AD9852ASQZ datasheet(40/52 Pages) AD

40 / 52 page

AD9852

Rev. E | Page 40 of 52

EVALUATION OF OPERATING CONDITIONS

The first step in applying the AD9852 is to select the internal

clock frequency. Clock frequency selections greater than 200 MHz

require use of the thermally enhanced package (AD9852ASVZ);

clock frequency selections equal to or less than 200 MHz may

allow use of the standard (nonthermally enhanced) plastic

surface-mount package, but more information is needed to

make this determination.

The second step is to determine the maximum required

operating temperature for the AD9852 in a given application.

Subtract this value from 150°C, which is the maximum junction

temperature allowed for the AD9852. For the extended indust-

rial temperature range, the maximum operating temperature is

85°C, which results in a difference of 65°C. This is the maxi-

mum temperature gradient the device can experience due to

power dissipation.

The third step is to divide this maximum temperature gradient

by the thermal impedance to determine the maximum power

dissipation allowed for the application. For this example, 65°C

divided by the thermal impedance of the package yields a total

power dissipation limit of 4.1 W and 1.7 W for the thermally and

nonthermally enhanced packages, respectively. Therefore, for a

3.3 V nominal power supply voltage, the current consumed by the

device under full operating conditions must not exceed 515 mA

for the standard plastic package or 1242 mA for the thermally

enhanced package. The total set of enabled functions and

operating conditions for a given application must support these

current consumption limits.

Figure 59 and Figure 60 can be used to determine the suitability

of a given AD9852 application in terms of the power dissipation

requirements. These graphs assume that the AD9852 device is

soldered to a multilayer PCB according to the recommended best

manufacturing practices and procedures for a given package type.

This ensures that the specified thermal impedance specifications

are achieved.

THERMALLY ENHANCED PACKAGE

MOUNTING GUIDELINES

Refer to the AN-772 Application Note for details on mounting

devices with an exposed paddle.

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