JRC NJM3774D2, NJM3774FM3 Datasheet
NJM3774
Figure 1. Block diagram
DUAL STEPPER MOTOR DRIVER
■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE
RC
NJM3774
M
A1
M
B1
M
B2
M
A2
GNDC
2
V
R2
Phase
2
V
CC
C
1
V
R1
Phase
1
E
1
E
2
V
CC
SRQ
+
–
Logic
S
R
Q
+
–
Logic
+
–
V
MM2
V
MM1
Dis
1
Dis
2
NJM3774FM2
NJM3774D2
The NJM3774 is a switch-mode (chopper), constantcurrent 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 contains 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.
■ FEATURES
• Dual chopper driver
• 1000 mA continuous output current per channel
• Specially matched to the Dual DAC NJU39610
• Packages DIP22 / PLCC28
■ BLOCK DIAGRAM
NJM3774
Figure 2. Pin configurations
C
E
B2
B1
GND
C
RC
V
M
GND
GND
GND
GND
A1
GND
GND
GND
GND
GND
5
6
7
8
9
10
11
25
24
23
22
21
20
19
4
3
2
1
282726
12131415161718
V
R2
V
R1
CC
Phase
2
A2
2
Dis
M
M
1
Dis
M
1
Phase
2
1
2
V
MM1
E
1
V
MM2
NJM3774FM2
1
2
3
4
5
6
7
8
9
10
11
22
21
20
19
18
17
16
15
14
13
12
C
R2
A1
GND
GND
1
R1
CC
M
V
M
GND
GND
Phase
Dis
RC
V
M
Phase
V
V
2
2
A2
MM2
B2
2
E
2
C
1
Dis
1
V
MM1
M
B1
E
1
NJM
3774D2
■ PIN CONFIGURATIONS
■ PIN DESCRIPTION
PLCC DIP Symbol Description
1-3, 9, 5, 6 GND Ground and negative supply. Note: these pins are used thermally for heat-sinking. Make sure that all
13-17 17, 18 ground pins are soldered onto a suitably large copper ground plane for efficient heat sinking.
28
48MA2Motor output A, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
59V
MM2
Motor supply voltage, channel 2, +10 to +40 V.V
MM1
and V
MM2
should be connected together.
610E2Common emitter, channel 2. This pin connects to a sensing resistor RS to ground.
711M
B2
Motor output B, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
812M
B1
Motor output B, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
10 13 E
1
Common emitter, channel 1. This pin connects to a sensing resistor RS to ground.
11 14 V
MM1
Motor supply voltage, channel 1, +10 to +40 V. V
MM1
and V
MM2
should be connected together.
12 15 M
A1
Motor output A, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
18 16 Dis
1
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.
19 19 Phase
1
Controls the direction of motor current at outputs MA1 and MB1. Motor current flows from MA1 to M
B1
when Phase1 is HIGH.
20 20 V
R1
Ref. voltage, channel 1. Controls the threshold voltage for the comparator and hence the output
current.
21 21 C
1
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 • VR1 [V], i.e. 450
mV at VR1 = 2.5 V.
22 22 V
CC
Logic voltage supply, nominally +5 V.
23 1 RC 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.
24 2 C
2
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 • VR2 [V], i.e. 450 mV
at VR2 = 2.5 V.
25 3 V
R2
Ref. voltage, channel 2. Controls the threshold voltage for the comparator and hence the output
current.
26 4 Phase
2
Controls the direction of motor current at outputs MA2 and MB2. Motor current flows from MA2 to M
B2
when Phase2 is HIGH.
27 7 Dis
2
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.
NJM3774
Figure 3. Output stage with current paths
during turn-on, turn-off and phase shift.
■ 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, RS, 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 VR, 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.
Fast Current Decay
Slow Current Decay
Motor Current
Time
1 2
3
3
1
2
R
S
V
MM
External recirculation diodes
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