SLA7075M, SLA7076M,

SLA7077M, and SLA7078M

Motor Driver ICs

9

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SLA7060M Series

SLA7070M Series

RSExt

RSInt

FET Gate

Signal

FET Gate

Signal

Stepper Motor

Stepper Motor

PWM On

PWM Off

PWM On

Back EMF at Dead Time

+V

0

t

+V

0

0

0

t

t

t

PWM On

PWM Off

PWM On

Dead

Time

Dead

Time

Figure 3. Synchronous rectification operation. During Dead Time,

the Back EMF flows through the body diode of the MOSFET

PWM Off Period

The PWM off-time for the SLA7070M series is controlled

as a fixed time by an internal oscillator. It also is switched in 3

levels by current proportion (see the Electrical Characteristics

table).

In addition, the SLA7070M series provide a function that

decreases losses occurring when the PWM turns off. This func-

tion dissolves back EMF stored in the motor coil at MOSFET

turn-on, as well as at PWM turn-on (synchronous rectification

operation).

Figure 3 shows the difference in back EMF generative

system between the SLA7060M series and SLA7070M series.

The SLA7060M series performs on–off operations using only

the MOSFET on the PWM-on side, but the SLA7070M series

also performs on–off operations using only the MOSFET on the

PWM-off side. To prevent simultaneous switching of the MOS-

FETs at synchronous rectification operation, the IC has a dead

time of approximately 0.5 μs. During dead time, the back EMF

flows through the body diode on the MOSFET.