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| www.fairchildsemi.com FAN8902(KA3902) DC FAN Motor Controller Features * * * * * * * * * Built-in PWM current control circuit Built-in 5V regulator Low supply current Stalled motor current limitation Built-in over voltage protection (OVP) Built-in over current protection (OCP) Built-in load dump protection Built-in thermal shutdown (TSD) circuit Built-in under voltage lockout (UVLO) circuit Description The FAN8902 is a monolithic integrated circuit, designed for the PWM control of a DC fan motor current in an automotive systems. It allows the fan motor speed to be controlled linearly and efficiently. 14-DIP-300 Typical Application * DC for motor Control for Automotive Ordering Information Device FAN8902 Package 14-DIP-300 Operating Temperature -40C ~ +90C Rev. 1.0.2 May. 2000. (c)2000 Fairchild Semiconductor International 1 FAN8902(KA3902) Pin Assignments CMD 1 14 La CMDa 2 13 VCC CMDb 3 12 OUT SG 4 FAN8902 11 PG RT / CT 5 10 CS VREF 6 9 CL CH 7 8 NC Pin Definitions Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Pin Name CMD CMDa CMDb SGND RT / CT VREF CH NC CL CS PGND OUT VCC La Pin Function Descrition Motor current command input Optional OP amplifier output Optional OP amplifier (-) input Signal GND Oscillator time constant Voltage reference (5V) Maximum current reference input No connection Minimum current reference input Motor current sense voltage input Power GND Drive output VCC Motor current maximum reference input 2 FAN8902(KA3902) Internal Block Diagram Vref 6 Vref UVLO OVP 36V 13 VCC CH 7 - + 1.3V + - PWM TSD 12 OUT CMD 1 + + - 4R + - R PWM Comparator 11 PGND LOGIC La 14 CL 9 + 2 - + - x5 10 CS CMDa Oscillator 5 4 RT/CT SGND CMDb 3 3 FAN8902(KA3902) Absolute Maximum Ratings Parameter Supply voltage CMD input voltage Peak output current Power dissipation Symbol VCC VCMD IOPK PD Value 32 6 0.8 1 Unit V V A W Operating Voltage Parameter Power supply voltage Symbol VCC Min. 9.0 Typ. 12.0 Max 32.0 Unit V Temperature Characteristics Parameter Vref temperature stability Frequency stability Operating temperature Storage temperature Symbol VST FST TOPR TSTG Temp -40 ~ +90C -40 ~ +90C Value 200 20 ~ 30 -40 ~ +90 -60 ~ +150 Unit C C C C 4 FAN8902(KA3902) Electrical Characteristics (Unless otherwise, Ta=25C, VCC=5V, VM=12V) Parameter REFERENCE Reference voltage Line regulation Load regulation Start threshold voltage Threshold hysteresis PROTECTION Over voltage Frequency Duty cycle CURRENT SENSING INPUT Threshold voltage OUTPUT DRIVER Output voltage switching limit Low output voltage High output voltage Rising time Falling time TOTAL STANDBY CURRENT Start-up current Operating supply current IST ICC VCC=7V VCC=9V 1.0 6.0 1.5 8.0 mA mA VOLIM VOL1 VOL2 VOH1 VOH2 Tr Tf VCC=18V, Cld=1nF Iout=20mA Iout=200mA Iout=-20mA Iout=-200mA Cld=1nF Cld=1nF 10.0 9.0 15 100 100 0.4 2.2 200 200 V V V V V ns ns VTH(ST) VCMD=5V 0.19 0.20 0.21 V OVP fosc Duty 33 20 90 36 25 95 30 V kHz % OSCILLATOR (RT=75k, CT=1nF) Vref Vref1 Vref2 VTH(ST) VHYS Iref=1mA VCC=9V ~ 32V Iref=1mA ~ 10mA 4.75 7.5 1.0 5.0 50 10 8.0 1.2 5.25 150 50 8.5 1.4 V mV mV V V Symbol Conditions Min. Typ. Max. Units UNDER VOLTAGE LOCKOUT (UVLO) 5 FAN8902(KA3902) Application Information 1. UNDER VOLTAGE LOCKOUT (UVLO) ICC 6mA Vref & output driver TH(ST) THYS FAN8902 6.8V 8V VTH(ST) 8.0V 1.2V 1mA 13 2. CURRENT SENSING CIRCUIT M PWM comparator Imax=1V + - x5 Current amplifier PWM Logic 12 IM 10 RS VS VBAT R5 FAN8902 The peak current, IM(MAX)=VS/RS For example, if a required maximum current, IM(MAX)=20[A] 1V 5 R S = -------------- = 10 [ m ] 20A 3. THERMAL SHUTDOWN (TSD) When the chip, temperature rises up to 150C, the thermal shutdown (TSD) circuit is activated and the output driver turn off, and then turn on again at 125C. 6 FAN8902(KA3902) 4. OSCILLATOR COMPONENT SELECTION Vref VCT [V] RT V/CT CT + - Logic VH=3.0 T=40.0 VL=1.75 ID VL VH Td=1.0 TC=39.0 t [s] The oscillator timing components can be calculated as follows: T C = R T x C T x In [ ( Vref - V L ) ( Vref - V H ) ] TD = CT x [ ( VH - VL ) ID ] fosc = 1 ( TC + T D ) = 1.875 ( R T x C T ) Duty = T C x fosc x 100 For example, if fosc = 25kHz and duty = 95% C T = ( T D x ID ) ( VH - VL ) = 1000 [ pF ] R T = 1.875 ( fosc x C T ) = 1.875 ( 25kHz x 1000pF ) = 75 [ k ] 5. CURRENT COMMAND INPUT SECTION The current command I* selects the lower value between VCMD and VLa. VCMD CMD 1 La 14 VLa + + - I* 4R + R - Logic FAN8902 7 FAN8902(KA3902) 6. MOTOR STALL CURRENT LIMITATION + VBAT D1 C1 C2 M FAN8902 Q1 CMD 1 VCMD I* VLA R2 + + - R10 14 C4 Buffer-OP-amp + R - PWM COMP Logic VGS 12 R5 x5 Q2 R3 IM 4R 10 RS VRS VCS In the steady state, the terminal voltage on a motor is consisted of a back EMF and the voltage drop on the armarture resistors. When the motor happens to be stalled, the back EMF becomes zero, and the motor current (IM) is quickly increased until a maximum values. Therefore the duty of the pin #12 output becomes lower because of the increase of the sense voltage (VRS). Also it makes the voltage (VLa) be lowered, then it makes the duty become lower again. This mechanism makes the motor current hold very low value in the stalled motor state. The voltage on pin #14 (VLa) ia calculated as follows: R3 V La = V BAT x D x --------------------R2 + R3 Assumed the saturation voltage of Q1 is zero. We can choose the ratio of the resistors, R2 and R3, as follows: - Applied the rated voltage on motor, and then measured the current IRAT - Matched the maximum command current, VCMD,MAX to IRAT. VCMD,MAX = VLa,MAX = RS x IRAT x 5 x 5 for example, if RS = 10m and IRAT = 20[A] at VBAT = 13[V], VCMD,MAX = VLa,MAX = 10m x 20 x 25 = 5V - VLa,MAX = 5V = VBAT x 1 x R3 / (R2 + R3) Ratio = R3 / (R2 + R3) = VCMD,MAX / VBAT = 5 / 13 Therefore, R2 : R3 = 8 : 5 8 FAN8902(KA3902) VBAT Operating curve VMOTOR A B VLa curve x (1 / R) The voltage drop on the amarture resistance B' B" VMOTOR,STALL VLA VLA VCMD VLA IRAT The buffer OP-amp selects the lower command between VCMD and VLa so as to limit the stalled motor current to very low in the above figure. Because of much larger VLa than VCMD, the motor operating point stays at A. But the point gradually moves toward B' and then B" through the curve from the instance of stall as the below figure. VCMD VLa VCS Reduced switch-on time Motor current Uncontrolled without the FAN8902 Controlled with the FAN8902 Normal operation Stalled state 9 FAN8902(KA3902) 7. OPERATIONAL MODE SELECTION The FAN8902 has three operation modes as follows: - STOP: Turned-off the power MOSFET - LINEAR: Linearly controlled the power MOSFET - FULL-ON: Fully turned-on the power MOSFET The voltage, VSRT (PIN #9) and VMAX (PIN #7), in the application circuit are as follows: - VSRT (PIN #9) = Vref x R7 / (R5 + R6 + R7) - VMAX (PIN #7) = Vref x (R6 + R7) / (R5 + R6 + R7) IMAX Motor current [A] ISRT STOP VSRT LINEAR FULL-ON VMAX VBAT VCMD [V] 8. OVER VOLTAGE PROTECTOR (OVP) If the voltage, VBAT 36[V], the output (pin #12) is grounded, and the switching device (power MOSFET) is turned-off, and the motor is stopped. Then if the voltage, VBAT 36[V], the switching device is turned-on again, and the motor is operated. 9. TOTEM-POLE OUTPUT The FAN8902 has a single totem-pole output driver which can be drive current to peak 0.8[A]. 10 FAN8902(KA3902) Test Circuit IN 5 IN 4 IN 6 VCC SW 2 Iout TP 4 A CO 47F + Cid 1F 14 La 13 VCC 12 OUT 11 PG 10 CS 9 CL 8 NC FAN8902 CMD 1 CMDa 2 CMDb 3 SG 4 RT / CT 5 VREF 6 CH 7 R2 10k CT 1nF C2 + 22F RT 75k SW 1 R1 10k IN 1 TP 1 IN 2 TP 2 Iout TP 3 IN 3 11 FAN8902(KA3902) Typical Application VBAT + C1 C2 D1 M Q1 R1 R2 R10 Current command 1 CMD La 14 C4 NC 2 CMDa VCC 13 C3 NC 3 CMDb OUT 12 R4 4 CT 1000pF 5 RT 6 R5 7 R6 CH NC 8 NC VREF CL 9 R7 SG PG 11 + R3 FAN8902 RT / CT CS 10 RS 12 FAN8902(KA3902) 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. www.fairchildsemi.com 12/1/00 0.0m 001 Stock#DSxxxxxxxx 2000 Fairchild Semiconductor International 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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