LP3907TL-JSXSSLASHNOPB datasheet(48/58 Pages) TI1

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LP3907

SNVS511S – JUNE 2007 – REVISED APRIL 2016

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11.2 Layout Example

Figure 49. LP3907 DSBGA Layout Example

11.3 Thermal Considerations of WQFN Package

The LP3907 is a monolithic device with integrated power FETs. For that reason, it is important to pay special

attention to the thermal impedance of the WQFN package and to the PCB layout rules in order to maximize

power dissipation of the WQFN package.

The WQFN package is designed for enhanced thermal performance and features an exposed die attach pad at

the bottom center of the package that creates a direct path to the PCB for maximum power dissipation.

Compared to the traditional leaded packages where the die attach pad is embedded inside the molding

compound, the WQFN reduces one layer in the thermal path.

The thermal advantage of the WQFN package is fully realized only when the exposed die attach pad is soldered

down to a thermal land on the PCB board with thermal vias planted underneath the thermal land. Based on

thermal analysis of the WQFN package, the junction-to-ambient thermal resistance (RθJA) can be improved by a

factor of two when the die attach pad of the WQFN package is soldered directly onto the PCB with thermal land

and thermal vias, as opposed to an alternative with no direct soldering to a thermal land. Typical pitch and outer

diameter for thermal vias are 1.27 mm and 0.33 mm, respectively. Typical copper via barrel plating is 1 oz,

although thicker copper may be used to further improve thermal performance. The LP3907 die attach pad is

connected to the substrate of the device, and therefore, the thermal land and vias on the PCB board must be

connected to ground (GND pin).

For more information on board layout techniques, refer to AN–1187 Leadless Lead Frame Package (LLP)

(SNOA401) on http://www.ti.com. This application note also discusses package handling, solder stencil, and the

assembly process.

LP3907TL-JSXS/NOPB Datasheet(PDF) 48 Page - Texas Instruments