AD7731BR Analog Devices Inc, AD7731BR Datasheet - Page 27

• Manufacturer Part Number: AD7731BR
• Description: A/D Converter (A-D) IC
• Manufacturer: Analog Devices Inc

Specifications of AD7731BR

• Peak Reflow Compatible (260 C): No
• No. Of Bits: 24 Bit
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Features: Low-Noise, High-Throughput
• No. Of Channels: 6
• Interface Type: Serial
• Rohs Status: RoHS non-compliant
• Number Of Bits: 24
• Sampling Rate (per Second): 6.4k
• Data Interface: DSP, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 125mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With: EVAL-AD7731EBZ - BOARD EVALUATION FOR AD7731
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

REV. A
Nonchop Mode (SKIP = 0, CHP = 0)
With CHOP mode disabled and SKIP mode disabled, the only
function of the second stage filter is to give the overall frequency
response. Figure 11 shows the frequency response for the AD7731
with the second stage filter is set for normal FIR operation, chop
mode disabled, the decimal equivalent of the word in the SF bits
set to 1536 and a master clock frequency of 4.9152 MHz. The
response is analogous to that of Figure 9 with the three-times
larger SF word producing the same 200 Hz output rate. Once
again, the response will scale proportionally with master clock
frequency. The response is shown from dc to 100 Hz. The re-
jection at 50 Hz
The –3 dB frequency for the frequency response of the AD7731
with the second stage filter set for normal FIR operation and
chop mode enabled is determined by the following relationship:
In this case, f
ation is greater than 64.5 dB, is determined by:
In this case, f
REV. 0
Figure 11. Detailed Full Frequency Response of AD7731
(SKIP = 0, CHP = 0, SF = 1536)
–100
–110
–120
–10
–20
–30
–40
–50
–60
–70
–80
–90
f
0
f
3 dB
0
STOP
3 dB
STOP
10
= 7.8 Hz and the stop-band, where the attenu-
= 28 Hz.
0.039
1 Hz and 60 Hz
0.14
20
30
f
f
FREQUENCY – Hz
MOD
MOD
40
50
SF
SF
1
1
1 Hz is better than 88 dB.
60
70
CHP
CHP
80
0
0
90
100
–27–
Figure 12 shows the frequency response for the same set of
conditions as for Figure 11 but in this case the response in shown
out to 600 Hz. This plot is comparable to that of Figure 10. The
most notable difference is absence of the peaks in the response
at 200 Hz and 400 Hz. As a result, interference at these fre-
quencies will be effectively eliminated before being aliased back
to dc.
Table XVIII summarizes the settling time and subsequent through-
put rate for the various different modes.
Figure 12. Expanded Full Frequency Response of AD7731
(SKIP = 0, CHP = 0, SF = 1536)
–100
–110
–120
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
0
50
100 150 200 250 300 350 400
FREQUENCY – Hz
450
AD7731
500 550
600