AD7767 Analog Devices, AD7767 Datasheet - Page 16

• Manufacturer Part Number: AD7767
• Description: 24-Bit, 15 mW, 109 dB, 128 kSPS/64 kSPS/32 kSPS ADCs
• Manufacturer: Analog Devices

Specifications of AD7767

• Resolution (bits): 24bit
• # Chan: 1
• Sample Rate: 128kSPS
• Interface: Ser
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p
• Adc Architecture: SAR
• Pkg Type: SOP

AD7767
–100
–120
–140
–160
–100
–120
–140
–160
–100
–120
–140
–160
–20
–40
–60
–80
–20
–40
–60
–80
–20
–40
–60
–80
0
0
0
0
0
0
Figure 33. AD7767-1 Digital Filter Frequency Response
Figure 34. AD7767-2 Digital Filter Frequency Response
Figure 32. AD7767 Digital Filter Frequency Response
16k
8k
4k
32k
16k
8k
48k
24k
12k
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
64k
32k
16k
80k
40k
20k
96k
48k
24k
112k
56k
28k
128k
64k
32k
Rev. C | Page 16 of 24
ANALOG INPUT STRUCTURE
The AD7767/AD7767-1/AD7767-2 are configured as a differential
input structure. A true differential signal is sampled between the
analog inputs V
differential inputs provides rejection of signals that are common
to both the V
Figure 35 shows the equivalent analog input circuit of the
AD7767/AD7767-1/AD7767-2. The two diodes on each of the
differential inputs provide ESD protection for the analog inputs.
Take care to ensure that the analog input signal does not exceed
the reference supply voltage (V
in the Absolute Maximum Ratings section. If the input voltage
exceeds this limit, the diodes become forward biased and start
to conduct current. The diodes can handle 130 mA maximum.
The impedance of the analog inputs can be modeled as a parallel
combination of C1 and the network formed by the series con-
nection of R
pin capacitance. R
of serial resistors and the R
22 pF, and its value is dominated by the sampling capacitor.
SUPPLY AND REFERENCE VOLTAGES
The AD7767/AD7767-1/AD7767-2 operate from a 2.5 V supply
applied to the DV
operate between 1.7 V and 3.6 V. The AD7767/AD7767-1/
AD7767-2 operate from a reference input in the range of 2.2 V
to 2 × AV
supply voltage is 5 V, but a 2.5 V supply can also be used. When
using a 5 V reference, the recommended reference devices are
the ADR445, ADR435, or ADR425; when using 2.5 V, the ADR441,
ADR431, or
the reference input (V
and as a power supply to the AD7767/AD7767-1/AD7767-2
device. Therefore, when using a 5 V reference input, the full-scale
differential input range of the AD7767/AD7767-1/AD7767-2
is 10 V. See the Driving the AD7767 section for details on the
maximum input voltage.
DD
IN
applied to the V
ADR421
IN+
Figure 35. Equivalent Analog Input Structure
, C1, and C2. The value of C1 is dominated by the
IN+
and V
V
V
IN+
IN–
DD
IN
and V
is typically 1.4 kΩ, the lumped component
and AV
are recommended. The voltage applied to
REF+
IN−
GND
GND
IN−
pins.
) operates both as a reference supply
ON
C1
C1
, Pin 4 and Pin 5, respectively. Using
DD
REF+
REF+
of the switches. C2 is typically
AGND
AGND
V
V
pins. The interface is specified to
REF+
REF+
pin. The nominal reference
) by more than 0.3 V, as specified
D
D
D
D
R
R
IN
IN
C2
C2