A3952SW ALLEGRO [Allegro MicroSystems], A3952SW Datasheet - Page 9

• Manufacturer Part Number: A3952SW
• Description: FULL-BRIDGE PWM MOTOR DRIVER
• Manufacturer: ALLEGRO [Allegro MicroSystems]

PCB Layout
(>47 F electrolytic and 0.1 F ceramic capacitors are
recommended) as close to the device as is physically
practical. To minimize the effect of system ground I•R
drops on the logic and reference input signals, the system
ground should have a low-resistance return to the load
supply voltage.
ations” above.
Fixed Off-Time Selection
crease, low-level load-current regulation improves, EMI is
reduced, the PWM frequency will decrease, and ripple
current will increase. The value of t
optimization of these parameters. For applications where
audible noise is a concern, typical values of t
to be in the range of 15 to 35 s.
Stepper Motor Applications
performance of the device in microstepping/sinusoidal
stepper motor drive applications. When the average load
current is increasing, slow-decay mode is used to limit the
switching losses in the device and iron losses in the motor.
3952
FULL-BRIDGE
PWM MOTOR DRIVER
The load supply terminal, V
See also “Current Sensing” and “Thermal Consider-
With increasing values of t
The MODE terminal can be used to optimize the
LOGIC
V
BB
off
V
CC
BB
, switching losses de-
, should be decoupled
off
can be chosen for
Typical Bipolar Stepper Motor Application
off
are chosen
V
BB
PHASE
MODE
ENABLE
V
REF1
1
1
1
ENABLE
This also improves the maximum rate at which the load
current can increase (as compared to fast decay) due to
the slow rate of decay during t
current is decreasing, fast-decay mode is used to regulate
the load current to the desired level. This prevents tailing
of the current profile caused by the back-EMF voltage of
the stepper motor.
current to the load, slow-decay mode PWM is used
typically to limit the switching losses in the device and iron
losses in the motor.
DC Motor Applications
be controlled by PWM of the PHASE or ENABLE inputs, or
by varying the REF input voltage (V
(microprocessor controlled), PWM of the PHASE or
ENABLE input is used typically thus avoiding the need to
generate a variable analog voltage reference. In this case,
a dc voltage on the REF input is used typically to limit the
maximum load current.
ing at low or zero speed, PWM of the PHASE input is
selected typically. This simplifies the servo-control loop
because the transfer function between the duty cycle on
the PHASE input and the average voltage applied to the
PHASE
MODE
25 k
V
REF2
In stepper motor applications applying a constant
In closed-loop systems, the speed of a dc motor can
In dc servo applications that require accurate position-
+
2
2
2
47 F
0.5
820 pF
+5 V
V
CC
V
BB
off
. When the average load
LOGIC
REF
). In digital systems
Dwg. EP-048