The Si9961A is a linear actuator (voice coil motor) driver suit-
able for use in disk drive head positioning systems. The
Si9961A contains all of the power and control circuitry nec-
essary to drive the VCM that is typically found in 3
1
/
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 MOS-
FETs in a H-bridge configuration. The output crossover pro-
tection ensures no cross-conducting current and true Class
B operation during linear tracking. Externally programmable
gain switch at the input summing junction increases the res-
olution 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.
FEATURES
•
•
•
•
•
•
•
•
•
1.8 A H-Bridge Output
Class B Linear Operation
Externally Programmable Gain and Bandwidth
Undervoltage Head Retract
Programmable Retract Current
Low Standby Current
Rail-to-Rail Output Swing
Single 12 V Supply
System Voltage Monitor with Fault Output
FUNCTIONAL BLOCK DIAGRAM
V+
8
4
5
EXT
V
REF
7
V
REF
_
12
V
DD
18
Q1
Voltage
Monitor
8R
V
R
Q3
FAULT
V
CC
17
IA2
-
23
-
+
A2
OUTPUT
A
OUTPUT
B
R
+
A4
19
-
V
R
RETRACT
I
RET
Enable
OA2
9
6
11
22
Q2
Q4
V
R
Retract
Control
A5
-
Acceleration Error
+
R
V
R
7R
A3
-
+
GAIN
SELECT
10
1
2
24
3
13
21
15 14
16
20
R
INH
R
INL
R
FB
I
SENSE
OUT
I
SENSE
IN+
I
SENSE
IN
-
SA
GND
SB
Document Number: 70014
S-40845-Rev. H, 03-May-04
www.vishay.com
1
Si9961A
Vishay Siliconix
ABSOLUTE MAXIMUM RATINGS
Parameter
Voltages Referenced to Common Pin
V+ Supply Range
Pin (FAULT)
Pin (Output A & B, Source A & B)
Pin (All Others)
Maximum Clamp Current
Output A, Output B (Pulsed 10 ms at 10 % duty cycle)
Pin (All Others)
Storage Temperature
Operating Temperature
Junction Temperature (T
J
)
Power Dissipation (Package)
a
Thermal Impedance (Θ
JA
)
a
24-Pin SOIC
b
24-Pin SOIC
- 0.3 V to 16 V
-0.3 V to V
CC
+ 0.3 V
- 0.3 V to V
DD
+ 0.3 V
- 0.3 V to V+ + 0.3 V
± 1.8
± 20
- 65 to 150
0 to 70
150
3.125
40
W
°C/W
°C
A
mA
V
Limit
Unit
Notes:
a. Device Mounted with all leads soldered or welded to PC board.
b. Derate 25 mW/°C above 25 °C.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation
of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.
SPECIFICATIONS
Parameter
Symbol
Test Conditions
Unless Otherwise Specified
V+ = 12 V ± 10 %, V
DD
= 11.6 V ± 10 %
V
CC
= 5 V ± 10 %, V
REF-
= GND = 0 V
V
REF
= 5 V ± 5 %
I
OH
= 1.0 A, V
DD
= 10.2 V, OA
2
= V
REF
± 1 V
I
OL
= - 1.0 A, OA
2
= V
REF
± 1 V
I
F
= 1.0 A, ENABLE = High
Output V
RANGE
= V
REF
± 2 V
Measured at V
DD
SR
1
0.2
- 60
V
OS
I
B
SR
PSRR
A
VOL
V
O
V
OS
R
IN
CMRR
SR
V
CM
V
O
To GND
R
LOAD
= 10 kΩ, C
LOAD
= 100 pF to V
REF
I
SENSE
IN+ to I
SENSE
IN-
R
LOAD
= 10 kΩ, C
LOAD
= 100 pF to V
REF
at 5 kHz
2
3.9
- 0.3
V
REF
- 2
4
4.1
2
V
REF
+ 2
R
LOAD
= 10 kΩ to V
REF
V
REF
- 2
-5
5
1
50
at 10 kHz
Gain Select = High, IA
2
- = 5 V
R
LOAD
= 10 kΩ, C
LOAD
= 100 pF to V
REF
1
50
80
V
REF
+ 2
5
-8
- 50
1
60
8
50
12
16
10
Limits
C Suffix 0 to 70 °C
Min
b
Typ
a
Max
b
Unit
Bridge Outputs (A
4
, A
5
)
High Level Output Voltage
Low Level Output Voltage
Clamp Diode Voltage
Amplifier Gain
Dynamic Crossover Current
Slew Rate
Small Signal Bandwidth (- 3 dB)
Input Deadband
A
2
, Loop Compensation Amplifier
Input Offset Voltage
Input Bias Current
Unity Gain Bandwidth
Slew Rate
Power Supply Rejection Ratio
Open Loop Voltage Gain
Output Voltage Swing
A
3
, Current Sense Amplifier
Input Offset Voltage
Input Impedance
Small Signal Bandwidth (- 3 dB)
Common Mode Rejection Ratio
Slew Rate
Gain
Input Common-Mode Voltage Range
Output Voltage Swing
www.vishay.com
2
mW
kΩ
MHz
dB
V/µs
V/V
V
mV
nA
MHz
V/µs
dB
V
V
OH
V
OL
V
CL
8.0
9.1
0.6
1.1
2.5
18
V/V
mA
V/µS
MHz
mV
V
Document Number: 70014
S-40845-Rev. H, 03-May-04
Si9961A
Vishay Siliconix
SPECIFICATIONS
Parameter
Symbol
Test Conditions
Unless Otherwise Specified
V+ = 12 V ± 10 %, V
DD
= 11.6 V ± 10 %
V
CC
= 5 V ± 10 %, V
REF-
= GND = 0 V
V
REF
= 5 V ± 5 %
Limits
C Suffix 0 to 70 °C
Min
b
Unit
b
Typ
a
Max
Supply
I
CC
Supply Current (Normal)
I
V+
I
DD
I
CC
Supply Current (Standby)
I
V+
I
DD
V
DD
Range
V
CC
Range
V+ Range
Gain Select Switch
R
FB
Switch Resistance
R
INH
Switch Resistance
R
INL
Switch Resistance
V
REF
(EXT)
Input Current
External Voltage Range
Power Supply Monitor
V
CC
Undervoltage Threshold
Hysteresis
V+ Undervoltage Threshold
Hysteresis
Gain Select, RETRACT, ENABLE Input
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
FAULT Output
Output High Voltage
Output Low Voltage
Output High Sourcing Current
I
RET
Bias Voltage
Retract Output Pull-Up Voltage
Retract Output Pull-Down Current
Maximum Emergency Retract Current
Retract Current V
DD
Supply Rejection Ratio
Retract Current Temperature Coefficient
V
OH
V
OL
I
OHS
V(I
RET
)
V
OUT A
I
OUTB
I
OUTB
(Max)
I
OH
= - 100 µA
I
OL
= 1.6 mA
V
OUT
= 0 V
V
DD
= 10 V, R
RET
= 3.74 kΩ
V
DD
= 2.5 V to 14 V, I
OUTA
= 30 mA
V
DD
= 10 V, V
OUTB
= 5 V R
RET
= 3.74 kΩ
R
SB
= 0.5
Ω,
T
A
= 25 °C
V
DD
= 2 V, V
OUTB
= 0.7 V R
RET
= < 10
Ω
R
SB
= 0.5
Ω
V
DD
= 2 V to 14 V, R
RET
= 3.74 kΩ
V
DD
= 10 V, R
RET
= 3.74 kΩ
V
DD
- 1
22
40
3.0
- 0.3
%/V
%/°C
30
38
mA
V
CC
- 0.8
V
CC
- 0.33
0.25
400
0.66
0.50
1100
µA
V
V
IH
V
IL
I
IH
I
IL
V
IN
= 5 V
V
IN
= 0 V
-1
-1
3.5
1.5
1
1
V
µA
V
REF
= 5.0 V
9.1
V
REF
= 5.0 V
3.82
4.12
40
9.8
100
10.6
4.42
V
mV
V
mV
I
REF
V
REF
OA2 = V
REF
0.15
4.75
0.40
5
0.65
5.25
mA
V
IA2 - = 5 V
108
135
810
240
300
1800
Ω
V
DD
V
CC
V+
Static, No Load
RETRACT = High
ENABLE = Low
Static, No Load
RETRACT = High
ENABLE = High
Normal Mode
Retract Mode
10.2
2.0
4.5
10.8
5
12
0.01
2
5
0.2
0.8
11.6
5
13
0.01
0.4
1.6
13.2
14
5.5
13.2
V
mA
RETRACT Current Control (RETRACT = Low, Output Current from A to B)
V
Notes:
a. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing.
b. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum.
Document Number: 70014
S-40845-Rev. H, 03-May-04
www.vishay.com
3
Si9961A
Vishay Siliconix
PIN CONFIGURATION AND ORDERING INFORMATION
24-Pin SOIC
(Wide Body)
R
INH
R
INL
I
SENSE
OUT
FAULT
V
CC
I
RET
EXT V
REF
V+
RETRACT
1
2
3
4
5
6
7
8
9
24
23
22
21
20
19
18
17
16
15
14
13
Top View
R
FB
IA2
-
OA2
I
SENSE
(IN)
-
SOURCE B
OUTPUT B
V
DD
(Spindle Supply)
OUTPUT A
GND
SOURCE A
GND
I
SENSE
(IN)
+
ORDERING INFORMATION
Part Number
Si9961ACY
Si9961ACY-T1 Si9961ACY-T1-E3
Lead (Pb)-free
Part Number
Temperature
Range
0 to 70 °C
Package
SOIC-24
(Wide Body)
GAIN SELECT 10
ENABLE 11
V
REF
-
12
APPLICATIONS
Introduction
The Si9961A Voice Coil Motor (VCM) driver integrates the
active feedback and drive components of a head-positioning
servo loop for high-performance hard-disk applications. The
Si9961A operates from a 12 V (± 10 %) power supply and
delivers 1 A of steady-state output current. This device is
made possible by a power IC process which combines bipo-
lar, CMOS and complimentary DMOS technologies. CMOS
logic and linear components minimize power consumption,
bipolar front-ends on critical amplifiers provide necessary
accuracy, and complimentary (P- and N-Channel) DMOS
devices allow the transconductance output amplifier to oper-
ate from ground to V
DD
. Two user-programmable, current
feedback/input voltage ratios may be digitally selected to
optimize gain for both seek and track following modes, to
maximize system accuracy for a given DAC resolution. An
undervoltage lockout circuit monitors the V+ supply and gen-
erates a fault signal to trigger an orderly head-retract
sequence at a voltage level sufficient to allow the spindle
motor’s back EMF-generated voltage to supply the neces-
sary head parking energy. Head retract can also be com-
manded via a separate RETRACT input. VCM current during
retract can be user programmed with a single external resis-
tor. External components are limited to R/C filter components
for loop compensation and the resistors that are required to
program gain, retract current, and the load current sense.
User-Programmable Gains
During linear operation, the transconductance amplifiers’
gains (input voltage at V
IN
vs. VCM current, in Figure 1) are
set by external resistors R
3
-> R
5
, R
SA
, and R
SB
and selected
by gain input. After selecting a value for R
SA
and R
SB
that will
yield the desired VCM current level, the High and Low feed-
back gain ratios may be determined by the following:
High Gain =
( )
R
5
R
3
1
4 R
S
(GAIN SELECT Input = High)
Low Gain =
( )
R
5
R
4
(
1
4 R
S
(GAIN SELECT Input = Low)
Where R
S
= R
SA
= R
SB
Input offset current may then be calculated as:
1
I
OS
= 4 R
S
(
(R
S
+ R
IN
)
V
+ 5 V
IAS3
)
R
IN OSA2
)
Where R
IN
= R
3
or R
4
www.vishay.com
4
Document Number: 70014
S-40845-Rev. H, 03-May-04
Si9961A
Vishay Siliconix
Back EMF Supply
12 V
System
Supply
V+
4
5
5V
V
CC
23
C
L
R
L
9
6
11
22
R
RET
V
R
V
R
RETRACT
I
RET
ENABLE
OA2
Acceleration Error
+
R
7R
A3
GAIN
SELECT
mP
R
INH
R
INL
1
2
R
FB
24
I
SENSE
I
SENSE
I
SENSE
OUT
IN+
IN
-
3
13
21
A
15 14
10
+
GND
B
16 20
IA2
-
A2
FAULT
Voltage
Monitor
8R
V
R
Q1
Q3
8
EXT
V
REF
7
V
REF
_
5 V Ref
12
V
DD
18
I
OUT
VCM
17
mP
-
+
R
+
A4
Q2
Q4
OUTPUT
C2 R2
A
19
OUTPUT
B
-
V
R
Retract
Control
A5
-
-
R3
V
IN
R4
R5
R
SA
R
SB
Figure 1. Si9961A Typical Application
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. Maxi-
mum retract current may be calculated as:
A high ENABLE input puts both driver outputs in a high-
impedance state. The ENABLE function can be used to elim-
inate 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 sig-
nal 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 transconductance
amplifier to drive the voice coil motor (VCM). To ensure
proper operation, this amplifier must be compensated specif-
ically 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.)
I
OUT
= 175
×
I
ret
0.66 V
= 175
×
R
ret
Head retract can be initiated automatically by an undervolt-
age condition (either the 12 V or 5 V supplies on the
Si9961A) by connecting the FAULT output to the RETRACT
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