NCV4266

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8

Calculating Power Dissipation

in a Single Output Linear Regulator

The maximum power dissipation for a single output

regulator (Figure 18) is:

PD(max) + [VI(max) * VQ(min)]IQ(max)

(1)

) VI(max)Iq

where

is the maximum input voltage,

is the minimum output voltage,

is the maximum output current for the

application,

is the quiescent current the regulator

RqJA +

150oC * TA

PD

(2)

package section of the data sheet. Those packages with

the die temperature below 150

°C.

In some cases, none of the packages will be sufficient to

dissipate the heat generated by the IC, and an external

heatsink will be required.

SMART

REGULATOR®

Iq

Control

Features

Figure 18. Single Output Regulator with Key

Performance Parameters Labeled

}

Heatsinks

A heatsink effectively increases the surface area of the

package to improve the flow of heat away from the IC and

into the surrounding air.

Each material in the heat flow path between the IC and

the outside environment will have a thermal resistance.

Like series electrical resistances, these resistances are

RqJA + RqJC ) RqCS ) RqSA

(3)

where

resistance.

interface between them. These values appear in data sheets

of heatsink manufacturers.

Thermal, mounting, and heatsinking considerations are

discussed in the ON Semiconductor application note

AN1040/D.