LT6202C 查看數據表（PDF） - Linear Technology
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LT6202C Datasheet PDF : 28 Pages
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LT6202/LT6203/LT6204
TYPICAL APPLICATIONS
Single-Supply 16-Bit ADC Driver
Figure 5 shows the LT6203 driving an LTC1864 unipolar
16-bit A/D converter. The bottom half of the LT6203 is
in a gain-of-one configuration and buffers the 0V nega-
tive full-scale signal VLOW into the negative input of the
LTC1864. The top half of the LT6203 is in a gain-of-ten
configuration referenced to the buffered voltage VLOW and
drives the positive input of the LTC1864. The input range
of the LTC1864 is 0V to 5V, but for best results the input
range of VIN should be from VLOW (about 0.4V) to about
0.82V. Figure 6 shows an FFT obtained with a 10.1318kHz
coherent input waveform, from 8192 samples with no
windowing or averaging. Spurious free dynamic range is
seen to be about 100dB.
Although the LTC1864 has a sample rate far below the
gain bandwidth of the LT6203, using this amplifier is not
necessarily a case of overkill. The designer is reminded that
A/D converters have sample apertures that are vanishingly
small (ideally, infinitesimally small) and make demands on
the upstream circuitry far in excess of what is implied by
the innocent-looking sample rate. In addition, when an A/D
converter takes a sample, it applies a small capacitor to
its inputs with a fair amount of glitch energy and expects
the voltage on the capacitor to settle to the true value very
quickly. Finally, the LTC1864 has a 20MHz analog input
bandwidth and can be used in undersampling applications,
again requiring a source bandwidth higher than Nyquist.
VIN = 0.6VDC
±200mVAC
VLOW = 0.4VDC
+
1/2 LT6203
–
R1
1k
+
1/2 LT6203
–
R2
110Ω
R3
100Ω
C1
470pF
R4
100Ω
5V
+ LTC1864
16-BIT
250ksps
–
Figure 5. Single-Supply 16-Bit ADC Driver
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
–140
–150
0
fS = 250ksps
fIN = 10.131836kHz
12.5 25 37.5 50 62.5 75 82.5 100 112.5 125
FREQUENCY (kHz)
LT6202/03/04 F06
Figure 6. FFT Showing 100dB SFDR
SERIAL
DATA
OUT
LT6202/03/04 F05
620234fd
21
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