A3964SB Allegro Microsystems Inc, A3964SB Datasheet - Page 6

• Manufacturer Part Number: A3964SB
• Description: IC MOTOR DRIVER PWM DUAL 24-DIP
• Manufacturer: Allegro Microsystems Inc

Specifications of A3964SB

• Applications: Stepper Motor Driver
• Number Of Outputs: 1
• Current - Output: ±800mA
• Voltage - Load: 5 V ~ 30 V
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 24-DIP (0.300", 7.62mm)
• Operating Current: 85mA
• Operating Temperature Classification: Commercial
• Package Type: PDIP
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (max): 5.25V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

where t
load, V
specified in the electrical characteristics table. When the
motor is rotating, the back EMF generated will influence
the above relationship. For brush dc motor applications,
the current regulation is improved. For stepper motor
applications when the motor is rotating, the effect is
dependent on the polarity and magnitude of the motor’s
back EMF.
worst case internal PWM load current regulation in the
system:
PWM of the Phase and Enable Inputs. The PHASE and
ENABLE inputs can be pulse width modulated to regulate
load current. Typical propagation delays from the PHASE
and ENABLE inputs to transitions of the power outputs are
specified in the electrical characteristics table. If the
internal PWM current control is used, the comparator
blanking function is active during phase and enable
transitions. This eliminates false tripping of the over-
current comparator caused by switching transients
(see “RC Blanking” above).
Enable PWM. Toggling the ENABLE input turns ON and
OFF the selected source and sink drivers. The corre-
sponding pair of flyback and ground clamp diodes conduct
after the drivers are disabled, resulting in fast current
decay. When the device is enabled the internal current
control circuitry will be active and can be used to limit the
load current in a slow current-decay mode.
Phase PWM. Toggling the PHASE terminal selects which
sink/source pair is enabled, producing a load current that
varies with the duty cycle and remains continuous at all
times. This can have added benefits in bidirectional brush
3964
DUAL FULL-BRIDGE
PWM MOTOR DRIVER
Set V
PWM current control operating in slow decay mode, use
an oscilloscope to measure the time the output is low
(sink ON) for the output that is chopping. This is the
typical minimum on time (t
C
t
cal characteristics table. When the new value of C
been set, the value of R
value for t
of C
case load-current regulation then can be measured in
the system under operating conditions.
ON(min)
T
The following procedure can be used to evaluate the
then should be increased until the measured value of
T
BB
) is equal to the nominal design value. The worst-
OFF
REF(IN)
is equal to t
is the motor supply voltage and t
= R
OFF
to 0 volts. With the load connected and the
T
C
= R
T
, R
T
C
ON(min)
LOAD
T
(with the artificially increased value
T
is the series resistance of the
max as specified in the electri-
should be decreased so the
ON(min)
typ) for the device. The
ON(min)
max is
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
T
has
dc servo motor applications as the transfer function
between the duty cycle on the PHASE input and the
average voltage applied to the motor is more linear than in
the case of ENABLE PWM control (which produces a
discontinuous current at low current levels).
Miscellaneous Information. An internally generated
dead time prevents crossover currents that can occur
when switching phase.
should the junction temperature reach +165 C (typical).
This is intended only to protect the device from failures
due to excessive junction temperatures and should not
imply that output short circuits are permitted. The hyster-
esis of the thermal shutdown circuit is approximately 15 C.
Current Sensing. The actual peak load current (I
be above the calculated value of I
turn off of the drivers. The amount of overshoot can be
approximated by:
where V
EMF voltage of the load, R
tance and inductance of the load respectively, and t
specified in the electrical characteristics table.
ground trace IR drops, each current-sensing resistor
should have a separate return to the ground terminal of the
device. For low-value sense resistors, the IR drops in the
PCB can be significant and should be taken into account.
The use of sockets should be avoided as their contact
resistance can cause variations in the effective value of
R
tioned effects but can result in excessive heating and
power loss in the sense resistor. The selected value of R
should not cause the absolute maximum voltage rating of
1.0 V, for the SENSE terminal, to be exceeded. The
recommended value of R
S
.
Thermal protection circuitry turns OFF all drivers
To minimize current sensing inaccuracies caused by
Generally, larger values of R
I
BB
OS
is the motor supply voltage, V
R
(V
S
APPLICATION NOTES
BB
– [(I
I
TRIP
0.5
TRIP
max
S
LOAD
is in the range of:
• R
L
LOAD
LOAD
and L
50%
S
TRIP
reduce the aforemen-
) + V
LOAD
due to delays in the
BEMF
BEMF
are the resis-
]) • t
is the back-
PWM
PEAK
PWM
) will
is
S