LP3983 datasheet(7/8 Pages) POWER

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LP3983

LP3983-datasheet

Oct.-2005

7-7

Thermal Considerations

Thermal protection limits power dissipation in

LP3983. When the operation junction temperature

exceeds 165°C, the OTP circuit starts the thermal

shutdown function turn the pass element off. The

pass element turn on again after the junction

temperature cools by 30°C.

For continue operation, do not exceed absolute

maximum operation junction temperature 125°C. 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 LP3983, 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-23-6 package is 250°C/W.

PD(MAX) = (125°C−25°C) / 250 = 400mW (SOT-23-6)

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.

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