3951
FULL-BRIDGE
PWM MOTOR DRIVER
For both cases, care must be taken to ensure that the
maximum current ratings of the device are not exceeded.
The load current will limit at a value
ILOAD = VREF/(10•RS).
CAUTION: When the direction of the motor is changed
abruptly, the kinetic energy stored in the motor and load
inertia will be converted into current that charges the VBB
supply bulk capacitance (power supply output and
decoupling capacitance). Care must be taken to ensure
the capacitance is sufficient to absorb the energy without
exceeding the voltage rating of any devices connected to
the motor supply.
See also, the section on brake operation under
“Functional Description”, above.
Stepper Motor Applications
The A3951SB and A3951SW may be used for
bidrectional control of bipolar stepper motors with continu-
ous output currents to 2 A and peak start-up currents as
high as 3.5 A.
+5 V
PHASE
ENABLE
1
VBB
2
3
4
LOGIC
5
6 VCC
7
8
VBB
V
BB
16
47 µF
15
14
13
12
11
10
9
Dwg. EP-047-1
Typical DC Servo Motor Application
LOGIC
VCC
VBB
VBB
+5 V
+ 47 µF
ENABLE 1
PHASE1
0.5 Ω
V
REF2
VREF1
PHASE2
ENABLE 2
VBB
VCC
LOGIC
www.allegromicro.com
25 kΩ
820 pF
Typical Bipolar Stepper Motor Application
Dwg. EP-048-1
9