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
a73 Controlled-Velocity Head Parking
a73 Zero Deadband
a73 High Transconductance Bandwidth
a73 User-Adjustable Transconductance Gain
a73 ±800 mA Load Current
a73 Dual Under-Voltage Monitors
with Flag and User-Selectable Trip Points
a73 Internal Thermal Shutdown Circuitry
a73 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
1312
10
9SENSE
IN–
IN
A+
IN
A–
GROUND
AB
GROUND
AB
GROUND
AB
GROUND
AB
IN
B–
IN
B+
+
B
-
+
-
A
+
-
11