SI9961A Datasheet, PDF (1/9 Pages) Vishay Siliconix – 12-V Voice Coil Motor Driver

12-V Voice Coil Motor Driver
Si9961A
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 Si9961A is a linear actuator (voice coil motor) driver
suitable for use in disk drive head positioning systems. The
Si9961A 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 Si9961A 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 Si9961A is constructed on a self-isolated BiC/DMOS
power IC process. The IC is available in both standard and
lead (Pb)-free, 24-pin SO packages 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-40845—Rev. H, 03-May-04
17 _OUTPUT
A
19 OUTPUT
B
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