ML4411 데이터 시트보기 (PDF) - Micro Linear Corporation

부품명

상세내역

일치하는 목록

ML4411

Sensorless Spindle Motor Controller

Micro Linear Corporation 

FUNCTIONAL DESCRIPTION

The ML4411 provides closed-loop commutation for

3-phase brushless motors. To accomplish this task, a VCO,

integrating Back-EMF Sampling error amplifier and

sequencer form a phase-locked loop, locking the VCO to

the back-EMF of the motor. The IC also contains circuitry

to control motor current with either linear or constant off-

time PWM modes. Braking and power fail detection

functions are also provided on chip. The ML4411 is

designed to drive external power transistors (N-channel

sinking transistors and PNP sourcing transistors) directly.

Start-up sequencing and motor speed control are

accomplished by a microcontroller. Speed sensing is

accomplished by monitoring the output of the VCO,

which will be a signal which is phased-locked to the

commutation frequency of the motor.

BACK-EMF SENSING AND COMMUTATOR

The ML4411 contains a patented back-EMF sensing

circuit which samples the phase which is not energized

(Shaded area in figure 2) to determine whether to increase

or decrease the commutator (VCO) frequency. A late

commutation causes the error amplifier to charge the

filter (RC) on pin 20, increasing the VCO input while

early

commutation causes pin 20 discharge. Analog speed

control loops can use pin 20 as a speed feedback voltage.

The input impedance of the three PH inputs is about 8Ký

to GND. When operating with a higher voltage motor, the

PH inputs should be divided down in voltage so that the

ML4411/ML4411A

maximum voltage at any PH input does not exceed VCC.

NEUTRAL

0

60

120

180

240

300

0

Figure 2. Typical motor phase waveform with Back-EMF

superimposed (Ideal Commutation)

VCO AND PHASE DETECTOR CALCULATIONS

The VCO should be set so that at the maximum frequency

of operation (the running speed of the motor) the VCO

control voltage will be no higher than VCCMIN – 1V. The

VCO maximum frequency will be:

FMAX = 0.05 × POLES × RPM

where POLES is the number of poles on the motor and

RPM is the maximum motor speed in Revolutions Per

ΦA

ΦB

ΦC

8K

+

ROTATION

SENSE

–

NEUTRAL

SIMULATOR

ΦA + ΦB + ΦC

6

MULTIPLEXER

8K

IRC =

Va – Vb

8K

SIGN

a+

CHANGER b –

COMMUTATION

LOGIC

+

I(PIN 21)

LOOP FILTER

RC

R

VCO

C1

C2

VCO /TACH OUT

DIS PWR

FIGURE 1. BACK EMKF sensing block diagram

5

Share Link: