SLA7026M 查看數據表（PDF） - Allegro MicroSystems
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SLA7026M Datasheet PDF : 12 Pages
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SLA7024M, SLA7026M, AND SMA7029M
HIGH-CURRENT PWM,
UNIPOLAR STEPPER MOTOR
CONTROLLER/DRIVERS
APPLICATIONS INFORMATION
REGULATING THE PWM OUTPUT CURRENT
The output current (and motor coil current) waveform is illustrated in
Figure 1. Setting the PWM current trip point requires various external
components:
Vb = Reference supply (typically 5 V)
R1, R2 = Voltage-divider resistors in the reference supply circuit
RS = Current sensing resistor(s)
NOTE: The maximum allowable VREF input voltage is 2.0 V.
The voltage-divider must be selected accordingly.
Normal PWM (Full-Current/Running) Mode
IOUT is set to meet the specified running current for the motor (Figure 2)
and is determined by:
IOUT ≈
VREF
RS
(1)
or, if VREF is not known
IOUT ≈
R2
R1 + R2
•
Vb
RS
(2)
PHASE A
I OUT
0
PHASE A
Dwg. WK-001
FIGURE 1. PHASE A COIL CURRENT WAVEFORM
Vb
VCC INPUT
V BB
B
R1
R3
B
R2
R5
C1
V REF
PEAK
CURRENT
DETECTOR
C3
td
PWM
OFF-TIME
CONTROL
CONTROL
LOGIC
A
A
CURRENT
CONTROL
&
RECIRCULATING
CURRENT
CONTROL
SENSE
RS
Dwg. EK-009
FIGURE 2. PWM CONTROL (RUN MODE)
115 Northeast Cutoff, Box 15036
™
Worcester, Massachusetts 01615-0036 (508) 853-5000
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