AD7899ARZ-1 Analog Devices Inc, AD7899ARZ-1 Datasheet - Page 13

• Manufacturer Part Number: AD7899ARZ-1
• Description: 14-BIT BIPOLAR INPUT SINGLE SUPPLY ADC
• Manufacturer: Analog Devices Inc

Specifications of AD7899ARZ-1

• Rohs Compliant: YES
• Number Of Bits: 14
• Sampling Rate (per Second): 400k
• Data Interface: Parallel
• Number Of Converters: 1
• Power Dissipation (max): 125mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (0.300", 7.50mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7899CBZ - BOARD EVAL FOR AD7899
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Effective Number of Bits
The formula given in Equation 1 relates the SNR to the number
of bits. Rewriting the formula, as in Equation 2, it is possible to
obtain a measure of performance expressed in effective number
of bits (N).
The effective number of bits for a device can be calculated directly
from its measured SNR. Figure 11 shows a typical plot of effec-
tive number of bits versus frequency for an AD7899.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities will create distortion
products at sum and difference frequencies of mfa ± nfb where
m, n = 0, 1, 2, 3 . . ., etc. Intermodulation terms are those for
which neither m nor n are equal to zero. For example, the sec-
ond order terms include (fa + fb) and (fa – fb) while the third
order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb).
The AD7899 is tested using two input frequencies. In this case
the second and third order terms are of different significance.
The second order terms are usually distanced in frequency from
the original sine waves while the third order terms are usually at
a frequency close to the input frequencies. As a result, the
N =
–100
–120
–140
–20
–40
–60
–80
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0
0
SNR − 1.76
0
6.02
50000
INPUT FREQUENCY – kHz
100
FREQUENCY – Hz
100000
1000
150000
f s = 400kHz
f IN = 100kHz
SNR = 80.5dB
–55 C
+125 C
+25 C
200000
10000
(2)
second and third order terms are specified separately. The cal-
culation of the intermodulation distortion is as per the THD
specification where it is the ratio of the rms sum of the indi-
vidual distortion products to the rms amplitude of the fundamental
expressed in dBs. In this case, the input consists of two, equal
amplitude, low distortion sine waves. Figure 12 shows a typical
IMD plot for the AD7899.
AC Linearity Plots
The plots in Figure 13 show typical DNL and INL for the
AD7899.
–0.50
–1.00
–0.50
–1.00
–100
–120
–140
1.00
1.00
0.50
0.50
–20
–40
–60
–80
0
0
0
0
0
0
2000
2000
4000
4000
50000
6000
6000
FREQUENCY – Hz
ADC – Code
ADC – Code
100000
8000
8000
10000 12000 14000
10000 12000 14000
150000
AD7899
16000
16000
200000