CS5233−3

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9

the ambient air (

from the formula below:

TJ(MAX) + TA(MAX) ) qJA

PD(MAX)

Maximum ambient temperature and power dissipation are

determined by the design, while

package manufacturer. The maximum junction temperature

for operation of the CS5233−3 within specification is

150

°C. The maximum power dissipation of a linear

regulator is given as

PD(MAX) + (VIN(MAX) * VOUT(MIN))

ILOAD(MAX) ) VIN(MAX)

IGND(MAX)

It is possible to change the effective value of

a heatsink to the design. A heatsink serves in some manner

to raise the effective area of the package, thus improving the

flow of heat from the package into the surrounding air. Each

material in the path of heat flow has its own characteristic

thermal resistance, all measured in

°C per watt. The thermal

resistances are summed to determine the total thermal

resistance between the die junction and air. There are three

components of interest: junction−to−case thermal resistance

(

heatsink−to−air thermal resistance (

equation for junction−to−air thermal resistance is

qJA + qJC ) qCS ) qSA,or

qJA + qJC ) qSA for qCS + 0

The value of

Packaging Information section of this data sheet.

considered zero, since heat is conducted out of the package

the IC leads and tab are soldered directly to the PC board.

Modification of

management. For surface mount components, this means

modifying the amount of trace metal that connects to the IC.

The thermal capacity of PC board traces is dependent on

how much copper area is used, if the IC is in direct contact

with the metal, whether the metal surface is coated with

some type of sealant, and whether there is airflow across the

PC board. The chart provided below shows heatsinking

capability of a square, single sided copper PC board trace.

The area is given in square millimeters, and it is assumed

there is no airflow across the PC board.

Figure 12. Thermal Resistance Capability of

Copper PC Board Metal Traces

70

0

2000

50

60

40

30

20

10

0

4000

6000