voltage of the AD7767 is V
pin is supplied with a 5 V supply (the
common mode is at 2.5 V. This means that the maximum inputs
that can be applied on the AD7767 differential inputs are a
5 V p-p input around 2.5 V.
An analog voltage of 2.5 V supplies the AD7767 AV
However, the AD7767 allows the user to apply a reference
voltage of up to 5 V. This provides the user with an increased
full-scale range, offering the user the option of using the
AD7767 with a larger LSB voltage size. Figure 39 shows the
maximum and minimum inputs to the AD7767.
Figure 39. Maximum Differential Inputs to the AD7767
V
V
V
V
0V
0V
REF
REF
REF
REF
2
2
REF
applied to the device. The common-
A
IN+
REF
/2. Where the AD7767 V
V
OFFSET
ADR445
V
V
IN+
IN–
Figure 41. Driving the AD7767 from a Single-Ended Source
R1
R4
C3
or ADR425), the
R1
C1
DD
R5
pin.
8
1
ADA4941-1
Rev. 0 | Page 20 of 24
R2
R2
REF+
7
2
2× V
R
C
V
CM
V
FB
FB
SS+
SS–
6
3
DIFFERENTIAL SIGNAL SOURCE
An example of some recommended driving circuitry that can
be employed in conjunction with the AD7767/AD7767-1/
AD7767-2 is shown in Figure 40. Figure 40 shows how the
ADA4841-1
AD7767-1/AD7767-2 from a differential source. Each of the
differential paths is driven by an ADA4841-1 device.
SINGLE-ENDED SIGNAL SOURCE
In the case where the AD7767 is being supplied from a single-
ended source, the application circuit in Figure 41 can be used to
drive the AD7767 device. Figure 41 shows how the
single-to-differential amplifier can be used to create a fully
differential input to the AD7767. The single-ended signal input
is applied to the positive input of the ADA4941-1 device.
Arrange the values of the resistor elements to create a 2.5 V
common-mode input to the AD7767/AD7767-1/AD7767-2
device. R3 and C2 default to 3.3 Ω and 10 nF, respectively.
A
A
5
4
IN+
IN–
2× V
Figure 40. Driving the AD7767 from a Fully Differential Source
CM
R3
R3
C2
device can be used to drive an input to the AD7767/
499Ω
499Ω
1kΩ
1kΩ
4
5
V
V
IN+
IN–
AD7767
ADR425
ADA4841-1
ADA4841-1
V
AV
2.5V
REF+
1
2
499Ω
3.3nF
499Ω
3.3nF
DD
3.3Ω
3.3Ω
10nF
4
5
V
V
ADA4941-1
IN+
AD7767
IN–
ADR425
V
AV
2.5V
REF+
1
2
DD