EVAL6208N Datasheet, PDF (20/27 Pages) STMicroelectronics – DMOS DRIVER FOR BIPOLAR STEPPER MOTOR

L6208
Output Current Capability and IC Power Dissipation
In Fig. 24, 25, 26 and 27 are shown the approximate relation between the output current and the IC power dis-
sipation using PWM current control driving a two-phase stepper motor, for different driving sequences:
– HALF STEP mode (Fig. 24) in which alternately one phase / two phases are energized.
– NORMAL DRIVE (FULL-STEP TWO PHASE ON) mode (Fig. 25) in which two phases are energized
during each step.
– WAVE DRIVE (FULL-STEP ONE PHASE ON) mode (Fig. 26) in which only one phase is energized at
each step.
– MICROSTEPPING mode (Fig. 27), in which the current follows a sine-wave profile, provided through
the V_ref pins.
For a given output current and driving sequence 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 guar-
antee a safe operating junction temperature (125°C maximum).
Figure 24. IC Power Dissipation versus Output Current in HALF STEP Mode.
HALF STEP
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 = 30 kHz (slow decay)
Figure 25. IC Power Dissipation versus Output Current in NORMAL Mode (full step two phase on).
NORM AL DRIVE
10
I_A
I _OUT
8
6
P_D [W ]
4
I_B
I _OUT
2
0
0 0.5 1 1.5 2 2.5 3
I _OUT [A ]
Test Conditions:
Supply Volt age =24 V
No PWM
fSW = 30 kHz (slow decay)
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