CAT4109, CAV4109

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9

Application Information

Power Dissipation

can be calculated as follows:

voltage or high ambient temperature can cause the

CAT4109/CAV4109 to enter thermal shutdown. In

Thermal dissipation of the junction heat consists

primarily of two paths in series. The first path is the junction

to the case (

package style, and the second path is the case to ambient

(

layout. The overall junction to ambient (

resistance is equal to:

For a given package style and board layout, the operating

following equation:

When mounted on a double−sided printed circuit board

with two square inches of copper allocated for “heat

spreading”, the resulting

For example, at 60

°C ambient temperature, the maximum

power dissipation is calculated as follow:

+

(150 * 60)

74

+ 1.2 W

Recommended Layout

Bypass capacitor C1 should be placed as close to the IC as

possible. RSET resistors should be directly connected to the

GND pin of the device. For better thermal dissipation,

multiple via can be used to connect the GND pad to a large

ground plane. It is also recommended to use large pads and

traces on the PCB wherever possible to spread out the heat.

The LEDs for this layout are driven from a separate supply

(VLED+), but they can also be driven from the same supply

connected to VDD.

Figure 15. Recommended Layout