in hard disk drives. Extensive programmable control features and
direction of an external microcontroller. The large-scale integration
鈩?/div>
(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
碌C-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擄C
Load Supply Voltage, V
CC(PWR)
..........
7.0 V
Spindle Output Current, I
OUT(S)
.........
鹵
1.6 A
Voice-Coil Output Current, I
OUT(S)
....
鹵
0.9 A
Output Current, I
OUT(S)
......................
鹵
1.6 A
Logic Supply Voltage V
CC(D)
...............
6.0 V
Operating Temperature Range,
T
A
.....................................
0
擄
C to +70
擄
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
鈥?/div>
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
鈩?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
ALLEGRO
1
2
3
4
5
6
7
8
