SI9961ACY_02 View Datasheet(PDF) - Vishay Semiconductors
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Description
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SI9961ACY_02 Datasheet PDF : 8 Pages
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Si9961
Vishay Siliconix
PIN CONFIGURATION
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)+
Order Number: Si9961ACY
APPLICATIONS
Introduction
User-Programmable Gains
The Si9961 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 Si9961
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 bipolar, 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 operate 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 generates 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 necessary head parking energy. Head retract can
also be commanded via a separate RETRACT input. VCM
current during retract can be user programmed with a single
external resistor. 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.
www.vishay.com
4
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 feedback
gain ratios may be determined by the following:
ǒ ǓR5 1
High Gain + R3 4 RS
ǒ ǓR5 1
Low Gain + R4 4 RS
(GAIN SELECT Input = High)
(GAIN SELECT Input = Low)
Where RS = RSA = RSB
Input offset current may then be calculated as:
1
IOS + 4 RS
ǒ Ǔ ǒ
ǒRS
) RINǓ
RIN VOSA2
)
5 VIAS3Ǔ
Where RIN = R3 or R4
Document Number: 70014
S-20883—Rev. G, 24-Jun-02
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