RT8015 datasheet(13/15 Pages) RICHTEK

13 / 15 page

RT8015

DS8015-03

March 2011

www.richtek.com

The maximum power dissipation depends on operating

ambient temperature for fixed TJ(MAX) and thermal

resistance

θJA. For RT8015 package, the Figure 3 of de-

rating curves allows the designer to see the effect of rising

ambient temperature on the maximum power allowed.

The thermal resistance

θJA of SOP-8 (Exposed Pad) is

determined by the package design and the PCB design.

However, the package design had been designed. If

possible, it

’ s useful to increase thermal performance by

the PCB design. The thermal resistance

θJA can be

decreased by adding a copper under the exposed pad of

SOP-8 (Exposed Pad) package.

As shown in Figure 4, the amount of copper area to which

the SOP-8 (Exposed Pad) is mounted affects thermal

performance. When mounted to the standard SOP-8

(Exposed Pad) pad (Figure 4.a),

θJA is 75°C/W. Adding

copper area of pad under the SOP-8 (Exposed Pad) (Figure

4.b) reduces the

θJA to 64°C/W. Even further, increasing

the copper area of pad to 70mm2 (Figure 4.e) reduces the

θJA to 49°C/W.

Figure 3. Derating Curve for Package

(b) Copper Area = 10mm

θJA = 64°C/W

θJA = 54°C/W

(a) Copper Area = (2.3 x 2.3) mm

θJA = 75°C/W

Figure 4. Thermal Resistance vs. Copper Area Layout

Thermal Design

(d) Copper Area = 50mm

θJA = 51°C/W

(e) Copper Area = 70mm

θJA = 49°C/W

0.4

0.8

1.2

1.6

2.4

100

120

140

Ambient Temperature (

°C)

Copper Area

70mm

50mm

30mm

10mm

Min. layout

(

°C)

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