CN-0227 Datasheet, PDF (1/5 Pages) Analog Devices – High Performance, 16-Bit, 250 MSPS Wideband Receiver with Antialiasing Filter

Circuit Note
CN-0227
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Devices Connected/Referenced
AD9467
16-Bit, 250 MSPS Analog-to-Digital
Converter
ADL5562
3.3 GHz Ultralow Distortion RF/IF
Differential Amplifier
High Performance, 16-Bit, 250 MSPS Wideband Receiver with Antialiasing Filter
EVALUATION AND DESIGN SUPPORT
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
The circuit, shown in Figure 1, is a wideband receiver front end
based on the ADL5562 ultralow noise differential amplifier driver
and the AD9467 16-bit, 250 MSPS analog-to-digital converter.
The third-order Butterworth antialiasing filter is optimized based
on the performance and interface requirements of the amplifier
and ADC. The total insertion loss due to the filter network and
other components is only 1.8 dB.
The overall circuit has a bandwidth of 152 MHz with a pass band
flatness of 1 dB. The SNR and SFDR measured with a 120 MHz
analog input are 72.6 dBFS and 82.2 dBc, respectively.
CIRCUIT DESCRIPTION
The circuit accepts a single-ended input and converts it to
differential using a wide bandwidth (3 GHz) M/A-COM
ECT1-1-13M 1:1 transformer. The ADL5562 3.3 GHz differential
amplifier has a differential input impedance of 400 Ω when
operating at a gain of 6 dB and 200 Ω when operating at a gain
of 12 dB. A gain option of 15.5 dB is also available.
The ADL5562 is an ideal driver for the AD9467, and the fully
differential architecture through the low-pass filter and into the
ADC provides good high frequency common-mode rejection,
as well as minimizes second-order distortion products. The
ADL5562 provides a gain of 6 dB or 12 dB depending on the input
connection. In the circuit, a gain of 6 dB was used to compensate
for the insertion loss of the filter network and transformer
(approximately 1.8 dB), providing an overall signal gain of 3.9 dB.
1.7dB LOSS
5.7dB GAIN
1.2dB LOSS
0.5dB LOSS
0.1dB LOSS
ANALOG INPUT
+6.0dBm FS AT 10MHz
XFMR
1:1 Z
ECT1-1-13M
INPUT
Z = 50Ω
OVERALL GAIN = 3.9dB
+5V
0.1µF
33Ω
Z_I = 400Ω
0.1µF
VIP2
VIP1
VIN1
VIN2
33Ω
15Ω ^0.1µF
6Ω
ADL5562
G = 6dB
6Ω
243Ω
243Ω
15Ω _0.1µF
62pF
22nH
0.1µF _20Ω
FILTER
12pF
511Ω
530Ω
22nH
0.1µF
20Ω
62pF
+3.3V +1.8V
AD9467
16-BIT
250MSPS
ADC
3.5pF
INTERNAL
INPUT Z
FS = 2V p-p DIFF
203Ω
38.6Ω 269Ω
Figure 1. 16-Bit, 250 MSPS Wideband Receiver Front End (Simplified Schematic: All Connections and Decoupling Not Shown)
Gains, Losses, and Signal Levels Measured Values at 10 MHz
Rev. A
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