- 您现在的位置：买卖IC网 > PDF目录378256 > 8904 (Allegro MicroSystems, Inc.) 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING PDF资料下载
参数资料
| 型号： | 8904 |
| 厂商： | Allegro MicroSystems, Inc. |
| 英文描述： | 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING |
| 中文描述： | 3相无刷直流电动机控制器/驱动器，反电动势遥感 |
| 文件页数： | 9/18页 |
| 文件大小： | 744K |
| 代理商： | 8904 |
8904
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
www.allegromicro.com
9
If the motor moves, the back-EMF detection and direction
circuit waits for the correct polarity of back-EMF zero crossing
(output crossing through centertap). If the correct polarity of
back-EMF is not detected, a watchdog circuit commutates the
output until the correct back-EMF is detected. Correct back-
EMF sensing is indicated by the FCOM signal, which toggles
every time the back-EMF completes a zero crossing (see
waveforms below). FCOM is available at the DATA OUT
terminal.
True back-EMF zero crossings are used by the adaptive
commutation delay circuit to advance the state sequencer
(commutate) at the proper time to synchronously run the motor.
See next section.
Adaptive commutation delay.
The adaptive commuta-
tion delay circuit uses the back-EMF zero-crossing indicator
signal (FCOM) to determine an optimal commutation time for
efficient synchronous switching of the output drivers. When the
FCOM signal changes state, one of the delay capacitors (C
D1
or
C
D2
) is discharged at approximately twice the rate of the
charging current. When the capacitor reaches the 2.5 V thresh-
old, a commutation occurs. During this discharge period, the
other delay capacitor is being charged in anticipation of the next
FCOM state change. In addition, there is an interruption to the
charging, which is set by the blanking duration (see waveform
below, V
CWD,
and next section). This additional charging delay
causes the commutation to occur at slightly less than 50% of the
FCOM on or off duration, to compensate for delays caused by
winding inductance.
Functional Description (cont’d)
The typical delta voltage change during normal operation in
the commutation capacitors (C
D1
& C
D2
), will range between
1.5 V and 2.0 V. The commutation capacitor values can be
determined from:
C
DX
= I
CD
x t / V
CD
where V
CD
= 1.5 V, I
CD
= 20 μA, and t = (60/rpm)/(#motor
poles x 3), duration of each state.
To avoid the capacitors charging to the supply rail, the value
selected should provide adequate margin, taking into account the
effects of capacitor tolerance, charging current, etc.
Blanking and watchdog timing functions.
The
blanking and watchdog timing functions are derived from one
timing capacitor C
WD .
During normal commutation, at the beginning of each new
sequencer state, a blanking signal is created until the watchdog
capacitor C
WD
is charged to the threshold V
TL
(see waveforms
below). This blanking signal prohibits the back-EMF compara-
tors from tripping due to the discharging of inductive energy and
voltage settling transients during sequence state transitions. The
duration of this blanking signal depends on the size of the C
WD
capacitor and the programmed charge current, I
CWD
(via D26-
27). This blanking pulse also interrupts the commutation delay
capacitors C
D1
and C
D2
from charging (see previous section).
The ability to select the minimum charge current for C
WD
is
particularly useful during start-up, where the duration of the
diode recirculation current is highest. In applications where
high motor speeds are experienced, the charge current can be
increased so that the blanking period does not encroach signifi-
cantly into the period of each sequencer state and does not cause
相关PDF资料 |
PDF描述 |
|---|---|
| 8905 | 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING |
| 8906 | BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING |
| 8909 | 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING AND POWER DMOS OUTPUTS |
| 8910 | T-1 Subminiature Lamps |
| 8920 | DUAL SCHOTTKY DIODE |
相关代理商/技术参数 |
参数描述 |
|---|---|
| 8904010543 | 功能描述:EMI/RFI 抑制器及铁氧体 EMI WASHER, ALUMINUM MESH RoHS:否 制造商:Fair-Rite 产品:Ferrite Cores 阻抗:365 Ohms 容差: 最大直流电流: 最大直流电阻: 工作温度范围:- 55 C to + 125 C 封装 / 箱体: 端接类型:SMD/SMT |
| 8904011740 | 制造商:Laird Technologies Inc 功能描述:ELECTROGROUND EMI WASHERS |
| 8904-0175-44 | 制造商:Laird Technologies Inc 功能描述: |
| 8904-0176-44 | 制造商:Laird Technologies Inc 功能描述: |
| 8904-025 | 功能描述:THRM CNDCTV TAPE 600MMX40MX.25MM 制造商:3m 系列:* 零件状态:有效 标准包装:1 |
发布紧急采购，3分钟左右您将得到回复。