Preliminary
Where T
J(MAX)
is the maximum operation junction
temperature, T
A
is the ambient temperature and the
θ
JA
is
the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT9013, where T
J(MAX)
is the maximum junction
temperature of the die (125°C) and T
A
is the operated
ambient temperature. The junction to ambient thermal
resistance
θ
JA
(θ
JA
is layout dependent) for WDFN-6L 2x2
package is 165°C/W, SOT-23-5 package is 250°C/W and
SC-70-5 package is 333°C/W on the standard
JEDEC 51-3 single-layer thermal test board. The maximum
power dissipation at T
A
= 25°C can be calculated by
following formula :
P
D(MAX)
= (125°C
−
25°C) / 165 = 0.606 W for
WDFN-6L 2x2 packages
P
D(MAX)
= (125°C
−
25°C) / 250 = 0.400 W for SOT-23-5
packages
P
D(MAX)
= (125°C
−
25°C) / 333 = 0.300 W for SC-70-5
packages
The maximum power dissipation depends on operating
ambient temperature for fixed T
J(MAX)
and thermal resistance
θ
JA
. For RT9013 packages, the Figure 2 of derating curves
allows the designer to see the effect of rising ambient
temperature on the maximum power allowed.
0.7
0.6
RT9013
Single Layer PCB
Power Dissipation (W)
0.5
SOT-23-5
0.4
0.3
0.2
0.1
0
0
12.5 25 37.5 50
WDFN-6L 2x2
SC-70-5
62.5 75
87.5 100 113 125
Ambient Temperature
(°C)
Figure 2. Derating Curves for RT9013 Packages
DS9013-05 August 2007
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