AD9265 Analog Devices, AD9265 Datasheet - Page 27

• Manufacturer Part Number: AD9265
• Description: 16-Bit, 125 MSPS/105 MSPS/80 MSPS, 1.8 V Analog-to-Digital Converter
• Manufacturer: Analog Devices

Specifications of AD9265

• Resolution (bits): 16bit
• # Chan: 1
• Sample Rate: 125MSPS
• Interface: LVDS,Par
• Analog Input Type: Diff-Uni
• Ain Range: (2Vref) p-p,1 V p-p,2 V p-p
• Adc Architecture: Pipelined
• Pkg Type: CSP

which SNR is a key parameter, differential double balun coupling
is the recommended input configuration (see Figure 68). In this
configuration, the input is ac-coupled and the CML is provided
to each input through a 33 Ω resistor. These resistors compensate
for losses in the input baluns to provide a 50 Ω impedance to
the driver.
In the double balun and transformer configurations, the value of
the input capacitors and resistors is dependent on the input fre-
quency and source impedance and may need to be reduced or
removed. Table 10 displays recommended values to set the RC
network. However, these values are dependent on the input
signal and should be used only as a starting guide.
ANALOG INPUT
ANALOG INPUT
2V p-p
0.1µF
P
A
0.1µF
0.1µF
Figure 69. Differential Input Configuration Using the ADL5562
0Ω
0Ω
Figure 68. Differential Double Balun Input Configuration
S
2
1
4
3
S
ADL5562
V
CC
5, 6, 7, 8
9
0.1µF
P
10
11
0.1µF
0.1µF
Rev. A | Page 27 of 44
20Ω
20Ω
33Ω
33Ω
0.1µF
0.1µF
100Ω
100Ω
Table 10. Example RC Network
Frequency
Range
(MHz)
0 to 100
100 to 300
An alternative to using a transformer-coupled input at fre-
quencies in the second Nyquist zone and higher is to use the
ADL5562 differential driver. The ADL5562 provides three
selectable gain options up to 15.5 dB. An example circuit is
shown in Figure 69; additional filtering between the ADL5562
output and the AD9265 input may be required to reduce out-of-
band noise. See the
0.1µF
0.1µF
0.1µF
15Ω
15Ω
R1
R1
10pF
5pF
C2
C1
C2
10pF
R2
R2
15Ω
15Ω
R1 Series
(Ω Each)
15
10
VIN+
VIN–
ADL5562
VIN+
VIN–
ADC
AD9265
C1 Differential
(pF)
18
10
VCM
VCM
data sheet for more information.
R2 Series
(Ω Each)
15
10
AD9265
C2 Shunt
(pF Each)
Open
10