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 .
8958
VOICE COIL
MOTOR DRIVER
ELECTRICAL CHARACTERISTICS (continued)
Limits
Characteristic
Current Sense Amplifier
Input Offset Voltage
Input Offset Drift
V
IO
∆V
IO
V
CM
= 6 V
V
CM
= 0 V to 12 V
—
—
—
Voltage Gain
Output Saturation Voltage
A
VS
V
SAT
V
ID
= -1 V to +1 V, V
CM
= 6 V
V
OUT
, I
OUT(SINK)
= 1.5 mA
V
CC
- V
OUT
, I
OUT(SOURCE)
= -1.5 mA
Park Function
PARK DRIVE Leakage Current
PARK DRIVE Saturation Voltage
PARK Input Threshold
PARK Input Current
PARK VOLTAGE Input Current
Under-Voltage Protection
UV Threshold
UV Threshold Hysteresis
UV Input Current
PWR OK Saturation Voltage
PWR OK Leakage Current
Auxiliary Functions
LIMIT Input Voltage
V
LIMIT(L)
V
LIMIT(H)
V
LIMIT
OUT
A
forced Low
OUT
A
forced High
Limit inactive
Open circuit
LIMIT Input Resistance
INHIBIT Input Threshold
INHIBIT Input Current
R
LIMIT
V
2
I
2
V
2
= 1.7 V
V
LIMIT
= 1.2 V to 1.8 V
0.7
—
1.2
1.45
—
0.7
—
0.8
2.2
—
1.50
10
1.1
—
—
2.3
1.8
1.55
—
1.7
200
V
V
V
V
kΩ
V
µA
V
UV
∆V
UV
I
UV
V
CE(SAT)
I
CEX
V
UV
= 1 V
I
C
= 5 mA
V
CEX
= 20 V
Low-to-High Trans., Other Input = 6 V
1.48
15
—
—
—
1.50
25
-0.5
—
—
1.52
45
-1.5
450
5.0
V
mV
µA
mV
µA
I
CEX
V
CE(SAT)
V
PARK
I
PARK
I
PARK V
V
PARK
= 1.7 V
V
CEX
= 20 V
I
C
= 200 mA
—
—
0.7
—
—
—
300
1.1
—
-150
100
500
1.7
100
-500
µA
mV
V
µA
nA
1.95
—
—
—
—
—
2.00
300
400
2.0
3000
8.0
2.05
500
700
mV
µV/V
µV/°C
—
mV
mV
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.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
8958
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
Terminal Name
LOGIC SUPPLY
INHIBIT
UV
1
and UV
2
LIMIT
GROUND
AB
PARK VOLTAGE
SENSE
IN–
IN
A+
IN
A–
OUT
A
OUT
B
LOAD SUPPLY
IN
B–
IN
B+
SENSE
IN+
GROUND
AB
PWR OK
GROUND
PARK
PARK DRIVE
SENSE
OUT
Function
V
CC
; logic supply voltage.
An active-high logic input that inhibits the output stages without initiating a park.
Under-voltage detection inputs. If not used, these terminals must be connected
to the logic supply (V
CC
).
A tri-state input that forces the output of amplifier A into saturation in either direction,
or allows normal linear operation.
Power amplifiers’ ground and thermal heat sink.
Auxiliary inverting input to power amplifier A.
Inverting input to current sense error amplifer.
Non-inverting input to power amplifier A.
Inverting input to power amplifier A.
Power amplifier A output to voice coil motor.
Power amplifier B output to voice coil motor.
V
BB
; load supply voltage.
Inverting input to power amplifier B.
Non-inverting input to power amplifier B.
Non-inverting input to current sense error amplifer.
Power amplifiers’ ground and thermal heat sink.
A logic low at this output indicates an under-voltage condition.
Circuit reference.
An active-high logic input that activates the park function.
Power transistor for retract current control on power down or park command.
Output of current sense error amplifier.
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