UC3717 [TI]
Stepper Motor Drive Circuit; 步进电机驱动电路
| 型号： | UC3717 |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | Stepper Motor Drive Circuit |
| 文件： | 总9页 (文件大小：517K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
UC1717
UC2717
UC3717
Stepper Motor Drive Circuit
FEATURES
DESCRIPTION
•
•
•
Half-step and Full-step Capability
The UC3717 has been designed to control and drive the current in
one winding of a bipolar stepper motor. The circuit consists of an LS-
TTL-compatible logic input, a current sensor, a monostable and an
output stage with built-in protection diodes. Two UC3717s and a few
external components form a complete control and drive unit for LS-
TTL or micro-processor controlled stepper motor systems.
Bipolar Constant Current Motor Drive
Built-in Fast Recovery Schottky
Commutating Diodes
•
•
•
Wide Range of Current Control 5-1000mA
Wide Voltage Range 10-45V
The UC1717 is characterized for operation over the full military tem-
perature range of -55°C to +125°C, the UC2717 is characterized for
-25°C to +85°C, and the UC3717 is characterized for 0°C to +70°C.
Designed for Unregulated Motor Supply
Voltage
•
•
Current Levels can be Selected in Steps
or Varied Continuously
Thermal Overload Protection
ABSOLUTE MAXIMUM RATINGS (Note 1)
Voltage
Logic Supply, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7V
Output Supply, VM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45V
Input Voltage
Logic Inputs (Pins 7, 8, 9). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6V
Analog Input (Pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vcc
Reference Input (Pin 11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V
Input Current
Note 1: All voltages are with respect to ground, Pins
4,5, 12, 13. Pin numbers refer to DIL-16 package. Cur-
rents are positive into, negative out of the specified ter-
minal.
Note 2: Consult Packaging Section of Databook for in-
formation on thermal limitations and considerations of
package.
Logic Inputs (Pins 7, 8, 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA
Analog Inputs (Pins 10, 11). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -10mA
±
Output Current (Pins 1, 15) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A
Junction Temperature, TJ. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
Storage Temperature Range, TS . . . . . . . . . . . . . . . . . . -55°C to +150°C
BLOCK DIAGRAM
7/95
UC1717
UC2717
UC3717
CONNECTION DIAGRAMS
PACKAGE PIN FUNCTION
DIL-16 (TOP VIEW)
J or N Package
PLCC-20 (TOP VIEW)
Q Package
FUNCTION
N/C
PIN
1
BOUT
Timing
VM
2
3
4
Gnd
N/C
5
6
Gnd
VCC
I1
7
8
9
Phase
N/C
I0
Current
VR
Gnd
N/C
Gnd
Vm
AOUT
Emitters
10
11
12
13
14
15
16
17
18
19
20
RECOMMENDED OPERATING CONDITIONS
PARAMETER
MIN
4.75
10
TYP
MAX UNITS
Supply Voltage, VCC
5
5.25
40
800
2
V
V
mA
µs
Supply Voltage, VM
Output Current. IM
Rise Time Logic Inputs, tR
Fall Time Logic Inputs, tF
Ambient Temperature, TA
UC1717
20
2
µs
-55
-25
0
125
85
°C
°C
°C
UC2717
UC3717
70
Unless otherwise specified, these specifications apply for VCC = 5V, TA = TJ.
ELECTRICAL CHARACTERISTICS
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX UNITS
Supply Current, ICC
25
mA
V
High-Level Input Voltage, Pins 7, 8, 9
Low-Level Input Voltage, Pins 7, 8, 9
High-Level Input Current, Pins 7, 8, 9
Low Level Input Current, Pins 7, 8, 9
Comparator Threshold Voltage
2.0
0.8
20
V
VI = 2.4V
VI = 0.4V
µA
mA
mV
mV
mV
µA
µA
V
-0.4
390
230
65
IO = 0, I1 = 0, VR = 5.0V
IO = 1, I1 = 0, VR = 5.0V
IO = 0, I1 = 1, VR = 5.0V
420
250
80
440
270
90
Comparator Input Current
Output Leakage Current
Total Saturation Voltage Drop
Total Power Dissipation
-20
20
IO = 1, I1 = 1, TA = +25°C
100
4.0
2.1
3.1
35
IM = 500mA
IM = 500mA, fS = 30kHz
1.4
2.9
30
W
IM = 800mA, fS = 30kHz
W
Cut Off Time, tOFF
VM = 10V, tON≥ 5µs (See Figure 5 and 6)
TA = +25°C; dVc/dt ≥ 50mV/µs (See Figure 5 and 6)
25
µs
µs
°C
Turn Off Delay, tD
1.6
2.0
+180
Thermal Shutdown Junction Temperature
+160
2
UC1717
UC2717
UC3717
Figure 3: Typical Sink Saturation Voltage vs Output Current
Figure 1
Figure 2: Typical Source Saturation Voltage vs Output Current
Figure 4: Typical Power Losses vs Output Current
FUNCTIONAL DESCRIPTION
The UC3717 drive circuit shown in the block diagram in-
cludes the following functions:
(1) Phase Logic and H-Bridge Output Stage
(2) Voltage Divider with three Comparators for current control
(3) Two Logic inputs for Digital current level select
(4) Monostable for off time generation
Input Logic: If any of the logic inputs are left open, the
circuit will treat it as a high level input.
Phase Input: The phase input terminal, pin 18, controls
the direction of the current through the motor winding.
The Schmidt-Trigger input coupled with a fixed time de-
lay assures noise immunity and eliminates cross conduc-
tion in the output stage during phase changes. A low
level on the phase input will turn Q2 on and enable Q3
while a high level will turn Q1 on and enable Q4. (See
Figure 7).
Figure 5: Connections and Component Values as in Figure 6.
across the source transistors. The Schottky diodes allow
the current to circulate through the winding while the sink
transistors are being switched off. The diodes across the
sink transistors in conjunction with the Schottkys provide
the path for the decaying current during phase reversal.
(See Figure 7).
Output Stage: The output stage consists of four Dar-
lington transistors and associated diodes connected in
an H-Bridge configuration. The diodes are needed to pro-
vide a current path when the transistors are being
switched. For fast recovery, Schottky diodes are used
PHASE INPUT
Low
Q1, Q4
Off
Q2, Q3
On
High
On
Off
3
UC1717
UC2717
UC3717
Figure 6
ing causing the current to decay. The time is determined
by the external timing components RT and CT as:
I0
0
1
0
1
I1
0
0
1
1
CURRENT LEVEL
100%
TOFF = 0.69 RTCT
60%
If a new trigger signal should occur during TOFF, it is ig-
nored.
19%
Current Inhibit
Current Control: The voltage divider, comparators and
monostable provide a means for current sensing and
control. The two bit input (I0, I1) logic selects the desired
comparator. The monostable controls the off time and
therefore the magnitude of the current decrease. The
time duration is determined by RT and CT connected to
the timing terminal (pin 2). The reference terminal (pin
11) provides a means of continuously varying the cur-
rent for situations requiring half-stepping and micro-
stepping. The relationship between the logic input
signals at pin 7 and 9 in reference to the current level is
shown in Table 1. The values of the different current lev-
els are determined by the reference voltage together
with the value of the external sense resistor RS (pin 16).
Single-Pulse Generator: The pulse generator is a
monostable triggered on the positive going edge of the
comparator. Its output is high during the pulse time and
this pulse switches off the power feed to the motor wind-
Note: Dashed lines indicate current decay paths.
Figure 7: Simplified Schematic of Output Stage
4
UC1717
UC2717
UC3717
FUNCTIONAL DESCRIPTION (cont.)
Overload Protection: The circuit is equipped with a
thermal shutdown function, which will limit the junction
temperature by reducing the output current. It should be
noted however, that a short circuit of the output is not
permitted.
Operation: When the voltage is applied across the motor
winding the current rises linearly and appears across the
external sense resistor as an analog voltage. This volt-
age is fed through a low pass filter RC, CC to the voltage
comparator (pin 10). At the moment the voltage rises be-
yond the comparator threshold voltage the monostable is
triggered and its output turns off the sink transistors. The
current then circulates through the source transistor and
the appropriate Schottky diode. After the one shot has
timed out, the sink transistsor is turned on again and the
procedure repeated until a current reverse command is
given. By reversing the logic level of the phase input (pin
8), both active transistors are being turned off and the
opposite pair turned on. When this happens the current
must first decay to zero before it can reverse. The cur-
rent path then provided is through the two diodes and the
power-supply. Refer to Figure 7. It should be noted at
this time that the slope of the current decay is steeper,
and this is due to the higher voltage build up across the
winding. For better speed performance of the stepping
motor at half step mode, the phase logic level should be
changed at the same time the current inhibit is applied. A
typical current wave form is shown in Figure 8.
Figure 9
The timing diagram in Figure 10 shows the required sig-
nal input for a two phase, full step, stepping sequence.
Figure 11 shows a one phase, full step, stepping se-
quence, commonly referred to as wave drive. Figure 12
shows the required input signal for a one phase-two
phase stepping sequence called half-stepping.
The circuit of Figure 13 provides the signal shown in Fig-
ure 10, and in conjunction with the circuit shown in Fig-
ure 9, will implement a pulse-to-step two phase, full step,
bidirectional motor drive.
The schematic of Figure 14 shows a pulse to half step
circuit generating the signal shown in Figure 12. Care
has been taken to change the phase signal the same
time the current inhibit is applied. This will allow the cur-
rent to decay faster and therefore enhance the motor
performance at higher step rates.
Figure 8
APPLICATIONS
A typical chopper drive for a two phase bipolar perma-
nent magnet or hybrid stepping motor is shown in Figure
9. The input can be controlled by a microprocessor, TTL,
LS or CMOS logic.
Using the UC3717 to drive the L298 provides a uniquely
packaged state-of-the-art high power stepper motor con-
trol and drive. See Figure 15.
5
UC1717
UC2717
UC3717
FUNCTIONAL DESCRIPTION (cont.)
Figure 10: Phase Input Signal for Two Phase Full Step Drive (4 Step Sequence)
Figure 11: Phase and Current-Inhibit Signal for Wave Drive (4 Step Sequence)
Figure 12: Phase and Current-Inhibit Signal for Half Stepping (8 Step Sequence)
Figure 13: Full Step Bidirectional Two Phase Drive Logic
6
UC1717
UC2717
UC3717
Figure 14: Half-Step, Bidirectional Drive Logic
CONSIDERATION
Half-Stepping: In the half step sequence the power in-
put to the motor alternates between one or two phases
being energized. In a two phase motor the electrical
phase shift between the windings is 90 degrees. The
torque developed is the vector sum of the two windings
energized. Therefore when only one winding is energized
the torque of the motor is reduced by approximately
30%. This causes a torque ripple and if it is necessary to
compensate for this, the VR input can be used to boost
the current of the single energized winding.
which rise in an exponential manner as the frequency or
step rate is increased. The power losses can not be cal-
culated by I2R where I is the chopping current level and
R the DC resistance of the coil. Actual measurements in-
dicate the effective resistance may be many times larger.
Therefore, for 100% duty cycle the current must be lim-
ited to a value which will not overheat the motor. This
may not be necessary for lower duty cycle operation.
Interference: Electrical noise generated by the chopping
action can cause interference problems, particularly in
the vicinity of magnetic storage media. With this in mind,
printed circuit layouts, wire runs and decoupling must be
considered. 0.01 to 0.1µF ceramic capacitors for high fre-
quency bypass located near the drive package across
V+ and ground might be very helpful. The connection
and ground leads of the current sensing components
should be kept as short as possible.
Ramping: Every drive system has inertia and must be
considered in the drive scheme. The rotor and load iner-
tia plays a big role at higher speeds. Unlike the DC motor
the stepping motor is a synchronous motor and does not
change its speed due to load variations. Examining typi-
cal stepping motors, torque vs. speed curves indicates a
sharp torque drop off for the start-stop without error
curve, even with a constant current drive. The reason for
this is that the torque requirements increase by the
square of the speed change, and the power need in-
creases by the cube of the speed change. As it can be
seen, for good motor performance controlled accelera-
tion and deceleration should be considered.
Ordering Information
UNITRODE TYPE NUMBER
UC3717N - 16 Pin Dual-in-line (DIL) "Bat Wing" Package
UC1717J - 16 Pin Dual-in-line Ceramic Package
UC1717SP - 16 Pin Dual-in-line Hermetic Power Package
Iron Core Losses: Some motors, especially the Tin-Can
type, exhibit high iron losses mostly due to eddy currents
7
UC1717
UC2717
UC3717
Figure 15: UC3717 with L298 Power Amplifier
UNITRODE INTEGRATED CIRCUITS
7 CONTINENTAL BLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603)424-3460
8
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