17

SLA7024M, SLA7026M, SLA7027MU, SLA7022MU, SLA7029M,

SMA7022MU, SMA7029M, SLA7020M, SLA7021M and SDK03M

Fig. 1 Waveform of coil current (Phase A excitation ON)

Fig. 3 Circuit for fixing the coil current

Fig. 4 Circuit for fixing the coil current

Fig. 5 Circuit for fixing the coil current

Fig. 2 Circuit for fixing the coil current

Application Note

s Determining the output current

Fig. 1 shows the waveform of the output current (motor coil

current). The method of determining the peak value (lo) of

the output current based on this waveform is shown below.

<Parameters for determining the output current lo>

: Reference supply voltage

: Voltage-divider resistors for the reference supply

voltage

: Current detection resistor

(1) Normal rotation mode

lo is determined as follows when current flows at the

maximum level during motor rotation. See Fig. 2, 3 and

4.

lo =

•

...................................................

q

(2) Power down mode

The circuits in Fig. 5, 6 and 7 (rx and Tr) are added in

order to decrease the coil current. lo is then determined

as follows.

•

.......................................

w

1+

To determine rx, equation w can be modified to obtain

equation e.

1

.............................. e

1

–1

–

.

.

.

.

0

Phase A

Phase A

SLA7022MU

SLA7029M

SMA7022MU

SMA7029M

SLA7020M

SLA7021M

7,(9)

3,(13)

SLA7024M

SLA7026M

SLA7027MU

9,(10)

3,(14)

SDK03M

10

3

13 15

SLA7022MU

SLA7029M

SMA7022MU

SMA7029M

SLA7020M

SLA7021M

7,(9)

3,(13)

Power down

signal

.

.