8958
LOGIC
SUPPLY
INHIBIT
UV
1
UV
2
LIMIT
GROUND
AB
GROUND
AB
PARK
VOLTAGE
SENSE
IN–
IN
A+
IN
A–
OUT
A
1
2
3
4
5
6
7
8
9
9
B
10
11
12
1.5 V
+
V
CC
VOICE COIL MOTOR DRIVER
24
23
22
21
20
19
18
17
SENSE
OUT
PARK
DRIVE
PARK
GROUND
PWR OK
GROUND
AB
GROUND
AB
SENSE
IN+
IN
B+
IN
B–
LOAD
SUPPLY
OUT
B
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.
Data Sheet
26300.5A
+
A
-
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
* Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated but
should be avoided.
-
+
-
V
BB
16
15
14
13
Dwg. PP-054
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
Always order by complete part number, e.g.,
A8958CLB .
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
