參數(shù)資料
型號: UC17132L
英文描述: 8-bit MCU for automotive with Flash or ROM, 10-bit ADC, 5 timers, SPI, LINSCI", active CAN
中文描述: 單外設(shè)驅(qū)動
文件頁數(shù): 7/9頁
文件大?。?/td> 547K
代理商: UC17132L
UC1717
UC2717
UC3717
Figure 14:
Half-Step, Bidirectional Drive Logic
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 V
R
input can be used to boost
the current of the single energized winding.
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.
Iron Core Losses:
Some motors, especially the Tin-Can
type, exhibit high iron losses mostly due to eddy currents
which rise in an exponential manner as the frequency or
step rate is increased. The power losses can not be cal-
culated by I
2
R 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 0.1
μ
F 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.
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
CONSIDERATION
7
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UC17133L 8-bit MCU for automotive with Flash or ROM, 10-bit ADC, 5 timers, SPI, LINSCI", active CAN
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