JRC NJM3775E3, NJM3775D2, NJM3775FM2 Datasheet
DUAL STEPPER MOTOR DRIVER
■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE
The NJM3775 is a switch-mode (chopper), constantcurrent driver with two channels: one for each winding
of a two-phase stepper motor. NJM3775 is equipped
with a Disable input to simplify half-stepping operation.
The NJM3775 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.
■ FEATURES
• Dual chopper driver
NJM3775D2
NJM3775FM2
NJM3775E3
NJM3775
• 750 mA continuous output current per channel
• Digital filter on chip eliminates external filtering components
• Packages DIP22 / PLCC28 / EMP24(batwing)
■ BLOCK DIAGRAM
C
Phase
1
NJM3775
V
CC
RC
V
CC
+
—
V
Dis
R1
1
1
—
+
+
—
R
S
SRQ
E
1
Q
M
A1
Logic
Logic
M
B1
V
MM1
V
MM2
M
B2
M
A2
Figure 1. Block diagram
Phase
Dis
V
2
2
R2
GNDC
2
E
2
■ PIN CONFIGURATIONS
NC
1
2
MB
1
E
3
1
4
MA
1
5
VMM
GND
GND
VR
Phase
Dis
RC
1
1
C
1
1
1
6
7
8
9
10
11
NJM
3775E3
Figure 2. Pin configurations
24
23
22
21
20
19
18
17
16
15
14
1312
NC
MB
E
2
MA
VMM
GND
GND
VR
C
2
Phase
Dis
V
cc
NJM3775
M
1
B1
E
2
2
2
2
2
2
2
M
V
MM1
GND
GND
V
Phase
Dis
RC
1
A1
R1
C
1
1
1
3
4
5
6
3775D2
7
8
9
10
11
NJM
22
21
20
19
18
17
16
15
14
13
12
M
B2
E
2
M
A2
V
MM2
GND
GND
V
R2
C
2
Phase
Dis
2
V
CC
MM2
GND
GND
V
432
5
M
A2
E
6
2
7
M
B2
8
M
B1
NJM3775FM2
GND
9
E
10
1
11
M
A1
2
12131415161718
MM1
GND
GND
V
GND
1
GND
R2
V
GND
282726
GND
GND
C
25
Phase
2
24
Dis
2
23
V
CC
22
RC
21
Dis
1
20
Phase
1
19
C
1
R1
V
2
■ PIN DESCRIPTION
EMP DIP PLCC Symbol Description
2 1 [8] M
32[10]E
43[11]M
54[12]V
B1
1
A1
MM1
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, Make sure that all ground pins are soldered onto a suitably large copper ground plane
28] for efficient heat sinking.
87[18]V
98[19]C
R1
1
10 9 [20] Phase
11 10 [21] Dis
12 11 [22] RC Clock oscillator RC pin. Connect a 12 kohm resistor to V
13 12 [23] V
CC
14 13 [24] Dis
15 14 [25] Phase
16 15 [26] C
17 16 [27] V
20 19 [4] V
21 20 [5] M
22 21 [6] E
23 22 [7] M
2
R2
MM2
A2
2
B2
Motor output B, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
Common emitter, channel 1. This pin connects to a sensing resistor RS to ground.
Motor output A, channel 1. Motor current flows from MA1 to MB1 when Phase1 is HIGH.
Motor supply voltage, channel 1, +10 to +40 V. V
MM1
and V
should be connected together.
MM2
Reference voltage, channel 1. Controls the comparator threshold voltage and hence the output
current.
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.
Controls the direction of motor current at outputs MA1 and MB1. Motor current flows from MA1 to
1
M
when Phase1 is HIGH.
B1
Disable input for channel 1. When HIGH, all four output transistors are turned off, which results
1
in a rapidly decreasing output current to zero.
and a 4 700 pF capacitor to ground
CC
to obtain the nominal switching frequency of 23.0 kHz and a digital filter blanking time of 1.0µs.
Logic voltage supply, nominally +5 V.
Disable input for channel 2. When HIGH, all four output transistors are turned off, which results
2
in a rapidly decreasing output current to zero.
Controls the direction of motor current at outputs MA2 and MB2. Motor current flows from MA2 to
2
M
when Phase2 is HIGH.
B2
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.
Reference voltage, channel 2. Controls the comparator threshold voltage and hence the output
current.
Motor supply voltage, channel 2, +10 to +40 V. V
MM1
and V
should be connected together.
MM2
Motor output A, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
Common emitter, channel 2. This pin connects to a sensing resistor RS to ground.
Motor output B, channel 2. Motor current flows from MA2 to MB2 when Phase2 is HIGH.
NJM3775
■ FUNCTIONAL DESCRIPTION
Each channel of the NJM3775 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 com- parator. 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. 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 flipflop, which turns off the upper output transistor. The turn-off of one channel is independent of the other channel.
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
NJM3775 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 turn-on, turn-off and phase shift are shown in figure 3.
V
1
MM
2
3
R
S
Motor Current
1 2
Fast Current Decay
Slow Current Decay
3
Figure 3. Output stage with current paths
during turn-on, turn-off and phase shift.
Time
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