AD7894AR-10 Analog Devices Inc, AD7894AR-10 Datasheet - Page 11

• Manufacturer Part Number: AD7894AR-10
• Description: A/D Converter (A-D) IC
• Manufacturer: Analog Devices Inc

Specifications of AD7894AR-10

• Peak Reflow Compatible (260 C): No
• No. Of Bits: 14 Bit
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Features: +5V, 14?Bit, Serial ADC In 8?Pin SOIC
• No. Of Channels: 1
• Interface Type: Serial
• Rohs Status: RoHS non-compliant
• Number Of Bits: 14
• Sampling Rate (per Second): 200k
• Data Interface: Serial
• Number Of Converters: 1
• Power Dissipation (max): 27.5mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Dynamic Performance (Mode 1 Only)
With a conversion time of 5 s, the AD7894 is ideal for wide
bandwidth signal processing applications. These applications
require information on the ADC’s effect on the spectral con-
tent of the input signal. Signal to (Noise + Distortion), Total
Harmonic Distortion, Peak Harmonic or Spurious Noise and
Intermodulation Distortion are all specified. Figure 11 shows a
typical FFT plot of a 10 kHz, 10 V input after being digitized
by the AD7894-10 operating at a 160 kHz sampling rate. The
signal to (noise + distortion) ratio is 80.24 dB and the total
harmonic distortion is –96.35 dB.
The formula for signal to (noise + distortion) ratio (see Ter-
minology section) is related to the resolution or number of bits
in the converter. Rewriting the formula, below, gives a mea-
sure of performance expressed in effective number of bits (N):
where SNR is Signal to (Noise + Distortion) Ratio.
The effective number of bits for a device can be calculated from
its measured signal to (noise + distortion) ratio. Figure 12
shows a typical plot of effective number of bits versus frequency
for the AD7894 from dc to f
quency is 160 kHz. The plot shows that the AD7894 converts
an input sine wave of 10 kHz to an effective numbers of bits of
13.00, which equates to a signal to (noise + distortion) level of
80.02 dB.
REV. 0
Figure 12. Effective Number of Bits vs. Frequency
–100
–120
–140
–20
–40
–60
–80
14
13
12
11
10
9
0
10
0
10
Figure 11. AD7894 FFT Plot
20
N
FREQUENCY – kHz
FREQUENCY – kHz
(SNR –1.76)
30
SAMPLING
100
6.02
40
/2. The sampling fre-
50
f
F
SNR = 80.24dB
THD = –96.35dB
S
IN
= 160kHz
60
= 10kHz
70
1000
80
–11–
Power Considerations
In the automatic power-down mode the part may be operated at
a sample rate that is considerably less than 160 kHz. In this
case, the power consumption will be reduced and will depend
on the sample rate. Figure 13 shows a graph of the power con-
sumption versus sampling rates from 1 Hz to 100 kHz in the
automatic power-down mode. The conditions are 5 V supply
+25 C. The SCLK pin was held low and no data was read from
the part.
Figure 13. Power vs. Sampling Rate in Automatic Power-
Down Mode
100
100
0.1
90
80
70
60
50
40
30
20
10
10
82
81
80
79
78
0
1
10
–40
1
Figure 14. SNR + D vs. Temperature
f
F
S
IN
Figure 15. THD vs. Frequency
= 160kHz
= 10kHz
–20
10
SAMPLING FREQUENCY – Hz
0
FREQUENCY – kHz
TEMPERATURE – C
100
100
20
1000
40
10000
60
AD7894
100000
80
1000