Circuit Note

CN-0227

Devices Connected/Referenced

AD9467

16-Bit, 250 MSPS Analog-to-Digital

Converter

Circuits from the Lab™ reference circuits are engineered and

tested for quick and easy system integration to help solve today’s

analog, mixed-signal, and RF design challenges. For more

ADL5562

3.3 GHz Ultralow Distortion RF/IF

Differential Amplifier

High Performance, 16-Bit, 250 MSPS Wideband Receiver with Antialiasing Filter

Rev. A

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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.

0.1µF

ADL5562

G = 6dB

3.5pF

530Ω

0.1µF

33Ω

33Ω

243Ω

0.1µF

0.1µF

XFMR

1:1 Z

ECT1-1-13M

ANALOG INPUT

+6.0dBm FS AT 10MHz

OVERALL GAIN = 3.9dB

INPUT

Z = 50Ω

INTERNAL

INPUT Z

AD9467

16-BIT

250MSPS

ADC

20Ω

20Ω

243Ω

511Ω

12pF

15Ω

15Ω

22nH

22nH

0.1µF

0.1µF

62pF

62pF

VIP2

VIN2

6Ω

6Ω

269Ω

38.6Ω

203Ω

+5V

+1.8V

VIP1

VIN1

+3.3V

1.2dB LOSS

0.5dB LOSS

1.7dB LOSS

5.7dB GAIN

FS = 2V p-p DIFF

FILTER

0.1dB LOSS

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