SKT672-070-E Datasheet, PDF (7/18 Pages) ON Semiconductor – Stepping Motor Driver

STK672-070-E
Functional Description
External Excitation Chopper Drive Block Description
VCC1
IOFF
L2
D1
ION
Enable φA (control signal)
Current
divider
L1
Divider
CR
oscillator
800kHz
45kHz
S
MOSFET _AND
Q ^{Latch circuit}
R Noise
filter
Vref
A=1
–
+
Rs
Driver Block Basic Circuit Structure
A13263
Since this hybrid IC adopts an external excitation method, no external oscillator circuit is required.
When a high level is input to φA in the basic driver block circuit shown in the figure and the MOSFET is turned on, the
comparator + input will go low and the comparator output will go low. Since a set signal with the PWM period will be
input, the Q output will go high, and the MOSFET will be turned on as its initial value.
The current ION flowing in the MOSFET passes through L1 and generates a potential difference in Rs. Then, when the
Rs potential and the Vref potential become the same, the comparator output will invert, and the reset signal Q output
will invert to the low level. Then, the MOSFET will be turned off and the energy stored in L1 will be induced in L2 and
the current IOFF will be regenerated to the power supply. This state will be maintained until the time when an input to
the latch circuit set pin occurs.
In this manner, the Q output is turned off and on repeatedly by the reset and set signals, thus implementing constant
current control. The resistor and capacitor on the comparator input are spike removal circuit elements and synchronize
with the PWM frequency. Since this hybrid IC uses a fixed frequency due to the external excitation method and at the
same time also adopts a synchronized PWM technique, it can suppress the noise associated with holding a position
when the motor is locked.
Input Pin Functions
Pin No.
11
10
15
8, 9, 12
13
7
Symbol
CLK
CWB
ENABLE
M1, M2, M3
RESET
Vref
Function
Phase switching clock
Rotation direction setting (CW/CCW)
Output cutoff
Excitation mode setting
System reset
Current setting
Pin circuit type
Built-in pull-up resistor CMOS Schmitt trigger input
Built-in pull-up resistor CMOS Schmitt trigger input
Built-in pull-up resistor CMOS Schmitt trigger input
Built-in pull-up resistor CMOS Schmitt trigger input
Built-in pull-up resistor CMOS Schmitt trigger input
Input impedance 6kΩ (typ.) ±30%
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