AD9239 查看數據表（PDF） - Analog Devices
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AD9239 Datasheet PDF : 41 Pages
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AD9239
For applications where SNR is a key parameter, differential
transformer coupling is the recommended input configuration
(see Figure 47 to Figure 49), to achieve the true performance of
the AD9239.
Regardless of the configuration, the value of the shunt capacitor, C,
is dependent on the input frequency and may need to be reduced
or removed.
1.25V p-p
ADT1-1WT
1:1 Z RATIO 33Ω C
50Ω 0.1µF
0.1μF
*CDIFF
33Ω
C
VIN + x
ADC
AD9239
VIN – x AGND
*CDIFF IS OPTIONAL
Figure 47. Differential Transformer-Coupled Configuration
for Baseband Applications
1.25V p-p
L
0.1μF
ADT1-1WT
1:1 Z RATIO
L
65Ω
250Ω
L
33Ω
2.2pF
33Ω
VIN + x
ADC
AD9239
VIN – x
0.1μF
Figure 48. Differential Transformer-Coupled Configuration
for Wideband IF Applications
1.25V p-p 0.1μF
ADT1-1WT
1:1 Z RATIO
33Ω
250Ω
L
33Ω
VIN + x
ADC
AD9239
VIN – x
0.1μF
Figure 49. Differential Transformer-Coupled Configuration
for Narrow-Band IF Applications
1.25V p-p
BALUN
1:1 Z
0.1µF
0.1µF
33Ω
66Ω
0.1µF
4.7pF
33Ω
BALUN
1:1 Z
Data Sheet
VIN + x
ADC
AD9239
VIN – x
Figure 50. Differential Balun-Coupled Configuration
for Wideband IF Applications
Single-Ended Input Configuration
A single-ended input may provide adequate performance in
cost-sensitive applications. In this configuration, SFDR and
distortion performance can degrade due to input common-mode
swing mismatch. If the application requires a single-ended input
configuration, ensure that the source impedances on each input
are well matched in order to achieve the best possible performance.
A full-scale input of 1.25 V p-p can be applied to the ADC’s
VIN + x pin while the VIN − x pin is terminated. Figure 51
details a typical single-ended input configuration.
1.25V p-p
49.9Ω
0.1µF
0.1µF
C
33Ω
*CDIFF
25Ω 33Ω
C
VIN + x
ADC
AD9239
VIN – x
*CDIFF IS OPTIONAL
Figure 51. Single-Ended Input Configuration
Rev. E | Page 20 of 40
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