ALLEGRO 3967 DATA SHEET

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REF

RC

SLEEP

OUT

LOAD

SUPPLY

GND

GND

SENSE

OUT

STEP

DIR

MS

1

÷8

2

2

3

4

2B

5

BB2

V

2

6

7

2

8

9

2A

10

11

12

1

TIMER

TRANSLATOR

& CONTROL

LOGIC

PWM

ABSOLUTE MAXIMUM RATINGS

at TA = +25°C

Load Supply Voltage, VBB............. 30 V

Output Current, I

Continuous ..................... ±750 mA

Peak................................. ±850 mA

Logic Supply Voltage, VCC........... 7.0 V

Logic Input Voltage Range, V

(tw >30 ns)............. -0.3 V to +7.0 V

(tw <30 ns)................ -1 V to +7.0 V

Sense Voltage, V
Reference Voltage, V
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.

OUT

............... 0.68 V

SENSE

REF

PFD

24

23

RC

1

22

RESET

21

OUT

1B

LOAD

20

V

BB1

SUPPLY

19

GND

18

GND

SENSE

1

17

OUT

16

1A

ENABLE

15

LOGIC

V

CC

14

SUPPLY

MS

2

13

Dwg. PP-075-2

IN

................ V

1

CC

Data Sheet

26184.24C

3967

MICROSTEPPING DRIVER

WITH TRANSLATOR

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 capabil­ity 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 unavail­able or over-burdened.

Internal circuit protection includes thermal shutdown with hyster­esis, under-voltage lockout (UVLO) and crossover-current protection.
Special power-up sequencing is not required.

The A3967SLB is supplied in a 24-lead SOIC with copper batwing
tabs. The tabs are at ground potential and need no insulation. A lead-

*

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

Always order by complete part number:

Part Number Package

A3967SLB 24-lead batwing SOIC

A3967SLB-T 24-lead batwing SOIC; Lead-free

3967

MICROSTEPPING DRIVER
WITH TRANSLATOR

FUNCTIONAL BLOCK DIAGRAM

LOGIC

SUPPLY

REF.

SUPPLY

STEP

RESET

SLEEP

ENABLE

V

PF

V

CC

REF

RC

DIR

MS

MS

1

1

2

14

1

23

10

11

22

12

13

3

15

24

PFD

2

RC

LOAD

UVLO

AND

FAULT

DETECT

V

BB1

20

16

21

17

5

9

4

8

OUT

OUT

SENSE

V

BB2

OUT

OUT

SENSE

1A

1B

1

2A

2B

2

3

3

DAC

DAC

+-

PWM LATCH
BLANKING
MIXED DECAY

PWM TIMER

PWM TIMER

PWM LATCH
BLANKING
MIXED DECAY

+-

SENSE

CONTROL LOGIC

÷8

TRANSLATOR

2

SUPPLY

76

1918

Dwg. FP-050-3A

Table 1. Microstep Resolution Truth Table

MS

1

MS

2

Resolution

L L Full step (2 phase)
H L Half step
L H Quarter step
H H Eighth step

2

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
Copyright © 2002, 2003 Allegro MicroSystems, Inc.

3967

MICROSTEPPING DRIVER

WITH TRANSLAT OR

ELECTRICAL CHARACTERISTICS at T

= +25°C, V

A

= 30 V, VCC = 3.0 V to 5.5V (unless otherwise

BB

noted)

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Output Drivers

Load Supply Voltage Range V

BB

Operating 4.75 – 30 V

During sleep mode 0 – 30 V

Output Leakage Current I

Output Saturation Voltage V

CE(sat)

Clamp Diode Forward Voltage V

CEX

V

= V

OUT

V

OUT

Source driver, I

Source driver, I

Sink driver, I

Sink driver, I

IF = 750 mA – 1.4 1.6 V

F

BB

= 0 V – <-1.0 -20 µA

= -750 mA

OUT

= -400 mA

OUT

= 750 mA – 0.65 1.3 V

OUT

= 400 mA – 0.21 0.5 V

OUT

– <1.0 20 µA

– 1.9 2.1 V

– 1.7 2.0 V

Motor Supply Current I

Control Logic

Logic Supply Voltage Range V

Logic Input Voltage V

V

Logic Input Current I

I

Maximum STEP Frequency f

Blank Time t

BLANK

Fixed Off Time t

BB

CC

IN(1)

IN(0)

IN(1)

IN(0)

STEP

off

IF = 400 mA – 1.1 1.4 V

Outputs enabled – – 5.0 mA

RESET high

– – 200 µA

Sleep mode – – 20 µA

Operating 3.0 5.0 5.5 V

VIN = 0.7V

VIN = 0.3V

CC

CC

0.7V

CC

– – 0.3V

-20 <1.0 20 µA

-20 <1.0 20 µA

––V

CC

V

500* – – kHz

R

= 56 kΩ, C

t

R

= 56 kΩ, Ct = 680 pF 30 38 46 µs

t

= 680 pF 700 950 1200 ns

t

continued next page …

www.allegromicro.com

3

3967

MICROSTEPPPING DRIVER
WITH TRANSLATOR

ELECTRICAL CHARACTERISTICS at TA = +25°C, VBB = 30 V, VCC = 3.0 V to 5.5V (unless otherwise
noted)

Limits

Characteristic Symbol Test Conditions

Control Logic (cont’d)

Mixed Decay Trip Point PFDH – 0.6V

PFDL – 0.21V

Ref. Input Voltage Range V

Reference Input Impedance Z

Gain (G

(note 3)

Thermal Shutdown Temp. T

Thermal Shutdown Hysteresis ∆T

UVLO Enable Threshold V

UVLO Hysteresis ∆V

Logic Supply Current I

) Error

m

REF

REF

E

UVLO

UVLO

CC

Operating 1.0 – V

V

= 2 V, Phase Current = 38.37% † – – ±10 %

G

J

J

REF

V

= 2 V, Phase Current = 70.71% † – – ±5.0 %

REF

V

= 2 V, Phase Current = 100.00% † – – ±5.0 %

REF

Increasing V

Outputs enabled – 50 65 mA

Outputs off – – 9.0 mA

Sleep mode – – 20 µA

CC

* Operation at a step frequency greater than the specifi ed minimum value is possible but not warranteed.
† 8 microstep/step operation.
NOTES: 1. Typical Data is for design information only.

2. Negative current is defi ned as coming out of (sourcing) the specifi ed device terminal.

3. EG = ([V

REF

/8] – V

SENSE

)/(V

REF

/8)

Min. Typ. Max. Units

CC

CC

120 160 200 kΩ

– 165 – °C

–15–°C

2.45 2.7 2.95 V

0.05 0.10 – V

–V

–V

CC

V

4

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 [phone]

Functional Description

3967

MICROSTEPPING DRIVER

WITH TRANSLAT OR

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-, quarter­and eighth-step modes. The current in each of the two
output H-bridges is regulated with fixed off time pulse­width modulated (PWM) control circuitry. The H-bridge
current at each step is set by the value of an external
current sense resistor (R

), a reference voltage (V

S

REF

), 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 automati­cally 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 MS

and MS2 as

1

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 wind­ing. The size of the increment is determined by the state
of inputs MS

and MS2 (see table 1).

1

Microstep Select (MS1 and MS

MS1 and MS

select the microstepping format per

2

). Input terminals

2

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 (I

TRIP

).
Initially, a diagonal pair of source and sink outputs are
enabled and current flows through the motor winding and

. When the voltage across the current-sense resistor

R

S

equals the DAC output voltage, the current-sense com­parator 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 R

and the voltage at the V

S

input with a

REF

transconductance function approximated by:

max = V

I

TRIP

The DAC output reduces the V

REF

/8R

REF

S

output to the
current-sense comparator in precise steps (see table 2 for
% I

max at each step).

TRIP

= (% I

I

TRIP

max/100) x I

TRIP

TRIP

max

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.

(C

T

The off time, over a range of values of C
1500 pF and R

= 12 kΩ to 100 kΩ is approximated by:

T

= RTC

t

off

, is determined by

off

) and capacitor

T

= 470 pF to

T

T

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5