NJM3771
Figure 1. Block diagram
s
BLOCK DIAGRAM
DUAL STEPPER MOTOR DRIVER
s
GENERAL DESCRIPTION
s
PACKAGE OUTLINE
RC
NJM 3771
V
MM1
V
MM2
M
A1
M
B1
M
B2
M
A2
GND
C
2
V
R2
CD
2
Phase
2
V
CC
C
1
V
R1
CD
1
Phase
1
E
1
E
2
V
CC
S
R
Q
+
+
Logic
S
R
Q
+
+
Logic
+
NJM3771FM2
NJM3771E3
NJM3771D2
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
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
NJM3771
C
MM2
E
B2
B1
GND
MM1
C
RC
V
M
GND
GND
GND
GND
Phase
CD
A1
GND
GND
GND
GND
GND
1
5
6
7
8
9
10
11
25
24
23
22
21
20
19
4
3
2
1
28
27
26
12
13
14
15
16
17
18
V
R2
V
R1
CD
1
CC
2
2
A2
V
M
M
V
M
Phase
2
1
2
E
1
NJM 3771FM2
1
2
3
4
5
6
7
8
9
10
11
22
21
20
19
18
17
16
15
14
13
12
B1
E
MM1
A1
GND
GND
1
1
R1
C
CC
M
V
M
GND
GND
Phase
CD
V
RC
M
V
M
Phase
CD
V
V
R2
2
2
A2
MM2
B2
1
E
2
1
C
2
NJM
3771D2
Figure 2. Pin configurations
s
PIN DESCRIPTION
Refer to Figure 2
EMP
DIP
PLCC
Symbol
Description
2
1
8
M
B1
Motor output B, channel 1. Motor current flows from M
A1
to M
B1
when Phase
1
is HIGH.
3
2
10
E
1
Common emitter, channel 1. This pin connects to a sensing resistor to ground.
4
3
11
V
MM1
Motor supply voltage, channel 1, 10 to 40 V. V
MM1
and V
MM2
should be connected together.
5
4
12
M
A1
Motor output A, channel 1. Motor current flows from M
A1
to M
B1
when Phase
1
is HIGH.
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
13-17,28
Make sure that all ground pins are soldered onto a suitably large copper ground
plane for efficient heat sinking.
8
7
18
Phase
1
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.
9
8
19
CD
1
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."
10
9
20
V
R1
Reference voltage, channel 1. Controls the threshold voltage for the comparator and hence
the output current. Input resistance is typically 2.5 kohms,
20%.
11
10
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
(0.450 / 2.5) V
R1
, i.e. 450 mV at V
R1
= 2.5 V.
12
11
22
V
CC
Logic voltage supply, nominally +5 V.
13
12
23
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.
14
13
24
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
(0.450 / 2.5) V
R1
, i.e. 450 mV at V
R1
= 2.5 V.
15
14
25
V
R2
Reference voltage, channel 2. Controls the threshold voltage for the comparator and hence
the output current. Input resistance is typically 2.5 kohms,
20%.
16
15
26
CD
2
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."
17
16
27
Phase
2
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.
20
19
4
M
A2
Motor output A, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
21
20
5
V
MM2
Motor supply voltage, channel 2, 10 to 40 V. V
MM1
and V
MM2
should be connected together.
22
21
6
E
2
Common emitter, channel 2. This pin connects to a sensing resistor to ground.
23
22
7
M
B2
Motor output B, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
s
PIN CONFIGURATIONS
1
2
3
4
5
6
8
9
10
11
22
21
20
19
18
17
16
15
14
13
12
GND
MA
1
MA
2
GND
NC
NJM
3771E3
MB
1
E
1
VMM
1
NC
MB
2
E
2
VMM
2
VR
2
CD
2
C
2
RC
23
24
GND
GND
Phase
2
7
VR
1
CD
1
C
1
V
CC
Phase
1
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.
Figure 3. Output stage with current paths
during turn -on, turn-off and phase shift
FAST Current Decay
SLOW Current Decay
Motor Current
Time
1
3
2
3
2
1
R
s
NJM3771
Figure 4. Definitions of symbols
Figure 5. Definition of terms
50 %
V
CH
t
on
t
off
V
E
| V V |
MA
MB
t
d
t
t
f =
s
ton toff
+
D =
t
t
on
off
+
1
t
on
I I
M OL
I
CC
I I I
I IH IL
I
A
3 300 pF
V
CC
I
I
C
A
V
E
V
V
V
MM
C
820 pF
1 k
R
S
R
T
T
C
C
R
C
15 k
I MM
I
RC
RC
NJM 3771
20
12
11
V
MM1
V
MM2
M
A1
M
B1
M
B2
M
A2
GND
C
2
V
R2
CD
2
Phase
2
V
CC
C
1
V
R1
CD
1
Phase
1
E
1
E
2
V
CC
22
19
16
13
S
R
Q
15
14
5, 6, 17, 18
+
+
Logic
21
S
R
Q
+
+
Logic
+
3
1
4
2
10
9
8
7
V
V
V
I
IH
IL
V
V
A
R
V
V
CH
C
M
MA
s
ABSOLUTE MAXIMUM RATINGS
Parameter
Pin no. (DIP)
Symbol
Min
Max
Unit
Voltage
Logic supply
11
V
CC
0
7
V
Motor supply
3, 20
V
MM
0
45
V
Logic inputs
7, 8, 15, 16
V
I
-0.3
6
V
Comparator inputs
10, 13
V
C
-0.3
V
CC
V
Reference inputs
9, 14
V
R
-0.3
7.5
V
Current
Motor output current
1, 4, 19, 22
I
M
-700
+700
mA
Logic inputs
7, 8, 15, 16
I
I
-10
-
mA
Analog inputs
10, 13
I
A
-10
-
mA
Oscillator charging current
12
I
RC
-
5
mA
Temperature
Operating junction temperature
T
J
-40
+150
C
Storage temperature**
T
S
-55
+150
C
** Circuit only. The packaging can handle max 60
C
s
RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Min
Typ
Max
Unit
Logic supply voltage
V
CC
4.75
5
5.25
V
Motor supply voltage
V
MM
10
-
40
V
Motor output current ***
I
M
-650
-
650
mA
Junction temperature ****
T
J
-20
-
+125
C
Rise time logic inputs
t
r
-
-
2
s
Fall time logic inputs
t
f
-
-
2
s
Oscillator timing resistor
R
T
2
15
20
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.
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
I
CC
-
38
50
mA
Total power dissipation
P
D
V
MM
= 40 V, I
M1
= 450 mA, I
M2
= 0 mA.
1.4
1.6
W
Notes 2, 3.
V
MM
= 40 V, I
M1
= I
M2
= 318 mA.
1.6
1.8
W
Notes 2, 3.
Turn-off delay
t
d
T
a
= +25
C, dV
C
/dt
50 mV/
s.
-
1.0
1.5
s
Note 3.
Logic Inputs
Logic HIGH input voltage
V
IH
2.0
-
-
V
Logic LOW input voltage
V
IL
-
-
0.6
V
Logic HIGH input current
I
IH
V
I
= 2.4 V
-
-
20
A
Logic LOW input current
I
IL
V
I
= 0.4 V
-0.4
-
-
mA
Reference Inputs
Input resistance
R
R
T
a
= +25
C
-
5
-
kohm
Input current
I
R
T
a
= +25
C, V
R
= 2.5 V.
0.5
1.0
mA
Turn-off voltage
V
TO
20
29
38
mV
Comparator Inputs
Threshold voltage
V
CH
R
C
= 1 kohms, V
R
= 2.5 V
430
450
470
mV
| V
CH1
- V
CH2
| mismatch
V
CH,diff
R
C
= 1 kohms
-
1
-
mV
Input current
I
C
-10
-
1
A
Motor Outputs
Lower transistor saturation voltage
I
M
= 500 mA
-
1.00
1.20
V
Lower transistor leakage current
V
MM
= 41 V, V
E
= V
R
= 0 V, V
C
= V
CC
-
-
300
A
Lower diode forward voltage drop
I
M
= 500 mA
-
1.10
1.25
V
Upper transistor saturation voltage
I
M
= 500 mA
-
1.20
1.35
V
Upper transistor leakage current
V
MM
= 41 V, V
E
= V
R
= 0 V, V
C
= V
CC
-
-
300
A
Upper diode forward voltage drop
I
M
= 500 mA
-
1.00
1.25
V
Chopper Oscillator
Chopping frequency
f
s
C
T
= 3300 pF, R
T
= 15 kohms
25.0
26.5
28.0
kHz
s
THERMAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Thermal resistance
Rth
J-GND
DIP package.
-
11
-
C/W
Rth
J-A
DIP package. Note 2.
-
40
-
C/W
Rth
J-GND
PLCC package.
-
9
-
C/W
Rth
J-A
PLCC package. Note 2.
-
35
-
C/W
Rth
J-GND
EMP package.
-
13
-
C/W
Rth
J-A
EMP package. Note 2.
-
42
-
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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