Fairchild FAN8621B 12v spindle motor and voice coil motor driver ic Datasheet

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FAN8621B
12V Spindle Motor and Voice Coil Motor Driver IC
Features
Description
General
The FAN8621B, is a Bipolar monolithic stand-alone IC,
designed for 12V HDD applications.The internal power
stage consists of vertical PNP and NPN TRs for both SPM
and VCM, thus minimizing voltage drop, and increasing
drive capability up to 2A for SPM and 1.2A for VCM. This
device includes soft commutation drive to reduce audible
noise and intelligent retract function for decreased bouncing.
•
•
•
•
Hysteresis power on reset with delay function
5V, 12V supplies monitoring
Thermal shut down(TSD)
Programmable precision regulator usging minimal
external component
• Three state control input to reduce number of PINs
Spindle Motor(SPM)
•
•
•
•
•
•
•
•
•
•
•
ASIC based start-up
Internal back-EMF processing
Internal sensorless commutation
Internal SPM speed control with SFLL(Syncronized
Frequency Lock Loop).
Linear SPM current control
Selectable Motor Speed (5400/7200 RPM)
Soft commutation circuitry to reduce acoustic noise
Adjustable brake delay time
Maximum 2A start-up current capability
Internal and external spindle brake
Speed lock indicator output
48-QFPH-1414
Voice Coil Motor (VCM)
•
•
•
•
•
Intelligent retract (decreased bouncing)
1.2A internal VCM power driver
Selectable transconductance
4V precision reference output
Two PWM input (fine/coarse) for VCM set point
Typical Applications
Ordering Information
• Hard disk drive(HDD)
Device
Package
Operating Temp.
FAN8621B
48-QFPH-1414
0 ~ 70°C
Rev. 1.0.0
May. 2000.
©2000 Fairchild Semiconductor International
1
FAN8621B
Pin Assignments
B
2
FAN8621B
Pin Definitions
Pin Number
Pin Name
IO
Pin Function Description
1
VCNT
A
Speed controller output. Range 3.8V to 0.5V
2
CSOFT
A
Capacitor for soft commutation
3
ADJ
A
Adjust external regulator voltage (VREF)
4
SENSE5
A
5V power line sensing
5
VDD
P
5V power line
6
FG
O
Frequency generation for spindle rotation speed. Typically
1.08KHz (5400RPM)
7
VREF
P
Regulator voltage output. This voltage is controlled by pin 3
voltage
8
CLK
I
System clock. Digital clock input as a time reference
9
HALFVCC
P
1/2 VCC
10
POR
O
Power on reset. H : normal, L: power fail
11
CDLY
A
Define POR delay time
12
GAINSEL
I
Sense amplifier gain selection. H : High gain (8), L : Low gain (2)
13
PWMH
I
Coarse PWM input for VCM set point
14
PWML
I
Fine PWM input for VCM set point
15
CFVCM
A
Output of PWM inputs to voltage converter
16
VCMREF4V
P
4V reference output for VCM
17
CRET
A
Define retract delay time.
18
VCC
P
12V power line
19
FILOUT
A
Filtered output of PWM inputs. This voltage define VCM set point
20
SENSE
A
Non-inverting input of differential amplifier for VCM current
sensing
21
CRET2
A
Power for retract when power down
22
PVCC
P
12V power line for VCM
23
VCM-
A
Negative output terminal of VCM power amplifier
24
RRET
A
Adjust maximum retract current
25
SENSEOUT
A
Output of differential amplifier for VCM current sensing
26
PGND
P
Ground for VCM
27
VCM+
A
positive output terminal of VCM power amplifier
28
ERRIN
A
Inverting input of VCM error amplifier
29
VDD
P
5V power line
30
ERROUT
A
Output of VCM error amplifier
31
SUBGND
P
Ground for spindle motor
32
W
A
Spindle W phase output
3
FAN8621B
Pin Definitions (Continued)
Pin Number
Pin Name
IO
Pin Function Description
33
PCS
A
Spindle current sensing.
34
V
A
Spindle V phase output
35
SUBGND
P
Ground for spindle
36
N
A
Spindle N phase output
37
U
A
Spindle U phase output
38
PVCC
P
12V power line for spindle
39
CCOMP
A
Current controller output. This Voltage define spindle output
current
40
BRAKE
A
Gating signal for external brake
41
CBRAKE
A
Charged back-EMF to supply brake power when power down
42
SENSE12
A
12V power line sensing
43
GND
P
Ground
44
CNTL1
I
Control input for spindle . H: spindle enable, Z: Spindle bias
enable, L: brake
45
CNTL2
I
Start-up clock and soft commutation. H: Start-up clock , L : soft
commutation.
46
CNTL3
I
Control input for VCM. H: VCM enable, Z : VCM disable, L:
retract
47
READY
O
Speed lock indicator when speed is within 0.7% speed error
range. H : speed locked, L: unlocked
48
RPMSEL
I
Target spindle speed selection. L : 5400 rpm, H: 7200 rpm with
5MHz Clock
4
FAN8621B
Internal Block Diagram
VCC
CDLY
POR
11
10
VREF
ADJ
7
3
VDD VDD VCC
5
29
18
VDD
TSD
25K
SENSE12
42
SENSE5
4
7K
CSOFT
Retract
External
Brake
U
FG
Generator
6
SPM bias enable
CNTL2
CNTL3
44
Commutation
Sequencing
&
Spindle Control
SPM output on
Three State
Input
Control
45
BRAKE
41
CBRAKE
38
PVCC
36
N
37
U
34
V
32
W
35
SUBGND
31
SUBGND
39
CCOMP
U
V
W
N
SPM
Three Phase
Power Driver
Back-EMF
Processing
&
Zero Cross Detector
Triangle Wave
Generator
2
clock
CNTL1
40
1.3V
11K
9K
FG
Bandgap
Reference
&
Bias
Power
Management
start-up clock
hard/soft
46
Brake
VCM
on/off
VDD
Retract
FG
i spll
Real
Speed
READY
47
RPMSEL
48
Speed
Discriminator
&
Speed Lock
Indicator
8
PWMH
13
PWML
14
CFVCM
15
GAINSEL
12
16
VCMREF4V
VCC
22
PVCC
27
VCM+
9
clock
power
amp
PWMs
Decorder
&
2nd orderFilter
U
V
VCM
Gain Selection
W
sense
amp
VCM+
SENSE
gain
2,8
VCMREF4V
24
23
VCM-
26
PGND
20
SENSE
VCMREF4V
Intelligent
Retract
21
HALFVCC
gain
14
Retract
GND
PCS
error
amp
Counter
&
Timing Control
43
33
power
amp
1
CLK
VCMREF4V
VCM
H-bridge
Power Driver
i spll
Speed
Reference
VCNT
pre
amp
Current
Limiting
17
19
28
CRET2 RRET CRET FILOUT ERRIN
5
30
ERROUT
25
SENSEOUT
FAN8621B
Absolute Maximum Ratings(Ta = 25°C)
Parameter
Symbol
Value
Unit
Supply voltage (signal)
VDD
6.0
V
Supply voltage (signal)
VCC
15.0
V
Supply voltage (power)
PVCC
15.0
V
Storage Temperature
TSTG
−55 ~ 125
°C
Power dissipation
3.0
PD
note
W
Maximum Junction Temperature
TJ
150
°C
Operating Ambient Temperature
TAMB
0 ~ 70
°C
NOTE:
1. When mounted on 50mm × 50mm × 1mm PCB (Phenolic resin material)
2. Power dissipation is reduced 16mV / °C for using above Ta=25°C.
3. Do not exceed Pd and SOA(Safe Operation Area).
Power Dissipation Curve
Pd[mW]
3,000
2,000
1,000
0
0
25
50
75
100
125
150
175
Ambient temperature, Ta [°C]
Recommanded Operating Coditions (Ta = 25°C)
Parameter
Symbol
Min.
Typ.
Max.
Unit
Supply voltage (signal)
VDD
4.5
5.0
5.5
V
Supply voltage (signal)
Vcc
10.8
12.0
13.2
V
Supply voltage (power)
PVCC
10.8
12.0
13.2
V
6
FAN8621B
Electrical Characteristics
(Ta=25°C, unless otherwise specified)
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
IDD1
CNTL1=L,CNTL2=CNTL3=Z (brake)
80-
100
120
mA
VDD Line supply current2
IDD2
CNTL1= CNTL2 =CNTL3=Z
(SPM bias enable)
25
35
45
mA
VDD Line supply current3
IDD3
CNTL1=CNTL3=H,CNTL2=Z
(SPM,VCM enable)
25
35
45
mA
VDD Line supply current4
IDD4
CNTL1=CNTL2=Z,CNTL3= L (retract)
25
35
45
mA
VCC Line supply current1
ICC1
CNTL1=L,CNTL2=CNTL3=Z (brake)
2
7
12
mA
VCC Line supply current2
ICC2
CNTL1= CNTL2 =CNTL3=Z
(SPM bias enable)
4
9
15
mA
VCC Line supply current3
ICC3
CNTL1=CNTL3=H,CNTL2=Z
(SPM,VCM enable)
10
20
60
mA
VCC Line supply current4
ICC4
CNTL1=CNTL2=Z,CNTL3=L (retract)
12
19
25
mA
POWER SUPPLIES
SUPPLY CURRENT
VDD Line supply current1
SUPPLY MONITOR
Threshold voltage1 for VCC
VTH12A
VCC=sweep,VDD=5V
9.05
9.40
9.75
V
Threshold voltage2 for VCC
VTH12B
VCC=sweep,VDD=5V
8.75
9.10
9.45
V
Hysteresis on VCCcomparator
VHYS12
VCC=sweep,VDD=5V
0.15
0.3
0.45
V
Threshold voltage1 for VDD
VTH5A
VCC=12V,VDD=sweep
3.45
3.90
4.15
V
Threshold voltage2 for VDD
VTH5B
VCC=12V,VDD=sweep
3.30
3.75
4.00
V
Hysteresis on V comparator
VHYS5
VCC=12V,VDD=sweep
0.08
0.15
0.23
V
ICPOR
−18.0
−14
−10
µA
VTHPOR
1.1
1.3
1.5
V
POWER ON RESET GENERATOR
Charging current for POR cap
POR threshold voltage
Output high voltage
VPORH
VCC = 12V, VDD= 5V, POR output
current is 1mA
4.5
-
Vdd
V
Output low voltage
VPORL
VCC = 12V, VDD= 5V, POR output
current is 1mA
0
-
0.5
V
CONTROL INPUTs(CNTL1,CNTL2,CNTL3)
Control input low voltage
VCTL
CNTL1=CNTL2=CNTL3=sweep
0.8
1.3
1.7
V
Control input high voltage
VCTH
CNTL1=CNTL2=CNTL3=sweep
1.85
2.3
2.75
V
Control input low current
ICTl
CNTL1=CNTL2=CNTL3=sweep
-290
-200
-110
µA
Control input high current
ICTH
CNTL1=CNTL2=CNTL3=sweep
55
110
190
µA
7
FAN8621B
Electrical Characteristics (Contnued)
(Ta=25°C, unless otherwise specified)
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
SPINDLE MOTOR (SPM)
FG FREQUENCY GENERATOR
FG frequency
FFG
CLK=5MHz,RPMSEL=L (5400 RPM)
0.97
1.08
1.18
KHz
FG duty
DFG
FFG = 1.08KHz
45
50
50
%
FG output high voltage
VFGH
FG output current is 1mA
4.5
-
VDD
V
FG output low voltage
VFGL
FG output current is 1mA
-
-
0.5
V
READY high output
VRDH
CNTL1=H,within ±0.7% motor speed
error,
4.5
-
VDD
V
READY low output
VRDL
READY output current is 1mA
-
-
0.5
V
READY SIGNAL GENERATION
SINDLE OUTPUT SATURATION VOLTAGE
VSUU
IU=1A
0.2
0.6
1.0
V
VSaturation voltage upper
VSVU
IV=1A
0.2
0.6
1.0
V
W Saturation voltage upper
VSWU
IW=1A
0.2
0.6
1.0
V
U Saturation voltage lower
VSUL
IU=1A
0.2
0.4
0.8
V
V Saturation voltage lower
VSVL
IV=1A
0.2
0.4
0.8
V
W Saturation voltage lower
VSWL
IW=1A
0.2
0.4
0.8
V
U Saturation voltage upper
RPMSELECT INPUT
RPMSEL threshold voltage
VRPH
-
1.1
1.5
1.7
V
RPMSEL input high current
IRPHI
-
60
91
110
µA
RPMSEL input low current
IRPLO
-
-5
0
5
µA
Speed controller high voltage
VCNTH
-
3.5
3.8
4.2
V
Speed controller low voltage
VCNTL
-
-
-
0.5
V
High voltage of linear range
VLIMITH
-
3.15
3.5
3.85
V
Low voltage of linear range
VLIMITL
-
1.15
1.5
1.85
V
F/I converter charge current
ISPLLC
-
-70
-50
-40
µA
F/I converter discharge current
ISPLLD
-
40
52
70
µA
Transeconductance gain of
SPM
GMSPM
RPCS=0.33Ω
0.6
0.8
1.0
-
Limit voltage of current amp
VLIMIT1
RPCS = 0.33Ω
-
0.57
-
V
Limit voltage of current amp
VLIMIT2
RPCS = 0.33Ω
Equivalent output resistance
RCC
SPEED CONTROLLER
CURRENT LIMITTER
-
-
0
-
V
-
20
-
KΩ
-
3.3
-
V
-
-
2.0
%
-
-
2.0
%
EXTERNAL REGULATOR
Regulator output voltage
VREG
Regulator line regulation
RLINE
Regulator load regulation
RLOAD
VADJ(pin3) = 1.3V
IO= 500mA
8
FAN8621B
Electrical Characteristics (Contnued)
(Ta=25°C, unless otherwise specified)
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
SPINDLE MOTOR (Continued)
BRAKE
Cbrake output voltage
VBC
-
11
11.3
11.8
V
Brake output high voltage
VBH
-
11
−
−
V
Brake output low voltage
VBL
-
-
-
0.5
V
Soft commutation high voltage
VSOFTH
-
3.1
-
3.7
V
Soft commutation low voltage
VSOFTL
-
1.4
1.7
2.0
V
Discharging current
ISOFTC
-
30
45
60
µA
Charging current
ISOFTD
-
-60
-45
-30
µA
-
-
1.8
V
-
−10
0
10
µA
SOFT COMMUTATION
DRIVE OUTPUTS (U,V,W)
Total voltage Drop
Leakage current
VDROPS
IMOTOR = 1A
ILEAKS
VOICE COIL MOTOR CIRCUIT(VCM)
PWM INPUTS
PWMH/PWML high input
voltage
VPWMH
-
2.8
-
-
V
PWMH/PWML low input voltage
VPWML
-
-
-
2.2
V
PWMH charge/discharge
current
IPWMH
-
650
670
690
µA
PWML charge/discharge current
IPWML
-
10
10.5
11
µA
PWM current ratio
IRATIO
63
64
65
Internal resister
RFVCM
-
-
3
-
kΩ
Maximum phase shift
DF
Measure at 500Hz, CCFVCM = 1nF
-
-
−2
deg
Cut-off frequency
FCO
-
-
100
-
KHz
Attenuation at 1MHz
FITER
-
-
70
-
dB
IPWMH/IPWML
VCN PWM FILTER
Filter output voltage1
VCVCM1
PWMH=PWML=0%
5.6
6.00
6.40
V
Filter output voltage2
VCVCM2
PWMH=PWML=50%
3.8
4.0
4.2
V
Filter output voltage3
VCVCM3
PWMH=PWML=100%
1.6
2
2.4
V
VCM reference voltage 4V
VREF4
CNTL3 = 5V, VREF4V output
current=1mA
3.8
4
4.2
V
VCM reference voltage 1/2 VCC
VREF6
HALFVCC output current =1µA
5.9
6.0
6.1
V
VCM REFERENCE
9
FAN8621B
Electrical Characteristics (Contnued)
(Ta=25°C, unless otherwise specified)
Parameter
Symbol
Condition
Min.
Typ.
Max.
Unit
VSOH
-
10.8
-
-
V
Amp low output voltage
VSOL
-
-
-
1.2
V
Input offset voltage
VOSS
-
−15
0
15
mV
Short circuit current
ISSC
-
10
-
-
mA
Unity gain bandwidth
BGS
-
-
2
-
MHz
SENSE AMPLIFIER
Amp high output voltage
Voltage gain 1
AVS1
GAINSEL : L
-
18
-
dB
Voltage gain 2
AVS2
GAINSEL : H
-
6
-
dB
ERROR AMPLIFIER
Amp high output voltage
VEOH
-
10.8
-
-
V
Amp low output voltage
VEOL
-
-
-
1.2
V
Input offset voltage
VOSE
-
−15
0
15
mV
Open loop gain
AVE
-
-
80
-
dB
Unity gain bandwidth
BGE
-
-
2
-
MHz
Short circuit current
ISSE
-
8
-
-
mA
VPOH
-
11.5
-
-
V
Output low voltage
VPOL
-
-
-
0.5
V
Input offset voltage
VOSP
-
−15
0
15
mV
Gain
APO
-
21.2
22
23.8
dB
Unity gain bandwidth
BGP
-
-
2
-
MHz
POWER AMPLIFIER
Output high voltage
Total voltage Drop
Leakage current
VDROPV
when VCM current is 0.7A
-
-
1.5
V
−20
0
20
µA
PWMH=PWML=50% Duty
−20
0
20
mA
-
ILEAKV
VCM AMP TOTAL
VCM offset current
VVCMOS
VCM transconductance low gain
GMVH
GAINSEL = H,sense resister is 1Ω
0.05
0.12
0.14
A/V
VCM transconductance high
gain
GMVL
GAINSEL = L,sense resister is 1Ω
0.35
0.45
0.55
A/V
Min operating voltage of CRET2 VCRET2
-
2.0
-
-
V
Cret charge current
ICRET
-
-70
-85
-100
µA
Max. retract sink current
IRCT
-
-
125
-
mA
Retract reference voltage
VRET
-
0.75
0.9
1.05
V
Retract current limit resister
RIRET
-
-
3
-
KΩ
Leakage current of output TR
ILRET
-
−10
0
10
µA
VRTSAT
-
-
0.4
0.7
V
Operating temperature
TTSD
-
135
150
165
°C
Thermal hystereis
THYS
-
20
30
40
°C
RETRACT FUNCTION
Sink saturation voltage
THERMAL SHUT DOWN
10
FAN8621B
Application Informations
General
The FAN8621B is a stand alone combination chip consisting of Spindle Motor (SPM) and Voice Coil Motor (VCM)circuit for
HDD applications. The speed control of SPM is achieved by internal Synchronous Phase Locked Loop (SPLL). The
FAN8621B supplies adjustable regulated power with external component and signals READY indicating SPM is locked
within some speed range (typically ±0.7% speed error). Current set point is applied by two PWM signals and VCM current is
monitored by external sense resistor. VCM circuit generates 4 voltage references for testing. Fig.1 shows overall interfacing of
FAN8621B with external and HDD motors
POR
Vreg3.3
Power
Management
CNTL1
CNTL2
CNTL3
Interface
RPMSEL
READY
DIGITAL
ASIC
SPM
FG
PWMH
PWML
GAINSEL
VCM
VCMREF4V
CLK
Retract/Brake
TSD
Figure 1. Overall Interfacing of the FAN8621B
The control signals have three status and their function is summarized as follows;
Pin Status
H
Z
L
SPM
enable(1)
bias enable
disable
Brake
disable
disable
enable
Commutation
hard
Hard
soft
Start Clock
high(2)
low(2)
-
Signals
CNTL1
CNTL2
CNTL3
GAINSEL
VCM
enable
disable
disable
Retract
disable
disable
enable
Start-up hold
normal
normal
hold(3)
Sense Amp gain
2
2
8
Table 1. Control PIN function
Notes:
1. SPM bias + SPM Output Driver enable
2. Makes SPM Open Loop (Start-up) Commutation Signal
3. Test Only when READY is low
11
FAN8621B
Spindle Motor Driver
The spindle motor driver has two operating modes : hard commutation in start-up and acceleration mode and soft commutation
in steady state to reduce acoustic noise.
Start-up and Acceleration
To spin up the motor, open mode start-up clock must be fed to CNTL2 pin in range 20 ~ 200Hz depending on number of platter and motor RPM. This HIGH and OPEN signal commutates motor current in turn while back-EMF comparator checks
back-EMF level. When the back-EMF detects motor position, then operating mode is changed from start-up mode to acceleration mode. Also internal commutation logic starts sensorless commutation.
Speed Control
Spindle motor speed is defined by system clock and RPMSEL (pin48) . For your reference, see table2
POR
CNTL1
soft
commutation
CNTL2
CNTL3
VCM
enable
+0.7%
TARGET
RPM
-0.7%
start-up
SPEED
hard
commutatio
n
INTERNAL
READY
READY
user
option
0.27sec
Figure 2. Typical Control Sequence of the FAN8621B
Speed and rotor position of spindle motor is measured by back-EMFs. Back-EMF comparator detects zero crossing point
(ZCP) of unexcited phase back-EMF. The output frequency of comparator multiplied by 3 represents motor speed FG ( pin6).
FG frequency is calculated as follows
FG = motor RPM/60 × pole number/2 × phase number
Pin Value
System clock
(CLK, pin8)
Speed
5400 rpm
5MHz
7200 rpm
3600rpm
3.333MHz
4800rpm
Table 2. RPM selection
For example, 8 pole, three phase 5400 rpm motor,
fFG = 5400 / 60 × 8 / 2 × 3 = 1080Hz
12
Rpm selection
(RPMSEL, pin48)
L
H
L
H
FAN8621B
The spindle motor speed is controlled by SPLL which consists of Synchronous F/I converter , loop filter , and inner current
control loop. F/I converter compares RPM reference time with 12 FG time one rotation of spindle for 8 pole motor. The time
difference is converted into charge/discharge current source, and fed to loop filter consisting of external RC network. Loop filter acts ad speed controller and it’s output becomes spindle output current set point. If spindle motor speed is greater than target speed, switch s2 is turned on, thus decreasing output voltage of loop filter. Current limiting during start-up is achieved by
sensing the voltage across the sense resistor connected PCS (pin 33). This limit the loop filer output. The output of loof filter is
compared with internal 2.5V reference. If the difference is over 0.75V, the output is limited and scaled down. When the output
of loof filter is 1.75V(2.5V-0.75V), the output of limitter is 0. The maximum output of limitter is 0.4V when the output of loof
filter is over 3.25V. So spindle output current is linearly controlled by level shifted current set point driving high side vertical
PNP TR of spindle output driver. Overall concept of SPM speed control is shown Figure3.
U
V
W
N
VDD
FG
6
speed
discriminator
&
speed lock
indicator
CLK
8
counter/logic
READY
47
i spll
Freal
Fref
s1
39
s2
C39
i spll
1
48
33
I spindle
RPMSEL
R1
R33
C1a
C1b
Figure 3. Speed Control of SPM
Indirect Rotor Position Sensing and Commutation
The back-EMF comparator detects the instant at which the back-EMF in the unexcited phase cross as zero. The commutation
timing and sequencing for driver outputs is determined by internal commutation logic based on back-EMF ZCP (zero crossing
point). Commutation is initiated in advance of ZCP, 30° (electrical) for hard commutation and 1° for soft commutation, respectively. In BLDC motor with trapezoidal type back-EMF, phase current waveforms look like step wave, which generates audible noise. In soft commutation mode (CNTL2 pin45 is LOW), the two phase currents overlap with some current slope. This
slope is determined by internal PWM pattern and external capacitor, CSOFT. The soft commutation using current slope of the
motor reduce acoustic noise and voltage spark which is generated on the motor coil at the commutation.
Spindle Output Driver
Spindle Output driver contains vertical PNP TR for high side and NPN TR for low side. For one commutation period, PNP TR
is controlled linearly by the difference between the current set point VCNT(pin1) and sensed current PCS (pin33), while NPN
TR is fully turned on. This scheme provides low voltage drop in linear current control application. The total voltage drop is
about 1.8V in 2A current rating. Maximum spindle current is defined as follows;
0.57V
Ispindle ( max ) = -------------------------------------R33 + Rmetal
Where Rmetal is internal metal resistance(typically 50mΩ). If R33 is 150mΩ, the maximum spindle current is 2A.
Spindle Brake
There are two braking modes; internal and external braking. Spindle is braked when CNTL1 (pin44) is LOW by turning all
low side driver on. In case of power failure, brake power is supplied by charged capacitor connected CBRAKE (pin41). Gate
signal for two external MOSFET is issued from BRAKE (pin40) with time delay, which is defined by internal resistor (2.8M)
and external capacitor.
13
FAN8621B
18
41
C41
PVCC
2.8M
VDD
V
37
M40a
40
34
W
32
C40
M40b
brake
33
R33
Figure 4. Brake Function Block
Voice Coil Motor Driver
VCM Current Set Point
VCM current set point is defined by two PWM signals. External capacitor connected CFVCM (pin15) is charged and/or discharged depending on status of PWM signals. The voltage, level shifted by 4V, is filtered by an internal 2-nd order filter and
converted into DC voltage, FILOUT (pin19) ranging from VCMREF4V+2V to VCMREF4V-2V. The cutoff frequency of the
2nd order filter is about 100KHz, so the PWM frequency must be grater than 100KHz. For more resolution of VCM current set
point, the value of two internal current sources for PWMH and PWML is not equal. The weight is 64, so it is good that frequency of PWMH is different that of PWML. When PWM signal is LOW, CFVCM (pin15) voltage increases This voltage is
limited by internal 4V reference and resistor, RFVCM.
VDD
VDD VCMREF4V
R fvcm
ipwml
ipwmh
=4K
20K
PWMH
13
PWML
14
ipwml
80pF
20K
80pF
19
ipwmh
15
C15
Figure 5. Current Set Point with PWMs
Sense Amplifier
Current sense amplifier amplifies the differential voltage across the sense resistor which is in series with VCM coil. This
amplified voltage is level shifted by VCMREF4V. The amplifier gain is set to 2 or 8 depending on GAINSEL. The output of
the current sense amplifier is available at SENSEOUT( pin25).
14
FAN8621B
VCM Current Loop Error Amplifier
The inverting input of error amplifier is summing point of VCM current set point (FILOUT) and actual VCM current (SENSEOUT). The output of error amplifier is proportional to the dynamically compensated voltage difference between FILOUT and
SENSEOUT. This output voltage is level shifted to VCMREF4V via connecting non-inverting input of error amplifier internally to VCMREF4V. The dynamic compensation is achieved by external RC network connected to ERRIN (pin28) and
ERROUT (pin30 )
VCM Power Amplifier
The VCM power amplifier is a linear H-bridge type power driver consist of two NPN TR and two vertical PNP TR to reduce
voltage drop. Total voltage drop is 1.5V at 0.7A. The differential gain of power amplifier is 14.
If open loop gain of power and error amplifier is very large, the overall DC gain of VCM driver is calculated as follow
1
R25
1
Gm = ----------- ⋅ -------------------------------------------------- ⋅ ---------R19 R20 + R metal ( VCM ) A VS
where R20 is VCM current sense resistor and Avs is gain of sense amplifier. Rmetal(VCM) is internal metal resistance(typically 0.05ohm). If R25 is equal to R19, R20 = 1Ω, and Rmetal(VCM) = 0, then overall DC gain is determined by the gain of sense
amplifier. For Example,GAINSEL is low,
1 = 1
--- = 0.125
Gm = ---------A VS
8
And if GAINSEL is high, then
1
1
Gm = ---------- = --- = 0.5
A VS
2
power
amp
30
27
C30
VCMREF4V
error
amp
R28
VCC
R27
D27
9
28
C27
power
amp
C9
VCM
23
R19
gain
14
19
D20
sense
amp
R25
R20
38
25
20
gain
2,8
VCMREF4V
Figure 6. Current Control of VCM
15
FAN8621B
VCM Retract
Power fail condition or when VCM retract command is issued on CNTL3 (pin46) LOW, retract circuit is activated. The retract
current is limited by internal and external resistor connected RRET (pin24) and retract delay time is adjusted by external
capacitor connected CRET (pin 17). The voltage on CRET2 (pin21) charged by spindle back-EMF serves as retract power.
22
37
D21
34
21
32
bandgap
reference
C21
I rct=
300 Iret
20
1.3V
retract
TSD
por
Riret
I ret
3k
2.0V
27
I cret
12u
17
C17
24
R24
Figure 7. Retract Function Block
Retract delay time and maximum retract current is defined as follows;
1.25
T retdly = C17 ⋅ ----------I cret
2.0
I rct ( max ) = 300 ⋅ I ret = 300 ⋅ ------------------------3K + R24
Power Management
Supplies Monitoring and Reference
The voltage reference circuit generates precision 1.3V volt reference, other voltage and current reference. Precision low voltage monitor circuitry senses 5V, 12V supplies. These supplies are individually divided down by resistor divider and then compared with internal 2.5V reference to determine the set-point low voltage condition. Low voltage condition can be changed by
adding external resistor on SENSE5 (pin4), SENSE12 (42).
Power On Reset (POR)
When low voltage is detected, POR (pin10) is lowered immediately and fed to external controller. The retract and braking
sequence is started. If low voltage condition is removed, the POR becomes high with delay. This time delay is based on charging of the CDLY (pin11) capacitor with internal current source.
16
FAN8621B
VCC VDD
VDD
icpor
25K
7K
42
10
4
9K
11K
2.5V
2.5V
TSD
11
C11
Figure 8. Power Line Sensing and POR
POR delay time is calculated by following formula
2.5
T dly = C11 ⋅ -----------I cpor
Regulator
An external passive element and two resistors generate regulated 3.3V supply suitable for external digital logic operating at the
reduced voltage. Regulator output voltage is defined by resistor divider
R3a
V reg = 1.3  1 + -----------

R3b
VDD
bandgap
reference
1.3V
7
Q7
3.3V
R3a
3
R3b
Figure 9. Regulator Output for Digital ASIC
17
FAN8621B
Thermal Shut Down
A TSD circuit is included to protect the chip from damaging during momentary shorts that might occur during prototyping and
troubleshooting. The trip temperature is set to 150°C with 30°C hysteresis. A thermal fault starts retract and braking operation
and also makes POR pin low.
18
FAN8621B
Typical Application Circuits
5V
25K
VDD
10
R3b
C11
Q7
11
VCC
R3a
5V
7
CDLY POR
3
VREF
TSD
12V
D5
5
ADJ
29
18
VDD VDD VCC
V
7K
M40a
BRAKE
42
Bandgap
Reference
&
Bias
Power
Management
SENSE12
4
SENSE5
Retract
1.3V
11K
9K
FG
FG
Generator
6
CSOFT
2
C2
Triangle Wave
Generator
clock
External
Brake
U
CBRAKE
PVCC
38
CNTL2
CNTL3
U
SPM bias enable
44
Three State
Input
Control
45
Commutation
Sequencing
&
Spindle Control
SPM output on
start-up clock
hard/soft
46
Brake
VCM
on/off
Retract
V
W
Real
Speed
47
RPMSEL
48
i spll
CCOMP
CLK
C1b
8
14
15
C15
12
GAINSEL
VCMREF4V
16
32
SPM
39
ispll
VCC
error
amp
12.7K
9
12.7K
U
V
W
VCM
Gain
Selection
sense
amp
VCM+
SENSE
gain
2,8
VCMREF4V
RRET
CRET2
21
R24
19
C17
ERRIN ERROUT
28
R19
30
12V
19
C30
D21
17
R28
C21
CRET FILOUT
24
23
PGND
Intelligent
Retract
43
VCM-
26
VCMREF4V
Retract
SENSEOUT
25
R25
12V
C9
D20
gain
14
CFVCM
GND
D27
HALFVCC
clock
PWMs
Decorder
&
2nd orderFilter
C39
VCM
VCM+
27
VCNT
Counter
&
Timing Control
R33
22
power
amp
VCMREF4V
12V
PVCC
R20
13
PWML
34
33
VCM
H-bridge
Power Driver
power
amp
PWMH
37
PCS
R1
C1a
36
SUBGND 35
pre
amp
Current
Limiting
Speed
Discriminator
&
Speed Lock
Indicator
Speed
Reference
1
12V
SUBGND 31
VDD
FG
READY
W
M40b
N
CNTL1
C40
41
C41
U
V
W
N
SPM
Three Phase
Power Driver
Back-EMF
Processing
&
Zero Cross Detector
40
SENSE
20
R27
C27
FAN8621B
Parts List
Part NO.
Value
Type
R1
280K
1/8W
R3A
15K
1/8W
R3B
10K
1/8W
R19
6K
1/8W
R20
1
1/2W
R24
2.2K
1/8W
R25
4K
1/8W
R27
30
1/4W
R28
2.2K
1/4W
R33
0.33
1W
C1A
1µ
ELECTROLYTIC, 6V
C1B
0.22µ
CERAMIC, 6V
C2
27n
CERAMIC, 6V
C11
0.047µ
CERAMIC, 16V
C15
0.68n
CERAMIC, 10V
C17
1µ
ELECTROLYTIC, 16V
C21
2.2µ
ELECTROLYTIC,16V
C30
33n
CERAMIC,16V
C39
0.1µ
CERAMIC,16V
C40
0.47µ
ELECTROLYTIC,16V
C41
2.2µ
ELECTROLYTIC,16V
Q7
KSH29
D-PACK
M40A
SSD2003
8SOP
M40B
SSD2003
8SOP
D5
RB4110
SOT23
D20
RB4110
SOT23
D21
RB4110
SOT23
D27
RB4110
SOT23
20
FAN8621B
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY
PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY
LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER
DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES
OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR
INTERNATIONAL. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body,
or (b) support or sustain life, and (c) whose failure to
perform when properly used in accordance with
instructions for use provided in the labeling, can be
reasonably expected to result in a significant injury of the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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