Si9961
Vishay Siliconix
12-V Voice Coil Motor Driver
FEATURES
D 1.8-A H-Bridge Output
D Undervoltage Head Retract
D Rail-to-Rail Output Swing
D Class B Linear Operation
D Programmable Retract Current D Single 12-V Supply
D Externally Programmable Gain and
D Low Standby Current
D System Voltage Monitor with Fault Output
Bandwidth
DESCRIPTION
The Si9961 is a linear actuator (voice coil motor) driver suitable
for use in disk drive head positioning systems. The Si9961
contains all of the power and control circuitry necessary to
drive the VCM that is typically found in 31/2-inch hard disk
drives and optical disk drives. The driver is capable of
delivering 1.8 A at a nominal supply of 12 V.
operation during linear tracking. Externally programmable
gain switch at the input summing junction increases the
resolution and dynamic range for a given DAC. The head
retract circuitry can be activated by either an undervoltage
condition or an external command. An external resistor is
required to set the VCM current during retract.
The Si9961 provides all necessary functions including a motor
current sense amplifier, a loop compensation amplifier and a
power amplifier featuring four complementary MOSFETs in a
H-bridge configuration. The output crossover protection
ensures no cross-conducting current and true Class B
The Si9961 is constructed on a self-isolated BiC/DMOS power
IC process. The IC is available in 24-pin SO package for
operation over the commercial, C suffix (0 to 70_C)
temperature range.
FUNCTIONAL BLOCK DIAGRAM
EXT
V+
8
V
REF
V
V
REF–
DD
7
12
18
Q1
Q3
4
5
FAULT
V
R
Voltage
Monitor
V
CC
8 R
17
19
OUTPUT
A
23
A2
–
+
IA2–
R
A4
+
OUTPUT
B
–
Q2
Q4
V
R
V
9
6
R
RETRACT
Retract
Control
I
RET
11
Enable
OA2
A5
22
–
+
Acceleration Error
R
V
R
7 R
A3
–
+
GAIN
10
SELECT
1
2
24
3
13
21
15 14
16 20
R
INH
R
INL
R
FB
I
I
I
SA
GND
SB
SENSE
OUT
SENSE
IN+
SENSE
IN–
Document Number: 70014
S-20883—Rev. G, 24-Jun-02
www.vishay.com
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