SI9961 Datasheet, PDF (1/8 Pages) Vishay Siliconix – 12-V Voice Coil Motor Driver

12-V Voice Coil Motor Driver
Si9961
Vishay Siliconix
FEATURES
D 1.8-A H-Bridge Output
D Class B Linear Operation
D Externally Programmable Gain and
Bandwidth
D Undervoltage Head Retract D Rail-to-Rail Output Swing
D Programmable Retract Current D Single 12-V Supply
D Low Standby Current
D System Voltage Monitor with Fault Output
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.
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
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 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+
V_REF V_REF–
8
7
12
4
FAULT
V_CC
5
23
IA2–
RETRACT ⁹
I_RET
6
Enable ¹¹
OA2 ²²
GAIN ₁₀
SELECT
Voltage
Monitor
– ^A2
R
+
V_R
V_R
Acceleration Error
R
V_R
V_R
8R
+
A4
–
Retract
Control
–
A5
+
7 R _A3
–
+
V_DD
18
Q1
Q3
Q2
Q4
1
R_INH
2
R_INL
24
R_FB
3
I_SENSE
OUT
13
21
15 14
16 20
I_SENSE I_SENSE SA GND SB
IN+ IN–
Document Number: 70014
S-20883—Rev. G, 24-Jun-02
17 _OUTPUT
A
19 OUTPUT
B
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