Ordering number : EN8337 Monolithic Digital IC DC Fan Motor Speed Control IC LB8502M Overview The LB8502M easily and simply implements feedback-based motor speed control in combination with a general-purpose motor driver IC. Compared to open-loop control, the use of speed feedback allows the motor speed precision to be improved and the speed fluctuations due to load variations to be minimized. • LB8502M: For use as a driver IC that increases the motor speed as the command voltage rises (three-phase systems) Features • Achieves linear speed control Applications can set the slope of the change in motor speed with change in the input duty. • Minimized speed fluctuations in the presence of line or load variations • Allows a minimum speed to be set • Soft start function • Settings using external capacitors and resistors (to support easier mass production of end products) • Supports both PWM duty and analog voltage control inputs Specifications Absolute Maximum Ratings at Ta = 25°C Parameter Symbol Conditions Supply voltage VCC max VCC pin Output current IO max E0 pin Allowable power dissipation Pd max When mounted on a circuit board *1 Ratings Unit 18 V 3 mA 0.87 W Operating temperature Topr -30 to +95 °C Storage temperature Tstg -55 to +150 °C *1 Specified circuit board : 114.3 × 76.1 × 1.6mm3, glass epoxy. 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To verify symptoms and states that cannot be evaluated in an independent device, the customer should always evaluate and test devices mounted in the customer' s products or equipment. 32807 TI PC B8-8968 No.8337-1/11 LB8502M Allowable Operating Ranges at Ta = 25°C Parameter Symbol Conditions Ratings Unit Supply voltage range 1 VCC1 VCC pin 7.5 to 17 Supply voltage range 2 VCC2 VCC pin, with VCC shorted to 6VREG 5.5 to 6.5 Output current IO V 2.5 mA IREG -5 mA CTL pin voltage VCTL 0 to VREG V LIM pin voltage VLIM 0 to VREG V 6V constant voltage output E0 pin V current Electrical Characteristics at Ta = 25°C, VCC = 12V Parameter Symbol Ratings Conditions min Supply current Unit typ ICC max 4.5 6.5 mA 6V constant voltage output (VREG pin) Output voltage VREG 6.0 6.2 V Line regulation ∆VREG1 VCC = 8 to 17V 5.8 40 100 mV Load regulation ∆VREG2 IO = 0 to 5mA 50 100 Temperature coefficient ∆VREG3 Design target* 0 mV mV/°C Integrating Amplifier Block Common-mode input voltage VICM 0 VREG- 2.0 V 1.0 V range High-level output voltage VOH IEO = -0.2mA Low-level output voltage VOL IEO = 0.2mA VREG - 1.2 V VREG - 0.8 0.8 FGIN pin High-level input voltage VFGH 3.0 VREG V Low-level input voltage VFGL 0 1.5 V Input open voltage VFGO VREG - 0.5 VREG V Hysteresis VFGS High-level input current IFGH VFGIN = 6VREG Low-level input current IFGL VFGIN = 0V 0.2 0.25 0.4 V -10 0 10 µA -140 -110 µA RC pin High-level output voltage VOH(RC) 3.2 3.45 3.7 V Low-level output voltage VOL(RC) 0.8 0.95 1.05 V Clamp voltage VCLP(RC) 1.6 V CTL pin High-level input voltage VCTH 2.0 VREG V Low-level input voltage VCTL 0 1.0 V Input open voltage VCTO VREG - 0.5 VREG V High-level input current ICTH VFGIN = 6VREG 10 µA Low-level input current ICTL VFGIN = 0V -10 0 -140 -110 µA C pin High-level input voltage VOH(C) 3.8 4.0 4.2 V Low-level input voltage VOL(C) 0.05 0.1 0.2 V IB(LIM) -1 0 µA VILIM 0 VREG- 2.0 V LIM pin Input bias current Common-mode input voltage range *The design specification items are design guarantees and are not measured. No.8337-2/11 LB8502M Package Dimensions unit : mm (typ) 3086B 5 6.4 1 0.15 0.1 (1.5) 1.7max 4.4 6 0.63 5.0 10 0.35 (0.5) 1.0 SANYO : MFP10S(225mil) Pin Assignment EO EI GND LIM FGIN 10 9 8 7 6 LB8502M 1 2 3 4 5 RC VREG VCC C CTL Top view Pin Functions Pin Pin No. Description 1 RC One-shot multivibrator pulse width setting. Connect a resistor between this pin and VREG, and a capacitor between this 2 VREG 3 VCC 4 C pin and ground. 6V regulator output. Connect a capacitor between this pin and ground for stabilization. Power supply. Connect a capacitor between this pin and ground for stabilization. Duty pulse signal smoothing and soft start time setting. Connect a capacitor between this pin and VREG. 5 CTL Duty pulse signal input. The speed is controlled by the duty of this pulse signal. 6 FGIN FG pulse input 7 LIM 8 GND 9 EI 10 EO Minimum speed setting. Normally, the 6V regulator level is resistor divided to set this pin's input level. Ground pin One-shot multivibrator output and integrating amplifier input. A capacitor must be connected between this pin and EO for this integration. Integrating amplifier output. No.8337-3/11 LB8502M Block Diagrams and Application Examples When the FG signal is output to another circuit board Driver IC 12V VCC LB8502M VREG 6VREG C4 6VREG FGIN C5 EDGE R3 FG FGIN One-shot multivibrator RC EI C3 R1 C2 LIM EO VCTL R2 VREF C C1 CTL signal 180kΩ CTL CTL GND No.8337-4/11 LB8502M Speed Control Diagrams The slope is determined by the external constant connected to the RC pin. (RPM) For a smaller RC time constant For a larger RC time constant Speed Minimum speed Determined by the LIM pin voltage Low← CTL pin (PWM DUTY) Low ← EO pin voltage (V) 0% Set minimum speed →High → High Variable speed Low on duty (%) (V) Full speed High on duty CTL pin 6VREG EO voltage EO pin LIM voltage 0V Startup Timing (soft start) VCC pin CTL pin EO pin Stop Stop Full speed Soft start The slope can be changed with the capacitor connected to the C pin (A larger capacitor increases the slope.) Full speed No.8337-5/11 LB8502M Supplementary Operational Descriptions The LB8502M accepts a duty pulse input and an FG signal from the driver IC, and generates the driver IC control voltage so that the FG period (motor speed) becomes proportional to the control voltage. Driver IC LB8502M FGIN CTL signal FG CTL Closed feedback loop EO VTH As shown in the figure below, the LB8502M generates a pulse signal from edges on the FG signal and then generates a pulse width waveform determined by the RC time constant in a one-shot multivibrator. The LB8502M then integrates that pulse waveform to create the output driver IC control voltage (a DC voltage). FG EDGE pulse Slope due to the RC time constant RC pin One-shot multivibrator TRC(s) = 0.85RC It is also possible to change the slope of the VCTL/speed relationship as shown in the speed control diagram in the previous section by changing the pulse width with the RC time constant. Note, however, that since pulses determined by this RC time constant are used, variation in the RC components will appear as speed control errors. No.8337-6/11 LB8502M Pin Setting Procedures (Provided for reference purposes) 1. RC pin The one-shot multivibrator pulse width can be calculated with the following equation. TRC(s) ≈ 0.85 × R × C..................................................... Equation 1 If the FG signal frequency at full motor speed is fFG (Hz) and the control duty desired for full speed is DUTY (for example: 50% → 0.5), the values of the resistor and capacitor connected to the RC pin can be determined from the following equation. R × C = DUTY/(3 × 0.85 × fFG) ..................................... Equation 2 Note that if "rpm" is the full motor speed, since one revolution will be two FG periods, the following equation gives the FG frequency, fFG (Hz). fFG(Hz) = 2rpm/60 ......................................................... Equation 3 For reference purposes, the following table lists the RC pin external component values determined from equations 2 and 3 when the control duty at full speed will be 80% for a variety of full motor speed values. Note that the capacitor value must be in the range 0.01µF to 0.015µF due to the RC pin discharge capacity of the IC. Full motor speed R×C R C 10000rpm 0.94 × 10-3 63kΩ 0.015µF 8000rpm 1.18 × 10-3 78kΩ 0.015µF 6000rpm 1.57 × 10-3 105kΩ 0.015µF 4000rpm 2.39 × 10-3 157kΩ 0.015µF 2000rpm 4.68 × 10-3 312kΩ 0.015µF The table below lists the RC pin external component values when the control duty for full motor speed is changed for a full motor speed of 10,000rpm. Duty at full speed R×C R C 80% (= 0.8) 0.94 × 10-3 94kΩ 0.01µF 60% (= 0.6) 0.71 × 10-3 71kΩ 0.01µF 40% (= 0.4) 0.47 × 10-3 47kΩ 0.01µF Also, note that the FG frequency can be determined from the following equation for various control duty input states. fFG = DUTY/(3 × 0.85 × RC).......................................... Equation 4 2. C Pin Since a capacitor that can smooth the pin voltage is connected to the C pin, if the CTL pin input signal frequency is f (Hz), then the capacitor must meet the following condition. (Here, R is the IC internal resistance of 180kΩ (typical).) 1/f = t < RC Note that the larger the capacitor, the longer the soft start time will be and its response to changes in the input signal will be slower. CTL pin VREF circuit CTL circuit 180kΩ C pin A capacitor that can smooth the pin voltage is connected here. 1/f = t < CR No.8337-7/11 LB8502M 3. LIM pin The LIM pin external component values can be derived as follows for the case where a motor whose maximum speed of 10,000rpm is to be achieved with an 80% duty, and a minimum speed of 3000rpm is to be set. Ra = minimum speed/full speed = 3000/10,000 = 0.3 Full-speed duty × Ra = 0.8 × 0.3 = 0.24 LIM pin voltage = 4 × 0.24 ≈ 1V From the above, the required LIM pin voltage is about 1V. To generate this 1V level by resistor dividing the 6 V regulator level, the resistor ratio will be 5: 1, and the resistors connected to the LIM pin will have the following values. Between 6VREG and LIM pin : 50kΩ Between LIM pin and GND : 10kΩ (RPM) 12000 10000 8000 6000 4000 Minimum speed 2000 0 0% 0V 20% 24% 1V 40% 60% CTL Duty (PWM duty) LIM pin voltage 80% 100% 4V No.8337-8/11 LB8502M Application Example 2 [Fixed Speed + Soft Start] With this circuit, the motor speed remains constant even if there are fluctuations in the supply voltage or static voltage. (RPM) Motor full speed 0% 20% 40% 60% 80% CTL signal (PWM duty) C pin voltage 0V 100% 4V Driver IC 12V VCC LB8502M VREG 6VREG FGIN EDGE One-shot multivibrator RC FG FGIN EI LIM EO VCTL VREF C 180kΩ CTL CTL signal CTL GND Input a fixed-duty signal to the CTL pin signal input as an input signal for which soft start is enabled at startup. Alternatively, apply a constant voltage to the C pin. (In this case, the CTL pin must be left open.) No.8337-9/11 LB8502M Application Example 3 [Analog Input] DC voltage speed control (RPM) Motor full speed Set minimum speed 0 0V 0.8V 1.6V 2.4V 3.2V 4.0V C pin voltage Driver IC 12V VCC VREG LB8502M 6VREG FGIN EDGE FG FGIN One-shot multivibrator RC EI LIM VCTL signal EO VCTL VREF C 180kΩ CTL CTL GND No.8337-10/11 LB8502M SANYO Semiconductor Co.,Ltd. assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all SANYO Semiconductor Co.,Ltd. products described or contained herein. SANYO Semiconductor Co.,Ltd. strives to supply high-quality high-reliability products, however, any and all semiconductor products fail or malfunction with some probability. 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SANYO Semiconductor Co.,Ltd. shall not be liable for any claim or suits with regard to a third party's intellctual property rights which has resulted from the use of the technical information and products mentioned above. This catalog provides information as of March, 2007. Specifications and information herein are subject to change without notice. PS No.8337-11/11