8925 Просмотр технического описания (PDF) - Allegro MicroSystems

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8925

3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH LINEAR CURRENT CONTROL AND POWER DMOS OUTPUTS

Allegro MicroSystems 

8925

3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER

WITH LINEAR CURRENT CONTROL

AND POWER DMOS OUTPUTS

TERMINAL FUNCTIONS

Term.

1

2

3

4

6

7–17

18

19

20

21

22

23

24

26

28

29–39

40

42

43

44

Terminal Name

OUTB

LOGIC SUPPLY

LOGIC GROUND

OUTC

ENABLE

POWER GROUND

VSENSE

COMP.

REFERENCE

ERROR AMP.

LOAD SUPPLY

BRAKE

H1

H2

H3

POWER GROUND

FAULT

OUTA

TACH

POLE

Function

Power DMOS output.

VCC; low-current 12 V supply for the logic.

Low-level logic ground.

Power DMOS output.

Active high chip enable.

Power ground and thermal heat sink.

External precision resistor for sense-FET current.

Compensation; error amplifier output.

VREF; voltage input that sets the power output current.

Input that controls the current in the load.

VBB; high-current 12 V supply for the voice-coil motor.

A logic low turns OFF all source drivers and turns ON all sink drivers (shorts the windings to

ground).

High-level input from a Hall sensor.

High-level input from a Hall sensor.

High-level input from a Hall sensor.

Power ground and thermal heat sink.

A logic low at this output indicates a thermal shutdown, under -voltage fault, or an invalid Hall

input combination.

Power DMOS output.

Speed reference output; the H1 Hall input divided by the number of motor poles.

Designates four- or eight-pole motor; Low = 4 pole, High = 8 pole.

VSENSE

SENSE

AMPLIFIER

I OU.T

1200

R1

RS

R2

VREF

R3

C1

_-

++

COMP.

ERROR

AMPLIFIER

CHARGE

PUMP

V BB

SEQUENTIAL

LOGIC

OUT

C2

OUT

V

SUB

Dwg. EP-040

FUNCTIONAL DESCRIPTION

Power Outputs (OUTA, OUTB, and

OUTC). The power outputs of the A8925CEB

are DMOS transistors with a maximum rDS(on)

of 0.25 Ω. Intrinsic ground clamp and flyback

diodes clamp transient voltage spikes when

switching inductive loads. Internal charge

pump circuitry is used to drive the gates of

the N-channel source drivers to their required

gate voltages.

Current Control. Current in the load is

monitored by an internal sense amplifier that

produces an output current that is approxi-

mately one twelve hundredth that of the load

current (see Figure). This current is output to

the VSENSE terminal and develops a voltage

Continued next page...

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Worcester, Massachusetts 01615-0036 (508) 853-5000

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