NJM3772
Figure 1. Block diagram
■ BLOCK DIAGRAM
DUAL STEPPER MOTOR DRIVER
NJM3772D2 NJM3772FM2
■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE
The NJM3772 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 NJM3772 contains a clock oscillator, which is common
for both driver channels, a set of comparators and flip-flops
implementing the switching control, and two H-bridges with
internal recirculation diodes. Voltage supply requirements are
+5 V for logic and +10 to +45V for the motor. Maximum output
current is 1000mA per channel.
■ FEATURES
•Dual chopper driver
• 1000mA continuous output current per channel
• Specially matched to the Dual DAC NJU39610
• Packages DIP22 / PLCC28
RC
NJM 3772
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
S
RQ
+
—
Logic
S
RQ
+
—
Logic
+
—
V
MM2
V
MM1
V
BB2
V
BB1
NJM3772
Figure 2. Pin configurations
■ PIN DESCRIPTION
PLCC DIP Symbol Description
1-3, 9, 5, 6 GND Ground and negative supply. Note: these pins are used thermally for heat-sinking.
13-17 17, 18 Make sure that all ground pins are soldered onto a suitably large copper ground
28 plane for efficient heat sinking.
48M
A2 Motor output A, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
59V
BB2 Collector of upper output transistor, channel 2. For lowest possible power dissipation, connect a
series resistor RB2 to VMM2. See Applications information, External components.
610E
2Common emitter, channel 2. This pin connects to a sensing resistor RS to ground.
711M
B2 Motor output B, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
812M
B1 Motor output B, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
10 13 E1Common emitter, channel 1. This pin connects to a sensing resistor RS to ground.
11 14 VBB1 Collector of upper output transistor, channel 1. For lowest possible power dissipation, connect a
series resistor RB1 to VMM1. See Applications information, External components.
12 15 MA1 Motor output A, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
18 16 VMM1 Motor supply voltage, channel 1, +10 to +40 V. VMM1 and VMM2 should be connected together.
19 19 Phase1Controls the direction of motor current at outputs MA1 and MB1. Motor current flows from MA1 to MB1
when Phase1 is HIGH.
20 20 VR1 Reference voltage, channel 1. Controls the threshold voltage for the comparator and hence the
output current.
21 21 C1Comparator 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 VCH1= 0.18 • VR1 [V],
i.e. 450 mV at VR1 = 2.5 V.
22 22 VCC Logic voltage supply, nominally +5 V.
23 1 RC Clock oscillator RC pin. Connect a 15 kohm resistor to VCC and a 3300 pF capacitor to ground to
obtain the nominal switching frequency of 26.5 kHz.
24 2 C2Comparator 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 VCH2= 0.18 • VR2 [V],
i.e. 450 mV at VR2 = 2.5 V.
25 3 VR2 Reference voltage, channel 2. Controls the threshold voltage for the comparator and hence the
output current.
26 4 Phase2Controls the direction of motor current at outputs MA2 and MB2. Motor current flows from MA2 to MB2
when Phase2 is HIGH.
27 7 VMM2 Motor supply voltage, channel 2, +10 to +40 V.VMM1 and VMM2 should be connected together.
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
RC
V
M
Phase
V
V
2
A2
BB2
B2
2
E2
C1
VBB1
MB1
E1
NJM
3772D2
VMM2 VMM1
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
C
E
B2
B1
GND
C
RC
V
M
GND
GND
GND
GND
A1
GND
GND
GND
GND
GND
V
R2
V
R1
CC
Phase
2
A2
MM2
V
M
M
MM1
V
M
1
Phase
2
1
2
V
BB1
E
1
V
BB2
NJM3772FM2
■ PIN CONFIGURATIONS
NJM3772
■ FUNCTIONAL DESCRIPTION
Each channel of the NJM3772 consists of the following sections: an output H-bridge with four transistors, capable
of driving up to 1000 mA continuous current to the motor winding; a logic section that controls the output transis-
tors; 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 during the turn-on period. 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 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 paths during turn-on, turn-off and phase shift are shown in figure 3. Note that the upper recirculation
diodes are connected to the circuit externally.
Figure 3. Output stage with current paths
during turn-on, turn-off and phase shift.
External recirculation diodes
R
B
3
2
1
R
S
V
MM
BB
V
Fast Current Decay
Slow Current Decay
Motor Current
Time
1 2 3
NJM3772
Figure 4. Definition of symbols Figure 5. Definition of terms
50 %
V
CH
t
on
t
off
V
E
| V – V |
MA MB
f =
ston toff
+
D = t
t
on off
+
1t
on
t
t
t
d
I I
M OL
ICC
I I I
I IH IL
IA
3 300 pF
VCC
V
V
V
I
IH
IL
V
V
A
R
V
V
CH
C
I
I
C
A
VEV
V
M
MA
VMM
C
820 pF
1 kΩ
RS
RT
T
CC
RC
15 kΩ
I MM
VBB
IRC
RB
RC
9
1
22
MA1
MB1
MB2
MA2
GNDC2
VR2
Phase2
VCC
C1
VR1
Phase1E1
E2
VCC
11
8
42
S
RQ
3
5, 6, 17, 18
+
—
Logic
10
S
RQ
+
—
Logic
+
—
14
12
15
13
2120
19
VMM2
VMM1
VBB2
VBB1
16
7
Pin no.
refers to DIP-package
NJM3772
■ ABSOLUTE MAXIMUM RATINGS
Parameter Pin no. DIP package Symbol Min Max Unit
Voltage
Logic supply 22 VCC 07 V
Motor supply 7, 16 VMM 045 V
Output stage supply 9, 14 VBB 045 V
Logic inputs 4, 19 VI-0.3 6 V
Comparator inputs 2, 21 VC-0.3 VCC V
Reference inputs 3, 20 VR-0.3 7.5 V
Current
Motor output current 8, 11, 12, 15 IM-1200 +1200 mA
Logic inputs 4, 19 II-10 - mA
Analog inputs 2, 3, 20, 21 IA-10 - mA
Temperature
Operating junction temperature Tj-40 +150 °C
Storage temperature TS-55 +150 °C
Power Dissipation (Package Data)
Power dissipation at TGND = +25°C, DIP and PLCC package PD-5W
Power dissipation at TGND = +125°C, DIP package PD- 2.2 W
Power dissipation at TGND = +125°C, PLCC package PD- 2.6 W
■ RECOMMENDED OPERATING CONDITIONS
Parameter Symbol Min Typ Max Unit
Logic supply voltage VCC 4.75 5 5.25 V
Motor supply voltage VMM 10 - 40 V
Output stage supply voltage VBB VMM- 0.5 - VMM V
Motor output current IM-1000 - +1000 mA
Junction temperature ** TJ-20 - +125 °C
Rise and fall time, logic inputs tr, tf--2µs
Oscillator timing resistor RT21520kΩ
** See operating temperature chapter
NJM3772
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 cm2 PCB copper area with free air convection, TA = +25°C
3. Not covered by final test program
4. Switching duty cycle D = 30%, fs = 26.5 kHz
5. External resistors RB for lowering of saturation voltage
■ ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating conditions, unless otherwise noted. -20°C< TJ < 125°C
Parameter Symbol Conditions Min Typ Max Unit
General
Supply current ICC Note 4. - 60 75 mA
Total power dissipation PDVMM = 12 V, IM1= IM2= 750 mA. - 1.8 2.1 W
RB = 0.68 ohm. Notes 2, 3, 4, 5.
Total power dissipation PDVMM = 12 V, IM1 = 1000 mA, IM2 = 0 mA. - 1.8 2.2 W
RB = 0.47 ohm. Notes 2, 3, 4, 5.
Thermal shutdown junction temperature - 160 - °C
Turn-off delay tdTA = +25°C, dVC/dt ≥ 50 mV/µs, - 1.4 2.0 µs
IM = 100 mA. Note 3.
Logic Inputs
Logic HIGH input voltage VIH 2.0 - - V
Logic LOW input voltage VIL - - 0.8 V
Logic HIGH input current IIH VI = 2.4 V - - 20 µA
Logic LOW input current IIL VI = 0.4 V -0.4 - - mA
Comparator Inputs
Threshold voltage VCH RC = 1 kohm, VR = 2.50 V 430 450 470 mV
| VCH1 - VCH2 | mismatch VCH,diff RC = 1 kohm - 1 - mV
Input current IC-10 - 1 µA
Reference Inputs
Input resistance RRTA = +25°C - 5 - kohm
Input current IRVR = 2.50 V - 0.5 1.0 mA
Motor Outputs
Lower transistor saturation voltage IM = 750 mA - 0.6 0.9 V
Lower transistor leakage current VMM = 41 V, VE = VR = 0 V, VC = VCC - - 700 µA
Lower diode forward voltage drop IM = 750 mA - 1.2 1.5 V
Upper transistor saturation voltage IM = 750 mA. RB = 0.68 ohm. Note 5 - 0.6 0.9 V
Upper transistor saturation voltage IM = 750 mA. RB = 0.47 ohm. Note 3, 5 - 0.8 1.1 V
Upper transistor leakage current VMM VBB = 41 V, VE = VR = 0 V, VC = VCC - - 700 µA
Chopper Oscillator
Chopping frequency fsCT = 3300 pF, RT = 15 kohm 25.0 26.5 28.0 kHz
■ THERMAL CHARACTERISTICS
Parameter Symbol Conditions Min Typ Max Unit
Thermal resistance RthJ-GND DIP package - 11 - °C/W
RthJ-A DIP package. Note 2 - 40 - °C/W
RthJ-GND PLCC package - 9 - °C/W
RthJ-A PLCC package. Note 2 - 35 - °C/W
NJM3772
■ APPLICATIONS INFORMATION
Current control
The output current to the motor winding is determined by the voltage at the reference input and the sensing
resistor, RS.
Chopping frequency, winding inductance and supply voltage also affect the current, but to much less extent.
The peak current through the sensing resistor (and motor winding) can be expressed as:
IM,peak = 0.18 • ( VR / RS )[A]
i.e., with a recommended value of
0.47 ohm for the sensing resistor RS, a 2.5 V reference voltage will produce an output current of approximately
960 mA.
To improve noise immunity on the VR input, the control range may be increased to 5 V if RS is correspondingly
changed to 1 ohm.
Figure 7. Microstepping system with NJU39610 and NJM3772
ECECGND
RC
NJM3772
15 kΩ
3300 pF 820 pF
0.5 Ω
1 kΩ1 kΩ
0.5 Ω
820 pF
STEPPER
MOTOR
M
M
M
M
A1
B1
A2
B2
V
MM
VVVVV
CC MM1 BB1 MM2 BB2
+5 V
12
8
4
7
19
20
26
25
22 18 11 27 5
23 1, 2,
3, 9,
28, 13,
14, 15,
16, 17,
10 24 6
21
Phase
V
Phase
V
R2
1
R1
2
D1
D3
0.5 Ω
11
22
D1 - D4 are UF 4001 or
BYV 27, t 100 ns
rr
RSRS
0.5 Ω
RBRB
0.1 µF
V
MM
+
10 µF
D2
D4
Pin numbers refer to
PLCC package.
D0
D7
A0
A1
WR
CS
RESET
VV
NJU39610
6
10
4
12
2
14
9
27
15
7
28
1
16
25
To
mP
+2.5V
Sign
DA
1
1
Sign
DA
2
2
SS
V
DD
Ref
V (+5V)
CC
E
CE
C
GND
RC
NJM3772
15 kΩ
3300 pF 820 pF
0.5 Ω
1 kΩ1 kΩ
0.5 Ω
820 pF
STEPPER
MOTOR
M
M
A1
B1
V
MM
VVVVV
CC MM1 BB1 MM2 BB2
+5 V
12
19
22 18 11 27 5
23 1, 2,
3, 9,
28, 13,
14, 15,
16, 17,
10 24 6
21
Phase
V
Phase
V
R2
1
R1
2
D1
D3
0.5 Ω
1122
R
S
R
S
0.5 Ω
R
B
R
B
GND (V )
CC
+5 V
0.1 µF
V
MM
+
10 µF
D2
D4
D1 - D4 are UF 4001 or
BYV 27, t ≤ 100 ns.
rr
Pin numbers
refer to PLCC
package.
GND (V
)
MM
20
26
25
M
A2
M
B2
8
4
7
Figure 6. Typical stepper motor driver application with NJM3772
NJM3772
External components
The NJM3772 exhibits substantially less power dissipation than most other comparable stepper motor driver ICs on
the market. This has been achieved by creating an external voltage drop in series with the upper transistor in the
output H-bridge, see figure 3. The voltage drop reduces the collector-emitter saturation voltage of the internal
transistor, which can greatly reduce power dissipation of the IC itself. The series resistor, designated RB , shall be
selected for about 0.5 V voltage drop at the maximum output current. In an application with an output current of
1000 mA (peak), a 0.47 ohm,
1/2 W resistor is the best choice.
In low current applications where power dissipation is not a critical factor, the RB resistor can of course be
omitted, and the VMM and VBB pins (pins 5, 11, 18, 27) can all be connected directly to the motor supply voltage VMM.
Contributing to the low power dissipation is the fact that the upper recirculation diodes in the output H- bridge are
connected externally to the circuit. These diodes shall be of fast type, with a trr of less than 100 ns. Common types
are UF4001 or BYV27.
A low pass filter in series with the comparator input prevents erroneous switching due to switching transients.
The recommended filter component values, 1 kohm and 820 pF, are suitable for a wide range of motors and
operational conditions.
Since the low-pass filtering action introduces a small delay of the signal to the comparator, peak voltage across
the sensing resistor, and hence the peak motor current, will reach a slightly higher level than than what is defined
by the comparator threshold, VCH , set by the reference input VR (VCH = 450 mV at VR= 2.5 V).
The time constant of the low-pass filter may therefore be reduced to minimize the delay and optimize low-current
performance. Increasing the time constant may result in unstable switching. The time constant should be adjusted
by changing the CC value.
The frequency of the clock oscillator is set by the RT-CT timing components at the RC pin. The recommended
values result in a clock frequency (= switching frequency) of 26.5 kHz. A lower frequency will result in higher
current ripple, but may improve low-current level linearity. A higher clock frequency reduces current ripple, but
increases the switching losses in the IC and possibly the iron losses in the motor. If the clock frequency needs to
be changed, the CT capacitor value should be adjusted. The recommended RT resistor value is 15 kohm.
The sensing resistor RS, should be selected for maximum motor current. The relationship between peak motor
current, reference voltage and the value of RS is described under Current control above. Be sure not to exceed the
maximum output current which is 1200 mA peak when only one channel is activated. Or recommended output
current, which is 1000 mA peak, when both channels is activated.
NJM3772
Figure 8. Typical thermal resistance vs. PC Board copper area and suggested layout
Thermal resistance [°C/W]
PCB copper foil area [cm ]
2
80
70
60
50
40
30
20 5101520 30 3525
PLCC package
DIP package
28-pin PLCC
22-pin
DIP
Motor selection
The NJM3772 is designed for two-phase bipolar stepper motors, i.e., motors that have only one winding per
phase.
The chopping principle of the NJM3772 is based on a constant frequency and a varying duty cycle. This scheme
imposes certain restrictions on motor selection. Unstable chopping can occur if the chopping duty cycle exceeds
approximately 50%. See figure 5 for definitions. To avoid this, it is necessary to choose a motor with a low winding
resistance and inductance, i.e. windings with a few turns.
It is not possible to use a motor that is rated for the same voltage as the actual supply voltage. Only rated current
needs to be considered. Typical motors to be used together with the NJM3772 have a voltage rating of 1 to 6 V,
while the supply voltage usually ranges from 12 to 40 V.
Low inductance, especially in combination with a high supply voltage, enables high stepping rates. However, to
give the same torque capability at low speed, a reduced number of turns in the winding must be compensated by a
higher current. A compromise has to be made.
Choose a motor with the lowest possible winding resistance that still gives the required torque, and use as high
supply voltage as possible, without exceeding the maximum recommended 40 V. Check that the chopping duty
cycle does not exceed 50% at maximum current.
Phase inputs.
A logic HIGH on a Phase input gives a current flowing from pin MA into pin MB. A logic LOW gives a current flow in
the opposite direction. A time delay prevents cross conduction in the H-bridge when changing the Phase input.
Heat sinking.
Soldering the batwing ground leads onto a copper ground plane of 20 cm2 (approx. 1.8" x 1.8"), copper foil thick-
ness 35 µm, permits the circuit to operate with 750 mA output current, both channels driving, at ambient tempera-
tures up to 70°C. Consult figures 8, 9, 10 and 11 in order to determine the necessary copper ground plane area for
heat sinking at higher current levels.
Thermal shutdown.
The circuit is equipped with a thermal shutdown function that turns the output off at chip temperatures above
160°C. Normal operation is resumed when the temperature has decreased.
Operating temperature.
The max recommended operating temperature is 125°C. This gives an estimated lifelength of about 5 years at
continuous drive, A change of ±10° would increase/decrease the lifelength of the circuit about 5 years.
NJM3772
Figure 10. Power dissipation vs. motor
current, both channels on. Ta = 25°C
Figure 9. Power dissipation vs.
motor current. Ta = 25°CFigure 11. Maximum allowable
power dissipation vs. temperature
Figure 12. Typical lower transistor
saturation voltage vs. output current Figure 13. Typical lower diode voltage
drop vs. recirculating current Figure 14. Typical upper transistor
saturation voltage vs. output current
0 .20 .40 .60 .80 1.0 1.2
I
M
(A)
0
.5
1.0
1.5
2.0
2.5
P
D
(W)
3.0 NJM3772
MM = 12 V
V
Two channels on.
R = 0.68 ohm.
Two channels on.
R = 0.47 ohm.
One channel on.
R = 0.47 ohm.
B
B
P
D
(W)
0 .20 .40 .60 .80 1.0 1.2
I
M
(A)
0
.5
1.0
1.5
2.0
2.5
3.0
MM
= 12 V
V
V
MM
= 36 V
NJM3772
B
= 0.68
R
Ω
.2
.4
.6
.8
1.0
V
CE Sat, lt
(V)
0 .20 .40 .60 .80 1.0 1.2
I
M
(A)
NJM3772
1.2
T =25¡C
J
T =125¡C
J
V
CE Sat, ut
(V)
0 .20 .40 .60 .80 1.0 1.2
I
M
(A)
.2
.4
.6
.8
1.0
1.2 NJM3772
RB
= 0.68Ω
RB
= 0.47Ω
V
d
(V)
0 .20 .40 .60 .80 1.0 1.2
I
M
(A)
.2
.4
.6
.8
1.0
1.2
PBL 3772
Maximum allowable power dissipation [W]
Temperature [°C]
0 25 50 75 125 150
100
PLCC package
DIP package All ground pins soldered onto a
20 cm PCB copper area with
free air convection.
2
6
5
4
3
2
1
0
Batwing pin temperature
Ambient temperature
-25
■ TYPICAL CHARACTERISTICS
The specifications on this databook are only
given for information , without any guarantee
as regards either mistakes or omissions.
The application circuits in this databook are
described only to show representative
usages of the product and not intended for
the guarantee or permission of any right
including the industrial rights.
