LT1810 Просмотр технического описания (PDF) - Linear Technology
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LT1810
Linear Technology
LT1810 Datasheet PDF : 24 Pages
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LT1809/LT1810
TYPICAL APPLICATIONS
Driving A/D Converters
The LT1809/LT1810 have a 27ns settling time to 0.1% of
a 2V step signal and 20Ω output impedance at 100MHz
making it ideal for driving high speed A/D converters. With
the rail-to-rail input and output and low supply voltage
operation, the LT1809 is also desirable for single supply
applications. As shown in Figure 2, the LT1809 drives a
10Msps, 12-bit ADC, the LTC1420. The lowpass filter, R3
and C1, reduces the noise and distortion products that
might come from the input signal. High quality capacitors
and resistors, an NPO chip capacitor and metal-film surface
mount resistors, should be used since these components
can add to distortion. The voltage glitch of the converter,
due to its sampling nature, is buffered by the LT1809 and
the ability of the amplifier to settle it quickly will affect the
spurious-free dynamic range of the system. Figure 2 to
Figure 7 depict the LT1809 driving the LTC1420 at different
configurations and voltage supplies. The FFT responses
show better than 90dB of SFDR for a ± 5V supply, and 80dB
on a 5V single supply for the 1.394MHz signal.
VIN
1VP-P
5V
+
LT1809
–
–5V R2
1k
R1
1k
5V
R3
49.9Ω
LTC1420
+AIN PGA GAIN = 1
C1
–AIN REF = 2.048V
470pF
•
•
12 BITS
10Msps
•
–5V
1809 F02
Figure 2. Noninverting A/D Driver
0
VS = ±5V
AV = +2
–20
fSAMPLE = 10Msps
fIN = 1.394MHz
SFDR = 90dB
–40
–60
–80
–100
–120
0
1
2
3
4
5
FREQUENCY (MHz)
1809 F03
Figure 3. 4096 Point FFT Response
VIN 1k
2VP-P
1k
5V
–
LT1809
+
–5V
5V
49.9Ω
LTC1420
+AIN PGA GAIN = 1
470pF –AIN REF = 2.048V
•
••
12 BITS
10Msps
–5V
1809 F04
Figure 4. Inverting A/D Driver
0
VS = ±5V
AV = –1
–20
fSAMPLE = 10Msps
fIN = 1.394MHz
SFDR = 90dB
–40
–60
–80
–100
–120
0
1
2
3
4
5
FREQUENCY (MHz)
1809 F05
Figure 5. 4096 Point FFT Response
180910fa
19
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