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| 型号： | A8904SLP-T |
| 元件分类： | 运动控制电子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, 1.4 A, PDSO28 |
| 封装： | 1.20 MM HEIGHT, LEAD FREE, TSSOP-28 |
| 文件页数： | 18/18页 |
| 文件大小： | 736K |
| 代理商： | A8904SLP-T |
3-Phase Brushless DC Motor Controller/Driver
with Back EMF Sensing
A8904
9
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Functional Description
Overview of operation.
Each electrical revolution
contains six states that control the three half-bridge outputs.
Optimized switching from state to state is achieved through the
adaptive commutation circuitry. During any state, one output is
high, one is low and the other is high impedance. The back-EMF
at the high-impedance output is sensed and compared to the
voltage of the centertap and when the two signals are equivalent,
the FCOM signal toggles. A controlled delay is then introduced
before the sequencer commutates into the next state.
Linear current-mode control is employed to provide preci-
sion control of the motor speed while maintaining extremely
low electrical noise emissions. The speed control is realized
through a frequency-locked loop that processes the sensed
back-EMF signals from the stator phases to eventually produce a
TACH signal. The TACH signal is then compared to the desired
programmed speed, to produce an error. The error signal is then
used to linearly control the current through the low-side DMOS
power devices to obtain the correct speed.
Alternative control schemes can be introduced, giving the
user maximum exibility and optimization for each application.
An external tachometer signal applied to the SECTOR DATA
input, along with the internal speed reference can be used for
high-precision speed control. As another alternative, the user can
introduce external speed control by driving the FILTER terminal
directly.
Start-up routines are inherent in the solution to guarantee
reliable start-up. During start-up, a YANK feature allows rapid
transition to the nominal operating condition on the FILTER
terminal. This feature is also available when the external speed
control is used.
Dynamic braking can be introduced by either the external
BRAKE terminal or through the brake bit in the serial port.
A serial port allows the user to program various features and
modes of operation, such as motor speed, internal or external
speed control, internal or external speed reference, current limit,
sleep mode, direction, charge current (for blanking pulse), motor
poles, transconductance gain, and various diagnostic outputs.
Full device protection is incorporated, including program-
mable overcurrent limit, thermal shutdown, and undervoltage
shutdown on the logic supply.
Power outputs.
The power outputs of the A8904 are
n-channel DMOS transistors with a total source plus sink rDS(on)
of typically 1
Ω. An internal charge pump provides a voltage rail
above the load supply for driving the high-side DMOS gates.
Intrinsic ground clamp and yback diodes provide protection
when switching inductive loads. These diodes will also rectify
the motor back-EMF during power-down conditions. If neces-
sary, a transient voltage supply can be provided, by connecting
an external Schottky power diode or pass FET in series, between
the power source and the load supply (VBB). This FET or diode
effectively isolates the low impedance path through the power
source. A lter capacitor is also required to ‘hold up’ the rectied
signal, and is connected between the load supply and ground.
Back-EMF sensing motor start-up and running
algorithm.
The A8904 provides a complete self-contained
back-EMF sensing, start-up and running commutation scheme.
A state machine with six states, (shown in the tables below for
both forward and reverse direction) controls the three half-bridge
outputs. In each state, one output is high (sourcing current), one
low (sinking current), and one is OFF (high impedance or ‘Z’).
Motor back-EMF is sensed at the output that is OFF.
Sequencer State
(forward direction)
OUTA
OUTB
OUTC
1
High
Z
Low
2
High
Low
Z
3
Z
Low
High
4
Low
Z
High
5
Low
High
Z
6
Z
High
Low
Sequencer State
(reverse direction)
OUTA
OUTB
OUTC
1
High
Z
Low
6
Z
High
Low
5
Low
High
Z
4
Low
Z
High
3
Z
Low
High
2
High
Low
Z
At start-up, the outputs are always enabled in state 1. The
back-EMF is examined at the OFF output by comparing the out-
put voltage to the motor centertap voltage at CENTERTAP. The
motor will then either step forward, step backward or remain
stationary (if in a null-torque position).
If the motor does not move during the initial start-up state,
the outputs are commutated automatically by the start-up oscil-
lator. When suitable back-EMF signals are detected, the start-up
oscillator is overridden and the corresponding timing clock is
generated, providing synchronous back-EMF commutation. The
start-up oscillator period is determined by
tCST = (VCSTH - VCSTL) x CST / IST(charge)
where CST is the start-up capacitor.
If the motor moves, the back-EMF detection and direction
circuit waits for the correct polarity of back-EMF zero crossing
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相关代理商/技术参数 |
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| A8904SLPTR | 功能描述:IC CTRLR/DRVR DC MOTOR 28TSSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 电机和风扇控制器，驱动器 系列:- 标准包装:1 系列:- 应用:直流电机驱动器，步进电机驱动器 评估套件:- 输出数:1 或 2 电流 - 输出:750mA 电压 - 负载:10 V ~ 40 V 电源电压:4.5 V ~ 5.5 V 工作温度:-20°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-BFSOP（0.295"，7.50mm 宽） 供应商设备封装:24-SOP 包装:Digi-Reel® 其它名称:MTS62C19A-HS105DKR |
| A8904SLPTR-T | 功能描述:IC CTRLR/DRVR DC MOTOR 28TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 电机和风扇控制器，驱动器 系列:- 标准包装:1 系列:- 应用:直流电机驱动器，步进电机驱动器 评估套件:- 输出数:1 或 2 电流 - 输出:750mA 电压 - 负载:10 V ~ 40 V 电源电压:4.5 V ~ 5.5 V 工作温度:-20°C ~ 70°C 安装类型:表面贴装 封装/外壳:24-BFSOP（0.295"，7.50mm 宽） 供应商设备封装:24-SOP 包装:Digi-Reel® 其它名称:MTS62C19A-HS105DKR |
| A8905CLB | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING |
| A8906CLB | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:BIDIRECTIONAL 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING |
| A8909CLB | 制造商:ALLEGRO 制造商全称:Allegro MicroSystems 功能描述:3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING AND POWER DMOS OUTPUTS |
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