Preliminary PT2431 3-Phase Sensorless BLDC Motor Driver DESCRIPTION PT2431 is an integrated 12V-operationable 3-phase sensorless BLDC motor driver with advanced protections which include soft-start circuit, thermal shutdown, lock protection and output current limit. PT2431 is specially designed for sensorless motor and ideal for fan motor control requiring high power efficiency. And a direct PWM-control interface is built in to smooth the fan speed from low to high. Peripheral devices are limited to few so that it is not difficult to make the PCB layout tight and small. PT2431 uses a new multi-power BCD technology, requiring a single power supply of VDD = 5~12V, packed as TSSOP16 package and displaying excellent power efficiency, is a perfect solution for comprising a compact, low-cost sensorless BLDC motor system. FEATURES Multi-power BCD technology Direct-PWM of 20~50 KHz for fan speed control Adjustable soft-start time by an external capacitor Adjustable Lock protection time by an external capacitor Thermal protection of shutdown/release at 150 C/120C Over-current limit set by an external precision resistor FG output is offered, which gives the pulse signal as the hall sensor system APPLICATIONS 3-phase sensorless BLDC fan motor driver Fan for CPU or graphic card Fan for server BLOCK DIAGRAM Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, No. 233-1, Baociao Rd., Sindian Dist., New Taipei City 23145, Taiwan PT2431 APPLICATION CIRCUIT 5 ~ 12V 1 TEST FR 16 2 VREG OSC 15 3 FG GND 14 4 RD SOFT 13 5 COM PWM 12 6 VDD SGND 11 7 UO RF 10 8 WO VO 9 PT2431 Connect to BLDC motor PRE 1.2 2 October 2013 PT2431 ORDER INFORMATION Valid Part Number PT2431 Package Type 16-pin, HTSSOP, 173mil Top Code PT2431-HT PIN CONFIGURATION TEST 1 16 FR VREG 2 15 OSC FG 3 14 GND RD 4 13 SOFT COM 5 12 PWM VDD 6 11 SGND UO 7 10 RF WO 8 9 VO PT2431-HT PRE 1.2 PT2431-X 3 October 2013 PT2431 PIN DESCRIPTION PRE 1.2 Pin Name I/O TEST I VREG Description Pin No. Test mode , keep floating or low for normal operation 1 IO Regulator output pin. Connect a bypass capacitor of 2.2F to ground 2 FG O Pulse output signal with open-drain structure 3 RD O Lock mode signal with open-drain structure. Hi-Z for Lock mode 4 COM I Motor middle point connection for BEMF detection reference It is an optional. 5 VDD P High voltage power supply pin 6 UO O WO O VO O RF O SGND P High voltage ground signal 11 PWM I PWM input signal. 20~50KHz is allowed. 75K pull-up to VREG 12 SOFT IO Soft start control pin. Connect a capacitor of 1F to ground 13 GND P Low voltage ground signal 14 OSC IO Start-up frequency and Lock mode period setting pin Connecting a capacitor of 2200pF to ground causes 10S lock time 15 FR I Forward or reverse, change status when power off Heatsink P For heat dissipation Motor driving pin U. Connect to the U phase of motor coil Current flows in the order of U, W, V Motor driving pin W. Connect to the W phase of motor coil Current flows in the order of U, W, V Motor driving pin V. Connect to the V phase of motor coil Current flows in the order of U, W, V Output current sense signal Connect a 0.5 resistor to ground for 1A output current limit 7 8 9 10 16 back side 4 October 2013 PT2431 FUNCTION DESCRIPTION POWER SUPPLY PT2431 provides an internal voltage regulator to the analog and digital blocks, except output driver stage. The load of driver stage is motor wire, it presents inductive character and induces large current and voltage spike when motor start to rotate. It is needed to put a suitable bypass capacitor as close to VDD pin as possible to reduce these current spikes. Also, put a 15V zener diode to ward off large back-emf voltage from motor. PT2431 chip can be operated in the supply voltage range from 5.0 V to 12 V. Figure 1, Zener diode and bypass capacitor for VDD supply. SENSORLESS CONTROL The main structure of PT2431 is based on a three-phase sensorless control algorithm. The great benefit of sensorless control is to remove three position hall sensors from motor. It is useful to reduce cost and fabrication difficulty, and enhance motor’s reliability due to hall sensor’s weakness of temperature characteristic. The sensorless control method is to sense the BEMF (back electromotive force) voltage signal when the rotors of motor are commutating. The control algorithm computes and predicts the position of rotors. Hence, there are some disadvantages, such as the motor should move at minimum rate to generate sufficient BEMF to be sensed; a maximum rotation speed limitation to avoid the motor run out of idea control range, and the abrupt change of load would cause the control out of lock. SOFT START & OVER CURRENT PROTECTION The most difficult part of sensorless control is start-up stage. The rotors position are unknown, the disorder of BEMF signal would cause large current running through loads and MOS drivers. It is not health to MOS drivers and motor. To avoid the situation, it is better to clamp or control the current profile. PT2431 use an external capacitor at “SOFT” pin to perform a slope for clamping the current when motor is starting to rotate. It is possible to select a suitable capacitor for soft-start current profile. After the motor succeeded to start, PT2431 use an external precision resistor at “RF” pin to sense the phase current and shutdown the driver stage when the phase current exceed expected value. PRE 1.2 5 October 2013 PT2431 Figure 2, waveforms of phase voltage & phase current during start period. PWM INPUT AND SOFT-SWITCHING PT2431 can change motor rotation speed through external PWM control. The motor will run at full speed when the PWM signal is high or floating. The minimum PWM duty cycle will depend on the motor load. In general, the faster the motor can run, the minimum PWM duty cycle can reach. PT2431 allows a range from 20KHz to 50KHz PWM frequency. To lower the peak current of commutation and reduce audible noise, there is a soft-switching function cooperate with PWM signal. LOCK PROTECTION When the sensorless control can not determine any rotation BEMF, the control algorithm doubts the motor is locked by some reasons, and will force the motor into “lock protect” mode. After several seconds, the control algorithm will try to restart the motor. If the motor is released, it will keep running. But, if the motor is still locked, the control algorithm will back to lock mode and repeat to restart after several seconds. When control algorithm goes into “lock protection” mode, the “RD” pin will indicate a “HIGH” level. Figure 3, phase voltage of “lock protection” mode. OVER TEMPERATURE PROTECTION PT2431 embedded a thermal sense circuit. When chip junction temperature is heating over than 150℃. PT2431 will shutdown output driver stage; and when the chip temperature is lower than 120℃, PT2431 will let motor to work again. Figure 4, over temperature protection hysteresis FG OUTPUT To monitor the motor rotation speed, PT2431 provide an FG signal. The relation between FG frequency and RPM is: RPM = FG x 120 / POLE, where “POLE” is the number of motor’s poles. FORWARD AND REVERSE SETTING PT2431 provides motor rotating direction with forward or reverse status though FR pin setting. Make sure that the IC is turned off before change status. Keep FR pin floating or connect ground, the motor would rotate with UVW direction and reverse direction when FR pin is connected to high. PRE 1.2 6 October 2013 PT2431 ABSOLUTE MAXIMUM RATINGS Parameter VDD supply voltage Output pin current Input pin withstand voltage FG, RD pin withstand voltage FG, RD pin current Power dissipation 1 Power dissipation 2 Operating temperature Storage temperature Symbol VDD max Iout max Vin max Vd max Id max Pd max1 Pd max 2 Topr Tstg Conditions No break down UO, VO, WO pins PWM, OSC, SOFT, TEST, FR FG, RD pins FG, RD pins Independent IC Mounted on evaluation board(Note ) - Max. 15.6 0.8 6 15.6 5 0.3 1.2 -40 ~ +85 -40 ~ +150 Unit V A V V mA W W C C Note: Mounted on the designated board with heat-sink area. ELECTRICAL CHARACTERISTICS ( VDD=12V, T=25C unless otherwise specified ) Parameter Symbol Conditions VDD supply voltage VDD - Power supply current 1 IDD 1 PWM pin = VREG, without load Min Typ Max Unit 5.0 - 12 V 3.0 5.0 mA 0.6 1.0 0.6 1.0 -2.5 A OSC pin charge current Iosc 1 OSC pin OSC pin discharge current Iosc 2 OSC pin - 2.5 - VREG pin voltage Vreg No load 4.2 4.5 4.8 V Vreg*0.8 - - V Vreg*0.2 V 50 KHz Power PMOS Rdson RPdson Io = 500mA Power NMOS Rdson RNdson Io = 500mA PWM high input voltage Vpwmh PWM voltage rising PWM low input voltage Vpwml PWM voltage falling PWM input frequency Fpwm PWM pull-up resistance Rpwm - FG output low voltage Vfgl When Io = 0.5mA RD output low voltage Vrdl When Io = 0.5mA Current limiter voltage Vrf RF = 0.5 Lock re-start time 20 Trest External 2200pF capacitor Lock protection time Tlock External 2200pF capacitor Thermal shutdown Tshdn Temperature increasing, design target Trel Temperature decreasing, design target Thermal release PRE 1.2 7 A - 75 - K 0.1 0.2 V 0.1 0.2 V 0.45 0.5 0.55 V - 1 - S 10 150 120 S C C October 2013 PT2431 BILL OF MATERIALS FOR APPLICATION CIRCUIT U1 C1 1 TEST FR 16 2 VREG OSC 15 3 FG GND 14 4 RD SOFT 13 C4 R2 R3 5 ~ 12V PT2431 C3 5 COM PWM 12 6 VDD SGND 11 7 UO RF 10 8 WO VO 9 R1 C2 D1 Connect to BLDC motor Heat sink pad Part Value Unit C1 2.2 F Description Capacitor of 4.5V regulator. C2 1.0 F Bypass capacitor of supply voltage. C3 1.0 F Soft start profile capacitor. (Note 1) C4 2.2n F Capacitor of RC oscillator. (Note 2) R1 0.5 Over current detection resister. (Note 3) R2/R3 100K Pull high resisters. D1 15 V Zener diode. U1 PT2431 U1 Motor driver chip. Notes: 1 & 2. The value might be adjusted for best when different motor is applied. 3. Reduce the R1 value to 0.3when the operation current large than 600mA. PRE 1.2 8 October 2013 PT2431 PACKAGE INFORMATION 16 Pins, HTSSOP (Shrink Small Outline Package with Heat Sink) Symbol Min. Nom. Max. A - - 1.20 A1 0.00 - 0.15 A2 0.80 1.00 1.05 b 0.19 - 0.30 D 4.90 5.00 5.10 D1 1.70 - - E 6.4 E1 4.30 4.40 4.50 E2 1.50 - - 0.65BSC e L 0.45 0.60 1.00REF L1 θ 0.75 0º - 8º Notes: 1. Refer to JEDEC MO-153 AB/ABT 2. Unit: mm PRE 1.2 9 October 2013 PT2431 IMPORTANT NOTICE Princeton Technology Corporation (PTC) reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and to discontinue any product without notice at any time. PTC cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a PTC product. No circuit patent licenses are implied. Princeton Technology Corp. 2F, 233-1, Baociao Road, Sindian Dist., New Taipei City 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw PRE 1.2 10 October 2013