SLA7042 查看數據表（PDF） - Allegro MicroSystems

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SLA7042

MICROSTEPPING, UNIPOLAR PWM, HIGH-CURRENT MOTOR CONTROLLER/DRIVER

Allegro MicroSystems 

SLA7042M AND SLA7044M

MICROSTEPPING,

UNIPOLAR PWM, HIGH-CURRENT

MOTOR CONTROLLER/DRIVERS

REGULATING THE PWM OUTPUT CURRENT

The output current (and motor coil current) waveform

is illustrated in Figure 1. Setting the maximum PWM

current trip point to meet the specified full-step running

current for the motor, IOUT max (DATA input = 111X =

100% ratio), requires only a current-sensing resistor, RS,

and an input reference voltage, VREF/EN, between 0.4 V

and 2.5 V.

IOUT max

≈

VREF/EN

3 • RS

PHASE A

0

PHASE A

I OUT

Dwg. WK-001

FIGURE 1.␣ PHASE A COIL CURRENT WAVEFORM

SERIAL DATA INPUT ENABLE

In a minimum-component application, a voltage divider

provides VREF/EN and an npn transistor provides the

required pull-down to enable the serial data input as

shown in Figure 2.

IOUT max ≈

R2

R1 + R2

•

Vb

3 • RS

µP STEPPER MOTOR CONTROL

Alternative REFERENCE/ENABLE input configura-

tions provide for more complete motor control. A tri-state

logic element and a voltage divider allows a fixed refer-

ence voltage, with both output disable and data enable

functions. Complete µP control is usually accomplished

with a D/A converter as shown in Figure 3. Here, digital

control provides an output disable (>VDD - 1 V), VREF, and

VEN (<2.5 V).

ENABLE

DATA

SERIAL DATA

VDD

V BB

B

Vb

TO CHANNEL B

R1

VREF/EN

D/A

R2

B

PWM

OFF-TIME

CONTROL

Ø

CONTROL

LOGIC

A

A

DRIVE

SENSE

RS

FIGURE 2.␣ PWM CONTROL (RUN MODE)

Dwg. EK-011

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