February 1999
Figure 1. Block diagram.
PBL 377 70/1
High Performance
Stepper Motor Drive Circuit
16-pin plastic batwing DIP
28-pin plastic PLCC package*
20-pin SOIC-package
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.
GND
VCC
MA
MB
Phase
I1
I0
VR& &&&
–
+
–
+
–
≥1
Monostable
t = 0.69 • R • C
Current Sensor
Output Stage
off
Schmitt
Trigger Time
Delay
CTE
1≥1
≥1
≥1
VMM
VMM
T
T
PBL 377 70/1
+
PBL 377 70/1
PBL
377 70/1
* To be released
1
PBL 377 70/1
PBL 377 70/1
2
Maximum Ratings
Parameter Pin no. (refers to DIP) Symbol Min Max Unit
Voltage
Logic supply 6 VCC 07V
Motor supply 3, 14 VMM 060V
Logic inputs 7, 8, 9 VI-0.3 6 V
Comparator input 10 VC-0.3 VCC V
Reference input 11 VR-0.3 15 V
Current
Motor output current 1, 15 IM-1800 +1800 mA
Logic inputs 7, 8, 9 II-10 mA
Analog inputs 10, 11 IA-10 mA
Temperature
Operating junction temperature Tj-40 +150 °C
Storage temperature Ts-55 +150 °C
Recommended Operating Conditions
Parameter Symbol Min Typ Max Unit
Logic supply voltage VCC 4.75 5 5.25 V
Motor supply voltage VMM 10 55 V
Motor output current IM-1500 +1500 mA
Operating junction temperature Tj-20 +125 °C
Rise time logic inputs tr2µs
Fall time logic inputs tf2µs
Figure 2. Definition of symbols.
GND
VCC
Phase
I1
0
R
I I
M OL
ICC
I I I
I IH IL
IA
820 pF 1Ω
VCC VI
IH
IL
V
V
A
R
VC
I
I
C
VE
VM
MA
VMM
RR C
820 pF
C
1 kΩ
S
TT
C
R
C
56 kΩ
MA
MB
I
V
&&&&
–
+
–
+
–
+
≥1
Monostable
t = 0.69 • R • C
Current Sensor
Output Stage
off T T
Schmitt
Trigger Time
Delay
CTE
PBL 377 70/1
1≥1
≥1
≥1
10 216
1
15
14 3
6
8
7
9
11
4,5,
12,13
VMM
VMM
I MM
VCH
V
A
V
V
Pin no. refers
to DIL package
PBL 377 70/1
3
Electrical Characteristics
Electrical characteristics over recommended operating conditions. CT = 820 pF, RT = 56 kohm.
Ref.
Parameter Symbol fig. Conditions Min Typ Max Unit
General
Supply current ICC 2V
MM = 20 to 40 V, I0 = I1 = HIGH. 30 40 mA
VMM = 20 to 40 V, I0 = I1 = LOW, 48 65 mA
fs = 23 kHz
Total power dissipation PDfs = 28 kHz, IM = 1000mA, VMM = 36 V 1.9 2.3 W
Note 2, 4.
fs = 24 kHz, IM = 1000mA, VMM = 12 V 1.7 2.1 W
Note 2, 4.
fs = 28 kHz, IM = 1300m A, VMM = 36 V 2.7 3.2 W
Note 3, 4.
fs = 28 kHz, IM = 1500mA, VMM = 36 V 3.5 W
Note 3, 4.
Turn-off delay td3T
a
= +25°C, dVC/dt ≥ 50 mV/µs. 2.5 µs
Thermal shutdown junction temperature 170 °C
Logic Inputs
Logic HIGH input voltage VIH 2 2.0 V
Logic LOW input voltage VIL 2 0.8 V
Logic HIGH input current IIH 2V
I
= 2.4 V 20 µA
Logic LOW input current IIL 2V
I
= 0.4 V -0.4 mA
Analog Inputs
Comparator threshold voltage VCH 2V
R
= 5.0 V, I0 = I1 = LOW 400 415 430 mV
Comparator threshold voltage VCM 2V
R
= 5.0 V, I0 = HIGH, I1 = LOW 240 250 265 mV
Comparator threshold voltage VCL 2V
R
= 5.0 V, I0 = LOW, I1 = HIGH 70 80 90 mV
Input current IC2 -20 µA
Motor Outputs
Lower transistor saturation voltage IM = 1000mA 0.5 0.8 V
IM = 1300, A 0.8 1.3 V
Lower diode forward voltage drop IM = 1000mA 1.3 1.6 V
IM = 1300m A 1.5 1.8 V
Upper transistor saturation voltage IM = 1000 A 1.1 1.3 V
IM = 1300mA 1.3 1.6 V
Output leakage current I0 = I1 = HIGH, Ta = +25°C 100 µA
Monostable
Cut off time toff 3V
MM = 10 V, ton ≥ 5 µs 273135µs
Thermal Characteristics Ref.
Parameter Symbol Fig. Conditions Min Typ Max Unit
Thermal resistance RthJ-BW DIL package. 11 °C/W
RthJ-A 15 DIL package. Note 2. 40 °C/W
RthJ-BW PLCC package. 9 °C/W
RthJ-A 15 PLCC package. Note 2. 35 °C/W
RthJ-BW SO package 11 °C/W
RthJ-A SO package 40 °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 cm2 PCB copper area with free air convection. Ta = +25°C.
3. DIL package with external heatsink (Staver V7) and minimal copper area. Typical RthJ-A = 27.5°C/W. Ta = +25°C.
4. Not covered by final test program.
PBL 377 70/1
4
Figure 3. Pin configurations.
Pin Description
SOIC DIP PLCC* Symbol Description
11 10 M
BMotor output B, Motor current flows from MA to MB when Phase is high.
2 2 11 T Clock oscillator. Timing pin connect a 56 kΩ resistor and a 820 pF in parallel between T
and Ground.
3, 18 3,14 4,12 VMM Motor supply voltage, 10 to 55 V. Pin 3(12) and pin 14(4) should be wired together.
4-7, 4-5, 1-3,9, GND Ground and negative supply. Note these pins are used for heatsinking. Make sure that all
14-17 12-13 13-17,28 ground pins are soldered onto a suitable large copper ground plane for efficient heat sinking.
86 18 V
CC Logic voltage supply normally +5 V.
97 19 I
1Logic 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%.
10 8 20 Phase Controls the direction of the motor current of MA and MB outputs. Motor current flows from
MA to MB when the phase input is high.
11 9 21 I0Logic 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%.
12 10 23 C Comparator input. This input senses the instaneous voltage across the sensing resistor,
filtered through an RC Network.
13 11 24 VRReference voltage. Controls the threshold voltage of the comparator and hence the output
current.Input resistance: typically 6.8 kΩ ± 20%.
19 15 6 MAMotor output A, Motor current flows from MA to MB when Phase is high.
20 16 8 E Common emitter. Connect the Sence resistor between this pin and ground.
* To be released
B
T
MM
GND
GND
CC
1
Phase
E
M
GND
GND
V
C
I
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
A
V
MM
R
0
I
V
V
M
PBL
377 70/1N
N/C
A
N/C
E
GND
B
T
N/C
V
C
N/C
I
Phase
I
V
GND
GND
GND
GND
N/C
N/C
MM
GND
GND
GND
GND
GND
CC
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
MM
R
0
1
V
V
M
M
PBL 377 70/1QN
B
T
MM
GND
GND
CC
1
Phase
E
M
GND
GND
V
C
I
1
2
3
4
5
6
7
8
20
19
18
17
16
15
14
9
A
V
MM
R
0
I
V
V
M
PBL
377 70/1SO
13
12
11
10
GND
GND
GND
GND
PBL 377 70/1
5
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 MA to MB and low
input from terminal MB to MA. 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 I0
and I1 inputs determines the current level
in the motor winding. Three fixed current
levels can be selected according to the
table below.
Motor current I0I1
High level 100% L L
Medium level 60% H L
Low level 20% L H
Zero current 0% H H
The specific values of the different
current levels are determined by the
reference voltage VR together with the
value of the sensing resistor RS.
The peak motor current can be
calculated as follows:
im = (VR • 0.080) / RS [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
current levels. The motor current is
sensed as a voltage drop across the
current sensing resistor, RS, 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, toff , which is determined by
the timing components RT and CT.
toff = 0.69 • RT • CT
The single pulse switches off the
power feed to the motor winding,
causing the winding to decrease during
toff .
If a new trigger signal should occur
during toff , 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 VMM is applied across
the motor winding, the current rise
follows the equation:
im = (VMM / R) • (1 - e-(R • t ) / L )
R = Winding resistance
L = Winding inductance
t = time
(see figure 6, arrow 1)
The motor current appears across the
external sensing resistor, RS, as an
analog voltage. This voltage is fed
through a low-pass filter, RCCC, 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).
Figure 4. 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
PBL 377 70/1
6
After the monostable has timed out,
the current has decayed and the analog
voltage across the sensing resistor is
below the comparator threshold level.
The sinking transistor then turns on
and the motor current starts to increase
again, The cycle is repeated until the
current is turned off via the logic inputs.
When both I1 and I0 are high, all four
transistors in the output H-bridge are
turned off, which means that inductive
current recirculates through two opposite
free-wheeling diodes (see figure 6, arrow
3). this method of turning off the current
results in a faster current decay than if
only one transistor was turned off and will
therefore improve speed performance in
half-stepping mode.
Heatsinking
The junction temperature of the chip
highly effects the lifetime of the circuit. In
high-current applications, the heatsinking
must be carefully considered.
The Rthj-a of the PBL 377 70/1 can be
reduced by soldering the ground pins to
a suitable copper ground plane on the
printed circuit board (see figure 14) or by
applying an external heatsink type V7 or
V8, see figure 14.
The diagram in figure 13 shows the
maximum permissible power dissipation
versus the ambient temperature in °C, for
heatsinks of the type V7, V8, or a 20 cm2
copper area respectively. Any external
heatsink or printed circuit board copper
must be connected to electrical ground.
For motor currents higher than approx
600 mA, some form of heatsinking is
recommended to assure optimal
reliability.
The diagrams in figures 12 and 13 can
be used to determine the required
heatsinking of the circuit. In some
systems, forced-air cooling may be
available to reduce the temperature rise
of the circuit.
Applications Information
Motor selection
Some stepper motors are not designed
for continuous operation at maximum
current. As the circuit drives a constant
current through the motor, its tempera-
ture can increase, both at low- and high-
speed operation.
Some stepper motors have such high
core losses that they are not suited for
switched-mode operation.
Figure 5. Motor current (I
M
),
Vertical : 200 mA/div,
Horizontal: 1 ms/div,
expanded part 100
µ
s/div.
Figure 6. Output stage with current paths
for fast and slow current decay.
Figure 7. Principal operating sequence.
200 mA/div 1 ms/div
100 µs/div
0
Fast Current Decay
Slow Current Decay
Motor Current
Time
1 2 3
3
21
External recirculation diodes
R
S
I
0A
I
1A
Ph
A
Ph
B
I
0B
I
1B
I
MA
I
MB
100%
–100%
60%
–60%
20%
–20%
100%
–100%
60%
–60%
Half step mode at 100 % Full step mode at 60 %
Stand by mode
at 20 %
Full step position
Half step position
PBL 377 70/1
7
Figure 8. Typical stepper motor driver application with PBL 377 70/1.
Figure 9. Typical source saturation vs.
output current.
In order to minimize electromagnetic
interference, it is recommended to route
MA and MB leads in parallel on the
printed circuit board directly to the
terminal connector. The motor wires
should be twisted in pairs, each phase
separately, when installing the motor
system.
Unused inputs
Unused inputs should be connected to
proper voltage levels in order to obtain
the highest possible noise immunity.
Ramping
A stepper motor is a synchronous motor
and does not change its speed due to
load variations. This means that the
torque of the motor must be large
enough to match the combined inertia of
the motor and load for all operation
modes. At speed changes, the requires
torque increases by the square, and the
required power by the cube of the speed
change. Ramping, i.e., controlled
acceleration or deceleration must then
be considered to avoid motor pull-out.
VCC , VMM
The supply voltages, VCC and VMM, can
be turned on or off in any order. Normal
dv/dt values are assumed.
Before a driver circuit board is
removed from its system, all supply
voltages must be turned off to avoid
destructive transients being generated
by the motor.
Switching frequency
The motor inductance, together with the
pulse time, toff, determines the switching
frequency of the current regulator. The
choice of motor may then require other
values on the RT, CT components than
those recommended in figure 6, to
obtain a switching frequency above the
audible range. Switching frequencies
above 40 kHz are not recommended
because the current regulation can be
affected.
Analog control
As the current levels can be continu-
ously controlled by modulating the VR
input, limited microstepping can be
achieved.
Sensor resistor
The RS resistor should be of a non-
inductive type power resistor. A 0.5 ohm
V
Sat
(V)
1.8
1.6
1.4
1.2
1.0
.8
.6
.4
.2
00 .20 .40 .60 .80 1.0
I
M
(A)
T
j
= 25°C
j
T = 125°C
V
Sat
(V)
1.8
1.6
1.4
1.2
1.0
.8
.6
.4
.2
00 .20 .40 .60 .80 1.0
I
M
(A)
T
j
= 25°C
j
T = 125 °C
Figure 10. Typical sink saturation vs.
output current.
V
F
(V)
1.8
1.6
1.4
1.2
1.0
.8
.6
.4
.2
00 .20 .40 .60 .80 1.0
I
M
(A)
j
T = 25°C
T
j
= 125°C
Figure 11. Typical lower diode voltage
drop vs. recirculating current.
Interference
As the circuit operates with switched-
mode current regulation, interference-
generation problems can arise in some
applications. A good measure is then to
decouple the circuit with a 0.1 µF
ceramic capacitor, located near the
package across the power line VMM and
ground.
Also make sure that the VRef input is
sufficiently decoupled. An electrolytic
capacitor should be used in the +5 V rail,
close to the circuit.
The ground leads between RS, CC and
circuit GND should be kept as short as
possible. This applies also to the leads
connecting RS and RC to pin 16 and pin
10 respectively.
STEPPER
MOTOR
Phase
I1B
I0B
820 pF
820 pF
2
4, 5
12, 13
Phase
I1A
I0A
1
15
1 kΩ
56 kΩ
1 Ω
820 pF
820 pF
Phase
I1
I0TC
E
V
MM
VCC
V
R
GND MA
MB
PBL 377 70/1
11 6 3, 14
8
7
9
210 16
4, 5
12, 13
1 kΩ
56 kΩ
1 Ω
A
B1
15
Phase
I
1
I
0
TCE
V
MM
V
CC
V
R
GND
PBL 377 70/1
11 6 3, 14
8
7
9
10 16
M
A
M
B
V (+5 V)
CC V
MM
V (+5 V)
CC V
MM
Pin no refers
to DIL package
Diodes are
UF 4001 or
BYV27
t≥100ns
PBL 377 70/1
8
resistor, tolerance ≤ 1%, is a good choice
for 800 mA max motor current at VR = 5V.
The peak motor current, im , can be
calculated by using the formula:
im = (VR • 0.080) / RS [A], at 100% level
External recirculation diodes
Recirculation diodes must be connected
across each motor terminal and the
supply voltage, VMM. The anodes shall be
connected to the motor terminals and the
cathodes to the VMM voltage. Ultra-fast
recovery diodes should be used for
maximum performance and reliability.
Ordering Information
Package Part No.
DIP Tube PBL 377 70/1NS
SO Tube PBL 377 70/1SOS
SO Tape & Reel PBL 377 70/1SOT
PLCC Tube PBL 377 70/1QNS
PLCC Tape & Reel PBL 377 70/1QNT
Information given in this data sheet is believed to be
accurate and reliable. However no responsibility is
assumed for the consequences of its use nor for any
infringement of patents or other rights of third parties
which may result from its use. No license is granted
by implication or otherwise under any patent or
patent rights of Ericsson Components AB. These
products are sold only according to Ericsson
Components' general conditions of sale, unless
otherwise confirmed in writing.
Specifications subject to change
without notice.
1522-PBL 377 70/1/1 Uen Rev.B
© Ericsson Components AB. 1999
Figure 15. Copper foil used as a heatsink.
Figure 14. Heatsinks, Staver, type V7 and V8 by Columbia-Staver UK.
Figure 12. Typical power dissipation vs.
motor current.
P
D
(W)
2.0
1.5
1.0
.5
00 .50 1.0 1.5
I
M
(A)
2.5
V
MM
= 36 V
V
MM
= 12 V
3.0
Figure 13. Allowable power dissipation vs.
ambient temperature.
50 150
T
Amb
(°C)
0
2.0
4.0
3.0
1.0
P
D
(W)
100
With Staver V7 (27.5°C/W)
With Staver V8 (37.5°C/W)
PCB heatsink (40°C/W)
Ericsson Components AB
SE-164 81 Kista-Stockholm, Sweden
Telephone: +46 8 757 50 00
Thermal resistance [°C/W]
PCB copper foil area [cm ]
2
90
80
70
60
50
40
30 5101520 303525
PLCC package
DIP package
16-pin
DIP
20-pin
SO
28-pin
PLCC
38.0 mm
18,5 mm
11,6 mm
38.0 mm
33,5 mm
38,5 mm
