Providing control and drive of the voice coil motor used for head
positioning in disk drive applications, the A8958CLB is a full-bridge
driver which 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
800 mA driver outputs provide very-low saturation voltage
drops and precise current control utilizing a single current-sensing
resistor connected in series with the load. Under-voltage lockout
disables the system in a controlled sequence if a fault condition occurs.
When activated by the under-voltage comparator, or a park com-
mand, the output power drivers change from a controlled current to a
user-determined constant park voltage. Other features include a power
ok flag, a limit input to force the outputs to their maximum level in either
polarity, an over-riding output disable to shut down both power amplifi-
ers and reduce quiescent supply current, and internal thermal shutdown
which disables the load (but still allowing the head to be parked) in the
event of excessive junction temperatures. The load is re-enabled when
the junction temperature returns to a safe level.
The A8958CLB is supplied in a 24-lead power SOIC for surface-
mount applications. The copper batwing construction provides for
maximum package power dissipation in a minimum package size. It is
rated for continuous operation over the temperature range of 0
C to
+70
C.
FEATURES
s
Controlled-Velocity Head Parking
s
Zero Deadband
s
High Transconductance Bandwidth
s
User-Adjustable Transconductance Gain
s
800 mA Load Current
s
Dual Under-Voltage Monitors
with Flag and User-Selectable Trip Points
s
Internal Thermal Shutdown Circuitry
s
Replaces UC3175
VOICE COIL MOTOR DRIVER
Data Sheet
26300.5A
* Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated but
should be avoided.
ABSOLUTE MAXIMUM RATINGS
at T
A
= 25
C
Supply Voltages, V
BB
and V
CC
............... 16 V
Output Current, I
OUT
............................
1.0 A
Park Drive Output Current, I
PARK
Continuous ................................ 250 mA
Peak .............................................. 1.0 A
Amplifier Input Voltage Range,
V
IN
..................................... -2.0 V to V
CC
Sense Input Voltage Range,
V
SENSE IN
............................ -0.3 V to V
CC
Comparator and Digital Inputs,
V
IN
.................................... -0.3 V to 10 V
I
IN
..............................................
10 mA
Power OK Output, V
CEX
......................... 20 V
I
C
................................................. 30 mA
Output Clamp Diode Current,
I
F
(pulsed) ..................................... 1.0 A
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
Always order by complete part number, e.g., A8958CLB .
8958
Dwg. PP-054
GROUND
OUT
B
OUT
A
V
CC
INHIBIT
PARK
VOLTAGE
LIMIT
PARK
LOGIC
SUPPLY
LOAD
SUPPLY
PARK
DRIVE
UV
1
UV
2
V
BB
1.5 V
PWR OK
SENSE
IN+
SENSE
OUT
1
2
3
4
5
6
7
8
9
24
23
22
21
20
19
18
17
16
15
14
13
12
10
9
SENSE
IN
IN
A+
IN
A
GROUND
AB
GROUND
AB
GROUND
AB
GROUND
AB
IN
B
IN
B+
+
B
-
+
-
A
+
-
11
8958
VOICE COIL
MOTOR DRIVER
www.allegromicro.com
ELECTRICAL CHARACTERISTICS at T
A
= +25
C, V
CC
= V
BB
= 12 V
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
Logic Supply Voltage Range
V
CC
Operating
8.0
12
16
V
Logic Supply UV Threshold
V
CC
High-to-low transition
--
2.8
3.0
V
Logic Supply UV Hysteresis
V
CC
--
200
--
mV
Supply Current
I
BB
V
OUT
= 6 V, no load
--
2.0
--
mA
I
CC
--
23
--
mA
Inhibited Supply Current
--
I
BB
+ I
CC
, V
2
1.7 V
--
3.0
8.0
mA
Thermal Shutdown Temp.
T
J
--
165
--
C
Thermal Shutdown Hysteresis
T
J
--
8.0
--
C
Output Power Drivers
Output Saturation Voltage
V
SAT
I
OUT
= 250 mA
--
250
--
mV
I
OUT
= 800 mA
--
450
--
mV
I
OUT
= -250 mA
--
750
--
mV
I
OUT
= -800 mA
--
950
--
mV
Total Saturation Voltage
V
SAT
I
LOAD
= 250 mA
--
1.0
1.4
V
I
LOAD
= 800 mA
--
1.4
2.0
V
Input Offset Voltage
V
IO
V
CM
= 6 V
--
5.0
8.0
mV
Input Offset Drift
V
IO
--
--
25
V/
C
Input Bias Current
I
IN
Except IN
A+
, V
CM
= 6 V
--
-150
-500
nA
IN
A+
to SENSE
IN+
= 12 k
, T
J
= 25
C
69
84
105
A/V
Input Offset Current
I
IO
IN
B
only, V
CM
= 6 V
--
--
200
nA
Differential Sense Input Current
I
ID
I
OUT
= 5 mA
--
300
--
A
I
OUT
= 500 mA
--
3.0
--
mA
Large Signal Gain
A
VS
V
OUT
= 2 V to 10 V, I
OUT
=
500 mA
1.5
5.0
--
V/mV
Slew Rate
SR
--
4.0
--
V/
s
Unity Gain Bandwidth
BW
Amplifier A
0.5
1.0
1.7
MHz
Amplifier B
0.5
2.0
2.2
MHz
Common-Mode Rejection
k
CMR
V
CM
= 1 V to 10 V
70
90
--
dB
Clamp Diode Forward Voltage
V
F
I
F
= 800 mA, V
2
1.7 V
--
1.0
1.2
V
High-Side Current Limit
I
OUT
T
J
= 25
C
--
1.0
1.2
A
Power Supply Rejection
k
SVR
V
CC
= 4 V to 15 V, V
CM
= 1.5 V
70
90
--
dB
(Source + Sink)
Continued next page...
Negative current is defined as coming out of (sourcing) the specified device terminal.
Typical Data is for design information only.
8958
VOICE COIL
MOTOR DRIVER
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Current Sense Amplifier
Input Offset Voltage
V
IO
V
CM
= 6 V
--
--
2.0
mV
Input Offset Drift
V
IO
V
CM
= 0 V to 12 V
--
--
3000
V/V
--
--
8.0
V/
C
Voltage Gain
A
VS
V
ID
= -1 V to +1 V, V
CM
= 6 V
1.95
2.00
2.05
--
Output Saturation Voltage
V
SAT
V
OUT
,
I
OUT(SINK)
= 1.5 mA
--
300
500
mV
V
CC
- V
OUT
, I
OUT(SOURCE)
= -1.5 mA
--
400
700
mV
Park Function
PARK DRIVE Leakage Current
I
CEX
V
CEX
= 20 V
--
--
100
A
PARK DRIVE Saturation Voltage
V
CE(SAT)
I
C
= 200 mA
--
300
500
mV
PARK Input Threshold
V
PARK
0.7
1.1
1.7
V
PARK Input Current
I
PARK
V
PARK
= 1.7 V
--
--
100
A
PARK VOLTAGE Input Current
I
PARK V
--
-150
-500
nA
Under-Voltage Protection
UV Threshold
V
UV
Low-to-High Trans., Other Input = 6 V
1.48
1.50
1.52
V
UV Threshold Hysteresis
V
UV
15
25
45
mV
UV Input Current
I
UV
V
UV
= 1 V
--
-0.5
-1.5
A
PWR OK Saturation Voltage
V
CE(SAT)
I
C
= 5 mA
--
--
450
mV
PWR OK Leakage Current
I
CEX
V
CEX
= 20 V
--
--
5.0
A
Auxiliary Functions
LIMIT Input Voltage
V
LIMIT(L)
OUT
A
forced Low
0.7
0.8
--
V
V
LIMIT(H)
OUT
A
forced High
--
2.2
2.3
V
V
LIMIT
Limit inactive
1.2
--
1.8
V
Open circuit
1.45
1.50
1.55
V
LIMIT Input Resistance
R
LIMIT
V
LIMIT
= 1.2 V to 1.8 V
--
10
--
k
INHIBIT Input Threshold
V
2
0.7
1.1
1.7
V
INHIBIT Input Current
I
2
V
2
= 1.7 V
--
--
200
A
Negative current is defined as coming out of (sourcing) the specified device terminal.
Typical Data is for design information only.
ELECTRICAL CHARACTERISTICS (continued)
Limits
Characteristic
Symbol
Test Conditions
Min.
Typ.
Max.
Units
8958
VOICE COIL
MOTOR DRIVER
www.allegromicro.com
Term.
Terminal Name
Function
1
LOGIC SUPPLY
V
CC
; logic supply voltage.
2
INHIBIT
An active-high logic input that inhibits the output stages without initiating a park.
3 & 4
UV
1
and UV
2
Under-voltage detection inputs. If not used, these terminals must be connected
to the logic supply (V
CC
).
5
LIMIT
A tri-state input that forces the output of amplifier A into saturation in either direction,
or allows normal linear operation.
6 & 7
GROUND
AB
Power amplifiers' ground and thermal heat sink.
8
PARK VOLTAGE
Auxiliary inverting input to power amplifier A.
9
SENSE
IN
Inverting input to current sense error amplifer.
10
IN
A+
Non-inverting input to power amplifier A.
11
IN
A
Inverting input to power amplifier A.
12
OUT
A
Power amplifier A output to voice coil motor.
13
OUT
B
Power amplifier B output to voice coil motor.
14
LOAD SUPPLY
V
BB
; load supply voltage.
15
IN
B
Inverting input to power amplifier B.
16
IN
B+
Non-inverting input to power amplifier B.
17
SENSE
IN+
Non-inverting input to current sense error amplifer.
18 & 19
GROUND
AB
Power amplifiers' ground and thermal heat sink.
20
PWR OK
A logic low at this output indicates an under-voltage condition.
21
GROUND
Circuit reference.
22
PARK
An active-high logic input that activates the park function.
23
PARK DRIVE
Power transistor for retract current control on power down or park command.
24
SENSE
OUT
Output of current sense error amplifier.
TERMINAL FUNCTIONS
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