LP78084 datasheet(19/20 Pages) POWER

19 / 20 page

Preliminary Datasheet

LP78084

LP78084 – 02 Ver. 1.1 Datasheet

Nov.-2007

Page 19 of 22

drop in capacitance value as their temperature increase from

25°C, an important consideration. The X5R generally

maintain their capacitance value within ± 20%. The X7R

type are desirable for their tighter tolerance of 10% over

temperature.

Power Dissipation and Junction Temperature

Specified regulator operation is assured to a junction

temperature of 160°C; the maximum junction temperature

should be restricted to 160°C under normal operating

conditions. This restriction limits the power dissipation the

regulator can handle in any given application. To ensure the

junction temperature is within acceptable limits, calculate

the maximum allowable dissipation, PD(max), and the actual

dissipation, PD , which must be less than or equal to PD( m a x )

The maximum-power-dissipation limit is determined using

the following equation:

Where:

TJ M AX is the maximum allowable junction temperature. RJA is

the thermal resistance junction-to-ambient for the package

TA is the ambient temperature.

The regulator dissipation is calculated using:

Power dissipation resulting from quiescent current is negligible.

Excessive power dissipation triggers the thermal protection

circuit.

LP78084 Datasheet(PDF) 19 Page - Lowpower Semiconductor inc