RT9193T Datasheet, PDF (9/12 Pages) Richtek Technology Corporation – 300mA, Thermal Folded Back CMOS LDO Regulator

P_D(MAX) = ( T_J(MAX) − T_A ) /θ_JA
Where T_J(MAX) is the maximum operation junction
temperature 125°C, T_A is the ambient temperature and
the θ_JA is the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT9193T, where T_J(MAX) is the maximum junction
temperature of the die (125°C) and T_A is the maximum
ambient temperature. The junction to ambient thermal
resistance (θ_JA 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 T_A = 25°C can be calculated by following formula :
P_D(MAX) = (125°C−25°C) / 333 = 300mW (SC-70-5)
P_D(MAX) = (125°C−25°C) / 250 = 400mW (SOT-23-5)
P_D(MAX) = (125°C−25°C) / 165 = 606mW (WDFN-6L 2x2)
The maximum power dissipation depends on operating
ambient temperature for fixed T_J(MAX) and thermal
resistance θ_JA. For RT9193T packages, the Figure 3 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
V_OUT Short to GND
V_OUT
I_OUT
0.4V
TSD
OTP
165 °C
Trip Point
110 °C
110 °C
IC Temperature
80 °C
Figure 2. Short Circuit Thermal Folded Back Protection
when Output Short Circuit Occurs
RT9193T
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 3. Derating Curve for Packages
DS9193T-06 April 2011
www.richtek.com
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