www.fairchildsemi.com 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. Typical Applications • CPU Cooling Fans • Instrumentation Fans • Desktop PC Fans 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). Ordering Information Device Package Operating Temp. FAN8461G 10-SSOP −30°C ~ 90°C FAN8461GX 10-SSOP −30°C ~ 90°C Rev.1.0.2 ©2003 Fairchild Semiconductor Corporation FAN8461G Block Diagram 8 7 4 6 5 VCC VM OUT1 OUT2 Commutation & Control & TSD Lock Detection & Auto Restart 10 AL 9 H+ 2 H- 1 LD VLDCP GND VLDCL 2 FG 3 FAN8461G Pin Definitions Pin Number Pin Name I/O Pin Function Description Remark 1 H− A Hall input - 2 H+ A Hall input + - 3 LD A Sawtooth wave generator for lock detector and automatic restart - 4 OUT1 A Motor output 1 5 GND P Ground 6 OUT2 A Motor output 2 - 7 VM P Motor power supply - 8 VCC P Logic power supply - 9 AL O Alram output Open collector 10 FG O Speed output Open collector - 3 FAN8461G Absolute Maximum Ratings (Ta = 25°C) Parameter Symbol Maximum power supply voltage Value Unit VCCMAX,VMMAX 32 V Rja 150 oC/W Maximum power dissipation PDMAX 800 mW Maximum output voltage VOMAX 36 V Thermal resistance note IOMAX 0.8 Maximum output peak current IOPEAK 1.2note A Maximum FG/Alarm output current IFG/AL 5 mA FG/Alarm output sustain voltage VFG/AL 36 V Hall output withstanding voltage VHO 36 V Operating temperature TOPR −30 ~ 90 °C Storage temperature TSTG −55 ~ 150 °C Maximum output current A note 1 : Should not exceed PD or ASO value. 2 : IOPEAK time is within 2us. Recommended Operating Conditions (Ta = 25°C) Parameter Supply voltage Symbol Min. Typ. Max. Unit VCC 2.8 − 28 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 × 114mm × 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 = 25°C, VCC = 12V unless otherwise specified) Parameter Symbol Conditions Min. Typ. Max. Unit - 4.5 7 mA Total Supply current ICC Lock Detector & Auto Restart LD charging current ILDC VLD=0V-->1.5V, VLD=1.5V 1.4 2.2 2.9 µA LD discharging current ILDD VLD=3V-->1.5V, VLD=1.5V 0.15 0.33 0.50 µA LD clamp voltage VLDCL - 2.3 2.6 2.9 V LD comparator voltage VLDCP - 0.4 0.6 0.8 V - 0.9 1.1 V 0.2 0.3 V 0.1 0.3 V Output Stage High side output saturation voltage VOSH IO=200mA Low side output saturation voltage VOSL IO=200mA Speed output(FG) & Lock Detection Output(AL) FG output saturation voltage VFGS IFG=5mA FG output leakage current IFGO VFG=12V - 0.1 10 µA AL output saturation voltage VALS IAL=5mA - 0.1 0.3 V IAL VAL=12V - 0.1 10 µA AL output leakage current - Hall Amplifier 6 Input range VHDC - 0 - VS-2.8 V Input offset VHOF - -10 - 10 mV 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; T C × (V –V ) LD LDCL LDCP = ---------------------------------------------------------------------ON I LDC T C × (V –V ) LD LDCL LDCP = ---------------------------------------------------------------------I LDD OFF T C × 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 TOFF SNSNSNS TON VLDCL VLDCP LD Tzero OUT2 OUT1 Tlock AL FG 1 rotation Motor Locked Lock Released Figure 1. Overall Timing Chart 8 FAN8461G 3. Hall Sensor Amplifier V+ RH CH1 IN+ 2 CH2 FAN8461G Ri Hall Sensor 1 IN- 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 H L Low Level L H L L L H Low Level H L L H ROTATING - - - H L or H LOCK - Remark 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. 175°C) TSD off:The circuit can be reactivated and begin to operate in a normal condition. (Typ. 150°C) 9 FAN8461G Typical Application Circuits 1 8 V+ 7 VCC VM CR 6 5 OUT1 OUT2 Lock Detection & Auto Restart AL 9 H+ 2 H- 1 LD VLDCP GND VLDCL 10 10 3 V+ Hall Sensor 4 Commutation & Control & TSD FG FAN8461G Package Dimensions (Unit: mm) 11 FAN8461G Typical Performance characreristics Low side TR saturation voltage High side TR saturation voltage VCC current consumption 2.5 5 VCE[V] ICC[mA] 2.0 4 VS=VM=12V 1.5 1.0 0.5 3 0 5 10 15 VCC[V] 12 20 25 30 0.0 0.0 0.1 0.2 0.3 0.4 Motor current[A] 0.5 0.6 0.7 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. 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. www.fairchildsemi.com 1/29/04 0.0m 001 Stock#DSxxxxxxxx 2002 Fairchild Semiconductor Corporation