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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

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.

Figure 25. IC Power Dissipation versus Output Current in NORMAL Mode (full step two phase on).

No PWM

f

SW

= 30 kHz (slow decay)

Test Conditions:

Supply Voltage = 24V

HALF STEP

0

0.25 0.5 0.75 1

1.25 1.5

0

2

4

6

8

10

No PWM

Test Conditions:

Supply Volt age =24 V

NORM AL DRIVE

0

0.25 0.5 0.75

1

1.25 1.5

0

2

4

6

8

10