February 1999
PBL 377 17/1
60 V Stepper Motor
Drive Circuit
Description
PBL 377 17/1 is a bipolar monolithic circuit intended to control and drive the current
in one winding of a stepper motor.
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 with built-in
protection diodes.
Two PBL 377 17/1 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 modes.
• Switched mode bipolar constant
current drive.
• Wide range of current control
5 - 1200 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.
• Built-in recirculation diodes.
Figure 1. Block diagram.
28-pin plastic
PLCC package *
16-pin plastic
batwing DIP
20-pin SO wide
batwing package
PBL37717/1
PBL
37717/1
PBL 37717/1
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 17/1
1
* To be released
PBL 377 17/1
2
Maximum Ratings
Parameter Pin no. *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-1200 +1200 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
* refers to DIL package
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-1000 +1000 mA
Operating junction temperature TJ-20 +125 °C
Rise time logic inputs tr2µs
Fall time logic inputs tf2µs
Fig
ure 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 17/1
11
≥1
≥1
10 2 16
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 17/1
3
Electrical Characteristics
Electrical characteristics over recommended operating conditions. unless otherwise noted -20°C≤ TJ≤ +125°C.
CT = 820 pF, RT = 56 kohm. Ref.
Parameter Symbol fig. Conditions Min Typ Max Unit
General
Supply current ICC 225mA
Total power dissipation PDfs = 28 kHz, IM = 500 mA, VMM = 36 V 1.4 1.7 W
Note 2, 4.
fs = 28 kHz, IM = 800 mA, VMM = 36 V 2.8 3.3 W
Note 3, 4.
Turn-off delay td3T
a = +25°C, dVC/dt ≥ 50 mV/µs. 0.9 1.5 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
Reference Input
Input resistance RRTa = +25°C 6.8 kohm
Comparator Inputs
Threshold voltage VCH 2V
R
= 5.0 V, I0 = I1 = LOW 400 415 430 mV
Threshold voltage VCM 2V
R
= 5.0 V, I0 = HIGH, I1 = LOW 240 250 265 mV
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 2 IM = 500 mA 0.9 1.2 V
IM = 800 mA 1.1 1.4 V
Lower diode forward voltage drop 2 IM = 500 mA 1.2 1.5 V
IM = 800 mA 1.3 1.7 V
Upper transistor saturation voltage 2 IM = 500 mA 1.0 1.25 V
IM = 800 mA 1.2 1.5 V
Upper diode forward voltage drop 2 IM = 500 mA 1.0 1.25 V
IM = 800 mA 1.2 1.45 V
Output leakage current 2 I0 = I1 = HIGH, Ta = +25°C 100 µA
Monostable
Cut off time toff 3V
MM = 10 V, ton ≥ 5 µs273135µs
Thermal Characteristics
Ref.
Parameter Symbol Fig. Conditions Min Typ Max Unit
Thermal resistance Rthj-c DIL package. 11 °C/W
Rthj-a 16 DIL package. Note 2. 40 °C/W
Rthj-c PLCC package. 9 °C/W
Rthj-a 16 PLCC package. Note 2. 35 °C/W
Rthj-c 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. DIP 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 17/1
4
Pin Description
DIP SO PLCC* Symbol Description
11 10M
B
Motor 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.
3,14 3,18 12,4 VMM Motor supply voltage, 10 to 60 V. VMM pins should be wired
together on PCB.
4,5, 4,5,6,7,14 1,2,3,9,13,
12,13 15,16,17 14,15,16,17
28 GND 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.
68 18V
CC Logic voltage supply normally +5 V.
79 19I
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%.
8 10 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.
91121I
0Logic 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%.
10 12 23 C Comparator input. This input senses the instaneous voltage across the
sensing resistor, filtered through a RC Network.
11 13 24 VRReference voltage. Controls the threshold voltage of the comparator and
hence the output current. Input resistance: typically 6.8kΩ ± 20%.
15 19 6 MAMotor output A, Motor current flows from MA to MB when Phase is high.
16 20 8 E Common emitter. Connect the sence resistor between this pin and ground.
* To be released
Figure 3. Pin configurations.
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 17/1SO
13
12
11
10
GND
GND
GND
GND
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 17/1N
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 17/1QN
PBL 377 17/1
5
Functional Description
The PBL 377 17/1 is intended to drive a
bipolar constant current through one
motor 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 • 0.083) / RS [A], at 100% level
im = (VR • 0.050) / RS [A], at 60% level
im = (VR • 0.016) / RS [A], at 20% 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 comparator
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 four diodes, connected in
an H-bridge. 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).
After the monostable has timed out, the
current has decayed and the analog
voltage across the sensing resistor is
below the comparator threshold level.
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 17/1
6
200 mA/div 1 ms/div
100 µs/div
0
Figure 7. Principal operating sequence.
3
21
R
S
Fast Current Decay
Slow Current Decay
Motor Current
Time
1 2 3
Figure 6. Output stage with current paths
for fast and slow current decay.
Figure 5. Motor current (I
M
),
Vertical : 200 mA/div, Horizontal: 1 ms/
div, expanded part 100
µ
s/div.
The sinking transistor then closes and
the motor current starts to increase
again, The cycle is repeated until the
current is turned off via the logic inputs.
By reversing the logic level of the
phase input (pin 8), both active
transistors are turned off and the
opposite pair turned on after a slight
delay. When this happens, the current
must first decay to zero before it can
reverse. This current decay is steeper
because the motor current is now forced
to circulate back through the power
supply and the appropriate sinking
transistor protection diode. This causes
higher reverse voltage build-up across
the winding which results in a faster
current decay (see figure 6, arrow 4).
For best speed performance of the
stepper motor at half-step mode opera-
tion, the phase logic level should be
changed at the same time the current-
inhibiting signal is applied (see figure 2).
Heatsinking
The junction temperature of the chip
highly effects the lifetime of the circuit. In
high-current applications, the
heatsinking must be carefully conside-
red.
The Rthj-a of the PBL 377 17/1 can be
reduced by soldering the ground pins to
a suitable copper ground plane on the
printed circuit board (see figure 16) or by
applying an external heatsink type V7 or
V8, see figure 15.
The diagram in figure 14 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 500
mA, heatsinking is recommended to
assure optimal reliability.
The diagrams in figures 13 and 14 can
be used to determine the required
heatsink 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
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
Phase shift here
gives fast
current decay
Phase shift here
gives slow
current decay
PBL 377 17/1
7
Figure 12. Typical upper diode voltage
drop vs. recirculating current.
Figure 11. Typical lower diode voltage
drop vs. recirculating current.
Figure 9. Typical source saturation vs.
output current. Figure 10. Typical sink saturation vs.
output current.
Figure 8. Typical stepper motor driver application with PBL 377 17/1.
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.
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 VR 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.
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 from being
generated by the motor.
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 17/1
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 17/1
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
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
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
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)
T
j
= 125°C
j
T = 25°C
PBL 377 17/1
8
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. 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 17/1 Uen Rev.B
© Ericsson Components AB 1999
Ericsson Components AB
SE-164 81 Kista-Stockholm, Sweden
Telephone: +46 8 757 50 00
Figure 15. Heatsinks, Staver, type V7 and V8 by Columbia-Staver UK.
Figure 16. Copper foil used as a heatsink.
Figure 13. Typical power dissipation vs.
motor current. Figure 14. Allowable power dissipation
vs. ambient temperature.
Analog control
As the current levels can be continuously
controlled by modulating the VR input,
limited microstepping can be achieved.
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 figure7, to obtain
a switching frequency above the audible
range. Switching frequencies above 40
kHz are not recommended because the
current regulation can be affected.
Sensor resistor
The RS resistor should be of a non-
inductive type, power resistor. A 1.0 ohm
resistor, tolerance ≤ 1%, is a good choice
for 415 mA max motor current at VR = 5V.
Thepeak motor current, im , can be
calculated by using the formulas:
im = (VR • 0.083) / RS [A], at 100% level
im = (VR • 0.050) / RS [A], at 60% level
im = (VR • 0.016) / RS [A], at 20% level
Ordering Information
Package Part No.
DIP Tube PBL 377 17NS
PLCC Tube *PBL 377 17QNS
SO Tube PBL 377 17SOS
SO Tape & Reel PBL 377 17SOT
* To be released
16-pin
DIP
20-pin
SO
28-pin
PLCC
Thermal resistance [°C/W]
PCB copper foil area [cm ]
2
90
80
70
60
50
40
30 5101520 303525
PLCC package
DIP and SO package
38.0 mm
18,5 mm
11,6 mm
38.0 mm
33,5 mm
38,5 mm
P
D
(W)
4
3
2
1
00 .20 .40 .60 .80 1.0
I
M
(A)
5
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)
