stk672-632b-e Sanyo Semiconductor Corporation, stk672-632b-e Datasheet - Page 23

• Manufacturer Part Number: stk672-632b-e
• Description: 2-phase Stepping Motor Driver
• Manufacturer: Sanyo Semiconductor Corporation

Input
Signals
(5) When mounting multiple drivers on a single PC board
(6) V CC operating limit
5V
GND
When mounting multiple drivers on a single PC board, the GND design should mount a V CC decoupling
capacitor, C1, for each driver to stabilize the GND potential of the other drivers. The key wiring points are as
follows.
When the output (for example F1) of a 2-phase stepping 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 V CC voltage. This is expressed by the following
formula.
VFB = V CC + eab
V CC : Motor supply voltage, I OH : 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 V CC falls below the allowable operating range of 46V, due
to the RM and I OH specifications.
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 V CC ≥ 0V.
Current path
F1
ON
= V CC + V CC + I OH x RM + Vdf (1.5 V)
A phase
19 18
Short
IC1
9
2
6
Motor
1
Thick and short
M
Input
R1
GND
V CC
AB phase
F2
OFF
19 18
eab is generated by the
mutual induction M.
IC2
STK672-632B-E
9
Thick
2
6
VFB
V CC
F1
OFF
Motor
2
A phase
eab
Input
M
19 18
IC3
9
GND
R1
AB phase
V CC
eab
Current path
2
6
Motor
3
F2
OFF
No. A1738-23/24
GND
24V