115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

SLA7050M

UNIPOLAR STEPPER-MOTOR

TRANSLATOR/PWM DRIVER

6

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

should be held to less than 0.5 V to avoid malfunctioning

operation. Both V

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

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

PWM current control. The maximum value of current

limiting (I

at the REF input with a transconductance function ap-

proximated by:

I

The required V

R

V

Typical application

SLA7050M