A3967SLB Allegro Microsystems Inc, A3967SLB Datasheet - Page 5

• Manufacturer Part Number: A3967SLB
• Description: IC MOTOR DRIVER PWM FULL 24SOIC
• Manufacturer: Allegro Microsystems Inc

Specifications of A3967SLB

• Applications: Stepper Motor Driver
• Number Of Outputs: 1
• Current - Output: ±750mA
• Voltage - Load: 4.75 V ~ 30 V
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• Operating Current: 65mA
• Operating Temperature Classification: Commercial
• Package Type: SOIC W
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

A3967
Device Operation. The A3967 is a complete microstep-
ping motor driver with built in translator for easy operation
with minimal control lines. It is designed to operate bipolar
stepper motors in full-, half-, quarter- and eighth-step
modes. The current in each of the two output full bridges
is regulated with fi xed off time pulse-width modulated
(PWM) control circuitry. The full-bridge current at each
step is set by the value of an external current sense resis-
tor (R
voltage controlled by the output of the translator.
phase current polarity to initial home state (see fi gures for
home-state conditions), and sets the current regulator for
both phases to mixed-decay mode. When a step command
signal occurs on the STEP input the translator automati-
cally sequences the DACs to the next level (see table 2 for
the current level sequence and current polarity). The mic-
rostep resolution is set by inputs MS
table 1. If the new DAC output level is lower than the pre-
vious level the decay mode for that full bridge will be set
by the PFD input (fast, slow or mixed decay). If the new
DAC level is higher or equal to the previous level then the
decay mode for that Full bridge will be slow decay. This
automatic current-decay selection will improve microstep-
ping performance by reducing the distortion of the current
waveform due to the motor BEMF.
Reset Input (RESET). The RESET input (active low)
sets the translator to a predefi ned home state (see fi gures
for home state conditions) and turns off all of the outputs.
STEP inputs are ignored until the RESET input goes high.
Step Input (STEP). A low-to-high transition on the
STEP input sequences the translator and advances the
motor one increment. The translator controls the input to
the DACs and the direction of current fl ow in each wind-
ing. The size of the increment is determined by the state of
inputs MS
At power up, or reset, the translator sets the DACs and
S
), a reference voltage (V
1
and MS
2
(see table 1).
REF
), and the DACs output
1
and MS
2
Functional Description
as shown in
Microstepping Driver with Translator
Microstep Select (MS
MS1 and MS
table 1. Changes to these inputs do not take effect until the
STEP command (see fi gure).
Direction Input (DIR). The state of the DIRECTION
input will determine the direction of rotation of the motor.
Internal PWM Current Control. Each full bridge is
controlled by a fi xed off-time PWM current-control cir-
cuit that limits the load current to a desired value (I
Initially, a diagonal pair of source and sink outputs are
enabled and current fl ows through the motor winding and
R
equals the DAC output voltage, the current-sense compara-
tor resets the PWM latch, which turns off the source driver
(slow-decay mode) or the sink and source drivers (fast- or
mixed-decay modes).
selection of R
transconductance function approximated by:
rent-sense comparator in precise steps (see table 2 for %
I
Fixed Off-Time. The internal PWM current-control
circuitry uses a one shot to control the time the driver(s)
remain(s) off. The one shot off-time, t
the selection of an external resistor (R
connected from the RC timing terminal to ground. The off
time, over a range of values of C
R
TRIP
T
S
. When the voltage across the current-sense resistor
= 12 kΩ to 100 kΩ is approximated by:
The maximum value of current limiting is set by the
The DAC output reduces the V
max at each step).
I
TRIP
2
= (% I
S
select the microstepping format per
and the voltage at the V
I
TRIP
TRIP
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
max = V
t
max/100) x I
off
1
and MS
= R
T
C
REF
T
T
= 470 pF to 1500 pF and
REF
2
/8R
). Input terminals
TRIP
off
T
output to the cur-
) and capacitor (C
REF
S
, is determined by
max
input with a
TRIP
).
5
T
)