LM3410XMFE datasheet(14/49 Pages) TI

14 / 49 page

VIN

DIM

AGND

PGND

COPPER

PGND

AGND

VIN

PCB

PGND

DIM

VSW

LEDs

LM3410, LM3410Q

SNVS541G – OCTOBER 2007 – REVISED MAY 2013

www.ti.com

Below is an example of a good thermal and electrical PCB design.

Figure 19. Boost PCB Layout Guidelines

This is very similar to our LM3410 demonstration boards that are obtainable via the Texas Instruments website.

The demonstration board consists of a two layer PCB with a common input and output voltage application. Most

of the routing is on the top layer, with the bottom layer consisting of a large ground plane. The placement of the

external components satisfies the electrical considerations, and the thermal performance has been improved by

adding thermal vias and a top layer “Dog-Bone”.

For certain high power applications, the PCB land may be modified to a "dog bone" shape (see Figure 20).

Increasing the size of ground plane and adding thermal vias can reduce the RθJA for the application.

Figure 20. PCB Dog Bone Layout

Thermal Design

When designing for thermal performance, one must consider many variables:

Ambient Temperature: The surrounding maximum air temperature is fairly explanatory. As the temperature

increases, the junction temperature will increase. This may not be linear though. As the surrounding air

temperature increases, resistances of semiconductors, wires and traces increase. This will decrease the

efficiency of the application, and more power will be converted into heat, and will increase the silicon junction

temperatures further.

Forced Airflow: Forced air can drastically reduce the device junction temperature. Air flow reduces the hot spots

within a design. Warm airflow is often much better than a lower ambient temperature with no airflow.

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LM3410XMFE Datenblatt(PDF) 14 Page - Texas Instruments