8980 datasheet(4/8 Pages) ALLEGRO

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8980

SUPERSERVO™

SPINDLE & VOICE-COIL

ACTUATION MANAGER/DRIVER

115 Northeast Cutoff, Box 15036

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

SPINDLE

The spindle function is a three-phase

back-EMF sensing motor controller and

driver. During start-up, internal circuitry

provides complete spindle control and drive.

At speed however, an external

microcontroller is used to provide speed

(phase/frequency) detection as well as

compensation.

ENERGY MANAGER

The management of available energy

is provided by automatic operating modes

envoked by the fault monitor or sleep-mode

manager. The fault monitor consists of an

over-velocity fault circuit, a V

CC(A) under-

voltage fault circuit, and a thermal fault circuit.

The operating modes include V

CC(PWR) isola-

tion, active rectification of spindle back-EMF

voltage to provide nearly lossless conversion

of spindle rotational inertia into power to

operate the voice-coil motor for parking the

TERMINAL FUNCTIONS

ANALOG SUPPLY

VCC(A); supplies all analog functions except for gate drive of power output transistors. For most

applications, VCC(A), VCC(D), and VCC(PWR) are connected together.

DIGITAL SUPPLY

VCC(D); supplies all digital functions. For most applications, VCC(A), VCC(D), and VCC(PWR) are

connected together.

LOAD SUPPLY

VCC(PWR); supplies all voice-coil and spindle power output transistors. This terminal is internally

connected to the source of the blocking FET used to isolate VM from VCC(PWR) on system failure

or shutdown. For most applications, VCC(A), VCC(D), and VCC(PWR) are connected together.

SUB

Substrate. This terminal must be connected to ground.

Supplies power to the voice-coil and spindle power output transistors. Connect this terminal to

the external flyback inductor for the dc-to-dc converter; internally connected to the drain of the

blocking FET.

LFLYBCK

External inductor for the dc-to-dc converter.

VBOOST(H)

Internally generated “high” voltage for driving the gates of all source-side power output

transistors. This source is regulated and requires a compensation capacitor from this terminal

to ground.

heads, actuator retract mode controlled by constant voltage, and

several sleep modes. In addition, a power-on reset function and two

programmable voltage references (V

REF and VREF(x2)) are provided that

are suitable for output to the user.

An onboard dc-to-dc converter generates two regulated “high”

(greater than the supply) voltages referred to as V

BOOST(H) and VBOOST(L).

These voltages supply critical functions with maximum immunity from

supply variations.

SERIAL INTERFACE

The serial interface is used to alter the control state of the device

from an external microcontroller or other digital CMOS source.

In addition to the various operational and diagnostic control states

(modes), all critical constants, variables, and parameters can be

adjusted through this interface. The serial interface is a synchronous

serial three-wire port with serial data input, clock, and load (active low)

functions. When LOAD is high, the serial interface is disabled and the

chip is not affected by changes in SER DATA IN or CLK SER. To

write data to the serial interface, CLK SER should be low prior to

LOAD going low. Once LOAD goes low, information at SER DATA IN

is read into the shift register on the positive-going transitions of

CLK SER.

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