STK672-630CN-E Datasheet, PDF (30/31 Pages) ON Semiconductor – 2-phase Stepper Motor Driver

STK672-630CN-E
(5) When mounting multiple drivers on a single board
When mounting multiple drivers on a single board, the GND design should mount a VCC decoupling capacitor, C1, for
each driver to stabilize the GND potential of the other drivers. The key wiring points are as follows.
24v
5V
Input
Signals
GND
9
Motor
1
IC1
2
6
19 ¹⁸
Input
Signals
9
Motor
2
IC2
2
6
19 ¹⁸
Input
Signals
9
Motor
3
IC3
2
6
19 ¹⁸
GND
Short
Thick and short
Thick
(6) VCC operating limit
When the output (for example F1) of a 2-phase stepper motor driver is turned OFF, the AB phase back electromotive
force eab produced by current flowing to the paired F2 parasitic diode is induced in the F1 side, causing the output
voltage VFB to become twice or more the VCC voltage. This is expressed by the following formula.
VFB = VCC + eab
= VCC + VCC + IOH x RM + Vdf (1.6V)
VCC: Motor supply voltage, IOH: Motor current set by Vref
Vdf: Voltage drop due to F2 parasitic diode and current detection resistor R1, RM: Motor winding resistance value
Using the above formula, make sure that VFB is always less than the MOSFET withstand voltage of 100V. This is
because there is a possibility that operating limit of VCC falls below the allowable operating range of 46V, due to the
RM and IOH specifications.
VCC
VCC
A phase
Current path
F1
ON
AB phase
A phase
eab is generated by the
mutual induction M.
VFB
M
eab
F2
VCC
OFF _F1
OFF
AB phase
eab
Current path
M
F2
OFF
R1
GND
R1
GND
The oscillating voltage in excess of VFB is caused by LCRM (inductance, capacitor, resistor, mutual inductance)
oscillation that includes micro capacitors C, not present in the circuit. Since M is affected by the motor characteristics,
there is some difference in oscillating voltage according to the motor specifications. In addition, constant voltage drive
without constant current drive enables motor rotation at VCC  0V.
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