JRC NJM3773E3, NJM3773FM3, NJM3773D2 Datasheet
NJM3773
Figure 1. Block diagram
RC
NJM3773
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
NJM3773FM2
NJM3773E3
NJM3773D2
The NJM3773 is a switch-mode (chopper), constant-current
driver with two channels: one for each winding of a two-phase
stepper motor. The NJM3773 is also equipped with a Disable
input to simplify half-stepping operation. The circuit is well
suited for microstepping applications together with an external
micro controller. The current control inputs are low current,
high impedance inputs, which allows the use of unbuffered
DAC or external high resistive resistor divider network. The
NJM3773 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,
including recirculation diodes. Voltage supply requirements
are +5 V for logic and +10 to +45 V for the motor. Maximum
output current is 750mA per channel.
■ FEATURES
• Dual chopper driver
• 750 mA continuous output current per channel
• High impedance current control inputs
• Digital filter on chip eliminates external filtering components
• Packages DIP22 / PLCC28 / EMP24(Batwing)
DUAL STEPPER MOTOR DRIVER
■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE
■ BLOCK DIAGRAM
NJM3773
■ PIN DESCRIPTION
EMP DIP PLCC Symbol Description
218MB1Motor output B, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
3210E
1
Common emitter, channel 1. This pin connects to a sensing resistor RS to ground.
4311M
A1
Motor output A, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
5412V
MM1
Motor supply voltage, channel 1, +10 to +40 V. V
MM1
and V
MM2
should be connected together.
6,7 5, 6, 1-3, 9, GND Ground and negative supply. Note: these pins are used thermally for heat-sinking.
18,19 17, 18 13-17, Make sure that all ground pins are soldered onto a suitably large copper ground plane
28 for efficient heat sinking.
8718V
R1
Reference voltage, channel 1. Controls the comparator threshold voltage and hence the
output current.
9819C
1
Comparator input channel 1. This input senses the instantaneous voltage across the
sensing resistor, filtered by the internal digital filter or an optional external RC network.
10 9 20 Phase
1
Controls the direction of motor current at outputs MA1 and MB1. Motor current flows from M
A1
to MB1 when Phase1 is HIGH.
11 10 21 Dis
1
Disable input for channel 1. When HIGH, all four output transistors are turned off, which
results in a rapidly decreasing output current to zero.
12 11 22 RC Clock oscillator RC pin. Connect a 12 kohm resistor to V
CC
and a 4 700 pF capacitor to ground
to obtain the nominal switching frequency of 23.0 kHz and a digital filter blanking time of 1.0µs.
13 12 23 V
CC
Logic supply voltage, nominally +5 V.
14 13 24 Dis
2
Disable input for channel 2. When HIGH, all four output transistors are turned off, which
results in a rapidly decreasing output current to zero.
15 14 25 Phase
2
Controls the direction of motor current at outputs MA2 and MB2. Motor current flows from M
A2
to MB2 when Phase2 is HIGH.
16 15 26 C
2
Comparator input channel 2. This input senses the instantaneous voltage across the
sensing resistor, filtered by the internal digital filter or an optional external RC network.
17 16 27 V
R2
Reference voltage, channel 2. Controls the comparator threshold voltage and hence the
output current.
20 19 4 V
MM2
Motor supply voltage, channel 2, +10 to +40 V.V
MM1
and V
MM2
should be connected together.
21 20 5 M
A2
Motor output A, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
22 21 6 E
2
Common emitter, channel 2. This pin connects to a sensing resistor RS to ground.
23 22 7 M
B2
Motor output B, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
Figure 2. Pin configurations
1
2
3
4
5
6
8
9
10
11
22
21
20
19
18
17
16
15
14
1312
GND
MA
1
Dis
1
MA
2
GND
NC
Phase
1
NJM
3773E3
MB
1
E
1
VMM
1
NC
MB
2
E
2
VMM
2
VR
1
VR
2
Dis
2
C
1
C
2
V
cc
RC
23
24
GND
GND
Phase
2
7
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
3773D2
E
B2
B1
GND
RC
GND
GND
GND
GND
GND
GND
GND
GND
GND
5
6
7
8
9
10
11
25
24
23
22
21
20
19
432
1
28
27
26
12131415161718
V
R2
V
R1
V
CC
Phase
2
M
A2
2
Dis
M
M
1
Dis
A1
M
1
Phase
C
2
C
1
2
V
MM1
E
1
V
MM2
NJM3773FM2
■ PIN CONFIGURATIONS
NJM3773
Figure 3. Output stage with current paths
during turn-on, turn-off and phase shift.
■ FUNCTIONAL DESCRIPTION
Each channel of the NJM3773 consists of the following sections: an output H-bridge with four transistors and four
recirculation diodes, capable of driving up to 750 mA 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 current-sensing resistor RS, effectively connected in series with the motor
winding. As the current increases, a voltage develops across the sensing resistor, which is fed back to the comparator. At the predetermined level, defined by the voltage at the reference input VR, the comparator resets the flipflop, which turns off the upper output transistor. The turn-off function of the two channels works independently of
each other. The current decreases until the clock oscillator triggers the flip-flops of both channels simultaneously,
which turns on the output transistors again, and the cycle is repeated.
To prevent erroneous switching due to switching transients at turn-on, the
NJM3773 includes a digital filter. The clock oscillator provides a blanking pulse which is used for digital filtering of
the voltage transient across the current sensing resistor during turn-on.
The current paths during constant current switching and phase shift are shown in figure 3.
Fast Current Decay
Slow Current Decay
Motor Current
Time
1 2
3
3
2
1
R
S
V
MM
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