Datasheet A4975 (Allegro) - 10

A4975 Full-Bridge PWM Microstepping Motor Driver Thermal Considerations.
Thermal protection circuitry drive applications (see figures 4 and 5). When the load current turns off all output transistors when the junction temperature is increasing, the slow current decay mode is used to limit the reaches approximately +165°C. This is intended only to protect switching losses in the driver and iron losses in the motor. This the device from failures due to excessive junction temperatures also improves the maximum rate at which the load current can and should not imply that output short circuits are permitted. The increase (as compared to fast decay) due to the slow rate of decay output transistors are re-enabled when the junction temperature during t cools to approximately +150°C. OFF. When the load current is decreasing, the mixed cur- rent decay mode is used to regulate the load current to the desired
Stepper Motor Applications.
The A4975 is used to level. This prevents tailing of the current profile caused by the optimize performance in microstepping/sinusoidal stepper motor back-EMF voltage of the stepper motor (see figure 3A). V VBB
BRIDGE A
BB
BRIDGE A BRIDGE B
V D VPFD PFD
1 16 1
+ 1B
9 8
D 47 μ µF
9 8
D 2B F 2B V REF REF
2 15 10 7 10 7
PHASE PHASE B D B D 0A
3 14 11 6
+5 V
6
+5 V Ω Ω ΩΩ
4 13
0.5 0.5
12 5 5
470 pF 30 k LOGIC LOGIC LOGIC LOGIC Ω Ω ΩΩ
5 12 13 4 4
30 k 30 k 0.50.5 470 pF 470 pF +5 V
6 11 11
D0B
14 3
0B
3
PHASE
7 10 15 2 2
V V REF A 47 REF 47 μ µ F + D
8 9
D V 2A D BB 2A 1A
16 1 1
V V PFD 1A PFD Dwg. EP-047-3 Dwg. EP-047-3
Figure 4 — Typical Application
MIXED DECAY SLOW DECAY MIXED DECAY SLOW DECAY Dwg. WK-004-3
Figure 5 — Microstepping/Sinusoidal Drive Current
Allegro MicroSystems, LLC 10 955 Perimeter Road Manchester, NH 03103-3353 U.S.A. www.allegromicro.com