LTC2282 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2282' PDF : 24 Pages View PDF
LTC2282
APPLICATIONS INFORMATION
ANALOG
INPUT
HIGH SPEED
DIFFERENTIAL
AMPLIFIER 25Ω
++
CM
––
25Ω
VCM
2.2μF
AIN+
LTC2282
12pF
AIN–
2282 F04
Figure 4. Differential Drive with an Amplifier
Figure 5 shows a single-ended input circuit. The impedance
seen by the analog inputs should be matched. This circuit
is not recommended if low distortion is required.
ANALOG
INPUT
0.1μF
1k 1k
25Ω
VCM
2.2μF
AIN+ LTC2282
25Ω
0.1μF
12pF
AIN–
2282 F05
Figure 5. Single-Ended Drive
The 25Ω resistors and 12pF capacitor on the analog
inputs serve two purposes: isolating the drive circuitry
from the sample-and-hold charging glitches and limiting
the wideband noise at the converter input.
For input frequencies above 70MHz, the input circuits of
Figure 6, 7 and 8 are recommended. The balun transformer
gives better high frequency response than a flux coupled
center tapped transformer. The coupling capacitors allow
the analog inputs to be DC biased at 1.5V. In Figure 8, the
series inductors are impedance matching elements that
maximize the ADC bandwidth.
ANALOG
INPUT
0.1μF
T1
0.1μF
12Ω
25Ω 0.1μF
25Ω 12Ω
T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
VCM
2.2μF
AIN+
LTC2282
8pF
AIN–
2282 F06
Figure 6. Recommended Front End Circuit for
Input Frequencies Between 70MHz and 170MHz
0.1μF
ANALOG
INPUT
T1
0.1μF
25Ω 0.1μF
25Ω
T1 = MA/COM, ETC 1-1-13
RESISTORS, CAPACITORS
ARE 0402 PACKAGE SIZE
VCM
2.2μF
AIN+
LTC2282
AIN–
2282 F07
Figure 7. Recommended Front End Circuit for
Input Frequencies Between 170MHz and 300MHz
VCM
ANALOG
INPUT
0.1μF
6.8nH
2.2μF
AIN+
25Ω 0.1μF
T1
0.1μF
25Ω 6.8nH
T1 = MA/COM, ETC 1-1-13
AIN–
RESISTORS, CAPACITORS, INDUCTORS
ARE 0402 PACKAGE SIZE
LTC2282
2282 F08
Figure 8. Recommended Front End Circuit for
Input Frequencies Above 300MHz
2282fb
14
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