SI9961A Ver la hoja de datos (PDF) - Vishay Semiconductors
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SI9961A Datasheet PDF : 10 Pages
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Si9961A
Vishay Siliconix
PIN CONFIGURATION AND ORDERING INFORMATION
RINH 1
RINL 2
ISENSE OUT 3
FAULT 4
VCC 5
IRET 6
EXT VREF 7
V+ 8
RETRACT 9
GAIN SELECT 10
ENABLE 11
VREF- 12
24-Pin SOIC
(Wide Body)
Top View
24 RFB
23 IA2-
22 OA2
21 ISENSE (IN)-
20 SOURCE B
19 OUTPUT B
18 VDD (Spindle Supply)
17 OUTPUT A
16 GND
15 SOURCE A
14 GND
13 ISENSE (IN)+
ORDERING INFORMATION
Part Number
Lead (Pb)-free
Part Number
Temperature
Range
Package
Si9961ACY
Si9961ACY-T1 Si9961ACY-T1-E3
0 to 70 °C
SOIC-24
(Wide Body)
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 VDD. 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 VIN vs. VCM current, in Figure 1) are
set by external resistors R3 -> R5, RSA, and RSB and selected
by gain input. After selecting a value for RSA and RSB that will
yield the desired VCM current level, the High and Low feed-
back gain ratios may be determined by the following:
( )R5 1
High Gain = R3 4 RS
(GAIN SELECT Input = High)
( )R5 1
Low Gain = R4 4 RS
(GAIN SELECT Input = Low)
Where RS = RSA = RSB
Input offset current may then be calculated as:
1
IOS = 4 RS
( ) (
(RS + RIN )
RIN VOSA2 +
5 VIAS3)
Where RIN = R3 or R4
www.vishay.com
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Document Number: 70014
S-40845-Rev. H, 03-May-04
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