Allegro A8980CJT Datasheet

8980

SUPERSERVO™ SPINDLE & VOICE-COIL

8980

ACTUATION MANAGER/DRIVER

SUPERSER VOTM SPINDLE & VOICE-COIL

The A8980CJT provides complete drive, management, and control of the voice-coil and spindle motor power actuation subsystems used in hard disk drives. Extensive programmable control features and

MULTIPLEXER

SER DATA IN

ENERGY MANAGER

BACK-EMF and

COMMUTATION LOGIC

SPIN-DEMAND

SERVO-DEMAND

SERVO CONTROL

SERIAL INTERFACE

ADJUST

C TAP

VOLTAGE REF.

REF(X2)

REF

system diagnostics are provided via a serial interface under the direction of an external microcontroller. The large-scale integration and use of advanced DABiC™ (digital/analog-BiCMOS) merged technologies results in minimum power dissipation, minimum operating voltage requirements, and minimum external components.

The spindle drive function incorporates a three-phase MOS power driver and a back-EMF sensing motor commutation scheme. Internal logic and analog circuitry provide complete start-up and µC-assisted run modes without the need for snubbers or other external components. Additional headroom is achieved by a proprietary circuit, which eliminates the need for an external current-sense resistor. Intrinsic ground clamp and flyback diodes are also provided.

Data Sheet

26310

ACTUATION MANAGER/DRIVER

Dwg. PP-048

The voice-coil function contains a 12-bit DAC, tunable low-pass and notch filters, and a full-bridge power driver. The MOS outputs provide increased available voltage and lower power dissipation over bipolar devices. Voice-coil current is sensed by internal circuitry that eliminates the need for an external current-sense resistor. Additional internal circuitry can be configured to provide an over-velocity fault limit by utilizing the internally monitored current of the voice-coil motor.

The spindle and voice-coil control functions are supplemented by an ENERGY MANAGER™ subsystem, which efficiently channels available power to protect the heads and the data disk during system failure or normal system shutdown. Synchronous rectification of spindle back-EMF voltage provides nearly lossless conversion of spindle rotational inertia into power to operate the voice coil motor for parking

ABSOLUTE MAXIMUM RATINGS

at T

= +25°C

Load Supply Voltage, V Spindle Output Current, I Voice-Coil Output Current, I

Output Current, I Logic Supply Voltage V

DISCONTINUED PRODUCT

Operating Temperature Range,

.....................................0°C to +70°C

Output current rating may be restricted to a value determined by system concerns and factors. These include: system duty cycle and timing, ambient temperature, and use of any heatsinking and/or forced cooling.

— FOR REFERENCE ONLY

CC(PWR)

...................... ±1.6 A

OUT(S)

CC(D)

.......... 7.0 V

......... ±1.6 A

OUT(S)

.... ±0.9 A

OUT(S)

............... 6.0 V

the heads. A dc-to-dc converter provides continuous operation at minimum supply voltages. In addition, the ENERGY MANAGER subsystem provides several sleep modes and latched fault states for undervoltage or thermal faults.

The A8980CJT is supplied in a 64-lead thin quad flatpack for surface-mount applications.

FEATURES

Voice Coil Motor Driver:

■ Low r

■ Lossless Current Sensing

■ Zero Deadband

■ User-Adjustable Transconductance Gain

MOS Outputs

DS(on)

■ Retract Circuitry Functional to 0 V

8980

SUPERSERVO™ SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER

FUNCTIONAL BLOCK DIAGRAM

ENERGY MANAGER

CONTROLLED RETRACT

DC-DC CONVERSION

SLEEP MODES

UV FAULT

THERMAL SHUTDOWN

POWER-ON RESET (TO µC)

REF

2 V

REF

UV TRIP ADJUST

FREQUENCY,

CONTROL

Spindle Motor Controller/Driver:

■ Low r

MOS Outputs

DS(on)

■ Back-EMF Circuitry Eliminates Hall-Effect Sensors

■ Programmable Slew Rate Eliminates Snubbers

■ Lossless Current Sensing

■ Improved Speed Disturbance Performance

■ Dynamic Braking with Delay

■ Active Braking

Servo Compensator/Notch:

■ Over-Velocity Fault Circuitry

■ 12-Bit Servo-Demand DAC

■ Programmable Complex Pole Low-pass-Filter

■ Programmable Notch Frequency, Depth, and Damping

OVER-VELOCITY FAULT

SERVO CONTROL

NOTCH

DEPTH, &

DAMPING

SLEW

RATE

TUNABLE

LOW-PASS

FILTER

8-BIT

SPIN-DEMAND

12-BIT

SERVO-

DEMAND

DAC

IN / OUT MUX

DAC

BACK-EMF AND

COMMUTATION LOGIC

CONFIGURATION

µC SERIAL INTERFACE

CONTROL

SERIAL DATA IN CLOCK DATA ENABLE

2 MHz CLOCK

RETRACT

ANALOG MUX 1 ANALOG MUX 2 DIGITAL MUX OUT

EXTERNAL COMMUTATION

TACH

Energy Manager:

■ 3.0 V to 5.5 V Operation

■ Independent Power-Down (Sleep) Modes for all

Functional Blocks

■ Efficient Synchronous Rectification Supplies Power During Blackout

■ Thermal Fault Shutdown Circuitry

■ Trimmed Bandgap Voltage Reference

■ Smart DAC Reference Generator

■ Programmable Voltage Reference for Relative Ground

■ Over-Velocity Fault Circuitry

■ Supply Under-Voltage Monitor with Adjustable

Trip Point

■ System Diagnostics Data Out

■ Power-On Reset Generator

Dwg. FP-028B

115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000

8980

SUPERSERVO™ SPINDLE & VOICE-COIL ACTUATION MANAGER/DRIVER

FUNCTIONAL DESCRIPTION

ACTUATOR

Servo-Demand DAC. A 12-bit DAC

is provided to bridge the DSP “soft” domain to the analog hardware domain. The term “demand” refers to the distinction between the newly requested voice-coil current and the prior current being supplied. The DAC, operating in straight binary format, spans the full dynamic range between a large signal velocity and a precision position mode. The DAC output is updated synchronously with the notch functions to avoid the creation of aliasing products.

Low-Pass Filter. This double, non-

intrinsic complex-pole low-pass filter is provided to attenuate undesirable, out-ofband information. The input of this discrete time filter is sampled synchronously with the 12-bit DAC and notch function in order to avoid aliasing products.

CC(A)

TRIP ADJ

ADJUST

(FROM SERIAL

INTERFACE)

FILTERED V

VEL

REF

V +

REF

V -

REF

BOOST(L)

CC(A)

UNDER-VOLTAGE

FAULT

CC(A)

OVER -

VELOCITY

FAULT

CC(D)

THERMAL

FAULT

REFERENCE

CC(D)

POWER

RESET

RETRACT

VOLTAGE

CC(PWR)

RETRACT MODE

SHUTDOWN / SLEEP

Notch Filter. This notch filter has a programmable center

frequency and programmable notch depth to provide truly independent control of notch damping. Enough range and granularity are provided to allow versatile and accurate out-of-band attenuation of undesirable energy sources.

Actuator Transconductance Amplifier. The final trans-

conductance function of the voice-coil actuation signal path is achieved by monitoring the load current and generating an error voltage to drive a local gm amplifier control loop. The error voltage is scaled by an external precision resistor (R

). This resistor does

gm(act)

not carry load current and is intended only for accurate determination of the transconductance. The function is:

and I

m(act)

OUT

5800

= A/V

gm(act)

= V

SERVO

• g

m(ACT)

Actuator Power Outputs. The voice-coil output driver is a

full-bridge power driver operating in a class-B mode. The power output devices are enhancement-mode MOS transistors. Special internal circuitry results in nearly zero cross-over distortion when switching from one source/sink pair to another.

POR OUT

RETRACT

BOOST(H)

BOOST(L)

BANDGAP

VOLTAGE

REFERENCE

BOOST(L)

FLYBACK

BOOST(H) BOOST(L)

BOOST(L)

REFERENCE

ADJUST

V + V

DC-TO-DC

CONVERTER

V V

SPINDLE MOTOR DRIVERS

(FROM SERIAL INTERFACE)

DC M

VOICE-COIL DRIVER

CC(A)

BOOST(H)

BOOST(L)

REF(x2)

CC(A)

÷2

REF

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