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
8
SPIN-DEMAND
12
SERVO-DEMAND
SERVO CONTROL
SERIAL INTERFACE
ADJUST
C TAP
VOLTAGE REF.
V
REF(X2)
REF
V
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
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
A
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,
T
.....................................0°C to +70°C
A
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)
V
REF
2 V
REF
UV TRIP ADJUST
g
m
R
gm
R
gm
g
FREQUENCY,
m
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
Copyright © 1992, 1994, Allegro MicroSystems, Inc.
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.
V
V
CC(A)
V
BG
TRIP ADJ
ADJUST
(FROM SERIAL
INTERFACE)
FILTERED
V
VEL
V
REF
V +
REF
2
V
REF
V -
REF
2
T
J
V
BG
BOOST(L)
V
CC(A)
UNDER-VOLTAGE
FAULT
BG
V
CC(A)
OVER -
VELOCITY
FAULT
V
CC(D)
THERMAL
FAULT
REFERENCE
V
V
CC(D)
POWER
ON
RESET
RETRACT
VOLTAGE
V
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:
g
and I
m(act)
OUT
5800
= A/V
R
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
V
RETRACT
V
M
V
BOOST(H)
V
BOOST(L)
V
BANDGAP
VOLTAGE
REFERENCE
BOOST(L)
L
FLYBACK
BOOST(H)
BOOST(L)
V
BOOST(L)
REFERENCE
ADJUST
ADJUST
V + V
DC-TO-DC
CONVERTER
V
V
SPINDLE
MOTOR DRIVERS
V
BG
(FROM SERIAL INTERFACE)
DC M
VOICE-COIL
DRIVER
V
CC(A)
x2
V
BOOST(H)
V
BOOST(L)
V
DC
V
REF(x2)
V
CC(A)
÷2
V
REF
8980
SUPERSERVO™
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.
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
voltage fault circuit, and a thermal fault circuit.
The operating modes include V
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
CC(A)
under-
CC(PWR)
isola-
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
) are provided that
REF(x2)
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.
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 V
DIGITAL SUPPLY V
LOAD SUPPLY V
SUB Substrate. This terminal must be connected to ground.
V
M
L
FLYBCK
V
BOOST(H)
; supplies all analog functions except for gate drive of power output transistors. For most
CC(A)
applications, V
; supplies all digital functions. For most applications, V
CC(D)
CC(A)
, V
CC(D)
, and V
CC(PWR)
are connected together.
connected together.
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 VM from V
or shutdown. For most applications, V
CC(A)
, V
CC(D)
, and V
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.
CC(A)
CC(PWR)
, V
CC(D)
CC(PWR)
, and V
CC(PWR)
on system failure
are
are connected together.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8980
SUPERSERVO™
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.
V
PF(GATE)
V
REF
Control voltage provided to drive the gate of an optional external enhancement-mode power
FET, augmenting the internal blocking FET between V
CC(PWR)
Programmable reference voltage output. This reference tracks V
and VM.
REF(x2)
and may be used as a
relative signal ground.
V
REF(x2)
Programmable reference voltage output. Derived from a trimmed internal bandgap reference.
May be used as the reference for system DAC and ADC.
POR
OUT
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
degrading below the BLACKOUT under-voltage
CC(A)
threshold.
TRIP ADJ V
UV (TRIP)
; trip threshold adjust input (an external resistor divider between V
and ground) for
CC(A)
the under-voltage BLACKOUT fault monitor. A capacitor at this terminal can provide for time
domain filtering.
CLK f
CLK(2MHz)
; reference for all internal analog signal-processing functions. Affects frequency
domain placement of all poles, zeros, and bandwidths.
SER DATA IN Non-inverting microcontroller serial-data input used for transferring data to all internal parameter
and mode-control registers.
CLK SER f
CLK(SER)
; reference for the serial data interface. Data is transferred on the positive-going edge
of this clock.
LOAD Active low. Begins and ends data transfer.
EXT XFR 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
AMUX
AMUX
DMUX
OUT
P
OUT
N
V
SENS(act)
1
2
OUT
synchronized to the f
CLK(2MHz)
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
V
; voice-coil power output. Full-bridge differential complement to V
OUT(P)
; voice-coil power output. Full-bridge differential complement to V
OUT(N)
The voltage at this terminal is proportional to voice-coil actuator current.
positive-going edge.
OUT(N)
OUT(P)
.
.
8980
SUPERSERVO™
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
R
gm(act)
A resistor between this terminal and V
SENS(act)
is used to adjust the forward transconductance
gain of the voice-coil transconductance amplifier.
RETRACT Active high retract input from the system. Continuous-time direct input to cause immediate
retract mode.
EXT ACT V
OP
1(IN)
OP
1(OUT)
VEL
INN
VEL
INP
VEL V
OUT
A
OUT
B
continuous-time input to the actuator gm amplifier provides diagnostic as well as feed-forward
access.
Operational amplifier inverting input. The non-inverting input is internally connected to V
Operational amplifier output. This undedicated operational amplifier functions in continuous time.
Inverting input of operational amplifier portion of over-velocity fault circuit.
Non-inverting input of operational amplifier portion of over-velocity fault circuit.
two comparators that provide the positive and negative velocity fault thresholds.
V
V
; summing junction at the input of the voice-coil transconductance amplifier. This direct
SERVO
; output of the over-velocity operational amplifier. Also internally connected to the inputs of
VEL
; spindle motor power output terminal.
OUT(A)
; spindle motor power output terminal.
OUT(B)
REF
.
OUT
C
V
OUT(C)
; spindle motor power output terminal.
C TAP Connection to spindle motor center tap; provides the differential reference for detection of back-
EMF zero crossings. If this terminal is not connected, the device will internally simulate the
centertap of the motor.
V
SENS(spin)
R
gm(spin)
f
com
EXT COM f
EXT SPIN V
mand current occurs at 2.00 V; full-scale positive demand current occurs at 4.00 V.
SW
IN
SW
OUT
SW
ON
The voltage at this terminal is proportional to the spindle motor current.
A resistor connected from this terminal to V
SENS(spin)
provides for adjusting the forward
transconductance gain of the spindle transconductance amplifier.
A digital logic output that goes low to high on a back-EMF zero crossing; provides tach-like
information to the spin controller.
; hard external commutation sequence start (positive-edge triggered). May be used to place
sync
spindle commutation edges in the inter-sector gap, or for phase-locking multiple spindle drivers.
; direct continuous time input to the spindle transconductance amplifier/driver. Zero de-
spin
Input for uncommitted analog switch.
Output of uncommitted analog switch.
Logic input for uncommitted analog switch; a high level connects SWIN to SW
OUT
.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8980
SUPERSERVO™
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
ADDRESS MAP AND DATA BIT ASSIGNMENTS
Address Data
Word Bit Function
00H 0 – 3 Blanking Time
4 – 7 Commutation Delay Time
01H 0 – 5 Coast Time
6 Commutation Multiplexer
7 Not used at this time
02H 0 – 3 Startup Time
4 – 7 Watchdog Time
03H 0 – 7 Spindle-Demand DAC Current
Magnitude
8 Reverse Commutation Mode
04H 0 – 3 Spindle Slew Rate Control
4 – 6 Spindle Multiplexer
7 Not used at this time
05H 0 – 3 Spindle Transconductance Amp.
Bandwidth
4 – 6 Spindle Transconductance Amp.
Local Zero
06H 0 – 3 Internal 6.25 kHz Oscillator
Frequency Trim
4 – 7 Not used at this time
07H 0 – 7 Not used at this time
Address Data
Word Bit Function
0CH 0 – 3 Notch Width (Zeta DZ3) Control
4 Notch Reset Control
5 – 7 Not used at this time
0DH 0 – 4 Low-Pass Filter Freq. Synth.
(Dn2) Control
5 – 7 Not used at this time
0EH 0 – 4 Notch Center Frequency
(Dn3) Control
5 – 7 Not used at this time
0FH 0 – 3 Actuator Bandwidth
(BW
4 – 6 Actuator Zero (Damping) Control
7 Not used at this time
10H 0 – 2 Retract Velocity Demand Voltage
3 – 5 Actuator Analog Multiplexer Input
Select
6 – 7 Not used at this time
11H 0 – 7 Sleep Mode Manager
12H 0 – 3 Fault Control Monitor
4 – 6 Programmable References
Voltage Select
7 Long Spindle Braking Delay
) Control
ACT
08H 0 – 11 Servo-Demand DAC Current
Magnitude
09H 0 – 7 Not used at this time
0AH 0 – 3 Low-Pass Filter Damping (Zeta)
Control
4 Not used at this time
5 Low-Pass Filter Reset Control
6 – 7 Not used at this time
0BH 0 – 3 Notch Depth (α3) Control
4 – 7 Not used at this time
13H 0 – 2 Analog Multiplexer-2 Selection
3 – 5 Digital Multiplexer Output
Selection
6 – 7 Not used at this time
14H 0 – 2 Analog Multiplexer-1 Selection
3 Chopper Stabilization of LP &
Notch Filters
4 Disable actuator retract during
fault
5 – 7 Not used at this time
15H 0 - 2 Actuator Power Voltage Amplifier
Deadband Trim
8980
SUPERSERVO™
SPINDLE & VOICE-COIL
ACTUATION MANAGER/DRIVER
Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such departures from the detail specifications as may be required to
permit improvements in the design of its products.
The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsibility
for its use; nor for any infringements of patents or other rights of third
parties which may result from its use.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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