February 1999
PBL 377 70/1
High Performance
Stepper Motor Drive Circuit
Description
PBL 377 70/1 is a bipolar monolithic circuit intended to control and drive the current in
one winding of a stepper motor. It is a high power version of PBL 377 17/1 and
special care has been taken to optimize the power handling capability without
suffering in reliability.
The circuit consists of a LS-TTL compatible logic input stage, a current sensor, a
monostable multivibrator and a high power H-bridge output stage. The circuit is
pin-compatible with the PBL 3717/2 industry-standard driver.
Two PBL 377 70/1 and a small number of external components form a complete
control and drive unit for LS-TTL or microprocessor-controlled stepper motor
systems.
Key Features
• Half-step and full-step operation.
• Switched mode bipolar constant
current drive
• Wide range of current control
5 -1800 mA.
• Wide voltage range 10 - 60 V.
• Designed for unstabilized motor
supply voltage.
• Current levels can be selected in
steps or varied continuously.
• Thermal overload protection.
VCC
Schmitt
Trigger
Phase
I1
I0
VR
&
&
&
&
≥1
Time
Delay
1
≥1
VMM
VMM
≥1
MA
MB
P
B
L
37
L
B /1
P 70
7
37
≥1
Output Stage
+
–
+
–
+
–
7
70
/
PB
Monostable
t = 0.69 • R • C
off
T T
1
L3
7
77
0/1
PBL 377 70/1
GND
Current Sensor
C
T
E
16-pin plastic batwing DIP
28-pin plastic PLCC package*
20-pin SOIC-package
Figure 1. Block diagram.
* To be released
1
PBL 377 70/1
Maximum Ratings
Parameter
Pin no. (refers to DIP)
Symbol
Min
Max
Unit
Voltage
Logic supply
Motor supply
Logic inputs
Comparator input
Reference input
Current
Motor output current
Logic inputs
Analog inputs
Temperature
Operating junction temperature
Storage temperature
6
3, 14
7, 8, 9
10
11
1, 15
7, 8, 9
10, 11
V
CC
V
MM
V
I
V
C
V
R
I
M
I
I
I
A
T
j
T
s
0
0
-0.3
-0.3
-0.3
-1800
-10
-10
-40
-55
7
60
6
V
CC
15
+1800
V
V
V
V
V
mA
mA
mA
°C
°C
+150
+150
Recommended Operating Conditions
Parameter
Symbol
Min
Typ
Max
Unit
Logic supply voltage
Motor supply voltage
Motor output current
Operating junction temperature
Rise time logic inputs
Fall time logic inputs
V
CC
V
MM
I
M
T
j
t
r
t
f
4.75
10
-1500
-20
5
5.25
55
+1500
+125
2
2
V
V
mA
°C
µs
µs
I
CC
V CC
6
Schmitt
Trigger
Time
Delay
1
≥1
V
V
3
≥1
15
1
I
MM
MM
MM
14
I
I
I
IH
I
IL
Phase
I
I
1
0
8
7
9
11
&
&
&
&
MA
MB
IM
I OL
IA
VR
≥1
≥1
+
–
Output Stage
V
V
Monostable
t = 0.69 • R • C
off
T T
2
T
1 kΩ
R
C
56 kΩ
R
T
820 pF
1Ω
C
T
R
S
M
MA
V
MM
V
CC
VI
V
V
IH
IL
VA
V
R
4,5,
+
–
+
–
GND
12,13
10
IC
IA
VC
VCH
C
Current Sensor
PBL 377 70/1
16
E
Pin no. refers
to DIL package
VE
820 pF
CC
Figure 2. Definition of symbols.
2
PBL 377 70/1
Electrical Characteristics
Electrical characteristics over recommended operating conditions. C
T
= 820 pF, R
T
= 56 kohm.
Parameter
Ref.
Symbol fig. Conditions
Min
Typ
Max
Unit
General
Supply current
I
CC
2
Total power dissipation
P
D
Turn-off delay
t
d
3
Thermal shutdown junction temperature
Logic Inputs
Logic HIGH input voltage
Logic LOW input voltage
Logic HIGH input current
Logic LOW input current
Analog Inputs
Comparator threshold voltage
Comparator threshold voltage
Comparator threshold voltage
Input current
V
IH
V
IL
I
IH
I
IL
V
CH
V
CM
V
CL
I
C
2
2
2
2
2
2
2
2
V
MM
= 20 to 40 V, I
0
= I
1
= HIGH.
V
MM
= 20 to 40 V, I
0
= I
1
= LOW,
f
s
= 23 kHz
f
s
= 28 kHz, I
M
= 1000mA, V
MM
= 36 V
Note 2, 4.
f
s
= 24 kHz, I
M
= 1000mA, V
MM
= 12 V
Note 2, 4.
f
s
= 28 kHz, I
M
= 1300m A, V
MM
= 36 V
Note 3, 4.
f
s
= 28 kHz, I
M
= 1500mA, V
MM
= 36 V
Note 3, 4.
T
a
= +25°C, dV
C
/dt
≥
50 mV/µs.
30
48
1.9
1.7
2.7
3.5
40
65
2.3
2.1
3.2
mA
mA
W
W
W
W
2.5
170
2.0
µs
°C
V
V
µA
mA
mV
mV
mV
µA
V
V
V
V
V
V
µA
µs
V
I
= 2.4 V
V
I
= 0.4 V
V
R
= 5.0 V, I
0
= I
1
= LOW
V
R
= 5.0 V, I
0
= HIGH, I
1
= LOW
V
R
= 5.0 V, I
0
= LOW, I
1
= HIGH
0.8
20
-0.4
400
240
70
-20
415
250
80
430
265
90
Motor Outputs
Lower transistor saturation voltage
Lower diode forward voltage drop
Upper transistor saturation voltage
Output leakage current
Monostable
Cut off time
t
off
3
I
M
= 1000mA
I
M
= 1300, A
I
M
= 1000mA
I
M
= 1300m A
I
M
= 1000 A
I
M
= 1300mA
I
0
= I
1
= HIGH, T
a
= +25°C
V
MM
= 10 V, t
on
≥
5
µs
27
0.5
0.8
1.3
1.5
1.1
1.3
0.8
1.3
1.6
1.8
1.3
1.6
100
35
31
Thermal Characteristics
Parameter
Ref.
Symbol Fig. Conditions
Min
Typ
Max
Unit
Thermal resistance
Rth
J-BW
DIL package.
Rth
J-A
15 DIL package. Note 2.
Rth
J-BW
PLCC package.
Rth
J-A
15 PLCC package. Note 2.
Rth
J-BW
SO package
Rth
J-A
SO package
11
40
9
35
11
40
°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. DIL package with external heatsink (Staver V7) and minimal copper area. Typical Rth
J-A
= 27.5°C/W. T
a
= +25°C.
4. Not covered by final test program.
3
PBL 377 70/1
GND
GND
GND
GND
V
MM
N/C
27
M
B 1
T
2
V
MM 3
GND
4
GND
5
GND
6
GND
7
V
CC 8
I
1 9
Phase
10
28
20
19
18
17
E
M
A
V
MM
GND
GND
GND
GND
V
R
C
I
0
M
B 1
T
2
V
MM 3
GND
4
GND
5
V
CC 6
I
1 7
Phase
8
16
15
14
E
M
A
V
MM
GND
GND
V
R
C
V
MM 12
GND
13
GND
14
GND
15
GND
16
GND
17
N/C
5
M
A 6
N/C
7
E
8
GND
9
M
B 10
26
4
3
2
1
N/C
25
N/C
24
V
R
23
C
PBL
377 70/1SO
16
15
14
13
12
11
PBL
377 70/1N
13
12
11
10
9
PBL 377 70/1QN
22
N/C
21
I
0
20
Phase
19
I
1
T
11
I
0
Figure 3. Pin configurations.
Pin Description
SOIC
DIP
PLCC*
Symbol
Description
1
2
3, 18
4-7,
14-17
8
9
10
11
12
13
19
20
1
2
3,14
4-5,
12-13
6
7
8
9
10
11
15
16
10
11
4,12
1-3,9,
13-17,28
18
19
20
21
23
24
6
8
M
B
T
V
MM
GND
V
CC
I
1
Phase
I
0
C
V
R
M
A
E
Motor output B, Motor current flows from M
A
to M
B
when Phase is high.
Clock oscillator. Timing pin connect a 56 kΩ resistor and a 820 pF in parallel between T
and Ground.
Motor supply voltage, 10 to 55 V. Pin 3(12) and pin 14(4) should be wired together.
Ground and negative supply. Note these pins are used for heatsinking. Make sure that all
ground pins are soldered onto a suitable large copper ground plane for efficient heat sinking.
Logic voltage supply normally +5 V.
Logic input. It controls, together with the I0 input, the current level in the output stage.
The controlable levels are fixed to 100, 60, 20, 0%.
Controls the direction of the motor current of M
A
and M
B
outputs. Motor current flows from
M
A
to M
B
when the phase input is high.
Logic input. It controls, together with the I1 input, the current level in the output stage. The
controlable levels are fixed to 100, 60, 20, 0%.
Comparator input. This input senses the instaneous voltage across the sensing resistor,
filtered through an RC Network.
Reference voltage. Controls the threshold voltage of the comparator and hence the output
current.Input resistance: typically 6.8 kΩ
±
20%.
Motor output A, Motor current flows from M
A
to M
B
when Phase is high.
Common emitter. Connect the Sence resistor between this pin and ground.
* To be released
4
V
CC 18
PBL 377 70/1
Functional Description
The PBL 377 70/1 is intended to drive a
bipolar constant current through one
winding of a 2-phase stepper motor.
Current control is achieved through
switched-mode regulation, see figure 5
and 6.
Three different current levels and zero
current can be selected by the input
logic.
The circuit contains the following
functional blocks:
• Input logic
• Current sense
• Single-pulse generator
• Output stage
Input logic
Phase input.
The phase input
determines the direction of the current in
the motor winding. High input forces the
current from terminal M
A
to M
B
and low
input from terminal M
B
to M
A
. A Schmitt
trigger provides noise immunity and a
delay circuit eliminates the risk of cross
conduction in the output stage during a
phase shift.
Half- and full-step operation is
possible.
Current level selection.
The status of I
0
and I
1
inputs determines the current level
in the motor winding. Three fixed current
levels can be selected according to the
table below.
Motor current
I
0
I
1
| V
MA
– V
MB
|
t
on
50 %
t
off
t
V
E
V
CH
t
d
t
1
f
s
=
t + t
on off
D=
t
on
t
on +
t
off
Figure 4. Definition of terms.
current levels. The motor current is
sensed as a voltage drop across the
current sensing resistor, R
S
, and
compared with one of the voltage
references from the divider. When the
two voltages are equal, the compara-tor
triggers the single-pulse generator. Only
one comparator at a time is activated by
the input logic.
Single-pulse generator
The pulse generator is a monostable
multivibrator triggered on the positive
edge of the comparator output. The
multivibrator output is high during the
pulse time, t
off
, which is determined by
the timing components R
T
and C
T
.
t
off
= 0.69 • R
T
• C
T
The single pulse switches off the
power feed to the motor winding,
causing the winding to decrease during
t
off
.
If a new trigger signal should occur
during t
off
, it is ignored.
Output stage
The output stage contains four
transistors and two diodes, connected in
an H-bridge. Note that the upper
recirculation diodes are connected to the
circuit externally. The two sinking
transistors are used to switch the power
supplied to the motor winding, thus
driving a constant current through the
winding. See figures 5 and 6.
Overload protection
The circuit is equipped with a thermal
shut-down function, which will limit the
junction temperature. The output current
will be reduced if the maximum permis-
sible junction temperature is exceeded.
It should be noted, however, that it is not
short circuit protected.
Operation
When a voltage V
MM
is applied across
the motor winding, the current rise
follows the equation:
i
m
= (V
MM
/ R) • (1 - e
-(R
•t)/L
)
High level
Medium level
Low level
Zero current
100%
60%
20%
0%
L
H
L
H
L
L
H
H
R = Winding resistance
L = Winding inductance
t
= time
(see figure 6, arrow 1)
The motor current appears across the
external sensing resistor, R
S
, as an
analog voltage. This voltage is fed
through a low-pass filter, R
C
C
C
, to the
voltage comparator input (pin 10). At the
moment the sensed voltage rises above
the comparator threshold voltage, the
monostable is triggered and its output
turns off the conducting sink transistor.
The polarity across the motor winding
reverses and the current is forced to
circulate through the appropriate upper
protection diode back through the source
transistor (see figure 6, arrow 2).
The specific values of the different
current levels are determined by the
reference voltage V
R
together with the
value of the sensing resistor R
S
.
The peak motor current can be
calculated as follows:
i
m
= (V
R
• 0.080) / R
S
[A], at 100% level
The motor current can also be
continuously varied by modulating the
voltage reference input.
Current sensor
The current sensor contains a reference
voltage divider and three comparators
for measuring each of the selectable
5
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