AD9852AST datasheet(33/42 Pages) AD

33 / 42 page

AD9852

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SOLDER MASK

OPENING

THERMAL LAND

Figure 59.

The thermal land itself must be able to distribute heat to an even

larger copper plane such as an internal ground plane. Vias must be

uniformly provided over the entire thermal pad to connect to this

internal plane. A proposed via pattern is shown in Figure 60. Via

holes should be small (12 mils, 0.3 mm) such that they can be

plated and plugged. These will provide the mechanical conduit

for heat transfer.

Figure 60.

Finally, a proposed stencil design is depicted for screen solder

placement. Note that if vias are not plugged, wicking will occur

which will displace solder away from the exposed heat sink and

the necessary mechanical bond will not be established.

Figure 61.

EVALUATION BOARD

An evaluation board is available that supports the AD9852 DDS

devices. This evaluation board consists of a PCB, software, and

documentation to facilitate bench analysis of the performance of

the AD9852 device. It is recommended that users of the AD9852

familiarize themselves with the operation and performance

capabilities of the device with the evaluation board. The evaluation

board should also be used as a PCB reference design to ensure

optimum dynamic performance from the device.

OPERATING INSTRUCTIONS

To assist in proper placement of the pin-header shorting-jumpers,

the instructions will refer to direction (left, right, top, bottom)

as well as header pins to be shorted. Pin #1 for each three pin-

header has been marked on the PCB corresponding with the

schematic diagram. When following these instructions, position

the PCB so that the text can be read from left to right. The

board is shipped with the pin-headers conﬁguring the board

as follows:

1. REFCLK for the AD9852 is conﬁgured as differential. The

differential clock signals are provided by the 100LVEL16

differential receiver.

2. Input clock for the 100LVEL16 is single-ended via J5. This

signal may be 3.3 V CMOS or a 2 V p-p sine wave capable of

driving 50

Ω (R8).

3. Both DAC outputs from the AD9852 are routed through

the two 120 MHz elliptical LP ﬁlters and their outputs con-

nected to J3 (Q) and J4 (I).

4. The board is set up for software control via the printer port

connector.

5. Conﬁgured for AD9852 operation.

Load the software from the CD onto the host PC’s hard disk.

Only Windows 9X/NT operating system is supported. Connect

a printer cable from the PC to the AD9852 Evaluation Board

printer port connector labeled “J11.”

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