Circuit Note

CN-0050

Rev. B | Page 3 of 3

On the underside of the ADL5330 and AD8318 chip scale

packages, there is an exposed compressed paddle. This paddle is

internally connected to the chip’s ground. Solder the paddle to

the low impedance ground plane on the printed circuit board to

ensure specified electrical performance and to provide thermal

relief. It is also recommended that the ground planes on all

layers under the paddle be stitched together with vias to reduce

thermal impedance.

COMMON VARIATIONS

This circuit can be used to implement a constant power out

function (fixed setpoint with variable input power) or a variable

power out function (variable setpoint with fixed or variable

input power). If a lower output power control range is desired,

the AD8318 log amp (60 dB power detection range) can be

replaced with either the AD8317 (50 dB power detection range)

or the AD8319 (45 dB power detection range). For a constant

output power function, the lowest dynamic range detector

(AD8319) is adequate because the loop always servos the

detector input power to a constant level.

The ADL5330 VGA, which is optimized for transmit applications,

can be replaced by the AD8368 VGA. The AD8368 is optimized

for receive application low frequencies of up to 800 MHz and

provides 34 dB of linear-in-dB voltage-controlled variable gain.

There are a number of DACs suitable for this application. All of

the following DACs have internal references:

Single: AD5660/AD5640/AD5620 (16-bit/14-bit/12-bit),

Dual: AD5663R/AD5643R/AD5623R (16-bit/14-bit/12-bit)

Quad: AD5664R/AD5644R/AD5624R (16-bit/14-bit/12-bit)

LEARN MORE

Dana Whitlow, Design and Operation of Automatic Gain Control

Loops for Receivers in Modern Communications Systems, Analog

Devices Wireless Seminar, Chapter 7, 2006.

MT-031 Tutorial, Grounding Data Converters and Solving the

Mystery of “AGND” and “DGND,” Analog Devices.

MT-073 Tutorial, High Speed Variable Gain Amplifiers, Analog

Devices.

MT-077 Tutorial, Log Amp Basics, Analog Devices.

MT-078 Tutorial, High Speed Log Amps, Analog Devices.

MT-101 Tutorial, Decoupling Techniques, Analog Devices.

Data Sheets

ADL5330

AD8318

AD8317

AD8319

ADL5330 Evaluation Board

AD8318 Evaluation Board

REVISION HISTORY

9/10—Rev. A to Rev. B

Changes to Figure 1 ..........................................................................1

Changes to Circuit Description Section.........................................1

Changes to Common Variations Section.......................................3

11/09—Rev. 0 to Rev. A

Updated Format ................................................................. Universal

Changes to Circuit Note Title..........................................................1

10/08—Revision 0: Initial Release

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