NJM3773
DUAL STEPPER MOTOR DRIVER
s
GENERAL DESCRIPTION
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.
s
PACKAGE OUTLINE
NJM3773D2
NJM3773E3
NJM3773FM2
s
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)
s
BLOCK DIAGRAM
Phase
1
Dis
1
V
R1
C
1
E
1
NJM3773
V
CC
V
–
+
CC
R
S
Q
M
A1
Logic
M
B1
V
MM1
+
–
V
MM2
M
B2
Logic
M
A2
RC
+
–
S
R
Q
Phase
2
Dis
2
V
R2
C
2
GND
E
2
Figure 1. Block diagram
NJM3773
s
PIN CONFIGURATIONS
4
V
MM2
3
GND
2
GND
1
GND
28
GND
M
B1 1
NC
1
MB
1
2
E
1
3
MA
1
4
VMM
1
5
GND
6
GND
7
VR
1
8
C
1
9
Phase
1
10
Dis
1
11
RC
12
24
23
22
21
22
21
20
19
18
M
B2
E
2
M
A2
V
MM2
GND
GND
V
R2
C
2
Phase
2
M
A2 5
E
2 6
M
B2 7
M
B1 8
GND
9
E
1 10
M
A1 11
27
V
R2
NC
MB
2
E
2
MA
2
VMM
2
GND
GND
VR
2
C
2
Phase
2
Dis
2
V
cc
E
1 2
M
A1 3
V
MM1 4
GND
5
GND
6
V
R1 7
C
1 8
Phase
1 9
Dis
1 10
RC
11
26
C
2
25
Phase
2
24
Dis
2
23
V
CC
NJM
3773E3
20
19
18
17
16
15
14
13
NJM
3773D2
17
16
15
14
13
12
NJM3773FM2
22
RC
21
Dis
1
20
Phase
1
19
C
1
V
MM1 12
GND
13
GND
14
GND
15
GND
16
GND
17
Dis
2
V
CC
Figure 2. Pin configurations
s
PIN DESCRIPTION
EMP
DIP
PLCC
Symbol
Description
2
3
4
5
6,7
18,19
8
9
10
11
12
13
14
15
16
17
20
21
22
23
1
2
3
4
5, 6,
17, 18
7
8
9
10
11
12
13
14
15
16
19
20
21
22
8
10
11
12
1-3, 9,
13-17,
28
18
19
20
21
22
23
24
25
26
27
4
5
6
7
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 R
S
to ground.
Motor output A, channel 1. Motor current flows from M
A1
to M
B1
when Phase
1
is HIGH.
Motor supply voltage, channel 1, +10 to +40 V. V
MM1
and V
MM2
should be connected together.
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.
V
R1
Reference voltage, channel 1. Controls the comparator threshold voltage and hence the
output current.
C
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.
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.
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.
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.
V
CC
Logic supply voltage, nominally +5 V.
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.
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.
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.
V
R2
Reference voltage, channel 2. Controls the comparator threshold voltage and hence the
output current.
V
MM2
Motor supply voltage, channel 2, +10 to +40 V.V
MM1
and V
MM2
should be connected together.
M
A2
Motor output A, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
E
2
Common emitter, channel 2. This pin connects to a sensing resistor R
S
to ground.
M
B2
Motor output B, channel 2. Motor current flows from M
A2
to M
B2
when Phase
2
is HIGH.
M
B1
E
1
M
A1
V
MM1
GND
V
R1 18
NJM3773
s
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 R
S
, 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 com-
parator. At the predetermined level, defined by the voltage at the reference input V
R
, the comparator resets the flip-
flop, 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.
V
MM
1
2
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.
NJM3773
s
ABSOLUTE MAXIMUM RATINGS
Parameter
Pin no. [DIP]
Symbol
Min
Max
Unit
Voltage
Logic supply
Motor supply
Logic inputs
Analog inputs
Current
Motor output current
Logic inputs
Analog inputs
Temperature
Operating junction temperature
Storage temperature
Power Dissipation (Package Data)
Power dissipation at T
GND
= +25°C, DIP and PLCC package
Power dissipation at T
GND
= +125°C, DIP package
Power dissipation at T
GND
= +125°C, PLCC package
12
4, 19
9, 10, 13, 14
7, 8, 15, 16
1, 3, 20, 22
9, 10, 13, 14
7, 8, 15, 16
V
CC
V
MM
V
I
V
A
I
M
I
I
I
A
T
j
T
stg
P
D
P
D
P
D
0
0
-0.3
-0.3
-850
-10
-10
-40
-55
-
-
-
7
45
6
V
CC
+850
-
-
+150
+150
5
2.2
2.6
V
V
V
V
mA
mA
mA
°C
°C
W
W
W
s
RECOMMENDED OPERATING CONDITIONS
Parameter
Symbol
Min
Typ
Max
Unit
Logic supply voltage
Motor supply voltage
Output emitter voltage
Motor output current
Operating junction temperature
Rise and fall time logic inputs
Oscillator timing resistor
V
CC
V
MM
V
E
I
M
T
J
t
r,
, t
f
R
T
4.75
10
-
-750
-20
-
2
5
-
-
-
-
-
12
5.25
40
1.0
+750
+125
2
20
V
V
V
mA
°C
µs
kΩ
| V
MA
– V
MB
|
Phase
1
9
Dis
1
V
R1
10
7
C
1
8
E
1
2
NJM3773
50 %
I
CC
V
CC
V
12
—
+
CC
t
on
t
off
R
S
Q
3
Logic
1
M
A1
M
B1
V
MM1
V
MM2
M
B2
M
A2
IM
I OL
I MM
4
12 k‰
+
V
E
( I
M
)
V
R
t
t
d
R
T
19
—
22
Logic
I
RC
RC
11
+
—
4 700 pF
20
S
R
Q
V
CC
C
T
Phase
2
I
I
I
IH
I
C
V
I
V
V
IH
t
14
13
16
15
C
2
I
C
I
A
V
C
V
Pin no. refers
to DIP package
5, 6, 17, 18
GND
21
E
2
V
Dis
2
V
R2
RC
t
b
I
IL
I
A
V
M
V
MA
V
MM
V
A
V
R
V
RC
A
V
E
IL
R
B
R
S
t
1
f
s
=
t + t
on
off
D=
t
on
t
on +
t
off
Figure 4. Definition of symbols
Figure 5. Definition of terms
NJM3773
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
Supply current
Total power dissipation
Total power dissipation
I
CC
I
CC
P
D
P
D
V
R
=500mV. Note 4.
Dis
1
= Dis
2
= HIGH.
V
MM
= 24 V, I
M1
= I
M2
= 500 mA.
Notes 2, 3, 4.
V
MM
= 24 V, I
M1
= 700 mA, I
M2
= 0 mA.
Notes 2, 3, 4.
T
A
= +25°C, dV
C
/dt
≥
50 mV/µs,
I
M
= 100 mA. Note 3. (one channel on).
-
-
-
-
-
-
55
7
2.0
1.7
160
1.1
70
10
2.3
2.0
-
2.0
mA
mA
W
W
°C
µs
Thermal shutdown junction temperature
Turn-off delay
t
d
Logic Inputs
Logic HIGH input voltage
Logic LOW input voltage
Logic HIGH input current
Logic LOW input current
Analog Inputs
Input current
Threshold voltage
| V
C1
- V
C2
| mismatch
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
Digital filter blanking time
f
s
t
b
V
IH
V
IL
I
IH
I
IL
I
A
V
C
V
C,diff
V
I
= 2.4 V
V
I
= 0.4 V
2.0
-
-
-0.2
-0.5
-
-
-
-
-
-
-
-
21.5
-
-
-
-
-0.1
-0.2
500
1
0.4
-
1.1
1.1
-
1.1
23.0
1.0
-
0.6
20
-
-
-
-
0.8
100
1.3
1.4
100
1.4
24.5
-
V
V
µA
mA
µA
mV
mV
V
µA
V
V
µA
V
kHz
µs
V
R
= 500mV
R
B
= 1 kohm. Note 3.
I
M
= 500 mA
V
MM
=41 V,T
A
= +25°C. Dis
1
= Dis
2
= HIGH.
I
M
= 500 mA
I
M
= 500 mA.
V
MM
=41 V,T
A
= +25°C. Dis
1
= Dis
2
= HIGH.
.
I
M
= 500 mA.
C
T
= 4 700 pF, R
T
= 12 kohm
C
T
= 4 700 pF. Note 3.
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
-
-
-
-
-
-
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, T
A
= +25°C.
3. Not covered by final test program.
4. Switching duty cycle D = 30%, f
s
= 23.0 kHz.
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