AD9100(RevA) View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
AD9100 Datasheet PDF : 12 Pages
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AD9100
IF INPUT
±100 mV
AD9100
POST-AMP
AD9618
T/H CLOCK
GAIN ADJ TO
UTILIZE MAX
ADC RANGE
ADC
ADC CLOCK
In the FFT spectrum below (see Figure 6), the 71.4 MHz IF is
observed at 1.4 MHz. Note that the highest frequency observed
(FS/2) is determined by the sample rate of the T/H.
0
–20
TRACK
–40
T/H CLOCK
20ns
HOLD
5ns
–60
"1"
OBSOLETE ADC CLOCK
"0"
Figure 4. IF Sampling with Track-and-Hold
This technique is not confined to processing Nyquist signals.
Figure 5 illustrates the spurious free dynamic range of the
AD9100 as a function of analog input signal level and
frequency. Without the output amplifier (2 V p-p input),
70 dB+ dynamic range is observed only to about 24 MHz. By
reducing the analog input to 200 mV p-p, >70 dB SFDR can be
maintained to 70 MHz IFs.
The optimum T/H input level for a particular IF can be deter-
mined by examining the T/H spurious and noise performance.
The highest input signal level which will provide the required
SFDR gives the lowest noise performance. When sampling
super Nyquist signals, the IF will be aliased to baseband and
can be observed by using FFT analysis.
–80
78
68 2 5
34
–100
DC
1.0
2.0
3.0
4.0
5.0
FREQUENCY – MHz
Figure 6. 71.4 MHz Signal Sampled at 10 MSPS with
200 mV p-p Input
Low Noise Applications
When processing low level single event signals in which noise
performance is the primary concern, amplification ahead of the
AD9100 can increase overall system signal to noise ratio. Front-
end amplification often results in an increase in hold mode
distortion levels because of the track mode limitations of the
amplifier which is used. Depending on the signal levels and
bandwidth, the AD9618 low noise high gain amplifier is a
possible candidate for this application. See Figure 7.
90
As a general rule, if the goal is maximize SNR (minimize noise),
pre-AD9100 amplification is recommended. When the system
goal is to maximize the spurious free dynamic range (minimize
80
200mV p-p INPUT
distortion), post-AD9100 amplification is recommended.
70
2V p-p INPUT
60
500mV p-p INPUT
50
0
10
20
30
40
50
60
70
INPUT FREQUENCY – MHz
Figure 5. AD9100 SFDR vs. Input Frequency at 10 MSPS
LOW
LEVEL
SOURCE
AD9618
AD9100
TO
ENCODER
Figure 7. Using AD9618 as Pre-Amp for AD9100
–8–
REV. A
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