Allegro A3957SLB, A3957SA Datasheet

3957

FULL-BRIDGE PWM

MICROSTEPPING MOTOR DRIVER

Data Sheet

29319.44†

A3957SLB

NO

1

CONNECT

CONNECT

GROUND

GROUND

LOGIC

SUPPLY

PHASE

CONNECT

NC NC

2

PFD

3

REF

NO

NC

4

RC

5

6

LOGIC

7

8

D

3

9

V

CC

10 15

11

D

2

NO

12

NC

V

BB

ABSOLUTE MAXIMUM RATINGS

Load Supply Voltage, VBB. . . . . . . . . 50 V

Output Current, I

(Continuous) . . . . . . . . . . . . . ±1.5 A*

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

Logic/Reference Input Voltage Range,

VIN. . . . . . . . . . -0.3 V to VCC + 0.3 V

Sense Voltage, VS. . . . . . . . . . . . . . . 1.0 V

Package Power Dissipation (TA = 25°C), P

A3957SA . . . . . . . . . . . . . . . . 2.08 W†

A3957SLB. . . . . . . . . . . . . . . 2.23 W†

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.

† Per SEMI G42-88 Specification, Thermal Test

Board Standardization for Measuring Junction­to-Ambient Thermal Resistance of Semiconductor
Packages..

OUT

NO

24

CONNECT
LOAD

23

SUPPLY

22

OUT

B

NO

21

NC

CONNECT

20

D

0

GROUND

19

GROUND

18

17

SENSE
NO

16

NC

CONNECT
OUT

A

NO

NC

14

CONNECT

13

D

1

Dwg. PP-056-4

D

The A3957SA and A3957SLB are designed for driving one winding of a

bipolar stepper motor in a microstepping mode. The outputs are rated for
continuous output currents to ±1.5 A and operating voltages to 50 V. Internal
pulse-width modulated (PWM) current control combined with an internal
four-bit nonlinear digital-to-analog converter allows the motor current to be
controlled in full-, half-, quarter-, eighth-, or sixteenth-step (microstepping)
modes. Nonlinear increments minimize the number of control lines necessary
for microstepping. Microstepping provides for increased step resolution, and
reduces torque variations and resonance problems at low speed.

Internal circuitry determines whether the PWM current-control circuitry
operates in a slow (recirculating) current-decay mode, fast (regenerative)
current-decay mode, or in a mixed current-decay mode in which the off time
is divided into a period of fast current decay with the remainder of the fixed
off time spent in slow current decay. The combination of user-selectable
current-sensing resistor and reference voltage, digitally selected output
current ratio; and slow, fast, or mixed current-decay modes provides users
with a broad, variable range of motor control.

Internal circuit protection includes thermal shutdown with hysteresis,
transient-suppression diodes, and crossover current protection. Special
power-up sequencing is not required.

The A3957S— is supplied in a choice of two power packages; a 16-pin
dual-in-line plastic package (suffix ‘A’), and a 24-lead plastic SOIC with
copper heat-sink tabs (suffix ‘LB’). The power tab is at ground potential and
needs no electrical isolation.

FEATURES

■ ±1.5 A Continuous Output Current

■ 50 V Output Voltage Rating

■ Internal PWM Current Control

■ 4-Bit Non-Linear DAC for 16-Bit Microstepping

■ Satlington™ Sink Drivers

■ Fast, Mixed Fast/Slow, and Slow Current-Decay Modes

■ Internal Transient-Suppression Diodes

■ Internal Thermal-Shutdown Circuitry

■ Crossover-Current and UVLO Protection

Always order by complete part number:

Part Number Package R

θJA

A3957SA 16-pin DIP 60°C/W 38°C/W —

A3957SLB 24-lead batwing SOIC 56°C/W — 6°C/W

R

θJC

R

θJT

3957

13

31120

2

171819

9

10

5

6

23

7

15

22

8

FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER

FUNCTIONAL BLOCK DIAGRAM (A3957SLB shown)

PHASE

GROUND

PFD

UVLO
& TSD

MIXED-DECAY

COMPARATOR

+
–

BLANKING

V

CC

R

T

PWM LATCH

R

Q

S

RC

C

T

LOGIC

SUPPLY

V

CC

BLANKING

GATE

+ –

V

TH

A

OUT

V

BB

CURRENT-SENSE

COMPARATOR

÷3

3

D

REF

+
–

D/A

2

D

B

OUT

1

D

LOAD

SUPPLY

0

D

SENSE

DISABLE

R

S

Dwg. FP-042-1

GROUND

D

OUT

LOAD

SUPPLY

PFD

REF

RC

GROUND

A3957SA

NO

1

2

0

3

B

4

5

6

7

8

LOGIC

V

BB

NC

V

16

CONNECT
SENSE

15

14

OUT

A

D

13

1

12

D

2

11

PHASE
LOGIC

10

CC

SUPPLY

9

D

Dwg. PP-056-3

3

For the ‘A’ package, pins 1 and 8 must

be externally connected together.

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

W
Copyright © 1998 Allegro MicroSystems, Inc.

3957

FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER

Table 1 — PHASE Truth Table

PHASE OUT

HH L

LL H

A

OUT

B

Table 2 — PFD Truth Table

V

PFD

≥3.5 V Slow Current-Decay Mode

1.2 V to 2.9 V Mixed Current-Decay Mode

≤0.8 V Fast Current-Decay Mode

Description

Table 3 — DAC Truth Table

DAC Data Current

D

D

D

3

2

HHHH 100 3.00

H H H L 95.7 3.13

H H L H 91.3 3.29

H H L L 87.0 3.45

H L H H 82.6 3.64

H L H L 78.3 3.83

H L L H 73.9 4.07

H L L L 69.6 4.31

L H H H 60.9 4.93

L H H L 52.2 5.74

L H L H 43.5 6.90

L H L L 34.8 8.62

L L H H 26.1 11.49

L L H L 17.4 17.24

D

1

0

Ratio, % V

REF/VS

L L L X All Outputs Disabled

where VS = I

• RS. See Applications section.

TRIP

3957

FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER

ELECTRICAL CHARACTERISTICS at TA = 25˚C, VBB = 5 V to 50 V, VCC = 4.5 V to 5.5 V (unless
otherwise noted.)

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Power Outputs

Load Supply Voltage Range V

Output Leakage Current I

Output Saturation Voltage V
(Forward or Reverse Mode)

CE(SAT)

Sense Current Offset I

BB

CEX

SO

Operating, I

V

= V

OUT

V

= 0 V — <-1.0 -50 µA

OUT

= ±1.5 A, L = 3 mH V

OUT

BB

CC

—50 V

— <1.0 50 µA

VS = 1.0 V:

Source Driver, I
Source Driver, I
Sink Driver, I
Sink Driver, I

IS - I

OUT

, I

OUT

= 850 mA, 20 30 40 mA

= -0.85 A — 1.1 1.2 V

OUT

= -1.5 A — 1.4 1.5 V

OUT

= 0.85 A — 0.5 0.7 V

OUT

= 1.5 A — 1.2 1.5 V

OUT

VS = 0 V, VCC = 5 V

Clamp Diode Forward Volt. V
(Sink or Source)

Motor Supply Current I
(No Load)

BB(ON)

I

BB(OFF)

F

IF = 0.85 A — 1.2 1.4 V

IF = 1.5 A — 1.5 1.7 V

— 2.0 4.0 mA

D0 = D1 = D2 = D

= 0.8 V — 1.0 50 µA

3

Control Circuitry

Logic Supply Voltage Range V

Reference Voltage Range V

CC

REF

UVLO Enable Threshold V

Operating 4.5 5.0 5.5 V

Operating 0.5 — 2.5 V

= 0 → 5 V 3.35 3.70 4.05 V

CC

UVLO Hysteresis 0.25 0.40 0.55 V

Logic Supply Current I

I

CC(OFF)

Logic Input Voltage V

Logic Input Current I

CC(ON)

IN(1)

V

IN(0)

IN(1)

I

IN(0)

D0 = D1 = D2 = D3 = 0.8 V — 14 17 mA

V

= 2.0 V — <1.0 20 µA

IN

V

= 0.8 V — <-2.0 -200 µA

IN

—42 50mA

2.0 — — V

— — 0.8 V

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

Continued next page…

3957

FULL-BRIDGE PWM
MICROSTEPPING
MOTOR DRIVER

ELECTRICAL CHARACTERISTICS at TA = 25˚C, VBB = 5 V to 50 V, VCC = 4.5 V to 5.5 V (unless
otherwise noted.)

Limits

Characteristic Symbol Test Conditions Min. Typ. Max. Units

Control Circuitry (continued)

Mixed-Decay Comparator V
Trip Points

PFD

Slow Current-Decay Mode 3.5 — — V

Mixed Current-Decay Mode 1.2 — 2.9 V

Fast Current-Decay Mode — — 0.8 V

Mixed-Decay Comparator V

IO(PFD)

—0±20 mV

Input Offset Voltage

Mixed-Decay Comparator ∆V

IO(PFD)

5.0 25 55 mV

Hysteresis

Reference Input Current I

Reference Divider Ratio V

REF

REF/VS

Digital-to-Analog Converter — 1.0 V < V
Accuracy*

Current-Sense Comparator V

IO(S)

V

= 0 V to 2.5 V — — ±5.0 µA

REF

at trip, D0 = D1 = D2 = D3 = 2 V — 3.0 — —

≤ 2.5 V — — ±3.0 %

REF

0.5 V < V

V

= 0 V — ±16 — mV

REF

≤ 1.0 V — — ±4.0 %

REF

Input Offset Voltage*

Step Reference SRCR D0 = D1 = D2 = D3 = 0.8 V — 0 — %
Current Ratio

D1 = 2 V, D0 = D2 = D3 = 0.8 V — 17.4 — %
D0 = D1 = 2 V, D2 = D3 = 0.8 V — 26.1 — %
D2 = 2 V, D0 = D1 = D3 = 0.8 V — 34.8 — %
D0 = D2 = 2 V, D1 = D3 = 0.8 V — 43.5 — %
D1 = D2 = 2 V, D0 = D3 = 0.8 V — 52.2 — %
D0 = D1 = D2 = 2 V, D3 = 0.8 V — 60.9 — %
D3 = 2 V, D0 = D1 = D2 = 0.8 V — 69.6 — %
D0 = D3 = 2 V, D1 = D2 = 0.8 V — 73.9 — %
D1 = D3 = 2 V, D0 = D2 = 0.8 V — 78.3 — %
D0 = D1 = D3 = 2 V, D2 = 0.8 V — 82.6 — %
D2 = D3 = 2 V, D0 = D1 = 0.8 V — 87.0 — %
D0 = D2 = D3 = 2 V, D1 = 0.8 V — 91.3 — %
D1 = D2 = D3 = 2 V, D0 = 0.8 V — 95.7 — %
D0 = D1 = D2 = D3 = 2 V — 100 — %

Thermal Shutdown Temp. T

Thermal Shutdown Hyst. ∆T

* The total error for the V

function is the sum of the D/A error and the current-sense comparator input offset voltage.

REF/VS

J

J

— 165 — °C
—15—°C

Continued next page…