NJM3776
DUAL CONTROLLER FOR HIGH-CURRENT STEPPER MOTOR
s
GENERAL DESCRIPTION
The NJM3776 is a switch-mode (chopper), constant-current
controller intended for controlling external transistors in a high
current stepper motor application. The NJM3776 has two channels,
one for each winding of a two-phase stepper motor. The NJM3776
is equipped with a Disable input to simplify half stepping operation.
The NJM3776 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 sections each containing four
outputs, two source and two sink, intended to drive an external H-
bridge. Voltage supply requirements are +5 V for logic and +10 to
+45 V for the outputs.
s
PACKAGE OUTLINE
NJM3776D2
s
FEATURES
• Suitable to drive any external MOS FET or bipolar power transistor
• Cross conduction prevented by time delay
• Digital filter on chip eliminates external filtering components
• Package
DIP24
s
BLOCK DIAGRAM
Phase 1
Dis 1 V
R1
C1
SGND 1
Pwr GND 1
1
NJM3776
–
T
1BL
R
S
Q
T
1AL
T
1AU
Logic
T
1BU
V
CC
V
CC
+
V
BB1
+
–
V
BB2
T
2BU
Logic
RC
+
–
T
2AU
T
2AL
T
2BL
S
R
Q
Phase 2
Dis 2 V
R2
C2
SGND 2
Pwr GND 2
Figure 1. Block diagram
NJM3776
s
PIN CONFIGURATION
PWR GND
1
1
T1BL
2
T1BU
3
T1AL
4
T1AU
5
VBB1
6
SGND
1
7
VR
1
8
C
1
9
Phase
1
10
Dis
1
11
RC
12
24
PWR GND
23
T2BL
22
T2BU
21
T2AL
20
T2AU
2
NJM
3776D2
19
VBB 2
18
SGND
17
VR
16
C
2
2
2
2
15
Phase
14
Dis
13
Vcc
2
Figure 2. Pin configuration
s
PIN DESCRIPTION
DIP
Symbol
Description
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
PWR GND
1
T1BL
T1BU
T1AL
T1AU
VBB1
SGND
1
VR
1
C
1
Phase
1
Dis
1
RC
Vcc
Dis
2
Phase
2
C
2
VR
2
SGND
2
VBB2
T2AU
T2AL
T2BU
T2BL
PWR GND
2
"Power Ground" from output channel 1. Connected to the ground path (see application examples).
Output, channel 1, B side lower transistor. The pin will sink current when phase is high.
Output, channel 1, B side upper transistor. The pin will source current when phase is low.
Output, channel 1, A side lower transistor. The pin will sink current when phase is low.
Output, channel 1, A side upper transistor. The pin will source current when phase is high.
Supply voltage for driving channel 1 outputs.
Sense ground channel 1. Logic ground reference and sense ground for the current control feedback-
loop.
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 channel 1 outputs T1AL, T1AU, T1BL and T1BU.
Disable input for channel 1. When HIGH, all four output transistors are turned off, which results in a
rapidly decreasing output current to zero.
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 1.0
µs.
Logic voltage supply, nominally +5 V.
Disable input for channel 2. When HIGH, all four output transistors are turned off, which results in a
rapidly decreasing output current to zero.
Controls the direction of channel 2 outputs T2AL, T2AU, T2BL and T2BU.
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.
Sense ground channel 1. Logic ground reference and sense ground for the current control feedback-
loop.
Supply voltage for driving channel 2 outputs.
Output, channel 2, A side upper transistor. The pin will source current when phase is high.
Output, channel 2, A side lower transistor. The pin will sink current when phase is low.
Output, channel 2, B side upper transistor. The pin will source current when phase is low.
Output, channel 2, B side lower transistor. The pin will sink current when phase is high.
"Power Ground" from output channel 2. Connected to the ground path (see application examples).
NJM3776
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FUNCTIONAL DESCRIPTION
Each channel of the NJM3776 consists of the following sections:
• An output section with four output transistors, two sourcing and two sinking, intended to drive the four transistors
in an external H-bridge. Each transistor is capable of driving up to 200 mA continuous current.
• 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 sourcing output transistor in the circuit. Consequently the correspond-ing lower external
transistor, in the H-bridge, is turned off. 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 NJM3776 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. Due to the high output drive capability, this transient might exceed the max.
allowed voltage on the C inputs and damage the circuit. A resistor is placed in the feedback loop in order to prevent
this transient from damaging the circuit.
The current paths during turn-on, turn-off and phase shift are shown in figure 3.
1
Vmm
2
3
Rs
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
NJM3776
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ABSOLUTE MAXIMUM RATINGS
Parameter
Voltage
Logic supply
Output supply
Logic inputs
Analog inputs
Current
Output current
Logic inputs
Analog inputs
t=1mS
Pin no.*
13
6, 19
10, 11, 14, 15
8, 9, 16, 17
2, 3, 4, 5, 20, 21, 22, 23
10, 11, 14, 15
8, 9, 16, 17
Symbol
V
CC
V
BB
V
I
V
A
I
O
I
I
I
A
T
j
T
stg
Min
0
0
-0.3
-0.3
-500
-10
-10
Max
7
45
6
V
CC
+500
-
-
Unit
V
V
V
V
mA
mA
mA
°C
°C
Temperature
Junction temperature
Storage temperature
-
-55
+150
+150
s
RECOMMENDED OPERATING CONDITIONS
Parameter
Logic supply voltage
Supply voltage
Output emitter voltage
Output current continuous (see text)
Operating ambient temperature
Rise and fall time logic inputs
Oscillator timing resistor
Symbol
V
CC
V
BB
V
E
I
M
T
A
t
r,
, t
f
R
T
Min
4.75
10
-
-200
0
-
2
Typ
5
-
-
-
-
-
12
Max
5.25
40
1.0
+200
+85
2
20
Unit
V
V
V
mA
°C
µs
kohm
V
OA
-
V
OB
Phase 1
10
Dis 1 V
R1
11
8
C1
9
SGND 1
7
Pwr GND 1
1
NJM3776
–
t
on
2
R
S
Q
4
5
Logic
3
T
1BL
T
1AL
T
1AU
T
1BU
t
off
50 %
I
CC
V
V
13
CC
CC
+
6
12 kΩ
+
V
BB1
V
C
I
BB
t
t
d
R
T
–
19
V
BB2
V
CH
Logic
I
RC
RC
12
+
–
4 700 pF
22 T
2BU
20 T
2AU
21 T
2AL
23 T
2BL
I
OU
I
OU
I
OL
I
OL
*
S
R
Q
V
CC
C
T
Phase 2
I
I
I
IH
I
R
V
I
V
V
IH
t
15 14
17
16
C2
18
SGND 2
Pwr GND 2
V
OA
V
OB
V
BB
24
V
Dis 2 V
R2
RC
t
b
I
IL
I
A
V
A
V
R
V
RC
V
CH
V
C
V
A
Rs
*
t
IL
1
f
s
=
t + t
on
off
D=
t
on
t
on +
t
off
*
For test purposes only
Figure 4. Definition of symbols and test circuit
Figure 5. Definition of terms
NJM3776
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ELECTRICAL CHARACTERISTICS
Electrical characteristics over recommended operating conditions, unless otherwise noted. 0°C
≤
T
j
≤
+125°C .
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
General
Supply current
Supply current
Total power dissipation
Thermal shutdown junction temperature
Turn-off delay
I
CC
I
CC
P
D
Note 3.
Dis
1
= Dis
2
= HIGH.
V
BB
= 24 V, I
BB1
= I
BB2
= 200 mA.
Notes 2, 3.
Note 2
-
-
-
-
-
65
7
0.2
160
1.1
70
10
0.3
-
2.0
mA
mA
W
°C
µs
t
d
dV
C
/dt
≥
50 mV/µs,
I
BB
= 100 mA. Note 2.
Logic Input
Logic HIGH input voltage
Logic LOW input voltage
Logic HIGH input current
Logic LOW input current
Analog Inputs
Input current
|V
C1
—V
C2
| mismatch
Motor Outputs
Lower transistor saturation voltage
Lower transistor leakage current
Upper transistor saturation voltage
Upper transistor leakage current
Chopper Oscillator
Chopping frequency
Digital filter blanking time
V
IH
V
IL
I
IH
I
IL
I
A
V
Cdiff
V
I
= 2.4 V
V
I
= 0.4 V
V
r
= 5 V
T
A
= 25°C Note 3
I
M
= 200 mA
Dis1 = Dis2 = High,T
A
=25°C
I
M
= 200 mA
Dis1 = Dis2 = High,T
A
=25°C
f
s
t
b
C
T
= 4 700 pF, R
T
= 12 kohm
C
T
= 4 700 pF. Note 3.
2.0
-
-
-0.2
-
-
-
-0.1
-
0.6
20
-
V
V
µA
mA
-
-
-
-
-
-
-
-
0.5
5
0.2
50
0.9
50
23.0
1.0
0.8
-
0.4
-
1.2
-
-
-
mA
mV
V
µA
V
µA
kHz
µs
s
THERMAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Thermal resistance
R
thJ-GND
R
thJ-A
Note 2
Note 2
-
-
28
45
-
-
°C/W
°C/W
Notes
1. All voltages are with respect to ground. Currents are positive into, negative out of specified terminal.
2. Not covered by final test program.
3. Switching duty cycle D = 30%, f
s
= 23.0 kHz.
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