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FAN8461G
Single Phase Full Wave BLDC Motor Driver
Description Features
* A wide range of operating voltage: 2.8V to 28V * Locked rotor protection with open collector output and auto retry * Open collector FG output. * Open collector Alarm output. * TSD protection. The FAN8461G is a single phase BLDC motor driver and it's typical application is DC cooling fans with wide range of supply voltage(3.3/5/12/24V).
Typical Applications
* CPU Cooling Fans * Instrumentation Fans * Desktop PC Fans
Ordering Information
Device FAN8461G FAN8461GX Package 10-SSOP 10-SSOP Operating Temp. -30C ~ 90C -30C ~ 90C
Rev.1.0.2
(c)2003 Fairchild Semiconductor Corporation
FAN8461G
Block Diagram
8 7
VCC VM
FG
10
4
OUT1
Commutation & Control & TSD
AL
9
H+ H-
2 1
6
OUT2
Lock Detection & Auto Restart
LD
3
VLDCP
5
GND
VLDCL
2
FAN8461G
Pin Definitions
Pin Number
1 2 3 4 5 6 7 8 9 10
Pin Name
H- H+ LD OUT1 GND OUT2 VM VCC AL FG
I/O
A A A A P A P P O O
Pin Function Description
Hall input Hall input + Sawtooth wave generator for lock detector and automatic restart Motor output 1 Ground Motor output 2 Motor power supply Logic power supply Alram output Speed output
Remark
-
Open collector Open collector
3
FAN8461G
Absolute Maximum Ratings (Ta = 25C)
Parameter
Maximum power supply voltage Thermal resistance Maximum power dissipation Maximum output voltage Maximum output current Maximum output peak current Maximum FG/Alarm output current FG/Alarm output sustain voltage Hall output withstanding voltage Operating temperature Storage temperature
note 1 : Should not exceed PD or ASO value. 2 : IOPEAK time is within 2us.
Symbol
VCCMAX,VMMAX Rja PDMAX VOMAX IOMAX IOPEAK IFG/AL VFG/AL VHO TOPR TSTG
Value
32 150 800 36 0.8
note
Unit
V
oC/W
mW V A A mA V V C C
1.2note 5 36 36 -30 ~ 90 -55 ~ 150
Recommended Operating Conditions (Ta = 25C)
Parameter
Supply voltage
Symbol
VCC
Min.
2.8
Typ.
-
Max.
28
Unit
V
Power Dissipation Curve
1.0
0.5
0
0
25
50
75
100
125
150
175
Ambient temperature, Ta [C]
PCB condition : When mounted on 76.2mm x 114mm x 1.57mm PCB (glass epoxy material).
4
FAN8461G
Equivalent Circuits
Description Pin No. Internal Circuit
VCC
Hall input
1,2
1
2
VCC
LD 3
3
VM
Output
4,6
4 6
9
10
FG/AL
9 , 10
5
FAN8461G
FAN8461G Electrical Characteristics
(Ta = 25C, VCC = 12V unless otherwise specified)
Parameter Total
Supply current
Symbol
ICC ILDC ILDD VLDCL VLDCP VOSH VOSL VFGS IFGO VALS IAL VHDC VHOF
Conditions
Min.
-
Typ.
4.5 2.2 0.33 2.6 0.6 0.9 0.2
Max.
7 2.9 0.50 2.9 0.8 1.1 0.3 0.3 10 0.3 10 VS-2.8 10
Unit
mA A A V V V V V A V A V mV
Lock Detector & Auto Restart
LD charging current LD discharging current LD clamp voltage LD comparator voltage VLD=0V-->1.5V, VLD=1.5V VLD=3V-->1.5V, VLD=1.5V IO=200mA IO=200mA IFG=5mA VFG=12V IAL=5mA VAL=12V 0 -10 1.4 0.15 2.3 0.4 -
Output Stage
High side output saturation voltage Low side output saturation voltage FG output saturation voltage FG output leakage current AL output saturation voltage AL output leakage current
Speed output(FG) & Lock Detection Output(AL)
0.1 0.1 0.1 0.1 -
Hall Amplifier
Input range Input offset
6
FAN8461G
Application Information
1. H-bridge motor driver(OUT1, OUT2)
Using an H-bridge to drive a single-phase BLDC motor provides several advantages for dc fans over a two phase motor commonly driven by two commutated low-side switches. A single phase motor has only two connections; hence, the H-bridge topology requires only two output terminals and two traces are needed on the fan PCB. Generally, this H-bridge method with single phase motor increases fan motor torque density over a typical unipolar drive method. In addition, the H-bridge topology eliminates the number of external component for snubbing and allows recirculation of winding current to maintain energy in a motor while switching occuers.
2. Locked Rotor Protection with Open Collector Output and Automatic Restart
When the rotor is locked, there is no change in input signal of hall amplifier and thus a internal TZERO pulse is not observed. A capacitor(CLD) connectied LD pin is continually charged by internal current source(ILDC) to internal threshold (VLDCL) resulting from no Tzero pulse. When the voltage,VCLD on LD pin, reaches VLDCL, high side output power TR is turned-off to protect motor during TOFF and the alarm output (AL) becomes floating high. When the VCLD reaches upper threshold,VLDCL, VCLD starts to decrease with internal current sink(ILDD) to the low threshold, VLDCP. At that time, the VCLD ramps up again and one of two outputs is turned on depending on locked rotor position during TON.The charging and discharging repeat until locked conditon is removed, or FAN8461G is powerd down. The overall time chart is shown in figure.1. The auto- retry time(TON), the motor protection time(TOFF), the locked rotor detection time(TLOCK) are proportional to external capacitor, CLD and each value can be calculated as follows;
C x (V -V ) LD LDCL LDCP = ---------------------------------------------------------------------ON I LDC C x (V -V ) LD LDCL LDCP = ---------------------------------------------------------------------I LDD
T
T
OFF
T
C x VLDCL LD -------------------------LOCK I
LDC
For example, CLD = 0.33uF, then TON= 0.3Sec,TOFF= 2Sec,TLOCK= 0.4Sec. This AL output can be used to inform a locked rotor condition to super IO or system controller. Because the AL output is open collector type, end user can pull up this pin with a external resistor to the supply voltage of their choice(that is 5 or 3.3V). It is recommednd that this AL output be higher than the GND potential.
7
FAN8461G
Rotor HH+
NSNSNSN
N
SNSNSNS
TOFF VLDCL VLDCP
TON
LD Tzero OUT2 OUT1 AL FG
Motor Locked Lock Released Tlock
1 rotation
Figure 1. Overall Timing Chart
8
FAN8461G
3. Hall Sensor Amplifier
V+
RH
IN+ 2 CH2
CH1
FAN8461G
1 IN-
Ri
Hall Sensor
Figure 2. Hall Sensor Interface
The hall current (IH) is determined as follows;
I H V CC = -------------------------( RH + Ri )
Where, RH is an external limiting resistor and Ri is input impedance of hall sensor. An external capacitor, CH1, can be used to reduce a power supply noise.CH2 can reduce the instant peak current using H-bridge's commutation. The input range of hall amplifier is between 0V and VCC-2.8V as shown in following figure.
VS V S - 2 .8 V VS / 2
GND
Figure 3. Hall Amplifier Input Range Table 1. Hall Sensor Outputs and Related Pin outputs
H+
H-
LD
OUT 1
OUT 2
AL
TACO
Remark
H L -
L H
Low Level Low Level -
L H -
H L -
L L H
L H L or H ROTATING LOCK
8. Open Collector FG Output for Speed Feedback
The FG output comes from the hall amplifier output. Because the FG output is open collector type, end user can pull up this pin with a external resistor to the supply voltage of their choice(that is 5 or 3.3V). This resulting output signal has two pulses per revolution on a four pole motor. It is recommednd that this FG output be higher than the GND potential.
9. Supply Voltage Consideration
A supply sustain capacitor(CR) should be placed as close to VCC pin with GND as layout permits. A reverse supply protection diode(DR) prevent motor current from recirculating to power source when phase commutation occur. This results in increasing VCC pin voltage. This capacitor absorbs motor recirculating current and limits VCC pin voltage. In general, large motor winding induactance and current need large value of CR.
10. Thermal Shutdown
TSD on: Two high side outputs are off.(Typ. 175C) TSD off:The circuit can be reactivated and begin to operate in a normal condition. (Typ. 150C)
9
FAN8461G
Typical Application Circuits 1
8
VCC VM
FG
10
V+ CR
7
4
OUT1
Commutation & Control & TSD
AL
9
V+
H+ H-
Hall Sensor
2 1
6
OUT2
Lock Detection & Auto Restart
LD
3
VLDCP
5
GND
VLDCL
10
FAN8461G
Package Dimensions (Unit: mm)
11
FAN8461G
Typical Performance characreristics
VCC current consumption
2.5
Low side TR saturation voltage High side TR saturation voltage
5
2.0 1.5 1.0 0.5 0.0 0.0 VS=VM=12V
ICC[mA]
4
3
VCE[V]
0
5
10
15 VCC[V]
20
25
30
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Motor current[A]
12
FAN8461G
13
FAN8461G
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 CORPORATION. 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.
www.fairchildsemi.com 1/29/04 0.0m 001 Stock#DSxxxxxxxx 2002 Fairchild Semiconductor Corporation
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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