AD12400 データシートの表示（PDF） - Analog Devices
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AD12400 Datasheet PDF : 24 Pages
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In addition to the radiation of heat into its environment, the
AD12400 module enables flow of heat through the mounting
studs and standoffs as they contact the motherboard. As
described in the Package Integrity/Mounting Guidelines
section, the module should be secured to the motherboard
using 2-56 nuts (washer use is optional). The torque on the nuts
should not exceed 32-inch ounces. Using a thermal grease at the
standoffs results in better thermal coupling between the board
and module. Depending on the ambient conditions, airflow can
be necessary to ensure the components in the module do not
exceed their maximum operating temperature. For reliability,
the most sensitive component has a maximum junction
temperature rating of 125°C.
Figure 21 and Figure 22 provide a basic guideline for two key
thermal management decisions: the use of thermal interface
material between the module bottom cover/mother board and
airflow. Figure 21 characterizes the typical thermal profile of an
AD12400 that is not using thermal interface material. Figure 22
provides the same information for a configuration that uses
gap-filling thermal interface material (in this case, Thermagon
T-flex™ 600 series, 0.040” thickness was used). One can see
from these profiles that the maximum die temperature is
reduced by approximately 2°C when thermal interface material
is used. Figure 21 and Figure 22 also provide a guideline for
determining the airflow requirements for given ambient
conditions. For example, a goal of 120°C die temperature in a
40°C ambient environment without the use of thermal interface
material requires an airflow of 100 LFM.
From a channel-matching perspective, the most important
consideration is external thermal influences. It is possible for
thermal imbalances in the end application to adversely affect
the dynamic performance. Due to the temperature dependence
of the image spur, substantial deviation from the factory cali-
bration conditions can have a detrimental effect. Unbalanced
thermal influences can cause gradients across the module, and
performance degradation may result. Examples of unbalanced
thermal influences may include large heat dissipating elements
near one side of the AD12400, or obstructed airflow that does
not flow uniformly across the module. The thermal sensitivity
of the module can be affected by a change in thermal gradient
across the module of 2°C.
AD12400
130
120
TYPICAL JUNCTION
110
100
90
80
70
CASE
60
50
AMBIENT
40
30
20
NO AIRFLOW
100 LFM
AIRFLOW CONDITION
300 LFM
Figure 21. Typical Temperature vs. Airflow with No Module/Board
Interface Material (Normalized to 60°C Module Case Temperature)
130
120
TYPICAL JUNCTION
110
100
90
80
70
CASE
60
50
AMBIENT
40
30
20
NO AIRFLOW
100 LFM
AIRFLOW CONDITION
300 LFM
Figure 22. Typical Temperature vs. Airflow with T-flex Module/Board
Interface Material (Normalized to 60°C Module Case Temperature Ambient)
PACKAGE INTEGRITY/MOUNTING GUIDELINES
The AD12400 is a printed circuit board (PCB)-based module
designed to provide mechanical stability and support the
intricate channel-to-channel matching necessary to achieve
high dynamic range performance. The module should be
secured to the motherboard using 2-56 nuts (washer use is
optional). The torque on the nuts should not exceed 32-inch
ounces.
The SMA edge connectors (AIN and ENC/ENC) are surface
mounted to the board in order to achieve minimum height of
the module. When attaching and routing the cables, one must
ensure they are stress-relieved and do not apply stress to the
SMA connector/board. The presence of stress on the cables may
degrade electrical performance and mechanical integrity of the
module. In addition to the routing precautions, the smallest
torque necessary to achieve consistent performance should be
used to secure the system cable to the AD12400’s SMA
connectors. The torque should never exceed 5-inch pounds.
Rev. A | Page 15 of 24
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