Preliminary
RT9012
For recommended operating conditions specification of
RT9012, where TJ(MAX) is the maximum junction
temperature of the die (125°C) and TA is the operated
ambient temperature. The junction to ambient thermal
resistance (θJA is layout dependent) for WDFN-8L 2x2
package is 108°C/W on the standard JEDEC 51-3 single-
layer thermal test board. The maximum power dissipation
at TA = 25°C can be calculated by following formula :
PD(MAX) = ( 125°C − 25°C ) / 108 = 0.926W for
WDFN-8L 2x2 packages
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA . For RT9012 packages, the Figure 3 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
Power Dissipation vs. Ambient Temperature
0.8
0.7
0.6
WDFN-8L 2x2
0.5
0.4
0.3
0.2
0.1
0
0
25
50
75
100
125
(°C)
Ambient Temperature
Figure 3. Derating Curves for RT9012 Packages
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DS9012-06 August 2007
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
