AD7891BS-2 Analog Devices Inc, AD7891BS-2 Datasheet - Page 19

• Manufacturer Part Number: AD7891BS-2
• Description: IC DAS 12BIT 8CH 44-MQFP
• Manufacturer: Analog Devices Inc
• Type: Data Acquisition System (DAS)r

Specifications of AD7891BS-2

• Rohs Status: RoHS non-compliant
• Resolution (bits): 12 b
• Sampling Rate (per Second): 500k
• Data Interface: Serial, Parallel
• Voltage Supply Source: Single Supply
• Voltage - Supply: 5V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 44-MQFP, 44-PQFP

Effective Number of Bits
The formula for signal-to-(noise + distortion) ratio (see Terminology
section) is related to the resolution or number of bits of the
converter. Rewriting the formula gives a measure of performance
expressed in effective number of bits (ENOB).
where SNR is the signal-to-(noise + distortion) ratio.
The effective number of bits for a device can be calculated from
its measured SNR. Figure 20 shows a typical plot of effective
number of bits versus frequency for the AD7891-1 and the
AD7891-2 from dc to 200 kHz. The sampling frequency is
500 kHz. The AD7891-1 inputs were configured for ± 10 V
operation. The AD7891-2 inputs were configured for 0 to 5 V
operation. The AD7891-1 plot only goes to 100 kHz as a
± 10 V sine wave of sufficient quality was unavailable at higher
frequencies.
Figure 20 shows that the AD7891-1 converts an input sine wave of
100 kHz to an effective number of bits of 11 which equates to a
signal-to-(noise + distortion) level of 68.02 dBs. The AD7891-2
converts an input sine wave of 200 kHz to an effective number
of bits of 11.07, which equates to a signal-to-(noise + distortion)
level of 68.4 dBs.
REV. D
0.048 (1.22)
0.042 (1.07)
ENOB
0.048 (1.22)
0.042 (1.07)
=
(
SNR
17
7
18
6
-
0.656 (16.66)
0.650 (16.51)
0.695 (17.65)
0.685 (17.40)
(PINS DOWN)
TOP VIEW
1 76
IDENTIFIER
.
PIN 1
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
)
/ .
6 02
44-Lead Plastic Leaded Chip Carrier [PLCC]
SQ
SQ
40
28
Dimensions shown in inches and (millimeters)
39
29
COMPLIANT TO JEDEC STANDARDS MO-047AC
0.056 (1.42)
0.042 (1.07)
OUTLINE DIMENSIONS
0.050
(1.27)
BSC
0.120 (3.05)
0.090 (2.29)
(P-44A)
0.180 (4.57)
0.165 (4.19)
–19–
0.032 (0.81)
0.026 (0.66)
0.021 (0.53)
0.013 (0.33)
0.020 (0.51)
MIN
Figure 20. Effective Number of Bits vs. Frequency
0.040 (1.01)
0.025 (0.64)
12.0
11.9
11.8
11.7
11.6
11.5
11.4
11.3
11.2
11.1
11.0
0.630 (16.00)
0.590 (14.99)
0
R
20
40
60
FREQUENCY – kHz
80
BOTTOM VIEW
AD7891-1 ENOB
(PINS UP)
100
120
AD7891-2 ENOB
140
160
AD7891
180
200