1
Features
THERMAL
SHUTDOWN
V
DDA
Pulse
Comp In
Sense
OUTA OUTB V
DDB
DIRECTION
IN1
IN0
V
CC
V
REF
Gnd
+
-
+
-
+
-
MONO-
STABLE
105
W
223
W
223
W
6K
W
00
01
10
11
s
Full/Half /Quarter Step
Operation
s
Output Current Up to 1 A
s
Motor Supply Voltage 10V
to 46V
s
Integrated Bootstrap
Lowers Saturation Voltage
s
Built In Protection Diodes
s
Externally Selectable
Current Level
s
Digital or Analog Control
of Output Current Level
s
Thermal Overload
Protection
s
Minimum External
Components
Package Options
CS3717A
1A H-Bridge Stepper Motor Driver
CS3717A
Description
The CS3717A controls and drives
one phase of a bipolar stepper
motor with chopper control of the
phase current. Current levels may
be selected in three steps by means
of two logic inputs which select one
of three current comparators. When
both of these inputs are high the
device is disabled. A separate logic
input controls the direction of cur-
rent flow. A monostable, pro-
grammed by an external RC net-
work, sets the current decay time.
The power section is a full H-bridge
driver with four internal clamp
diodes for current recirculation. An
external connection to the lower
emitters is available for the inser-
tion of a sensing resistor. Two
CS3717As and several external
components form a complete step-
per motor drive subsystem.
The recommended operating ambi-
ent temperature range is from 0 to
70C.
The CS3717A is supplied in a 16
lead PDIP.
Block Diagram
16L PDIP
(Internally Fused Leads)
1
OUTB
Pulse
V
DD
B
Gnd
V
CC
IN1
DIRECTION
Sense
OUTA
V
DD
A
Gnd
Gnd
V
REF
Comp In
IN0
Gnd
Power Supply Voltage (V
DDA
, V
DDB
) ............................................................50V
Logic Supply Voltage (V
CC
)..............................................................................7V
Logic Input Voltage (IN0, IN1, DIRECTION)................................................6V
Comparator Input............................................................................................V
CC
Reference Input Voltage..................................................................................15V
Output Current (DC Operation)...................................................................1.2A
Storage Temperature .................................................................55C to +150C
Operating Junction Temperature.............................................40C to +150C
Lead Temperature Soldering
Wave Solder(through hole styles only) ............10 sec. max, 260C peak
Absolute Maximum Ratings
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
A Company
Rev. 4/29/99
2
Electrical Characteristics: Refer to the test circuit V
DD
= 36V, V
CC
= 5V, T
A
= 25C; unless otherwise specified.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
CS3717A
Supply Voltage
10
46
V
Logic Supply Voltage
4.75
5.25
V
Logic Supply Current
7
15
mA
Reference Input Current
V
REF
= 5V
0.75
1.00
mA
s Logic Inputs
Input Low Voltage
0.8
V
Input High Voltage
2
V
Low Voltage Input Current
V
IN
= 0.4V
(DIRECTION)
-100
A
(IN0, IN1)
-400
A
High Voltage Input Current
V
IN
= 2.4V
10
A
s Comparators
Comparator Low
V
REF
= 5V
IN0 = Low
66
80
94
mV
Threshold Voltage
IN1 = High
Comparator Medium
V
REF
= 5V
IN0 = High
236
251
266
mV
Threshold Voltage
IN1 = Low
Comparator High
V
REF
= 5V
IN0 = Low
396
416
436
mV
Threshold Voltage
IN1 = Low
Comparator Input Current
20
A
Cutoff Time
R
T
= 56k
C
T
= 820pF
27
37
s
Turn Off Delay
2
s
Output Leakage Current
IN0 =IN1 = High
100
A
s Source Diode-Transistor Pair
Saturation Voltage
I
MOTOR
= -0.5A conduction period
1.7
2.1
V
recirculation period
1.10
1.35
V
Saturation Voltage
I
MOTOR
= -1A
conduction period
2.1
2.8
V
recirculation period
1.7
2.5
V
Leakage Current
V
S
= 46V
300
A
Diode Forward Voltage
I
MOTOR
= -0.5A
1.00
1.25
V
I
MOTOR
= -1A
1.3
1.7
V
s Sink Diode-Transistor Pair
Saturation Voltage
I
MOTOR
= 0.5A
1.20
1.45
V
I
MOTOR
= 1A
1.75
2.30
V
Leakage Current
V
S
= 46V
300
A
Diode Forward Voltage
I
MOTOR
= 0.5A
1.1
1.5
V
I
MOTOR
= 1A
1.4
2.0
V
3
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
CS3717A
Truth Table
IN0
IN1
Output Current
H
H
No Current
L
H
Low Current
H
L
Medium Current
L
L
High Current
16L
(Internally Fused Leads)
1
OUT B
Output connection with OUTA. The output stage is a H bridge
formed by four transistors and four diodes suitable for switching
applications.
2
Pulse
A parallel RC network connected to this pin sets the OFF time of
the lower power transistors. The pulse generator is a monostable
triggered by the rising edge of the output of the comparators
(t
OFF
= 0.69 R
T
C
T
).
3
V
DDB
Supply voltage input for half output stage.
4, 5, 12, 13
Gnd
Ground connection. Also conducts heat from die to printed
circuit copper.
6
V
CC
Supply voltage input for logic circuitry.
7
IN1
This pin and IN0 are logic inputs which select the outputs of the
three comparators to set the current level. Current also depends on
the sensing resistor and reference voltage. See truth table.
8
DIRECTION
This TTL-compatible logic input sets the direction of current
flow through the load. A high level causes current to flow from
OUTA (source) to OUTB (sink). A Schmitt trigger on this input
provides good noise immunity and a delay circuit prevents out-
put stage short circuits during switching.
9
IN0
See IN1.
10
Comp In
Input connected to the three comparators. The voltage across the
sense resistor is fed back to this input through the low pass filter
R
C
C
C
. The lower power transistors are disabled when the sense
voltage exceeds the reference voltage of the selected comparator.
When this occurs the current decays for a time set by R
T
C
T
,
t
OFF
= 0.69 R
T
C
T
.
11
V
REF
A voltage applied to this pin sets the reference voltage of the
three comparators, thus determining the output current (also
dependent on R
Sense
and the two inputs IN 0 and IN 1).
14
V
DDA
Supply voltage input for half output stage.
15
OUT A
See OUTB.
16
Sense
Connection to lower emitters of output stage for insertion of
current sense resistor.
Control of the motor
The stepper motor can rotate in either direction according
to the sequence of the input signals. It is possible to obtain
a full step, a half step and quarter step operation.
Full step operation
Both windings of the stepper motor are energized all the
time with the same current I
MA
= I
MB
.
IN0 and IN1 remain fixed at whatever torque value is
required.
Calling A the condition with winding A energized in one
direction and A in the other direction, the sequence for
full step rotation is:
AB
ABABAB etc.
4
Typical Performance Characteristics
Source Saturation Voltage vs. Output Current
(Conduction Period)
Source Saturation Voltage vs. Output Current
(Recirculation Period)
CS3717A
1
2
3
4
V
CE
SA
T
(V)
0.2
0.4
0.6
0.8
I (A)
0
1
2
3
4
V
CE
SA
T
(V)
0.2
0.4
0.6
0.8
I (A)
0
Comparator Threshold vs. Junction Temperature
Sink Saturation Voltage vs. Output Current
1
2
3
4
V
SA
T
(V)
0.2
0.4
0.6
0.8
I (A)
0
V
CX
(%)
40
160
T
J
(C)
0
20
40
60
80
100
60
80 100 120 140
20
The application diagram shows a typical application in
which two CS3717A's control a two phase bipolar stepper
motor.
Programming
The amplitude of the current flowing in the motor wind-
ing is controlled by the logic inputs IN0 and IN1. The
truth table (page 3) shows three current levels and an off
state. A high level on the Direction logic input sets the
direction of that current from OUTA to OUTB; a low level
from OUTB to OUTA.
It is recommended that unused inputs are tied to V
CC
or
(Gnd) as appropriate to avoid noise problems.
The current levels can be varied continuously by changing
V
REF
.
Application Information
For rotation in the other direction the sequence must be
reversed.
The torque of each step is constant in full step operation.
Half step operation
Power is applied alternately to one winding then both
according to the sequence:
AB
BABAABBABA etc.
Like full step this can be done at any current level; the
torque is not constant but is lower when only one winding
is energized.
A coil is turned off by setting IN0 and IN1 both high.
Quarter step operation
It is preferable to realize the quarter step operation at full
power otherwise the steps will be of very irregular size.
The extra quarter steps are added to the half step
sequence by putting one coil on half current according to
the sequence.
AB
ABBABABABA etc.
2 2 2
Motor selection
As the CS3717A provides constant current drive with a
switching operation, care must be taken to select stepper
motors with low hysteresis losses to prevent motor over-
heating.
L-C filter
To reduce EMI and chopping losses in the motor, a low
pass L-C filter can be inserted across the outputs of the
CS3717A as shown in the following diagram.
5
Application Information: continued
IN0
A
FULL STEP MOTOR DRIVE
1M = 500mA
HALF STEP MOTOR DRIVE
1M = 250mA
STAND BY WITH
HOLDING TORQUE
1M = 80mA
IN1
A
DIRECTION
A
DIRECTION
B
IN0
B
IN1
B
500 mA
I
MA
500 mA
I
MB
- 500 mA
- 500 mA
1
2
3
4
5
6
7
8
IN
OUT
Input and Output Sequences for Half Step and Full Step Operation
CS3717A
L
@
L
M
1
10
C
@
4 10
10
L
C
OUTA
CS3717A
OUTB
L
MOTOR
WINDING
(L
M
, R
M
)
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