Richtek RT7297B, Руководство пользователя

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RT7297B
12
DS7297B-02 September 2012 www.richtek.com
© Copyright 2012 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
(d) Copper Area = 50mm
2
,
θ
JA
= 51
°
C/W
(e) Copper Area = 70mm
2
,
θ
JA
= 49
°
C/W
Figure 7. Thermal Resistance vs. Copper Area Layout
Design
Figure 8. Derating Curve of Maximum Power Dissipation
(a) Copper Area = (2.3 x 2.3) mm
2
,
θ
JA
= 75
°
C/W
(b) Copper Area = 10mm
2
,
θ
JA
= 64
°
C/W
(c) Copper Area = 30mm
2
,
θ
JA
= 54
°
C/W
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
0 25 50 75 100 125
Ambient Temperature (°C)
Pow
e
r D
issi
pat
ion (
W
)
Copper Area
70mm
2
50mm
2
30mm
2
10mm
2
Min.Layout
Four-Layer PCB
The maximum power dissipation depends on the operating
ambient temperature for fixed T
J(MAX)
and thermal
resistanc e,
θ
JA
. The derating curve in Figure 8 of derating
curves allows the designer to see the effect of rising
ambient temperature on the maximum power dissipation
allowed.