CM3202-02 California Micro Devices Corporation, CM3202-02 Datasheet - Page 10

• Manufacturer Part Number: CM3202-02
• Description: Ddr Vddq And Termination Voltage Regulator
• Manufacturer: California Micro Devices Corporation

Application Info (cont’d)
Typical Thermal Characteristics
The overall junction to ambient thermal resistance
(
consists of two paths in the series. The first path is the
junction to the case (
package style and the second path is case to ambient
(
layout. The final operating junction temperature for any
condition can be estimated by the following thermal
equation:
When a CM3202-02 using TDFN-8 package is
mounted on a double-sided printed circuit board with
four square inches of copper allocated for “heat
spreading,” the θ
the over temperature limit of 170°C with an ambient
temperature of 85°C, the available power of the
package will be:
© 2007 California Micro Devices Corp. All rights reserved.
10
θ
θ
P
JA
CA
D
T
) for device power dissipation (P
JUNC
=
) thermal resistance which is dependent on board
170° C 85° C
------------------------------------ -
55° C
490 N. McCarthy Blvd., Milpitas, CA 95035-5112
=
=
T
T
AMB
AMB
–
⁄
W
+
JA
+
P
P
is approximately 55°C/W. Based on
D
D
=
×
×
1.5W
(
θ
(
θ
θ
JC
CA
JC
) which is defined by the
)
)
+
P
D
×
(
θ
CA
)
D
) primarily
●
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PCB Layout Considerations
The CM3202-02 has a heat spreader (exposed pad)
attached to the bottom of the TDFN-8 package in order
for the heat to be transferred more easily from the
package to the PCB. The heat spreader is a copper
pad with slightly smaller dimensions than the package
itself. By positioning the matching pad on the PCB top
layer to connect to the spreader during manufacturing,
the heat will be transferred between the two pads.
Figure 2
layout. Please note there are four vias to allow the heat
to dissipate into the ground and power planes on the
inner layers of the PCB. Vias must be placed
underneath the chip but this can result in solder
blockage. The ground and power planes need to be at
least 2 square inches of copper by the vias. It also
helps dissipation if the chip is positioned away from the
edge of the PCB, and away from other heat-dissipating
devices. A good thermal link from the PCB pad to the
rest of the PCB will assure the best heat transfer from
the CM3202-02 to ambient temperature.
Note: This drawing is not to scale
Ground Plane
Bottom Layer
Figure 2. Thermal Layout for TDFN-8 package
shows the CM3202-02 recommended PCB
●
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Vias (0.3mm Diameter)
Top View
Connects to Heat Spreader
Top Layer Copper
PRELIMINARY
●
CM3202-02
www.cmd.com
Pin Solder Mask
Thermal PAD
Solder Mask
05/25/07