NJM3774
DUAL STEPPER MOTOR DRIVER
s
GENERAL DESCRIPTION
The NJM3774 is a switch-mode (chopper), constant-
current driver with two channels: one for each winding of a
two-phase stepper motor. The NJM3774 is equipped with a
TTL level compatible Disable input to simplify half-stepping
operation. The circuit is well suited for microstepping
applications together with the matching dual DAC
NJU39610. In full/half stepping applications, the NJM3517
can be used as a phase generator (translator) to derive the
necessary signals for the NJM3774. The NJM3774 con-
tains a clock oscillator, which is common for both driver
channels, a set of comparators and flip-flops implementing
the switching control, and two output H-bridges. Voltage
supply requirements are +5 V for logic and +10 to +45 V for
the motor. Maximum output current is 1000mA per channel.
s
PACKAGE OUTLINE
NJM3774D2
NJM3774FM2
s
FEATURES
• Dual chopper driver
• 1000 mA continuous output current per channel
• Specially matched to the Dual DAC NJU39610
• Packages
DIP22 / PLCC28
s
BLOCK DIAGRAM
Phase
1
Dis
1
V
R1
C
1
E
1
NJM3774
V
CC
V
–
+
CC
R
S
Q
M
A1
Logic
M
B1
V
MM1
+
–
V
MM2
M
B2
Logic
M
A2
RC
+
–
S
R
Q
Phase
2
Dis
2
V
R2
C
2
GND
E
2
Figure 1. Block diagram
NJM3774
s
PIN CONFIGURATIONS
RC
1
C
2 2
V
R2 3
V
MM2 5
E
2 6
M
B2 7
M
B1 8
GND
9
E
1 10
V
MM1 11
25
24
23
Phase
2
22
V
CC
21
C
1
20
V
R1
19
Phase
1
18
GND
GND
GND
GND
GND
28
27
Dis
2
M
A2
26
4
3
2
1
V
R2
C
2
RC
V
CC
C
1
V
R1
Phase
1
Phase
2 4
GND
5
GND
6
Dis
2 7
M
A2 8
V
MM2 9
NJM3774FM2
22
21
20
19
NJM
3774D2
17
GND
16
Dis
1
15
M
A1
14
V
MM1
13
E
1
12
M
B1
M
A1 12
GND
13
GND
14
GND
15
GND
16
GND
17
Dis
1 18
E
2 10
M
B2 11
Figure 2. Pin configurations
s
PIN DESCRIPTION
PLCC
DIP
Symbol
Description
1-3, 9,
13-17
28
4
5
6
7
8
10
11
12
18
19
20
21
5, 6
GND
17, 18
8
9
10
11
12
13
14
15
16
19
20
21
M
A2
V
MM2
E
2
M
B2
M
B1
E
1
V
MM1
M
A1
Dis
1
Phase
1
V
R1
C
1
Ground and negative supply. Note: these pins are used thermally for heat-sinking. Make sure that all
ground pins are soldered onto a suitably large copper ground plane for efficient heat sinking.
Motor output A, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
Motor supply voltage, channel 2, +10 to +40 V.V
MM1
and V
MM2
should be connected together.
Common emitter, channel 2. This pin connects to a sensing resistor R
S
to ground.
Motor output B, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
Motor output B, channel 1. Motor current flows from M
A1
to M
B1
when Phase
1
is HIGH.
Common emitter, channel 1. This pin connects to a sensing resistor R
S
to ground.
Motor supply voltage, channel 1, +10 to +40 V. V
MM1
and V
MM2
should be connected together.
Motor output A, channel 1. Motor current flows from M
A1
to M
B1
when Phase
1
is HIGH.
Disable input (TTL level compatible) for channel 1. When HIGH, all four output transistors are turned
off, which results in a rapidly decreasing output current to zero.
Controls the direction of motor current at outputs M
A1
and M
B1
. Motor current flows from M
A1
to M
B1
when Phase
1
is HIGH.
Ref. voltage, channel 1. Controls the threshold voltage for the comparator and hence the output
current.
Comparator input channel 1. This input senses the instantaneous voltage across the sensing resistor,
filtered by an RC network. The threshold voltage for the comparator is V
CH1
= 0.18 • V
R1
[V], i.e. 450
mV at V
R1
= 2.5 V.
Logic voltage supply, nominally +5 V.
Clock oscillator RC pin. Connect a 15 kohm resistor to V
CC
and a 3300 pF capacitor to ground to obtain
the nominal switching frequency of 26.5 kHz.
Comparator input channel 2. This input senses the instantaneous voltage across the sensing resistor,
filtered by an RC network. The threshold voltage for the comparator is V
CH2
= 0.18 • V
R2
[V], i.e. 450 mV
at V
R2
= 2.5 V.
Ref. voltage, channel 2. Controls the threshold voltage for the comparator and hence the output
current.
Controls the direction of motor current at outputs M
A2
and M
B2
. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
Disable input (TTL level compatible) for channel 2. When HIGH, all four output transistors are turned
off, which results in a rapidly decreasing output current to zero.
22
23
24
22
1
2
V
CC
RC
C
2
25
26
27
3
4
7
V
R2
Phase
2
Dis
2
NJM3774
s
FUNCTIONAL DESCRIPTION
Each channel of the NJM3774 consists of the following sections: an output H-bridge with four transistors, capable
of driving up to 1000mA continuous current to the motor winding; a logic section that controls the output transistors;
an S-R flip-flop; and a comparator. The clock-oscillator is common to both channels.
Constant current control is achieved by switching the output current to the windings. This is done by sensing the
peak current through the winding via a resistor, R
S
, effectively connected in series with the motor winding during the
turn-on period. As the current increases, a voltage develops across the resistor, and is fed back to the comparator.
At the predetermined level defined by the voltage at the reference input V
R
, the comparator resets the flip-flop,
turning off the output transistors. The current decreases until the clock oscillator triggers the flip-flop, turning on the
output transistors, and the cycle is repeated.
The current paths during turn-on, turn-off and phase shift are shown in figure 3. Note that the upper recirculation
diodes are connected to the circuit externally.
External recirculation diodes
1
V
MM
2
3
R
S
Motor Current
1
2
3
Fast Current Decay
Slow Current Decay
Time
Figure 3. Output stage with current paths
during turn-on, turn-off and phase shift.
NJM3774
s
ABSOLUTE MAXIMUM RATINGS
Parameter
Pin no. [DIP-package]
Symbol
Min
Max
Unit
Voltage
Logic supply
Motor supply
Logic inputs
Comparator inputs
Reference inputs
Current
Motor output current
Logic inputs
Analog inputs
Temperature
Operating Junction temperature
Storage temperature
Power Dissipation (Package Data)
Power dissipation at T
GND
= +25°C, DIP and PLCC package
Power dissipation at T
GND
= +125°C, DIP package
Power dissipation at T
GND
= +125°C, PLCC package
22
9, 14
4, 7, 16, 19
2, 21
3, 20
8, 11, 12, 15
4, 7, 16, 19
2, 3, 20, 21
V
CC
V
MM
V
I
V
C
V
R
I
M
I
I
I
A
T
j
T
stg
P
D
P
D
P
D
0
0
-0.3
-0.3
-0.3
-1200
-10
-10
-40
-55
-
-
-
7
45
6
V
CC
7.5
+1200
-
-
+150
+150
5
2.2
2.6
V
V
V
V
V
mA
mA
mA
°C
°C
W
W
W
s
RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Min
Typ
Max
Unit
Logic supply voltage
Motor supply voltage
Motor output current
Operating Junction temperature
Rise and fall time, logic inputs
Oscillator timing resistor
V
CC
V
MM
I
M
T
J
t
r
, t
f
R
T
4.75
10
-1000
- 20
-
2
5
-
-
-
-
15
5.25
40
+1000
+125
2
20
V
V
mA
°C
µs
kΩ
Phase
1
19
Dis
1
V
R1
16
20
C
1
21
E
1
13
NJM3774
I
CC
V
CC
V
22
–
+
CC
R
S
Q
15
Logic
12
M
A1
M
B1
V
MM1
V
MM2
M
B2
M
A2
IM
I OL
I MM
| V
MA
– V
MB
|
14
15 kW
+
t
on
50 %
t
off
R
T
9
–
11
Logic
I
RC
RC
1
+
–
3 300 pF
8
S
R
Q
t
V
E
V
CH
t
d
V
CC
C
T
Phase
2
I
I
I
IH
I
R
V
I
V
V
IH
4
7
3
2
C
2
I
C
I
A
V
CH
V
5, 6, 17, 18
GND
10
E
2
Dis
2
V
R2
I
IL
I
A
1 kW
V
M
V
V
E
MA
V
A
V
R
C
820 pF
R
C
V
MM
t
IL
C
C
R
S
1
f
s
=
t + t
on
off
D=
t
on
t
on +
t
off
Figure 4. Definition of symbols
Figure 5. Definition of terms
NJM3774
s
ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating conditions unless otherwise noted, - 20°C
≤
T
J
≤
+125°C.
Parameter
General
Supply current
Total power dissipation
Total power dissipation
Thermal shutdown junction temperature
Turn-off delay
Logic Inputs
Logic HIGH input voltage
Logic LOW input voltage
Logic HIGH input current
Logic LOW input current
Comparator Inputs
Threshold voltage
| V
CH1
- V
CH2
| mismatch
Input current
Reference Inputs
Input resistance
Input current
Motor Outputs
Lower transistor saturation voltage
Lower transistor leakage current
Lower diode forward voltage drop
Upper transistor saturation voltage
Upper transistor leakage current
Chopper Oscillator
Chopping frequency
f
s
Symbol
Conditions
Min
Typ
Max
Unit
I
CC
P
D
P
D
Note 4.
V
MM
= 12 V, I
M1
= I
M2
= 750 mA.
Notes 2, 3, 4.
V
MM
= 12 V, I
M1
= 1000 mA, I
M2
= 0 mA.
Notes 2, 3, 4.
T
A
= +25°C, dV
C
/dt
≥
50 mV/µs.
I
M
= 100 mA. Note 3.
-
-
-
-
-
60
2.6
2.6
160
1.4
75
2.9
2.9
-
2.0
mA
W
W
°C
µs
t
d
V
IH
V
IL
I
IH
I
IL
V
CH
V
CH,diff
I
C
R
R
I
R
V
I
= 2.4 V
V
I
= 0.4 V
R
C
= 1 kohm, V
R
= 2.50 V
R
C
= 1 kohm
2.0
-
-
-0.4
430
-
-10
-
-
-
-
-
-
-
25.0
-
-
-
-
450
1
-
5
0.5
0.6
-
1.2
1.1
-
26.5
-
0.8
20
-
470
-
1
-
1.0
0.9
700
1.5
1.4
700
28.0
V
V
µA
mA
mV
mV
µA
kohm
mA
V
µA
V
V
µA
kHz
T
A
= +25°C
V
R
= 2.5 V
I
M
= 750 mA
V
MM
= 41 V, V
E
= V
R
= 0 V, V
C
= V
CC
I
M
= 750 mA
I
M
= 750 mA.
V
MM
= 41 V, V
E
= V
R
= 0 V, V
C
= V
CC
C
T
= 3300 pF, R
T
= 15 kohm
s
THERMAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Thermal resistance
Rth
J-GND
Rth
J-A
Rth
J-GND
Rth
J-A
DIP package.
DIP package. Note 2.
PLCC package.
PLCC package. Note 2.
-
-
-
-
11
40
9
35
-
-
-
-
°C/W
°C/W
°C/W
°C/W
Notes
1. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal.
2. All ground pins soldered onto a 20 cm
2
PCB copper area with free air convection, T
A
= +25°C.
3. Not covered by final test program.
4. Switching duty cycle D = 30%, f
s
= 26.5 kHz.
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