NJM3771
DUAL STEPPER MOTOR DRIVER
s
GENERAL DESCRIPTION
The NJM3771 is a stepper motor driver, which circuit is
especially developed for use in microstepping applications in
conjunction with the matching dual DAC (Digital-to-Analog
Converter) NJU39610.
The NJM3771 contains a clock oscillator, which is common
for both driver channels; a set of comparators and flip-flops
imple menting the switching control; and two H-bridges with
internal recirculation diodes. Voltage supply requirements are
+5 V for logic and +10 to +45 V for the motor. Maximum
output current is 650 mA per channel.
s
PACKAGE OUTLINE
NJM3771D2
NJM3771E3
s
FEATURES
• Dual chopper driver
• 650 mA output current per channel
• Selectable slow/fast current decay for improved high-
speed microstepping
• Specially matched to Dual DAC NJU39610
• Packages DIP22 / EMP24(Batwing) / PLCC28
NJM3771FM2
s
BLOCK DIAGRAM
Phase
1
CD
1
V
R1
C
1
E
1
NJM 3771
V
CC
V
–
+
CC
R
S
Q
M
A1
+
–
Logic
M
B1
V
MM1
+
–
V
MM2
M
B2
Logic
S
R
Q
M
A2
–
+
RC
+
–
Phase
2
CD
2
V
R2
C
2
GND
E
2
Figure 1. Block diagram
NJM3771
s
PIN CONFIGURATIONS
M
B1 1
NC
1
MB
1
2
E
1
3
MA
1
4
VMM
1
5
GND
6
GND
7
Phase
1
8
CD
1
9
VR
1
10
C
1
11
V
CC
12
24
NC
23
MB
2
22
E
2
21
MA
2
22
21
20
19
18
M
B2
3
GND
2
GND
1
GND
28
GND
26
CD
2
4
M
A2
E
1 2
V
MM1 3
M
A1 4
GND
5
GND
6
Phase
1 7
CD
1 8
V
R1 9
C
1 10
V
CC 11
E
2
V
MM2
M
A2
GND
GND
Phase
2
CD
2
V
R2
C
2
RC
V
MM2 5
E
2 6
M
B2 7
27
Phase
2
25
V
R2
24
C
2
23
RC
NJM
3771E3
20
VMM
2
19
GND
18
GND
17
Phase
2
16
CD
2
15
NJM
3771D2
17
16
15
14
13
12
M
B1 8
GND
9
E
1 10
V
MM1 11
NJM 3771FM2
22
V
CC
21
C
1
20
V
R1
19
CD
1
VR
2
14
C
2
13
RC
M
A1 12
GND
13
GND
14
GND
15
GND
16
GND
17
Figure 2. Pin configurations
s
PIN DESCRIPTION
Refer to Figure 2
EMP
DIP
PLCC
Symbol
Description
2
3
4
5
6,7,
18,19
8
9
10
11
1
2
3
4
5,6,
17,18
7
8
9
10
8
10
11
12
1-3,9,
13-17,28
18
19
20
21
M
B1
E
1
V
MM1
M
A1
GND
Phase
1
CD
1
V
R1
C
1
12
13
14
11
12
13
22
23
24
V
CC
RC
C
2
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 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.
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.
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.
Current decay control, channel 1. A logic HIGH on this input results in
slow
current decay,
a LOW results in
fast
current decay, see “Functional Description.”
Reference voltage, channel 1. Controls the threshold voltage for the comparator and hence
the output current. Input resistance is typically 2.5 kohms,
±20%.
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
(0.450 / 2.5) • V
R1
, 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
(0.450 / 2.5) • V
R1
, i.e. 450 mV at V
R1
= 2.5 V.
Reference voltage, channel 2. Controls the threshold voltage for the comparator and hence
the output current. Input resistance is typically 2.5 kohms,
±20%.
Current decay control, channel 2. A logic HIGH on this input results in
slow
current decay,
a LOW results in
fast
current decay, see “Functional Description.”
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.
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 to ground.
Motor output B, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
15
16
17
20
21
22
23
14
15
16
19
20
21
22
25
26
27
4
5
6
7
V
R2
CD
2
Phase
2
M
A2
V
MM2
E
2
M
B2
Phase
1 18
NJM3771
s
FUNCTIONAL DESCRIPTION
Each channel of the NJM3771 consists of the following sections: an H-bridge output stage, capable of driving up
to 650 mA continuous motor current (or 500 mA, both channels driven), a logic section that controls the output
transistors, an S-R flip-flop, and two comparators. The oscillator is common to both channels.
Constant current control is achieved by switching the current to the windings. This is done by sensing the (peak)
voltage across a current-sensing resistor, R
S
, effectively connected in series with the motor winding, and feeding
that voltage back to a comparator. When the motor current reaches a threshold level, determined by the voltage at
the reference input, V
R
, the comparator resets the flip-flop, which turns off the output transistors. The current
decreases until the clock oscillator triggers the flip-flop, which turns on the output transistors again, and the cycle is
repeated.
The current-decay rate during the turn-off portion of the switching cycle, can be selected fast or slow by the CD
input.
In slow current-decay mode, only one of the lower transistors in the H-bridge (those closest to the negative
supply) is switched on and off, while one of the upper transistors is held constantly on. During turn-off, the current
recirculates through the upper transistor (which one depends on current direction) and the corresponding free-
wheeling diode connected to V
MM
, see figure 3.
In fast current decay mode, both the upper and lower transistors are switched. During the off-time, the freewheel-
ing current is opposed by the supply voltage, causing a rapid discharge of energy in the winding.
Fast current decay may be required in half- and microstepping applications when rapid changes of motor current
are necessary. Slow current decay, however, gives less current ripple, and should always be selected, if possible,
to minimize core losses and switching noise.
2 1
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
NJM3771
s
ABSOLUTE MAXIMUM RATINGS
Parameter
Pin no. (DIP)
Symbol
Min
Max
Unit
Voltage
Logic supply
Motor supply
Logic inputs
Comparator inputs
Reference inputs
Current
Motor output current
Logic inputs
Analog inputs
Oscillator charging current
Temperature
Operating junction temperature
Storage temperature**
** Circuit only. The packaging can handle max 60°C
11
3, 20
7, 8, 15, 16
10, 13
9, 14
1, 4, 19, 22
7, 8, 15, 16
10, 13
12
V
CC
V
MM
V
I
V
C
V
R
I
M
I
I
I
A
I
RC
T
J
T
S
0
0
-0.3
-0.3
-0.3
-700
-10
-10
-
-40
-55
7
45
6
V
CC
7.5
+700
-
-
5
+150
+150
V
V
V
V
V
mA
mA
mA
mA
°C
°C
s
RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Min
Typ
Max
Unit
Logic supply voltage
Motor supply voltage
Motor output current ***
Junction temperature ****
Rise time logic inputs
Fall time logic inputs
Oscillator timing resistor
V
CC
V
MM
I
M
T
J
t
r
t
f
R
T
4.75
10
-650
-20
-
-
2
5
-
-
-
-
-
15
5.25
40
650
+125
2
2
20
V
V
mA
°C
µs
µs
kohm
*** In microstepping mode, “sine/cosine” drive where I
1
= 650 • cos(q) and I
2
= 650 • sin(q) mA, otherwise 500 mA/channel both
channels fully on.
****See operating temperature chapter.
Phase
1
7
CD
1
V
R1
8
9
C
1
10
E
1
2
NJM 3771
I
CC
V
V
11
–
+
CC
CC
| V
MA
– V
MB
|
R
S
Q
4
+
–
M
A1
M
B1
V
MM1
V
MM2
M
B2
M
A2
IM
I OL
I MM
Logic
1
t
on
50 %
t
off
3
15 kΩ
+
R
T
–
20
–
+
22
Logic
S
R
Q
19
t
V
E
V
CH
I
RC
RC
12
+
–
t
d
3 300 pF
V
CC
C
T
Phase
2
I
I
I
IH
I
IL
I
A
V
I
V
IH
V
IL
V
A
V
R
V
CH
V
C
820 pF
16
15
14
13
C
2
I
C
I
A
5, 6, 17, 18
GND
21
E
2
CD
2
V
R2
1 kΩ
R
C
V
E
V
M
V
MA
V
MM
t
C
C
R
S
1
f
s
=
t + t
on
off
D=
t
on
t
on +
t
off
Figure 4. Definitions of symbols
Figure 5. Definition of terms
NJM3771
s
ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating conditions, unless otherwise noted. -20°C < T
J
< +125°C
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
General
Supply current
Total power dissipation
I
CC
P
D
-
V
MM
= 40 V, I
M1
= 450 mA, I
M2
= 0 mA.
Notes 2, 3.
V
MM
= 40 V, I
M1
= I
M2
= 318 mA.
Notes 2, 3.
T
a
= +25°C, dV
C
/dt
≥
50 mV/µs.
Note 3.
38
1.4
1.6
50
1.6
1.8
1.5
mA
W
W
µs
Turn-off delay
Logic Inputs
Logic HIGH input voltage
Logic LOW input voltage
Logic HIGH input current
Logic LOW input current
Reference Inputs
Input resistance
Input current
Turn-off voltage
Comparator Inputs
Threshold voltage
| V
CH1
- V
CH2
| mismatch
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
Upper diode forward voltage drop
Chopper Oscillator
Chopping frequency
t
d
-
1.0
V
IH
V
IL
I
IH
I
IL
R
R
I
R
V
TO
V
CH
V
CH,diff
I
C
V
I
= 2.4 V
V
I
= 0.4 V
T
a
= +25°C
T
a
= +25°C, V
R
= 2.5 V.
2.0
-
-
-0.4
-
20
-
-
-
-
5
0.5
29
450
1
-
1.00
-
1.10
1.20
-
1.00
26.5
-
0.6
20
-
-
1.0
38
470
-
1
1.20
300
1.25
1.35
300
1.25
28.0
V
V
µA
mA
kohm
mA
mV
mV
mV
µA
V
µA
V
V
µA
V
kHz
R
C
= 1 kohms, V
R
= 2.5 V
R
C
= 1 kohms
430
-
-10
-
-
-
-
-
-
25.0
I
M
= 500 mA
V
MM
= 41 V, V
E
= V
R
= 0 V, V
C
= V
CC
I
M
= 500 mA
I
M
= 500 mA
V
MM
= 41 V, V
E
= V
R
= 0 V, V
C
= V
CC
I
M
= 500 mA
f
s
C
T
= 3300 pF, R
T
= 15 kohms
s
THERMAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Thermal resistance
Rth
J-GND
Rth
J-A
Rth
J-GND
Rth
J-A
Rth
J-GND
Rth
J-A
DIP package.
DIP package. Note 2.
PLCC package.
PLCC package. Note 2.
EMP package.
EMP package. Note 2.
-
-
-
-
-
-
11
40
9
35
13
42
-
-
-
-
-
-
°C/W
°C/W
°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.
3. Not covered by final test program.
4. Switching duty cycle D = 30%, f
S
= 26.5 kHz
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