SMA7036M 데이터 시트보기 (PDF) - Sanken Electric co.,ltd.

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SMA7036M

2-Phase Stepper Motor Unipolar Driver IC

Sanken Electric co.,ltd. 

2-Phase Stepper Motor Unipolar Driver IC (2-Phase Excitation)

SMA7036M

sDetermining the Output Current

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

rent). The method of determining the peak value of the output

current (IO) based on this waveform is shown below.

(Parameters for determining the output current IO)

Vb: Reference supply voltage

r1,r2: Voltage-divider resistors for the reference supply voltage

RS: Current sense resistor

(1) Normal rotation mode

IO is determined as follows when current flows at the maximum

level during motor rotation. (See Fig.2.)

IO ≅ r2 • Vb ................................................................ (1)

r1+r2 RS

(2) Power down mode

The circuit in Fig.3 (rx and Tr) is added in order to decrease the

coil current. IO is then determined as follows.

1

IOPD ≅

r1(r2+rX)

1+ r2 • rX

• .V..b...................................................... (2)

RS

Equation (2) can be modified to obtain equation to determine rx.

rX=

1

r1

1

Vb −1

Rs • IOPD

1

−

r2

Fig. 4 and 5 show the graphs of equations (1) and (2) respec-

tively.

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

IO

Phase A

0

Phase A

Fig. 2 Normal mode

Vb(5V)

r1

r2

3,(13)

7,(9)

RS

Fig. 3 Power down mode

Vb(5V)

r1

rx r2

Power down

signal

Tr

3,(13)

7,(9)

RS

Fig. 4 Output current IO vs. Current sense resistor RS

4

3

IO= r2 · Vb

r1+r2 RS

r1=510Ω

2

r2=100Ω

rx=∞

Vb=5V

1

0

0

1

2

3

4

Current sense resistor RS (Ω)

Fig. 5 Output current IOPD vs. Variable current sense resistor rx

2.0

1.5

RS =0.5Ω

1.0

RS =0.8Ω

IOPD=

1

1+r1r(2r2· +rrXX)

· Vb

RS

r1=510Ω

RS =1Ω

r2=100Ω

Vb=5V

0.5

00 200 400 600 800 1000 1200

Variable current sense resistor rX (Ω)

16 SMA7036M

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