Datasheet

.2 7pF
0.1 Fm
14-bit,
105 MSPS
A
IN+
A
IN–
VBG
ADS
5424
5V
THS
4509
CM
348 W
348 W
100 W
100
69.8 W
V
IN
From
50-
source
W
225 W
225 W
69.8 W
49.9 W
49.9 W
0.22 Fm 0.22 Fm
0.1 Fm
0.22 Fm
70
75
80
85
90
95
10 20 30 40 50 60 70
InputFrequency-MHz
SFDR(dBc)
SNR(dBFS)
SFDR(dBc),SNR(dBFS)
THS4509
www.ti.com SLOS454H –JANUARY 2005–REVISED NOVEMBER 2009
Figure 89 shows the two-tone FFT of the THS4509
and ADS5500 circuit with 65-MHz and 70-MHz input
frequencies. The SFDR is 90 dBc.
Figure 90. THS4509 and ADS5424 Circuit
Figure 89. THS4509 and ADS5500 2-Tone FFT
with 65-MHz and 70-MHz Inputs
THS4509 and ADS5424 Combined Performance
Figure 90 shows the THS4509 driving the ADS5424
ADC, and Figure 91 shows the combined SNR and
SFDR performance versus frequency with –1-dBFS
input signal level and sampling at 80 MSPS.
Figure 91. THS4509 and ADS5424 SFDR and SNR
As before, the THS4509 amplifier provides 10 dB of Performance vs Frequency
gain, converts the single-ended input to differential,
and sets the proper input common-mode voltage to
the ADS5424. Input termination and circuit testing is
the same as described above for the THS4509 and
ADS5500 circuit.
The 225-Ω resistors and 2.7-pF capacitor between
the THS4509 outputs and ADS5424 inputs (along
with the input capacitance of the ADC) limit the
bandwidth of the signal to about 100MHz (–3 dB).
Since the ADS5424 recommended input
common-mode voltage is 2.4 V, the THS4509 is
operated from a single power-supply input with V
S+
=
5 V and V
S–
= 0 V (ground).
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Product Folder Link(s): THS4509