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參數(shù)資料
| 型號： | ML4425IS |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 運動控制電子 |
| 英文描述： | Sensorless BLDC Motor Controller |
| 中文描述： | BRUSHLESS DC MOTOR CONTROLLER, 0.05 A, PDSO28 |
| 封裝： | SOIC-28 |
| 文件頁數(shù)： | 11/16頁 |
| 文件大?。?/td> | 167K |
| 代理商： | ML4425IS |
PRODUCT SPECIFICATION
ML4425
REV. 1.0.2 7/2/01
11
Figure 8. ML4425 Start-up Circuitry for Controlling the Align and Ramp Times
CAT
CAT
FB A
FB B
FB C
BACK
EMF
SAMPLER
CRT
CRT
CRR
–
+
1.5V
750nA
–
+
1.5V
750nA
VDD
VDD
CRR
500nA
VDD
SPEED
FB
TO
SPEED FB
FILTER
CVCO
RVCO
VOLTAGE
CONTROLLED
OSCILLATOR
VCO/TACH
TO RESET INPUT
OF COMMUTATION
STATE MACHINE
Run Mode (Back EMF Sensing)
At the end of ramp mode the controller goes into run mode.
In run mode, the back EMF sensing is enabled and commuta-
tion is now under the control of the phase locked loop. Motor
speed is now regulated by the speed control loop.
PWM Speed Control
Speed control is accomplished by setting a speed command
at SPEED SET with an input voltage from 0 to 6.9V (V
REF
).
The accuracy of the speed command is determined by the
external components R
VCO
and C
VCO
. There are a number of
methods that can be used to control the speed command of
the ML4425. One is to use a 10k
potentiometer from V
REF
to ground with the wiper connected to SPEED SET. If
SPEED SET is controlled from a microcontroller, one of its
DACs can be used with V
REF
as its input reference.
The speed command is compared with the sensed speed from
SPEED FB through a transconductance error amplifier. The
output of the speed error amplifier is SPEED COMP. SPEED
COMP is clamped between one diode drop above 3.9V
(approximately 4.6V) and one diode drop below 1.7V
(approximately 1V) to prevent speed loop “wind-up”. Speed
loop compensation components are connected to this pin as
shown in Figure 9. The speed loop compensation compo-
nents are calculated as follows:
Where f
SB
is the speed loop bandwidth in Hz.
Figure 9. Speed Control Loop Component Connections
The voltage on SPEED COMP is compared with a ramp
oscillator to create a PWM duty cycle. The PWM ramp oscil-
lator creates a sawtooth function from 1.7V to 3.9V as shown
in Figure 9. A negative clamp at one diode drop below 1.7V
(approximately 1V) starts the oscillator on power up. The
frequency of the ramp oscillator is set by a capacitor to
ground C
IOS
and is selected using the following equation:
Where f
PWM
is the PWM frequency in Hz. The PWM duty
cycle from the speed control loop is gated the current limit
one shot that controls the LA, LB, and LC output drivers.
C
SC
26.9
N
V
C
τ
m
2
f
SB
K
e
×
2.5
98.696
f
SB2
×
×
+
------------------------------------------------------------------------------------------
=
(9a)
R
SC
SB
SC
--------------------------------------
=
(9b)
–
+
+
–
SPEED SET
SPEED COMP
3.9V
1.7V
10k
20kHz
PWM ON/OFF
FROM ILIMIT
ONE-SHOT
FROM
SPEED FB
TO
GATING
LOGIC &
OUTPUT
DRIVERS
CT
CT
CSC
RSC
1.7V
VREF
C
T
----------------------------------
-------------
50
μ
A
×
=
(10)
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ML4425ISX | 功能描述:開關變換器、穩(wěn)壓器與控制器 BLDC Motor Control Sensorless RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| ML4426 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Bi-directional Sensorless BLDC Motor Controller |
| ML4426 WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4426CH | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Bi-directional Sensorless BLDC Motor Controller |
| ML4426CP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Bi-directional Sensorless BLDC Motor Controller |
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