1A Ultra Low Dropout Linear Regulator
TJ3964
Table. 1. Absolute Maximum Ratings of Thermal Resistance
No heat sink / No air flow / No adjacent heat source / TA = 25°C
Characteristic
Symbol
θJA-SOT23-5
θJA-SOP-8
Rating
265
Unit
Thermal Resistance Junction-To-Ambient / SOT23-5
Thermal Resistance Junction-To-Ambient / SOP-8
Thermal Resistance Junction-To-Ambient / SOT223
Thermal Resistance Junction-To-Ambient / TO252
°C/W
°C/W
°C/W
°C/W
165
θJA-SOT223
θJA-TO252
140
105
In case that there is no cooling solution and no heat sink / minimum copper plane area for heat sink, the
maximum allowable power dissipation of each package is as follow;
Characteristic
Symbol
Rating
Unit
Maximum Allowable Power Dissipation at TA=25°C / SOT23-5
Maximum Allowable Power Dissipation at TA=25°C / SOP-8
Maximum Allowable Power Dissipation at TA=25°C / SOT223
Maximum Allowable Power Dissipation at TA=25°C / TO252
PDMax-SOT23-5
PDMax-SOP-8
PDMax-SOT223
PDMax-TO252
0.378
0.606
0.714
0.952
W
W
W
W
- Please note that above maximum allowable power dissipation is based on the minimum copper
plane area which does not exceed the proper footprint of the package. And the ambient
temperature is 25°C.
If proper cooling solution such as heat sink, copper plane area, air flow is applied, the maximum allowable
power dissipation could be increased. However, if the ambient temperature is increased, the allowable
power dissipation would be decreased.
For example, in case of SOT-223 and TO-252 package, θJA-SOT223 is 140 °C/W and θJA-TO52 is 105 °C/W,
however, as shown in below graph, θJA could be decreased with respect to the copper plane area. So,
the specification of maximum power dissipation for an application is fixed, the proper copper plane area
could be estimated by following graphs. As shown in graph, wider copper plane area leads lower θJA.
Junction To Ambient Thermal Resistance, θJA
vs. 1 ounce Copper Area [SOT-223 Package]
Junction To Ambient Thermal Resistance, θJA
vs. 2 ounce Copper Area [TO-252 Package]
Dec. 2009 – Rev. 1.1
- 10 -
HTC
HTC [ HTC KOREA TAEJIN TECHNOLOGY CO. ]
