For recommended operating conditions specification of
RT9193, where TJ(MAX) is the maximum junction
temperature of the die (125°C) and TA is the maximum
ambient temperature. The junction to ambient thermal
resistance (θJA is layout dependent) for SOT-23-5 package
is 250°C/W, SC-70-5 package is 333°C/W and WDFN-6L
2x2 package is 165°C/W on standard JEDEC 51-3 thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by following formula :
PD(MAX) = (125°C−25°C) / 333 = 300mW (SC-70-5)
PD(MAX) = (125°C−25°C) / 250 = 400mW (SOT-23-5)
PD(MAX) = (125°C−25°C) / 165 = 606mW (WDFN-6L 2x2)
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. For RT9193 packages, the Figure 2 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
700
WDFN-6L 2x2
600
500
SOT-23-5
400
SC 70-5
300
200
100
0
0
25
50
75
100 125 150
Ambient Temperature (°C)
Figure 2. Derating Curve for Packages
DS9193-09 March 2007
RT9193
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