ML4411 데이터 시트보기 (PDF) - Micro Linear Corporation

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ML4411

Sensorless Spindle Motor Controller

Micro Linear Corporation 

BRAKING

As shown in figure 9, the braking circuit pulls the N-

Channel MOSFET gates high when BRAKE falls below a

1.4V threshold. After a power failure, CDLY is discharged

slowly through RDLY providing a delay for retract to occur

before the braking circuit is activated. The N-Channel

buffer (B1) tri-states when the BRAKE pin reaches 2.1V to

ensure that no charge from CBRK is lost through the pull-

down transistor in B1. To brake the motor with external

signals, first disable power by pulling pin 8 low, then pull

pin 26 below 1.4V using an open drain (or diode isolated)

output.

The bias current for the Braking circuits comes from

VCC2. When the N-Channel MOSFETs turn on, no

additional power is generated for VCC2 (motor back-EMF

rectified through out the MOSFET body diodes). After

VCC2 drops below 4V, Q2 turns off. Continued braking

relies on the CGS of the N-Channel MOSFETs to sustain

the MOSFET gate enhancement voltage.

ML4411/ML4411A

60

50

40

30

20

10

0

0

0.01 0.02 0.03 0.04 0.05

COS

Figure 8. ILIMIT Output Off-Time vs. COS.

CDLY

VCC2

16K

POWER FAIL

17

+5

4.5K

VCC2 – 3V

UVLO

+ P3 ONLY

A6

–

RDLY

26

COMM. LOGIC

DIS PWR

VCC2

BRAKE

VCC2

+

2.1V

+

A5

–

1.4V

A4

–

COMMUTATION

LOGIC

8 DIS PWR

UVLO

27 ILIMIT

28 ICMD

12 ISENSE

AV = 5

A1

+

A3

–

Q

ONE

SHOT

+

–

A2

1K

P1 . . . P3

VCC

Q2

VCC2

CBRK

7

Q1

TRI-

ST.

B1

VIN

N1 . . . N3

RSENSE

COS 13

VCC

COTA 6

Figure 9. Current Control, Output Drive and Braking Circuits.

9

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