NJM3771
DUAL STEPPER MOTOR DRIVER
■
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.
■
PACKAGE OUTLINE
NJM3771D2
( DIP22 )
NJM3771E3
( SOP24 )
■
FEATURES
●
Dual chopper driver
●
650mA output current per channel
●
Selectable slow / fast current decay for improved high-
speed microstepping
●
Specially matched to Dual DAC
NJU39610
●
Packages
DIP22-D2 / PLCC28-M2
SOP24 JEDEC 300 mil (Batwing)
■
BLOCK DIAGRAM
NJM3771FM2
( PLCC28 )
Figure 1. Block diagram
Ver.2011-12-08
-1-
NJM3771
■
PIN CONFIGURATION
Figure 2. Pin configurations
■
PIN DESCRIPTION
Refer to Figure 2.
SOP
2
3
4
5
6, 7,
18,19
8
9
10
11
DIP
1
2
3
4
5, 6,
17, 18
7
8
9
10
PLCC
8
10
11
12
1-3, 9,
13-17, 28
18
19
20
21
Symbol
M
B1
E
1
V
MM1
M
A1
GND
Description
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 2.5kohms, ±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)½
V
R1
, i.e. 450mV at V
R1
=2.5V.
Logic voltage supply, nominally +5 V.
Clock oscillator RC pin. Connect a 15 kohm resistor to V
CC
and a 3 300 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)½
V
R1
, i.e. 450mV at V
R1
=2.5V.
Reference voltage, channel 2. Controls the threshold voltage for the comparator and hence
the output current. input resistance is typically 2.5kohms, ±20%.
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”
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.
Phase
1
CD
1
V
R1
C
1
12
13
14
11
12
13
22
23
24
V
CC
RC
C
2
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
-2-
Ver.2011-12-08
NJM3771
■
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 freewheeling 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 freewheeling
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
Ver.2011-12-08
-3-
NJM3771
■
ABSOLUTE MAXIMUM RATINGS
Parameter
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
T
J
T
stg
-40
-55
+150
+150
°C
°C
1, 4, 19, 22
7, 8, 15, 16
10, 13
12
I
M
I
I
I
A
I
RC
-700
-10
-10
-
+700
-
-
5
mA
mA
mA
mA
11
3, 20
7, 8, 15, 16
10, 13
9, 14
V
CC
V
MM
V
I
V
C
V
R
0
0
-0.3
-0.3
-0.3
7
45
6
V
CC
7.5
V
V
V
V
V
Pin no. (DIP)
Symbol
Min
Max
Unit
■
RECOMMENDED OPERATING CONDITIONS
Parameter
Logic supply voltage
Motor supply voltage
Motor output current ***
Junction temperature ****
Rise time logic inputs
Fall time logic inputs
Oscillator timing resistor
Symbol
V
CC
V
MM
I
M
T
j
t
r
t
f
R
T
Min
4.75
10
-650
-20
-
-
2
Typ
5
-
-
-
-
-
15
Max
5.25
40
650
+125
2
2
20
Unit
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.
Figure 4. Definitions of symbols
Figure 5. Definition of terms
-4-
Ver.2011-12-08
NJM3771
■
ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating conditions, unless otherwise noted. -20°C
≤
T
j
≤
+125°C
Parameter
General
Supply current
Total power dissipation
P
D
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
f
S
C
T
= 3300 pF, R
T
= 15 kohms
25.0
26.5
28.0
kHz
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
-
-
-
-
-
-
1.00
-
1.10
1.20
-
1.00
1.20
300
1.25
1.35
300
1.25
V
µA
V
V
µA
V
V
CH
V
CH
,
diff
I
C
R
C
= 1 kohms, V
R
= 2.5 V
R
C
= 1 kohms
430
-
-10
450
1
-
470
-
1
mV
mV
µA
R
R
I
R
V
TO
T
a
= +25°C
T
a
= +25°C, V
R
= 2.5 V.
20
-
5
0.5
29
-
1.0
38
kohm
mA
mV
V
IH
V
IL
I
IH
I
IL
V
I
= 2.4 V
V
I
= 0.4 V
2.0
-
-
-0.4
-
-
-
-
-
0.6
20
-
V
V
µA
mA
t
d
I
CC
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
1.0
50
1.6
1.8
1.5
mA
W
W
µs
Symbol
Conditions
Min
Typ
Max
Unit
■
THERMAL CHARACTERISTICS
Parameter
Thermal resistance
Symbol
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.
SOP package.
SOP package. Note 2.
Conditions
Min
-
-
-
-
-
-
Typ
11
40
9
35
13
42
Max
-
-
-
-
-
-
Unit
°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
Ver.2011-12-08
-5-
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