NCV8502 Series

http://onsemi.com

11

CALCULATING POWER DISSIPATION IN A

SINGLE OUTPUT LINEAR REGULATOR

The maximum power dissipation for a single output

regulator (Figure 19) is:

PD(max) + [VIN(max) * VOUT(min)]IOUT(max)

) VIN(max)IQ

(eq. 1)

where:

application, and

RQJA +

150°C * TA

PD

(eq. 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®

Control

Features

Figure 19. Single Output Regulator with Key

Performance Parameters Labeled

}

Figure 20. 16 Lead SOW (Exposed Pad), qJA as a

Function of the Pad Copper Area (2 oz. Cu

Thickness), Board Material = 0.0625, G−10/R−4

40

70

90

100

0

200

400

800

80

60

50

600

HEAT SINKS

A heat sink 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 summed to

RqJA + RqJC ) RqCS ) RqSA

(eq. 3)

where:

functions of the package type, heatsink and the interface

between them. These values appear in heat sink data sheets

of heat sink manufacturers.