3967 Datasheet PDF - Allegro MicroSystems
| Part Number | 3967 | |
| Description | MICROSTEPPING DRIVER WITH TRANSLATOR | |
| Manufacturers | Allegro MicroSystems | |
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3967
MICROSTEPPING DRIVER WITH TRANSLATOR
REF 1
RC2 2
÷8
PWM
TIMER
24 PFD
23 RC1
SLEEP 3
22 RESET
OUT2B 4
LOAD
SUPPLY2
5 VBB2
GND 6
21 OUT1B
LOAD
VBB1 20 SUPPLY1
19 GND
GND 7
18 GND
SENSE2 8
17 SENSE1
OUT2A 9
16 OUT1A
STEP 10
DIR 11
MS1 12
TRANSLATOR
15 ENABLE
& CONTROL
LOGIC
VCC
14
LOGIC
SUPPLY
13 MS2
Dwg. PP-075-2
ABSOLUTE MAXIMUM RATINGS
at TA = +25°C
Load Supply Voltage, VBB ............. 30 V
Output Current, IOUT
Continuous ..................... ±750 mA*
Peak ................................. ±850 mA
Logic Supply Voltage, VCC ........... 7.0 V
Logic Input Voltage Range, VIN
(tw >30 ns) ............. -0.3 V to +7.0 V
(tw <30 ns) ................ -1 V to +7.0 V
Sense Voltage, VSENSE ............... 0.68 V
Reference Voltage, VREF ................ VCC
Package Power Dissipation,
PD ................................. See page 8
Operating Temperature Range,
TA ........................... -20°C to +85°C
Junction Temperature, TJ ......... +150°C
Storage Temperature Range,
TS ......................... -55°C to +150°C
* Output current rating may be limited by
duty cycle, ambient temperature, and heat
sinking. Under any set of conditions, do not
exceed the specified current rating or a
junction temperature of 150°C.
The A3967SLB is a complete microstepping motor driver with
built-in translator. It is designed to operate bipolar stepper motors in
full-, half-, quarter-, and eighth-step modes, with output drive capabil-
ity of 30 V and ±750 mA. The A3967SLB includes a fixed off-time
current regulator that has the ability to operate in slow, fast, or mixed
current-decay modes. This current-decay control scheme results in
reduced audible motor noise, increased step accuracy, and reduced
power dissipation.
The translator is the key to the easy implementation of the
A3967SLB. By simply inputting one pulse on the STEP input the
motor will take one step (full, half, quarter, or eighth depending on two
logic inputs). There are no phase-sequence tables, high-frequency
control lines, or complex interfaces to program. The A3967SLB
interface is an ideal fit for applications where a complex µP is unavail-
able or over-burdened.
Internal circuit protection includes thermal shutdown with hyster-
esis, under-voltage lockout (UVLO) and crossover-current protection.
Special power-up sequencing is not required.
The A3967SLB is supplied in a 24-pin SOIC with four internally
fused pins for enhanced thermal dissipation. The pins are at ground
potential and need no insulation. A lead (Pb) free (100% matte tin
leadframe) version is also available.
FEATURES
■ ±750 mA, 30 V Output Rating
■ Satlington® Sink Drivers
■ Automatic Current-Decay Mode Detection/Selection
■ 3.0 V to 5.5 V Logic Supply Voltage Range
■ Mixed, Fast, and Slow Current-Decay Modes
■ Internal UVLO and Thermal Shutdown Circuitry
■ Crossover-Current Protection
Part Number Pb-free* Package
Packing
A3967SLB-T
Yes 24-Lead SOIC 31 per tube
A3967SLBTR-T Yes 24-Lead SOIC 1000 per reel
*Pb-based variants are being phased out of the product line. The variants cited in this
footnote are in production but have been determined to be LAST TIME BUY. This
classification indicates that sale of this device is currently restricted to existing
customer applications. The variants should not be purchased for new design
applications because obsolescence in the near future is probable. Samples are no
longer available. Status change: October 31, 2006. Deadline for receipt fo LAST TIME
BUY orders: April 27, 2007. These variants include: A3967SLB and A3967SLBTR.
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3967
MICROSTEPPING DRIVER
WITH TRANSLATOR
Functional Description
Device Operation. The A3967 is a complete
microstepping 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 H-bridges is regulated with fixed off time pulse-
width modulated (PWM) control circuitry. The H-bridge
current at each step is set by the value of an external
current sense resistor (RS), a reference voltage (VREF), and
the DAC’s output voltage controlled by the output of the
translator.
At power up, or reset, the translator sets the DACs and
phase current polarity to initial home state (see figures 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
microstep resolution is set by inputs MS1 and MS2 as
shown in table 1. If the new DAC output level is lower
than the previous level the decay mode for that H-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 H-bridge will be slow
decay. This automatic current-decay selection will
improve microstepping 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 predefined home state (see figures
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 flow in each wind-
ing. The size of the increment is determined by the state
of inputs MS1 and MS2 (see table 1).
Microstep Select (MS1 and MS2). Input terminals
MS1 and MS2 select the microstepping format per
table 1. Changes to these inputs do not take effect until
the STEP command (see figure).
Direction Input (DIR). The state of the DIRECTION
input will determine the direction of rotation of the motor.
Internal PWM Current Control. Each H-bridge is
controlled by a fixed off time PWM current-control circuit
that limits the load current to a desired value (ITRIP).
Initially, a diagonal pair of source and sink outputs are
enabled and current flows through the motor winding and
RS. When the voltage across the current-sense resistor
equals the DAC output voltage, the current-sense com-
parator resets the PWM latch, which turns off the source
driver (slow-decay mode) or the sink and source drivers
(fast- or mixed-decay modes).
The maximum value of current limiting is set by the
selection of RS and the voltage at the VREF input with a
transconductance function approximated by:
ITRIPmax = VREF/8RS
The DAC output reduces the VREF output to the
current-sense comparator in precise steps (see table 2 for
% ITRIPmax at each step).
ITRIP = (% ITRIPmax/100) x ITRIPmax
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, toff, is determined by
the selection of an external resistor (RT) and capacitor
(CT) connected from the RC timing terminal to ground.
The off time, over a range of values of CT = 470 pF to
1500 pF and RT = 12 kΩ to 100 kΩ is approximated by:
toff = RTCT
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| Information | Total 16 Pages | |
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