Preliminary Datasheet
The power dissipation definition in device is :
PD = (VIN−VOUT) x IOUT + VIN x IQ
The maximum power dissipation depends on the thermal
resistance of IC package, PCB layout, the rate of
surroundings airflow and temperature difference between
junction to ambient.
The maximum power dissipation can be calculated by
following formula :
PD(MAX) = ( TJ(MAX) − TA ) /θJA
Where TJ(MAX) is the maximum operation junction
temperature 125°C, TA is the ambient temperature and
the θJA is the junction to ambient thermal resistance. For
recommended
operating
conditions specification
of
LP3982, 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 SC-70-5
package is 250°C/W.
PD(MAX) = (125°C−25°C) / 250 = 400mW (SC-70-5)
PD(MAX) = (125°C−25°C) / 165 = 606mW
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA.
LP3982
LP3982 – Ver. 1.0 Datasheet
Dec.-2006
Page 7 of 8
POWER [ LOWPOWER SEMICONDUCTOR INC ]
