CN-0268 Datasheet, PDF (1/6 Pages) Analog Devices – Resonant Approach to Designing a Band-Pass Filter for Narrow-Band, High IF, 16-Bit, 250 MSPS Receiver Front End

Circuit Note
CN-0268
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Devices Connected/Referenced
ADL5565
6 GHz Ultrahigh Dynamic Range Differential
Amplifier
AD9467 16-Bit, 200 MSPS/250 MSPS ADC
Resonant Approach to Designing a Band-Pass Filter for Narrow-Band, High IF, 16-Bit,
250 MSPS Receiver Front End
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 16-bit, 250 MSPS, narrow-band,
high IF receiver front end with an optimum interface between
the ADL5565 differential amplifier and the AD9467 ADC.
The AD9467 is a buffered input 16-bit, 200 MSPS or 250 MSPS
ADC with SNR performance of approximately 75.5 dBFS and
SFDR performance between 95 dBFS and 98 dBFS. The ADL5565
differential amplifier is suitable for driving IF sampling ADCs
because of its high input bandwidth, low distortion, and high
output linearity.
This circuit note describes a systematic procedure for designing
the interface circuit and the antialiasing filter that maintains
high performance and ensures minimal signal loss. A resonant
approach is used to design a maximally flat Butterworth fourth-
order band-pass filter with a center frequency of 200 MHz.
CIRCUIT DESCRIPTION
The advantages of using a differential amplifier to drive a high
speed ADC include signal gain, isolation, and source impedance
matching to the ADC. The ADL5565 allows pin-strappable gain
adjustments of 6 dB, 12 dB, or 15.5 dB. Alternatively, by applying
two external resistors to the inputs, finer gain steps can be achieved
within the 0 dB to 15.5 dB range. Additionally, the ADL5565
offers high output linearity, low distortion, low noise, and wide
input bandwidth. The 3 dB bandwidth is 6 GHz, and the 0.1 dB
flatness is 1 GHz. The ADL5565 is capable of achieving an
output third-order intercept (OIP3) of greater than 50 dB.
INPUT
Z = 50Ω
XFMR
1:1 Z
ECT1-1-13M
+3.3V
+3.3V +1.8V
0.1µF
5.6Ω 1nF
33Ω
Z_I = 200Ω
0.1µF
VIP2
VIP1
VIN1
VIN2
5Ω
ADL5565
G = 6dB
5Ω
5.6Ω 1nF
33Ω
39nH 150nH
8.2pF
2pF
39nH 150nH
15Ω
310Ω 180nH
530Ω
15Ω
FS = 2V p-p DIFF
AD9467
16-BIT
250MSPS
ADC
3.5pF
INTERNAL
INPUT Z
Figure 1. Resonant Filter Design for Narrow Band High IF Applications Using the ADL5565 Differential Amplifier and the AD9467 ADC
Rev. 0
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