SI9961ACY Vishay, SI9961ACY Datasheet - Page 5

• Manufacturer Part Number: SI9961ACY
• Description: IC, MOTOR DRIVER VOICE COIL 1.8A SOIC-24
• Manufacturer: Vishay
• Type: Voice Coil Motor Driverr

Specifications of SI9961ACY

• Motor Type: Voice Coil
• No. Of Outputs: 2
• Output Current: 1.8A
• Output Voltage: 9.1V
• Supply Voltage Range: 4.5V To 5.5V
• Driver Case Style: SOIC
• No. Of Pins: 24
• Operating Supply Voltage: - 0.3 V to + 16 V
• Supply Current: 13 mA
• Mounting Style: SMD/SMT
• Package / Case: SO-24
• Operating Temperature: 0 C to + 70 C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Head Retract
A low on the RETRACT input pin turns output devices Q1 and
Q4 on, and output devices Q2 and Q3 off. Maximum VCM
current can be set during head retract by adding an external
resistor between the IRET pin and ground. Maximum retract
current may be calculated as:
Head retract can be initiated automatically by an undervoltage
condition (either the 12-V or 5-V supplies on the Si9961A) by
connecting the FAULT output to the RETRACT input.
A high ENABLE input puts both driver outputs in a
high-impedance state. The ENABLE function can be used to
Document Number: 70014
S-40845—Rev. H, 03-May-04
I
OUT
+ 175 x I
mP
mP
ret
SELECT
System
Supply
+ 175 x
GAIN
R
12 V
RET
5 V
R
V
C
V
IN
L
L
CC
23
22
10
11
4
5
9
6
0.66 V
R
IA2−
ENABLE
OA2
ret
FAULT
RETRACT
I
RET
V
R
1
R
R3
INH
+
−
Acceleration Error
R
2
A2
R4
INL
V+
V
R
Voltage
Monitor
8
R
R
24
R
V
FB
R
FIGURE 1. Si9961A Typical Application
V
EXT
+
+
−
−
Retract
Control
REF
8 R
7 R
3
I
R5
SENSE
OUT
A3
A4
A5
7
V
R
I
SENSE
V
−
+
IN+
REF−
eliminate quiescent output current when power is applied but
the head has been parked, such as a sleep mode. A
sleep-mode power down sequence should be preceded by a
retract signal since a power failure during this state may not
provide adequate spindle-motor back EMF to permit head
retraction.
Transconductance Amplifier Compensation
The Si9961A features an integrated
amplifier to drive the voice coil motor (VCM). To ensure proper
operation, this amplifier must be compensated specifically for
the VCM being driven. As a first approximation, the torque
constant and inertia of the VCM may be ignored, although they
will have some influence on the final results, especially if large
values are involved. (See Figure 1.)
5-V Ref
I
13
SENSE
12
IN−
21
Q1
Q2
A
15
GND
R
V
SA
DD
14
18
16
B
Q3
Q4
20
R
SB
Back EMF Supply
Vishay Siliconix
OUTPUT
17
19
OUTPUT
A
B
transconductance
C2
Si9961A
VCM
I
OUT
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R2
5