AD8151AST datasheet(22/36 Pages) AD

22 / 36 page

AD8151

–22–

REV. 0

On this evaluation board all unused inputs are tied to VCC (GND).

All outputs, whether brought out to connectors or not, are tied

to VTT through a 49.9

Ω resistor. The AD8151 device is on the

component side of the board, while input terminations and output

back terminations are on the circuit side. The input signals from

the circuit side transit through via holes to the DUT’s pads. The

component-side output signals connect to via holes and to

circuit-side 49.9

Ω termination resistors.

Board Construction

For this board FR4 material was chosen over more exotic board

materials. Tests showed exotic materials to be unnecessary. This

is a 4-layer board. Power is bused on both external and internal

layers. Test structures showed microstrip performance to be

unaffected by the dc bias levels on the plane beneath it.

The manufacturing process should produce a controlled-

impedance board. The board stack consists of a 5-mil-thick

layer between external and internal layers. This allows the use of

an 8-mil-wide microstrip trace running from SMA connector to

the DUT’s pads. The narrow trace avoids the need to neck down

the trace width as DUT’s pads are approached and it helps to

control the microstrip trace impedance. The thin 5-mil dielectric

also helps to control crosstalk by way of confining the electro-

magnetic fields more between the trace and the plane below.

Configuration Programming

The board is configurable by one of two methods. For ease of

use, custom software is provided that controls the AD8151

programming via the parallel port of a PC. This requires a user-

supplied standard printer cable that has a DB-25 connector at

one end (parallel- or printer-port interface) and a Centronix-

type connector at the other that connects to P2 of the AD8151

evaluation board. The programming with this scheme is done in

a serial fashion, so it is not the fastest way to configure the AD8151

matrix. However, the user interface makes it very convenient to

use this programming method.

If a high-speed programming interface is desired, the AD8151

address and data buses are directly available on P3. The source

of the program signals can be a piece of test equipment, like the

Tektronix HFS-9000 digital test generator, or some other user-

supplied hardware that generates programming signals.

When using the PC interface, the jumper at W1 should be

installed and no connections should be made to P3. When using

the P3 interface, no jumper is installed at W1. There are loca-

tions for termination resistors for the address and data signals if

these are necessary.

Software Installation

The software to operate the AD8151 is provided on two 3.5"

floppy disks. The software is installed by inserting Disk 1 into

the floppy drive of a PC and running the “setup.exe” program.

This will routinely install the software and prompt the user

when to change to Disk 2. The setup program will also prompt

the user to select the directory for the program.

After running the software, the user will be prompted to identify

which (of three) software driver is used with the PC’s parallel

port. The default is LPT1, which is most commonly used. How-

ever, some laptops commonly use the PRN driver. It is also

possible that some systems are configured with the LPT2 driver.

If it is not known which driver is used, it is best to select LPT1

and proceed to the next screen. This will show a full array of

“buttons” that allows the connection of any input to output of

the AD8151. All of the outputs should be in the output “OFF”

state right after the program starts running. Any of the active

buttons can be selected with a mouse click, which will send out

one burst of programming data.

After this, the PC keyboard’s left or right arrow keyboard key

can be held down to generate a steady stream of programming

signals out of the parallel port. The CLOCK test point on the

AD8151 evaluation board can be monitored with an oscillo-

scope for any activity (user-supplied printer cable must be

connected). If there is a square-wave present, the proper soft-

ware driver is selected for the PC’s parallel port.

If there is no signal present, another driver should be tried by

selecting the Parallel Port menu item under the “File” pull-

down menu selection just under the title bar. Select a different

software driver and carry out the above test until signal activity

is present at the CLOCK test point.

Software Operation

Any button can be clicked in the matrix to program the input to

output connection. This will send the proper programming

sequence out the PC parallel port. Since only one input can be

programmed to a given output at one time, clicking a button in

a horizontal row will cancel the other selection that is already

selected in that row. However, any number of outputs can share

the same input.

A shortcut for programming all outputs to the same input is to

use the broadcast feature. After clicking on the Broadcast Con-

nection button, a screen will appear that will prompt for the

user to select which input should be connected to all outputs.

The user should type in an integer from 0 to 32 and then click

on OK. This will send out the proper program data and return

to the main screen with a full column of buttons selected under

the chosen input.

The Off column can be used to disable to whichever output one

chooses. To disable all outputs, the Global Reset button can be

clicked. This will select the full column of OFF buttons.

Two scratch-pad memories (Memory 1 and Memory 2) are

provided to conveniently save a particular configuration. How-

ever, these registers are erased when the program is terminated.

For long-term storage of configurations, the disk-storage memory

should be used. The Save and Load selections can be accessed

from the “File” pull-down menu under the title bar.

AD8151AST 数据表(PDF) 22 Page - Analog Devices

AD8151AST 数据表(HTML) 22 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

数据表下载