EVAL6208N Datasheet, PDF (21/27 Pages) STMicroelectronics – DMOS DRIVER FOR BIPOLAR STEPPER MOTOR

L6208
Figure 26. IC Power Dissipation versus Output Current in WAVE Mode (full step one phase on).
WAVE DRIVE
10
I_A
I _OUT
8
I_B
6
P_D [W]
4
2
0
0 0.5 1 1.5 2 2.5 3
I _OUT [A]
I _OUT
Test Conditions:
Supply Voltage = 24V
No PWM
fSW = 3 0 kHz (slow decay)
Figure 27. IC Power Dissipation versus Output Current in MICROSTEPPING Mode.
MICROSTEPPING
I_A
I_OUT
10
8
6
P_D [W]
4
I _OUT
I_B
2
0
0 0.5 1 1.5 2 2.5 3
I _OUT [A]
Test Conditions:
Supply Voltage = 24V
fSW = 30 kHz (slow decay)
fSW = 50 kHz (slow decay)
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. Therefore, it has to be taken into account very carefully.
Besides the available space on the PCB, the right package should be chosen considering the power dissipation.
Heat sinking can be achieved using copper on the PCB with proper area and thickness. Figures 28, 29 and 30
show the Junction-to-Ambient Thermal Resistance values for the PowerSO36, PowerDIP24 and SO24 packag-
es.
For instance, using a PowerSO package with copper slug soldered on a 1.5mm copper thickness FR4 board
with 6cm² dissipating footprint (copper thickness of 35µm), the R_th(j-amb) is about 35°C/W. Fig. 31 shows mount-
ing 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.
21/27