RT2515A
V
OUT
Short to GND
3.2
Maximum Power Dissipation (W)
Four-Layer PCB
2.8
2.4
2.0
1.6
1.2
0.8
0.4
0.0
V
OUT
I
LIM
I
LIM
＇
I
OUT
IC Temperature
Figure 4. Short Circuit Protection when Output Short
Circuit Occurs
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
P
D(MAX)
= (T
J(MAX)
−
T
A
) /
θ
JA
where T
J(MAX)
is the maximum junction temperature, T
A
is
the ambient temperature, and
θ
JA
is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance,
θ
JA
, is layout dependent. For
SOP-8 (Exposed Pad) package, the thermal resistance,
θ
JA
, is 49°C/W on a standard JEDEC 51-7 four-layer
thermal test board. The maximum power dissipation at T
A
= 25°C can be calculated by the following formula :
P
D(MAX)
= (125°C
−
25°C) / 49°C/W) = 2.04W for
SOP-8 (Exposed Pad) package
The maximum power dissipation depends on the operating
ambient temperature for fixed T
J(MAX)
and thermal
resistance,
θ
JA
. The derating curve in Figure 5 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 5. Derating Curve of Maximum Power Dissipation
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
8
DS2515A-02 November 2012
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
