Data Sheet

28210.1B*

UNIPOLAR STEPPER-MOTOR

TRANSLATOR/PWM DRIVER

Combining low-power CMOS logic with high-current, high-voltage

power FET outputs, the SLA7052M translator/driver provides complete
control and drive for a two-phase unipolar stepper motor with internal
fixed off time, pulse-width modulation (PWM) control of the output
current in a power multi-chip module (PMCMTM).

The CMOS logic section provides the sequencing logic, direction,

full/half-step control, synchronous/asynchronous PWM operation, and
a "sleep" function. The minimum CLOCK input is an ideal fit for
applications where a complex µP is unavailable or overburdened. TTL
or LSTTL may require the use of appropriate pull-up resistors to ensure
a proper input-logic high. For PWM current control, the maximum
output current is determined by the user's selection of a reference
voltage and sensing resistor. The NMOS outputs are capable of sinking
up to 3 A and withstanding 46 V in the off state. Ground-clamp and
flyback diodes provide protection against inductive transients. Special
power-up sequencing is not required.

Full-step (2 phase) and half-step operation are externally selectable.

Two-phase drive energizes two adjacent phases in each detent position
(AB-BC-CD-DA). This sequence mode offers an improved torque-
speed product, greater detent torque, and is less susceptable to motor
resonance. Half-step excitation alternates between the one-phase and
two-phase modes (A-AB-B-BC-C-CD D-DA), providing an eight-step
sequence.

The SLA7052M is supplied in an 18-pin single in-line power-tab

package with leads formed for vertical mounting (suffix LF871) or
horizontal mounting (suffix LF872). The tab is at ground potential and
needs no insulation. For high-current or high-frequency applications,
external heat sinking may be required. This device is rated for continu-
ous operation between -20°C and +85°C.

EATURES

3 A Output Rating

Internal Sequencer for Full or Half-Step Operation

PWM Constant-Current Motor Drive

Cost-Effective, Multi-Chip Solution

100 V, Avalanche-Rated NMOS

Low

DS(on)

NMOS Outputs (150 m

typical)

Advanced, Improved Body Diodes

Half-Step and Full-Step Unipolar Drive

Inputs Compatible with 3.3 V or 5 V Control Signals

Sleep Mode

Internal Clamp Diodes

Always order by complete part number, e.g., SLA7052MLF871 .

BSOLUTE

AXIMUM

ATINGS

Driver Supply Voltage, V

................. 46 V

Load Supply Voltage, V

................... 46 V

Output Current, I

............................ 3.0 A*

Logic Supply Voltage, V

................ 7.0 V

Logic Input Voltage Range,

........................... -0.3 V to V

+ 0.3 V

Sense Voltage, V

........................ ±2.0 V

Reference Input Voltage Range,

REF ...................................

-0.3 V to V

+ 0.3 V

Package Power Dissipation,

........................................ See Graph

Junction Temperature, T

............. +150°C

Operating Temperature Range,

................................. -20°C to +85°C

Storage Temperature Range,

............................... -30°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
junction temperature.
Internal filtering provides protection against transients
during the first 1 µs of the current-sense pulse.

SLA7052M

Motor

Driver

Sanken Power Devices

from Allegro MicroSystems

SLA7052M

UNIPOLAR STEPPER-MOTOR

TRANSLATOR/PWM DRIVER

www.allegromicro.com

Motor

Driver

Electrical characteristics: unless otherwise noted at T

= +25°C, V

= 24 V, V

= 5.0 V.

Limits

Characteristic

Symbol

Test Conditions

Min.

Typ.

Max.

Units

Output drivers

Driver Supply Volt. Range

Operating

Drain-Source Breakdown

(BR)DS

= 44 V, I

= 1 mA

100

Output On Resistance

DS(on)

= 3.0 A

150

270

Body Diode Forward Volt.

= 3.0 A

1.5

2.3

Driver Supply Current

REF

> 2.0 V (sleep mode)

100

µA

Control logic

Logic Supply Volt. Range

Operating

3.0

5.0

5.5

Logic Input Voltage

0.75V

0.25V

Logic Input Current

±1.0

µA

±1.0

µA

Max. Clock Frequency

clk

100*

kHz

PWM Off Time

off

µs

PWM Min. On Time

on(min)

5.0

µs

Ref. Input Voltage Range

REF

Operating

0.0

1.5

Sleep mode

2.0

Ref. Input Current

REF

±10

µA

Sense Voltage

Trip point

REF

Propagation Delay Time

PLH

Clock rising edge to output on

2.5

µs

PHL

Clock rising edge to output off

2.0

µs

Logic Supply Current

3.0

Typical values are given for circuit design information only.
*Operation at a clock frequency greater than the specified minimum value is possible but not warranted.

SLA7052M

UNIPOLAR STEPPER-MOTOR

TRANSLATOR/PWM DRIVER

www.allegromicro.com

Motor

Driver

Functional description

Device operation.

The SLA7052M is a complete

stepper-motor driver with built-in translator for easy
operation with minimal control lines. It is designed to
operate unipolar stepper motors in full-step or half-step
modes. The current in each pair of outputs, all n-channel
MOSFETs, is regulated with internal fixed off-time pulse-
width modulated (PWM) control circuitry.

When a step command signal occurs on the clock input

the translator automatically sequences to the next step.

Clock (step) input.

A low-to-high transition on the

clock input sequences the translator and advances the
motor one increment. The hold state is done by stopping
the CLOCK input regardless of the input level

Full/half-step select.

This logic-level input sets the

translator step mode. A logic low is two-phase, full step; a
logic high is half step. Changes to this input do not take
effect until the rising edge of the clock input.

CW/CCW (direction) input.

This logic-level input sets

the translator step direction. Changes to this input do not
take effect until the rising edge of the clock input.

Internal PWM current control.

Each pair of outputs is

controlled by a fixed off-time PWM current-control circuit
that limits the load current to a desired value (I

TRIP

Initially, an output is enabled and current flows through
the motor winding and R

. When the voltage across the

current-sense resistor equals the reference voltage, the
current-sense comparator resets the PWM latch, which
turns off the driver for the fixed off time during which the
load inductance causes the current to recirculate for the off
time period. The driver is then re-enabled and the cycle
repeats.

Synchronous operation mode.

This function pre-

vents occasional motor noise during a "hold" state, which
normally results from asynchronous PWM operation of
both motor phases. A logic high at the SYNC input is
synchronous operation; a logic low is asynchronous
operation. The use of synchronous operation during
normal stepping is not recommended because it produces
less motor torque and can cause motor vibration due to
stair-case current.

Sleep mode.

Applying a voltage greater than 2 V to the

REF pin disables the outputs and puts the motor in a free
state (coast). This function is used to minimize power
consumption when not in use. It disables much of the
internal circuitry including the output MOSFETs and
regulator. When coming out of sleep mode, wait 100 µs
before issuing a step command to allow the internal
circuitry to stabilize.

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

SLA7052M
UNIPOLAR STEPPER-MOTOR
TRANSLATOR/PWM DRIVER

Motor

Driver

Applications information

Layout.

The printed wirting board should use a heavy ground

plane.

For optimum electrical and thermal performance, the

driver should be soldered directly into the board.

The driver supply terminal, VBB, should be decoupled

with an electrolytic capacitor placed as close to the device
as possible.

To avoid problems due to capacitive coupling of the

high dv/dt switching transients, route the high-level, output
traces away from the sensitive, low-level logic traces.
Always drive the logic inputs with a low source impedance
to increase noise immunity.

Grounding.

A star ground system located close to the

driver is recommended. The logic supply return and the
driver supply return should be connected together at only a
single point -- the star ground.

Logic supply voltage, V

Transients at this terminal

should be held to less than 0.5 V to avoid malfunctioning
operation. Both V

and V

may be turned on or off

separately.

Logic inputs.

Unused logic inputs (CW/CCW, FULL/

HALF, or SYNC) must be connected to either ground or
the logic supply voltage.

Current sensing.

To minimize inaccuracies caused by

ground-trace IR drops in sensing the output current level,
the current-sense resistor, R

, should have an independent

ground return to the star ground of the device. This path
should be as short as possible. For low-value sense
resistors, the IR drops in the printed wiring board sense
resistor's traces can be significant and should be taken into
account. The use of sockets should be avoided as they can
introduce variation in R

due to their contact resistance.

PWM current control.

The maximum value of current

limiting (I

TRIP

) is set by the selection of R

and the voltage

at the REF input with a transconductance function ap-
proximated by:

TRIP

= V

REF

The required V

REF

should not be less than 0.1 V. If it is,

should be increased for a proportionate increase in

REF

Typical application

SLA7052M

UNIPOLAR STEPPER-MOTOR

TRANSLATOR/PWM DRIVER

www.allegromicro.com

Motor

Driver

Applications Information (cont'd)

Continuous

Discontinuous

mode

Normalized FET on resistance

Sync. signal generator

Reference voltage.

In the Typical Application shown,

resistors R

and R

set the reference voltage as:

REF

x R

)/(R

+ R

)

The trimming of R

allows for the resistor tolerances

and REF input current. The sum of R

should be less

than 50 k

to minimize the effect of I

REF

Minimum output current.

The SLA7052M uses fixed

off-time PWM current control. Due to internal logic and
switching delays, the actual load current peak will be
slightly higher than the calculated I

TRIP

value (especially

for low-inductance loads). These delays, plus the mini-
mum recommended V

REF

, limit the minimum value the

current-control circuitry can regulate. An application with
this device should maintain continuous PWM control in
order to obtain optimum torque out of the motor. The
boundary of the load current (I

O(min)

) between continuous

and discontinuous operation is:

O(min)

= [(V

+ V

)/R

] x [(1/e

toff/[Rm x Lm]

) - 1]

where V

= load supply voltage

= body diode forward voltage

= motor winding resistance

off

= PWM off time

= motor winding inductance

To produce zero current in a motor, the REF input

should be pulled above 2 V, turning off all drivers.

Synchronous operation mode.

If an external signal

is not available to control the synchronous operation
mode, a simple circuit can keep the SYNC input low while
the CLOCK input is active; the SYNC input will go high
(synchronous operation) when the CLOCK input stays low
("hold"). The RC time constant determines the sync
trransition timing.

Temperature effects on FET outputs.

Analyzing

safe, reliable operation includes a concern for the relation-
ship of NMOS on resistance to junction temperature.
Device package power calculations must include the
increase in on resistance (producing higher on voltages)
caused by increased operating junction temperatures. The
figure provides a normalized on-resistance curve, and all
thermal calculations should consider increases from the

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

SLA7052M
UNIPOLAR STEPPER-MOTOR
TRANSLATOR/PWM DRIVER

Motor

Driver

Applications Information (cont'd)

Allowable avalanche energy

Waveforms during avalanche breakdown

given +25°C limits, which may be caused by internal
heating during normal operation.

These power MOSFET outputs feature an excellent

combination of fast switching, ruggedized device design,
low on resistance, and cost effectiveness.

Avalanche energy capability.

There is a surge voltage

expected when the output MOSFET turns off, and this
voltage may exceed the MOSFET breakdown voltage
(V

(BR)DS

). However, the MOSFETs are avalanche type

and as long as the energy (E

(AV)

), which is imposed on the

MOSFET by the surge voltage, is less than the maximum
allowable value, it is considered to be within its safe
operating area. Note that the maximum allowable ava-
lanche energy is reduced as a function of temperature.

In application, the avalanche energy (E

(AV)

) dissipated

by the MOSFET is approximated as

(AV)

= V

DS(AV)

x 1/2 x I

x t

Output circuit for avalanche energy

calculations

SLA7052M

UNIPOLAR STEPPER-MOTOR

TRANSLATOR/PWM DRIVER

www.allegromicro.com

Motor

Driver

Terminal list

Terminal

Name

Terminal Description

OUT

Driver output for phase A

Not usable

OUT

Driver output for phase A\

GATE

Phase A MOSFET Gate

Logic power supply

SENSE

Phase A current sense

CLOCK

Step clock input

SYNC

Synchronous PWM control input

REF

Current set & "sleep" control

GND

Supply negative return

CW/CCW

Forward/reverse logic control input

FULL/HALF

Full step/half step logic control input

SENSE

Phase B current sense

Driver power supply

GATE

Phase B MOSFET Gate

OUT

Driver output for phase B\

Not usable

OUT

Driver output for phase B

The products described herein are manufactured in Japan by

Sanken Electric Co., Ltd. for sale by Allegro MicroSystems, Inc.

Sanken and Allegro reserve the right to make, from time to time,

such departures from the detail specifications as may be required to
permit improvements in the performance, reliability, or
manufacturability of its products. Therefore, the user is cautioned to
verify that the information in this publication is current before placing
any order.

When using the products described herein, the applicability and

suitability of such products for the intended purpose shall be reviewed
at the users responsibility.

Although Sanken undertakes to enhance the quality and reliability of

its products, the occurrence of failure and defect of semiconductor
products at a certain rate is inevitable.

Users of Sanken products are requested to take, at their own risk,

preventative measures including safety design of the equipment or
systems against any possible injury, death, fires or damages to society
due to device failure or malfunction.

Sanken products listed in this publication are designed and intended

for use as components in general-purpose electronic equipment or
apparatus (home appliances, office equipment, telecommunication
equipment, measuring equipment, etc.). Their use in any application
requiring radiation hardness assurance (e.g., aerospace equipment) is
not supported.

When considering the use of Sanken products in applications where

higher reliability is required (transportation equipment and its control
systems or equipment, fire- or burglar-alarm systems, various safety
devices, etc.), contact a Sanken sales representative to discuss and
obtain written confirmation of your specifications.

The use of Sanken products without the written consent of Sanken in

applications where extremely high reliability is required (aerospace
equipment, nuclear power-control stations, life-support systems, etc.) is
strictly prohibited.

The information included herein is believed to be accurate and

reliable. Application and operation examples described in this
publication are given for reference only and Sanken and Allegro
assume no responsibility for any infringement of industrial property
rights, intellectual property rights, or any other rights of Sanken or
Allegro or any third party that may result from its use.

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