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AD8323-EVAL

5 V CATV Line Driver Fine Step Output Power Control

Analog Devices 

AD8323

Single-Ended-to-Differential Input (Figure 8, Option 1)

Install the Mini-Circuits T1-6T-KK81 1:1 transformer in the

T1 location of the evaluation board. Place 0 Ω chip resistors at

locations JP1, JP2, and JP3 such that the signal coming in VIN+

is directed toward the transformer and the differential signal

coming out of the transformer is directed toward TP13 and

TP14. For 75 Ω input impedance, install 39.2 Ω resistors in R5

and R6 located on the back side of the evaluation board. In this

configuration the input signal must be applied to the VIN+ port

of the evaluation board from a single-ended 75 Ω signal source.

For input impedances other than 75 Ω, the correct value for R5

and R6 can be computed using the following equation:

( ) ( ) R5 = R6 = R , Desired Impedance = 2 × R 800

Differential Input (Figure 8, Option 2)

If a differential signal source is available, it may be applied

directly to both the VIN+ and VIN– input ports of the evaluation

board. In this case, 0 Ω chip resistors should be placed at loca-

tions R8, JP1, JP2, and JP3 such that the VIN+ and VIN– signals

are directed toward TP13 and TP14. Referring to Figure 8,

Option 2, a differential input impedance of 150 Ω can be

achieved by using a 165 Ω resistor for R7. For input imped-

ances other than 150 Ω, the correct value for R7 can be computed

using the following equation:

( ) Desired Impedance = R7 1600

DIFF IN

R6

T1

AD8323

R5

OPTION 1 DIFFERENTIAL INPUT TERMINATION

VIN+

VIN–

R7

AD8323

Installing the Visual Basic Control Software

To install the “CABDRIVE_23” evaluation board control soft-

ware, close all Windows applications and then run “SETUP.EXE”

located on Disk 1 of the AD8323 Evaluation Software. Follow

the on-screen instructions and insert Disk 2 when prompted to

do so. Enter the path of the directory into which the software

will be installed and select the button in the upper left corner to

complete the installation.

Running the Software

To invoke the control software, go to START -> PROGRAMS

-> CABDRIVE_23, or select the AD8323.EXE icon from the

directory containing the software.

Controlling the Gain/Attenuation of the AD8323

The slide bar controls the AD8323’s gain/attenuation, which is

displayed in dB and in V/V. The gain scales at 0.7526 dB per

LSB with the valid codes being from decimal 0 to 71. The gain

code (i.e., position of the slide bar) is displayed in decimal, binary,

and hexadecimal (see Figure 9).

POWER-UP, POWER-DOWN AND SLEEP

The “Power-Up” and “Power-Down” buttons select the mode

of operation of the AD8323 by controlling the logic level on the

asynchronous PD pin. The “Power-Up” button applies a

Logic 1 to the PD pin putting the AD8323 in forward transmit

mode. The “Power-Down” button applies a Logic 0 to the PD

pin selecting reverse mode, where the forward signal transmission

is disabled while a back termination of 75 Ω is maintained.

Checking the “Enable SLEEP Mode” box applies a Logic 0 to

the asynchronous SLEEP pin, putting the AD8323 into SLEEP

mode.

Memory Section

The “MEMORY” section of the software provides a convenient

way to alternate between two gain settings. The “X->M1” but-

ton stores the current value of the gain slide bar into memory

while the “RM1” button recalls the stored value, returning the

gain slide bar to that level. The “X->M2” and “RM2” buttons

work in the same manner.

OPTION 2 DIFFERENTIAL INPUT TERMINATION

Figure 8. Differential Input Termination Options

–10–

REV. 0

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