NJM3517
■ FUNCTIONAL DESCRIPTION
The circuit, NJM3517, is a high performance motor driver, intended to drive a stepper motor in a unipolar, bi-level
way. Bi-level means that during the first time after a phase shift, the voltage across the motor is increased to a
second voltage supply, V
SS
, in order to obtain a more-rapid rise of current, see figure 25.
The current starts to rise toward a value which is many times greater than the rated winding current. This com-
pensates for the loss in drive current and loss of torque due to the back emf of the motor.
After a short time, t
On
, set by the monostable, the bi-level output is switched off and the winding current flows from
the V
MM
supply, which is chosen for rated winding current. How long this time must be to give any increase in
performance is determined by V
SS
voltage and motor data, the L/R time-constant.
In a low-voltage system, where high motor performance is needed, it is also possible to double the motor voltage
by adding a few external components, see figure 4.
The time the circuit applies the higher voltage to the motor is controlled by a monostable flip-flop and determined
by the timing components R
T
and C
T
.
The circuit can also drive a motor in traditional unipolar way.
An inhibit input (INH) is used to switch off the current completely.
■ LOGIC INPUTS
All inputs are LS-TTL compatible. If any of the logic inputs are left open, the circuit will accept it as a HIGH level.
NJM3517 contains all phase logic necessary to control the motor in a proper way.
STEP — Stepping pulse
One step is generated for each negative edge of the STEP signal. In half-step mode, two pulses will be required to
move one full step. Notice the set up time, t
s
, of DIR and HSM signals. These signals must be latched during the
negative edge of STEP, see timing diagram, figure 6.
Figure 4.
Voltage
doubling with
external
transistors
Figure 3.
Typical
application
RC 12
STEP 7
DIR 6
HSM 10
INH 11
O
A
9
O
B
8
13 L
A
14 L
B
1 P
B2
2 P
B1
5 P
A2
4 P
A1
3 GND
V
CC
16
V
SS
15
NJM3517
PQR
Mono
F - F
Phase
Logic
P
A
P
B
STEP
CW / CCW
HALF / FULL STEP
NORMAL /INHIBIT
(Optional Sensor)
GND
V
CC
CMOS, TTL-LS
Input / Output-Device
V
SS
+ 5V
GND (V
CC
)
V
MM
R9
R8
R
T
C
T
C
3
C
4
C
5
+++
R11 R10
D2 D1
MOTOR
D3-D6
D3-D6 are
UF 4001 or
BYV 27
trr
<
100 ns
GND (V
MM
,V
SS
)
D3
+
RC 12
STEP 7
DIR 6
HSM 10
INH 11
O
A
9
O
B
8
13 L
A
14 L
B
1 P
B2
2 P
B1
5 P
A2
4 P
A1
3 GND
V
CC
16
V
SS
15
NJM3517
PQR
Mono
F - F
Phase
Logic
P
A
P
B
STEP
CW / CCW
HALF / FULL STEP
NORMAL /INHIBIT
(Optional Sensor)
GND
V
CC
CMOS, TTL-LS
Input / Output-Device
V
MM
+ 5V
GND (V
CC
)
R9
R8
R
T
C
T
C
3
C
4
++
R10
D1
1/2 MOTOR
GND (V
MM
,V
SS
)
R1
R2
Q1
Q3
C1
R12 R13
R4
R5
Q5
Q6
Equal to
Phase A
