19/25

L6229

4.1 OUTPUT CURRENT CAPABILITY AND IC POWER DISSIPATION

In Figure 25 is shown the approximate relation between the output current and the IC power dissipation using

PWM current control.

For a given output current the power dissipated by the IC can be easily evaluated, in order to establish which

package should be used and how large must be the on-board copper dissipating area to guarantee a safe op-

erating junction temperature (125°C maximum).

Figure 25. IC Power Dissipation versus Output Power.

4.2 THERMAL MANAGEMENT

In most applications the power dissipation in the IC is the main factor that sets the maximum current that can

be delivered by the device in a safe operating condition. Selecting the appropriate package and heatsinking con-

figuration for the application is required to maintain the IC within the allowed operating temperature range for

the application. Figures 26, 27 and 28 show the Junction-to-Ambient Thermal Resistance values for the

PowerSO36, PowerDIP24 and SO24 packages.

For instance, using a PowerSO package with copper slug soldered on a 1.5mm copper thickness FR4 board

mounting methods for this package. Using a multi-layer board with vias to a ground plane, thermal impedance

can be reduced down to 15°C/W.

Figure 26. PowerSO36 Junction-Ambient thermal resistance versus on-board copper area.

No PWM

f

Test Condition s:

Supply Voltage = 24 V

0

0.25

0.5 0.75

1

1.25

1.5

0

2

4

6

8

10

P

I

OUT

[A]

13

18

23

28

33

38

43

12

3

4

56

7

8

9

10

1 1

1 2

13

W ithout G round La yer

W ith Gr ound La yer

W ith Gr ound La yer + 16 via

Ho le s

sq . c m

ºC / W

On-Board Copper Area