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PDF IXMS150PSI Data sheet ( Hoja de datos )
| Número de pieza | IXMS150PSI | |
| Descripción | High Performance Dual PWM Microstepping Controller | |
| Fabricantes | IXYS Corporation | |
| Logotipo |  |
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High Performance Dual PWM Microstepping Controller
Type
IXMS150 PSI
Package
24-Pin Skinny DIP
Temperature Range
-40°C to +85°C
The IXMS150 is a high performance
monolithic 2-channel PWM controller.
Implemented in CMOS, the low power
IXMS150 precisely controls the current
in each of two separate power H-bridge
drivers using unique sampling and
www.DataSheets4iUgn.caolmprocessing techniques. Each
channel contains an error amplifier,
PWM, feedback amplifier, and protec-
tion circuitry. Protection features include
over/excess current shutdown, min/max
duty cycle clamp, under voltage lock-
out, dead time insertion, and a shutdown
input for over-temp or other external
fault circuitry. Other features include a
common oscillator, feedforward circuit
for motor supply compensation, and an
onchip negative bias generator.
The IXMS150 has been optimized for
microstep control of two phase step
motors. Due to its high level of accu-
Block diagram of IXMS 150
racy, the IXMS150 will allow a designer
to implement a control system with a
resolution in excess of 250 microsteps
per step, or 50,000 steps per revolution
with a 200 step per revolution step
motor. The IXMS150 greatly improves
positioning accuracy and virtually
eliminates low speed velocity ripple and
resonance effects at a fraction of the cost
of a board level microstepping system.
Other applications which the IXMS150
is designed for include control of two
single-phase (DC) motors or control of
synchronous reluctance motors. The
IXMS150 is ideal for robotics, printers,
plotters, and x-y tables and can facilita-
te the construction of very sophisticated
positioning control systems while signi-
ficantly reducing component cost, board
space, design time and systems cost.
Features
l Two complete, synchronous PWMs
l Command input range ±2.0 V full
scale
l ±0.625 V full scale current feedback
signal
l 1% gain matching between channels
without external trim
l 1.6% gain linearity
l Feedforward to compensate for
motor supply variations
l Only one sense resistor per H-bridge
needed
l Onboard two level current limiting
l Undervoltage lockout assures proper
behavior on power up and power
down
l Enable input for external over
temperature or fault circuit input
l Duty cycles limited for AC coupled
gate drive
l Wide range of built in dead time.
l On board negative power supply
generator
l Single +12 V supply operation
l 24-pin DIP package
Symbol
VDD
VIN
VO
PD
TA
Tstg
Definition
Supply voltage
Operating range
Common-mode-range
Differential Input voltage ¬
Input voltage ¬
Output voltage
Maximum power dissipation
Ambient temperature range
Storage temperature range
Max. Ratings
-0.3...15
10.8...13.2
-15...15
±30
-15...15
-0.3...VDD+0.3
500
V
V
V
V
V
V
mW
-40...85 °C
-55...125 °C
¬ Input voltage may not exceed either supply rail by more than 0.3 V at any time.
IXYS reserves the right to change limits, test conditions and dimensions.
© 1998 IXYS All rights reserved
Applications
l Full, half quarter, or microstepping
2-phase step motor position
controller
l Dual DC servo motor torque
controller
l Solenoid actuator force controller
l General 2-channel current-
commanded PWM control
I - 35
1 page  
IXMS 150
Application Information
Introduction
The advantages of step motors are well
known. They may be operated in an
open loop fashion, the accuracy of
which is mostly dependent on the
mechanical accuracy of the motor. They
move in quantized increments (steps)
which lends them easily to digitally
controlled motion systems. In addition,
their drive signals are square wave in
www.DataSheetn4aUt.ucroemand are therefore easily gene-
rated with relatively high efficiency due
to their ON/OFF characteristics.
But step motors are not free of prob-
lems. Their large pulse drive wave-
forms create mechanical forces which
excite and aggravate the mechanical
resonances in the system. These are
load dependent and difficult to control
since step motors have very little
damping of their own. At resonance a
step motor system is likely to lose
synchronization and therefore skip or
gain a step. Being an open loop system,
this would imply loss of position infor-
mation and would be unacceptable. A
common method of solving this problem
is to avoid the band of resonance
frequencies altogether, but this might
put severe limitations on system
performance. Steppers have 200 steps
per revolution or 1.8 degrees per step.
The highest resolution commercially
available steppers have 400 steps per
revolution or 0.9 degrees per step.
Microstepping Mode
One way to circumvent the problems
associated with step motors while still
retaining their open loop advantages is
to use them in the microstepping mode.
In this mode each of the steps is subdi-
vided into smaller steps or microsteps".
Applying currents to both phases of the
motor creates a torque phaser which is
proportional to the vector sum of both
currents. When the phasor completes
one turn (360 electrical degrees), the
motor moves exactly four full steps or
one torque cycle. Similarly, when that
phasor moves 22.5 electrical degrees
the motor will move (22.5/90) 100 =
25 % of a full step. Thus the position of
the motor is determined by the angle of
the torque phasor. When used with an
appropriate motor a positioning accu-
racy of 2 % of a full step can be achie-
ved, equaling 0.036 degrees for a 200
© 1998 IXYS All rights reserved
full steps per revolution motor. In this
manner the motor can be positioned to
any arbitrary angle. A common way to
control the angle of the torque phasor is
by applying to the motors phases two
periodic waveforms shifted by 90
electrical degrees.
Let the phase current equations be:
iA = IO cos θe
iB = IO sin θe
(1)
(2)
Note that θe is the electrical position.
The resulting torque generated by the
corresponding phases would then be:
TA = K0 iA = K0 I0 cos θe
TB = K0 iB = K0 I0 sin θe
(3)
(4)
where K0 is the torque constant of the
motor. Substituting Eqs. (1), (2) into (3),
(4) and doing vector summation the
resulting total generated torque mea-
sured on the motor shaft is given by:
Tg = K0 I0
(5)
Note that in this case we have zero
torque ripple.
Using this technique one can theore-
tically achieve infinite resolution with
any step motor. Since the drive current
waveforms are sinusoidal instead of
square, the step to step oscillations are
eliminated and the associated velocity
ripple. This greatly improves perfor-
mance at low rotational speeds and
helps avoid resonance problems. In an
actual application, the extent to which
these things are true depends on how
the two sinusoidal reference waveforms
are generated.
Seemingly we have lost the quantized
motion feature of a stepper when used
in this mode. This can be regained by
defining the term microsteps per step.
Each full step is subdivided into micro-
steps by applying to the motors phases
those intermediate current levels for
which their vector sum tracks the circle
of Fig. 2 and divides the full step (90
electrical degrees) into the require
number of microsteps. An example of
the required phase currents for full step
and four microstep per step operation
are shown in Fig. 1 and 2 respectively.
Phase Current Matching
Requirements
Assuming microstepping is being used
for resolution improvement and not as a
resonance avoidance technique, a step
motor can be selected knowing the
torque needed, its specified step
Fig. 1 Full Step Drive Waveforms
accuracy, and the required resolution or
the number of microsteps per step.
Next, one must determine the accuracy
required of the phase currents to main-
tain the accuracy of the complete
system. Equations (1) - (4) clearly
indicate that errors in the absolute
value or phase of the phase currents
will impact positioning accuracy.
Another observation is that by keeping
the ratio of the phase currents iA/iB
constant, errors in their value will result
Fig. 2 Four Microstep per Step Drive
Waveforms
I - 39
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