8980
S
UPER
S
ERVO
™
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
8980
TM
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
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 compo-
nents. 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
S
UPER
S
ERVO
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
C TAP
MULTIPLEXER
BACK-EMF and
COMMUTATION LOGIC
8
SPIN-DEMAND
12
SERVO-DEMAND
ABSOLUTE MAXIMUM RATINGS
at T
A
= +25°C
Load Supply Voltage, V
CC(PWR)
..........
7.0 V
Spindle Output Current, I
OUT(S)
.........
±
1.6 A
Voice-Coil Output Current, I
OUT(S)
....
±
0.9 A
Output Current, I
OUT(S)
......................
±
1.6 A
Logic Supply Voltage V
CC(D)
...............
6.0 V
Operating Temperature Range,
T
A
.....................................
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.
T
C
U Y
D L
O N
R O
P E
D C
E N
U E
IN ER
T F
N E
O R
C
IS OR
D F
—
SER DATA IN
SERIAL INTERFACE
SERVO CONTROL
ENERGY MANAGER
ADJUST
VOLTAGE REF.
V
REF(X2)
V
REF
Dwg. PP-048
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 E
NERGY
M
ANAGER
™ 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
the heads. A dc-to-dc converter provides continuous operation at
minimum supply voltages. In addition, the E
NERGY
M
ANAGER
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:
s
Low r
DS(on)
MOS Outputs
s
Lossless Current Sensing
s
Zero Deadband
s
User-Adjustable Transconductance Gain
s
Retract Circuitry Functional to 0 V
8980
S
UPER
S
ERVO
™
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)
V
REF
2V
REF
UV TRIP ADJUST
µC
SERIAL INTERFACE
OVER-VELOCITY FAULT
SERIAL DATA IN
CLOCK
DATA ENABLE
gm
SERVO CONTROL
NOTCH
FREQUENCY,
DEPTH, &
DAMPING
TUNABLE
LOW-PASS
FILTER
12-BIT
SERVO-
DEMAND
DAC
R
gm
2 MHz CLOCK
RETRACT
R gm
8-BIT
SPIN-DEMAND
DAC
IN / OUT MUX
CONFIGURATION
CONTROL
ANALOG MUX 1
ANALOG MUX 2
DIGITAL MUX OUT
g
m
SLEW
RATE
CONTROL
BACK-EMF AND
COMMUTATION LOGIC
EXTERNAL
COMMUTATION
TACH
Dwg. FP-028B
Spindle Motor Controller/Driver:
s
Low r
DS(on)
MOS Outputs
s
Back-EMF Circuitry Eliminates Hall-Effect Sensors
s
Programmable Slew Rate Eliminates Snubbers
s
Lossless Current Sensing
s
Improved Speed Disturbance Performance
s
Dynamic Braking with Delay
s
Active Braking
Servo Compensator/Notch:
s
Over-Velocity Fault Circuitry
s
12-Bit Servo-Demand DAC
s
Programmable Complex Pole Low-pass-Filter
s
Programmable Notch Frequency, Depth, and Damping
Energy Manager:
s
3.0 V to 5.5 V Operation
s
Independent Power-Down (Sleep) Modes for all
Functional Blocks
s
Efficient Synchronous Rectification Supplies Power
During Blackout
s
Thermal Fault Shutdown Circuitry
s
Trimmed Bandgap Voltage Reference
s
Smart DAC Reference Generator
s
Programmable Voltage Reference for Relative Ground
s
Over-Velocity Fault Circuitry
s
Supply Under-Voltage Monitor with Adjustable
Trip Point
s
System Diagnostics Data Out
s
Power-On Reset Generator
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1992, 1994, Allegro MicroSystems, Inc.
8980
S
UPER
S
ERVO
™
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.
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 g
m
amplifier control loop. The error voltage is
scaled by an external precision resistor (R
gm(act)
). This resistor does
not carry load current and is intended only for accurate determination
of the transconductance. The function is:
g
m(act)
= 5800 A/V
R
gm(act)
and I
OUT
= V
SERVO
• g
m(ACT)
.
Low-Pass Filter.
This double, non-
intrinsic complex-pole low-pass filter is
provided to attenuate undesirable, out-of-
band 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.
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.
VM
L FLYBACK
V DC+ V
M
V BOOST(H)
V BOOST(L)
V CC(A)
V BG
TRIP ADJ
VCC(D)
VCC(PWR)
V CC(A)
UNDER-VOLTAGE
FAULT
DC-TO-DC
CONVERTER
V BOOST(H)
POWER
ON
RESET
V BOOST(L)
POR
OUT
V BOOST(H)
V BOOST(L)
V DC
V BOOST(L)
ADJUST
(FROM SERIAL
INTERFACE)
FILTERED
V VEL
V
REF
2
V
REF
2
V BG
VCC(A)
RETRACT
VOLTAGE
REFERENCE
VOICE-COIL
DRIVER
V RETRACT
SPINDLE
MOTOR DRIVERS
V BOOST(L)
BANDGAP
VOLTAGE
REFERENCE
V BG
V BOOST(L)
V CC(A)
V
REF
+
V
REF
-
OVER -
VELOCITY
FAULT
RETRACT
MODE
REFERENCE
ADJUST
x2
VCC(A)
÷2
V REF(x2)
VCC(D)
T
ADJUST
(FROM SERIAL INTERFACE)
J
THERMAL
FAULT
SHUTDOWN /
SLEEP
V REF
V BG
8980
S
UPER
S
ERVO
™
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
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.
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 V
REF(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 V
BOOST(L)
.
These voltages supply critical functions with maximum immunity from
supply variations.
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
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.
TERMINAL FUNCTIONS
ANALOG SUPPLY
DIGITAL SUPPLY
LOAD SUPPLY
V
CC(A)
; supplies all analog functions except for gate drive of power output transistors. For most
applications, V
CC(A)
, V
CC(D)
, and V
CC(PWR)
are connected together.
V
CC(D)
; supplies all digital functions. For most applications, V
CC(A)
, V
CC(D)
, and V
CC(PWR)
are
connected together.
V
CC(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 V
M
from V
CC(PWR)
on system failure
or shutdown. For most applications, V
CC(A)
, V
CC(D)
, and V
CC(PWR)
are connected together.
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.
External inductor for the dc-to-dc converter.
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.
SUB
V
M
L
FLYBCK
V
BOOST(H)
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8980
S
UPER
S
ERVO
™
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
V
BOOST(L)
Internally generated intermediate voltage for driving the gates of all sink-side power output
transistors, the bandgap reference, and fault monitors. This source is regulated and requires
a compensation capacitor from this terminal to ground.
Control voltage provided to drive the gate of an optional external enhancement-mode power
FET, augmenting the internal blocking FET between V
CC(PWR)
and V
M
.
Programmable reference voltage output. This reference tracks V
REF(x2)
and may be used as a
relative signal ground.
Programmable reference voltage output. Derived from a trimmed internal bandgap reference.
May be used as the reference for system DAC and ADC.
Power-on reset for the application system. Active low guaranteed by design to be active on
power up. Also occurs as a result of V
CC(A)
degrading below the BLACKOUT under-voltage
threshold.
V
UV (TRIP)
; trip threshold adjust input (an external resistor divider between V
CC(A)
and ground) for
the under-voltage BLACKOUT fault monitor. A capacitor at this terminal can provide for time
domain filtering.
f
CLK(2MHz)
; reference for all internal analog signal-processing functions. Affects frequency
domain placement of all poles, zeros, and bandwidths.
Non-inverting microcontroller serial-data input used for transferring data to all internal parameter
and mode-control registers.
f
CLK(SER)
; reference for the serial data interface. Data is transferred on the positive-going edge
of this clock.
Active low. Begins and ends data transfer.
Direct clock gating data from temporary internal latch to control register. This continuous time
input is redundant to the XFR bit, which is embedded in the serial data format. It is internally
synchronized to the f
CLK(2MHz)
positive-going edge.
Analog input or output. Also used to drive internal nodes.
Analog input or output. Also used to drive internal nodes for calibration and measurement on
internal analog functions.
Non-inverting digital multiplexer output. Used to probe internal nodes allowing precise time-
domain measurements. Also used to extract internal status and diagnostic information.
V
OUT(P)
; voice-coil power output. Full-bridge differential complement to V
OUT(N)
.
V
OUT(N)
; voice-coil power output. Full-bridge differential complement to V
OUT(P)
.
The voltage at this terminal is proportional to voice-coil actuator current.
V
PF(GATE)
V
REF
V
REF(x2)
POR
OUT
TRIP ADJ
CLK
SER DATA IN
CLK SER
LOAD
EXT XFR
AMUX
1
AMUX
2
DMUX
OUT
OUT
P
OUT
N
V
SENS(act)
单片机
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