AD7766 Analog Devices, AD7766 Datasheet - Page 21

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

Specifications of AD7766

• 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

ANTIALIASING
The AD7766/AD7766-1/AD7766-2 sample the analog input
at a maximum rate of 1.024 MHz. The on-board digital filter
provides up to 100 dB attenuation for any possible aliasing
frequency in the range from the beginning of the filter stop
band (0.547 × ODR) to where the image of the digital filter pass
band occurs. This occurs at f
(f
Table 9 shows the attenuation achieved by various orders of
front-end antialias filters prior to the signal entering the AD7766/
AD7766-1/AD7766-2 at the image of the digital filter stop band,
which is 1.024 MHz − 0.547 × ODR.
Table 9. Antialias Filter Order
Model
AD7766
AD7766-1
AD7766-2
The
customers that require extra antialias protection. These devices
sample the signal internally at a rate of 20 MHz to achieve up to
a maximum of 156 kHz or 312 kHz output data rate. This
means that the first alias point of these devices when run at the
maximum speeds is 19.921 MHz and 19.843 MHz, respectively.
POWER DISSIPATION
The AD7766/AD7766-1/AD7766-2 offer exceptional perform-
ance at ultralow power. Figure 43, Figure 44, and Figure 45
show how the current consumption of the AD7766, AD7766-1,
and AD7766-2 scales with the MCLK frequency applied to the
device. Both the digital and analog currents scale as the MCLK
frequency is reduced. The actual throughput equals the MCLK
BAND OF INTEREST
MCLK
AD7764
− 0.547 × ODR), as shown in Figure 42.
Figure 42. AD7766/AD7766-1/AD7766 Spectrum
and
Filter Order
First
Second
Third
First
Second
Third
First
Second
Third
ANTIALIAS PROTECTION
DIGITAL FILTER 100dB
AD7765
∑-Δ devices are available to
MCLK
f
Attenuation at
1.024 MHz – 0.547 × ODR
27 dB
50 dB
70 dB
33 dB
62 dB
89 dB
38 dB
74 dB
110 dB
MCLK
FIRST IMAGE POINT
minus the filter stop band
– (0.547 × ODR)
IMAGE AT
DIGITAL FILTER
f
MCLK
f
MCLK
Rev. C | Page 21 of 24
frequency applied divided by the decimation rate employed by
the device in use. For instance, operating the AD7766 device with
an MCLK of 800 kHz results in an output data rate of 100 kHz
due to the decimate-by-8 filtering.
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
2.5
2.0
1.5
1.0
0.5
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
0
0
0
0
Figure 44. AD7766-1 Current vs. MCLK Frequency
Figure 45. AD7766-2 Current vs. MCLK Frequency
Figure 43. AD7766 Current vs. MCLK Frequency
100k
100k
100k
200k
200k
200k
300k
300k
300k
FREQUENCY (Hz)
FREQUENCY (Hz)
FREQUENCY (Hz)
400k
400k
400k
500k
500k
500k
AI
600k
AI
600k
600k
I
I
I
REF
REF
REF
DD
DD
700k
700k
700k
DI
DI
DD
DD
800k
800k
800k
DI
DD
900k
900k
900k
AI
AD7766
DD
1000k
1000k
1000k