8932-A
RET REF
V
FLT
V
BEMF
GROUND
UV
SET
R
OUT P
OUT
SWITCH
IN
N
OUT
SW
RETRACT
FAULT
MP
RESET
SIGNAL
SUPPLY
1
2
3
4
5
6
7
8
28
27
RET SET
V
SENS
V
LOAD
V
SENS FB
SGND
N
OUT
P
LOAD
SUPPLY
OUT
N
SGND
P
ACT
FB
PWR OFF
H GAIN
REFERENCE
ACT
VOICE-COIL MOTOR DRIVER
Providing control and drive of the voice-coil motor used for head
positioning in 5 V disk drive applications, the second-generation
A8932CLWA is a full-bridge driver that can be configured so that its
output current is a direct function of an externally applied control
voltage or current. This linear current control function is supplemented
by additional circuitry to protect the heads and the data disk during
system failure or normal system shutdown.
The two
±500
mA MOS driver outputs provide very low saturation
voltage and minimal power dissipation. Additional headroom is
achieved by the sense-FET structure eliminating the need for an exter-
nal current-sense resistor. Internal circuitry can be configured to
provide closed-loop velocity control of the actuator by utilizing the
generated back-EMF of the voice-coil motor. Thermal protection and
under-voltage lockout disables the system in a controlled sequence if a
fault condition occurs.
Data Sheet
26300.2A†
PROTECT
CIRCUIT
–
26
+
25
24
23
V
DD
22
21
–
9
10
11
12
13
14
+
V
REF
–
2V
+
20
19
18
17
PROTECT
CIRCUIT
+
–
16
15
V
CC
FEATURES
I
I
I
I
I
I
I
I
I
I
I
Class-B, 2
Ω
r
DS(on)
at 500 mA Output
Lossless Current Sensing
Zero Current-Loop Deadband
High Transconductance Bandwidth
User-Adjustable Transconductance Gain
Digital Transconductance Gain Switch (4:1 Ratio)
5 Volt Monitor with Selectable UV Trip Point
Retract Circuitry Functional to 0 Volts
Sleep Mode Function
Internal Back-EMF Velocity Loop Option
Internal Thermal Shutdown Circuitry
Dwg. PP-042B
ABSOLUTE MAXIMUM RATINGS
Supply Voltages, V
CC
and V
DD
............
6.0 V
Output Current, I
OUT
(peak) ...........
±600
mA
(continuous) ...........................
±500
mA
Analog Input Voltage Range,
V
IN
....................................
-0.3 V to V
CC
Logic Input Voltage Range,
V
IN
...............................
-0.3 V to +6.0 V
Package Power Dissipation,
P
D
.........................................
See Graph
Operating Temperature Range,
T
A
.....................................
0
°
C to +70
°
C
Junction Temperature, T
J
...............
+150
°
C
†
Storage Temperature Range,
T
S
................................ -55
°
C to +150
°
C
† Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated, but
should be avoided.
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 reliable operation the
specified maximum junction temperature should
not be exceeded.
Always order by complete part number, e.g.,
A8932CLWA
.
8932-A
VOICE-COIL MOTOR DRIVER
FUNCTIONAL BLOCK DIAGRAM
SIGNAL
SUPPLY
14
LOAD
SUPPLY
22
V
CC
ACT
FB 19
ERROR
–
AMP
I SENSE +
V
DD
VOLTAGE-SENSE
AMP
–
+
26
20
23
21
24
V
LOAD
SGND
P
OUT
P
OUT
N
SGND
N
V
SENS FB
V
SENS
IN
N
OUT
OUT
SW
ACT
15
REFERENCE
16
H GAIN
17
POWER
AMP
REF.
+
2V
POWER
CONTROL
LOGIC
+
–
PWR OFF
18
CURRENT-SENSE
AMP
I SENSE –
25
27
9
7
–
+
TSD
FAULT
12
MP
RESET 13
PROTECTION
CIRCUITRY
RETRACT
CONTROL
REF.
–
REF.
6
4
10
+
8
5
3
2
28
1
11
RETRACT
V
BEMF
UV
SET
RET REF
RET SET
R
OUT P
V
FLT
GROUND
SWITCH
Dwg. FP-024D
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
2.0
1.5
/W
R, C
AI 66
°
EE =
FR
JA
R
θ
1.0
0.5
0
25
50
75
100
125
AMBIENT TEMPERATURE IN
°C
150
Dwg. GP-034
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Copyright © 1992, 1995 Allegro MicroSystems, Inc.
8932-A
VOICE-COIL MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
CC
= V
DD
= 5.0 V, V
REF
= V
IN
= 2.0 V,
Load = 150
µ
H/3.5
Ω
(unless otherwise noted).
Limits
Characteristic
Error Amplifier
Input Offset Voltage
Current Gain
V
IO
A
iH
A
iL
Current Gain Linearity
E
L(adj)
I
LOAD
= 0 mA
H GAIN
≥
3.5 V
H GAIN
≤
0.7 V
I
OUT
= 5 mA to 500 mA, A
i
= A
iL
I
OUT
= 5 mA to 500 mA, A
i
= A
iH
Reference Voltage Range
Voltage-Sense Amplifier
Voltage Gain
Output Offset Voltage
Current-Sense Amplifier
Amplifier Error
Input Offset Voltage
Output Drivers
Total On Resistance
(Source + Sink)
Retract Output Voltage Error
Full Power Bandwidth
Uncommitted Op Amp
Voltage Gain
Unity Gain Bandwidth
Max. Load Capacitance
Slew Rate
Output Voltage
A
VS
BW
C
LOAD
SR
V
O
V
OSW
Max. Output Current
Input Offset Voltage
I
O
V
IO
V
SWITCH
≤
0.7 V
V
SWITCH
≥
3.5 V
—
—
—
—
2.5
2.5
—
—
91
1.0
40
4.2
—
—
±250
<±10
—
—
—
—
3.5
3.5
—
—
dB
MHz
pF
V/µs
V
V
µA
mV
E
OUT(PN)
BW
E
VD
V
iO
(R
s
x I
LOAD
/ (A
i
x V
SENSE
)) - 1
I
LOAD
= 0 mA, A
i
= A
iL
—
—
1.0
—
—
±25
—
mV
A
VD
V
OO
I
LOAD
= 0 mA
0.36
—
0.40
—
0.44
±25
—
mV
V
REF
—
7200
1800
—
—
1.5
—
8000
2000
—
—
—
±50
8800
2200
±10
±10
2.5
mV
—
—
%
%
V
Symbol
Test Conditions
Min.
Typ.
Max.
Units
r
DS(on)
I
LOAD
= 100 mA
I
LOAD
= 500 mA
V
OUT(P)
- V
OUT(N)
- V
RETSET
-3 dB
—
—
—
1.0
2.0
2.0
—
—
2.5
2.5
±100
—
Ω
Ω
mV
kHz
Continued next page…
Negative current is defined as coming out of (sourcing) the specified device terminal.
Typical Data is for design information only.
www.allegromicro.com
8932-A
VOICE-COIL MOTOR DRIVER
ELECTRICAL CHARACTERISTICS at T
A
= +25
°
C, V
CC
= V
DD
= 5.0 V, V
REF
= V
IN
= 2.0 V,
Load = 150
µ
H/3.5
Ω
(unless otherwise noted).
Limits
Characteristic
Miscellaneous
Supply Voltage
V
CC
V
DD
Under-Voltage Lockout Voltage
Fault Logic Output
V
CC
V
FAULT
Operating
Operating
V
CC
= V
DD
V
RETRACT
≥
3.5 V
V
RETRACT
≤
0.7 V
I
FAULT
Power-On Reset
V
MPRESET
V
FLT
= 2.25 V
V
RETRACT
≥
3.5 V
V
RETRACT
≤
0.7 V, I
MPREST
= 1.5 mA
Total Supply Current
I
CC
+ I
DD
Outputs Balanced, No Load
Sleep Mode, PWR OFF = V
CC
Logic Input Voltage
V
IN(0)
V
IN(1)
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
T
J
∆T
J
4.5
4.5
3.9
—
4.5
—
4.5
—
—
—
—
3.5
—
—
5.0
5.0
4.2
—
—
>20
—
—
—
—
—
—
165
20
5.5
5.5
4.35
500
—
—
—
800
10
2.0
0.7
—
—
—
V
V
V
mV
V
µA
V
mV
mA
mA
V
V
°C
°C
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Negative current is defined as coming out of (sourcing) the specified device terminal.
Typical Data is for design information only.
The products described here are manufactured under one or more
U.S. patents or U.S. patents pending.
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 performance, reliability, or
manufacturability of its products. Before placing an order, the user is
cautioned to verify that the information being relied upon is current.
Allegro products are not authorized for use as critical components
in life-support devices or systems without express written approval.
The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsi-
bility for its use; nor for any infringement 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
8932-A
VOICE-COIL MOTOR DRIVER
TERMINAL FUNCTIONS
Term.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Terminal Name
RET REF
V
FLT
V
BEMF
GROUND
UV
SET
R
OUT P
OUT
SWITCH
IN
N
OUT
SW
RETRACT
FAULT
MP
RESET
SIGNAL SUPPLY
ACT
REFERENCE
H GAIN
PWR OFF
ACT
FB
SGND
P
OUT
N
LOAD SUPPLY
OUT
P
SGND
N
V
SENS FB
V
LOAD
V
SENS
RET SET
Function
The reference supply for setting the voltage across the load during retract.
Reservoir (energy storage) capacitor used to operate fault circuitry.
Back-EMF voltage from spindle motor used to retract heads during loss of power.
Circuit reference.
Under-voltage trip point reference input. Set internally to 4.2 V but may be overridden by
external resistor divider. (Equation 4).
Source driver used for retract; externally connected to OUT
P
.
Output of uncommitted operational amplifier.
Logic input for transmission gate; a high level connects OUT to OUT
SW
.
Inverting input to uncommitted operational amplifier.
Transmission-gated output of uncommitted operational amplifier.
An active-low logic input that initiates the retract sequence.
A logic low at this MOS output indicates a thermal shutdown, under-voltage fault, or retract
command.
(Power-On Reset) A logic low at this open-collector output may be used to reset the
system on under-voltage fault or power on.
V
CC
; low-current supply voltage in the range of 4.5 V to 5.5 V.
Input which controls the current in the load. Transconductance gain is set with an external
resistor in series with this input (Equation 1).
V
REF
; reference input for all amplifiers; ac ground.
Logic input to switch the error amplifier transconductance gain: LOW = 2000,
HIGH = 8000.
An active-high logic input that puts the device in a “sleep mode”.
All fault circuitry remains active.
Input connection for feedback network which sets the error amplifier gain and bandwidth.
Power ground for the OUT
P
sink driver.
Power output. Sinks current when V
ACT
< V
REF
.
V
DD
; high-current supply voltage for the voice-coil motor.
Power output. Sinks current when V
ACT
> V
REF
.
Power ground for the OUT
N
sink driver.
Input connection for feedback network which sets the current-sense amplifier gain and
bandwidth. Also called gm SET.
An output voltage proportional to the load voltage. Used in conjunction with closed-loop
velocity control.
Voltage output representing load current (Equation 2). Also called MONITOR.
An external resistor divider to set the retract voltage across the load. Used in conjunction
with V
RET-REF
(Equation 3).
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