10

ML4411/ML4411A

APPLICATIONS

Figure 10 shows a typical application of the ML4411 in a

hard disk drive spindle control. Although the timing

necessary to start the motor in most applications would be

generated by a microcontroller, Fig. 11 shows a simple

“one shot” start-up timing approach.

Speed control can be accomplished either by:

1. Sensing the VCO OUT frequency with a

output form the Micro (PWM DAC).

2. Using analog circuitry for speed control. (Fig. 12).

OUTPUT STAGE HINTS

In the circuit in Figure 10, Q1, Q2, and Q3 are IRFR9024

or equivalent. Q4, Q5, and Q6 are IRFR024 or equivalent.

New MOSFET packaging technology such as the Little

packages, however have much lower thermal inertia and

dissipation capabilities than the larger packages, and care

should be taken not to exceed their rated current and

junction temperature.

Since the output section in a full bridge application

consists of three half-H switches, cross-conduction can

occur. Cross-conduction is the condition where an N-FET

and P-FET in the same phase of the bridge conduct

simultaneously. This could happen under two conditions

(see figure 13):

BRAKE

VCC

PH3

PH2

PH1

RC

+5V

ENABLE E/A

PWR FAIL

RESET

VCO/TACH OUT

GND

P1

P2

VCC2

P3

DIS PWR

N1

N2

N3

+5

1M

+12

+5

510K

0.22

+5

5K

5K

0.5

Q6

Q3

0.1

10

Q2

Q5

Q1

Q4

VCC2

1N5819

0.1

10

+12V

TO VCC

510

0.01

0.22

0.02

0.01

ENABLE ERROR AMP

RESET (FROM MICRO)

POWER FAIL TO MICRO

VCO OUT

DISABLE POWER

100pF

1

2

3

4

5

6

7

8

9

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15

+12

510

510

1K

1K

1K

Figure 10. ML4411 Typical Application