® RT8720B Single-Phase Full-Wave Fan Motor Driver General Description Features The RT8720B is a single-phase driver IC for fan motors. Rotation speed is controlled by supply voltage modulation. In the supply voltage control application, the fan speed slope is adjustable by the external voltage input. The RT8720B provides several protection features including lock protection, thermal shutdown, over-current protection and under-voltage protection. In thermal shutdown mode, the supply current is less than 100μA. The rotation frequency is generated by FG output. Low Supply Current Adjustable Voltage Control Fan Speed Supply Voltage Speed Control Smart Force Start-up Function Built-in Lock Protection Built-in Thermal Shutdown Built-in Over-Current Protection Built-in Frequency Generator with FG Output Signal Include Hall Bias Circuit RoHS Compliant and Halogen Free Ordering Information RT8720B Applications Package Type QU : UDFN-8SL 2x2 (U-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Single-Phase Fan Motor for Notebook or PC Pin Configurations Note : (TOP VIEW) Richtek products are : RoHS compliant and compatible with the current require- Suitable for use in SnPb or Pb-free soldering processes. OUT2 1 H+ 2 HB 3 H- 4 ments of IPC/JEDEC J-STD-020. 8 GND 9 7 6 5 OUT1 VCC SET FG UDFN-8SL 2x2 Marking Information 1V : Product Code 1VW W : Date Code Simplified Application Circuit Optional Supply Voltage RT8720B OUT2 D1 VCC D2 Pull-High Voltage C1 RFG Single-Phase Brushless DC Motor OUT1 H+ FG HB Floating DS8720B-01 March 2014 Hall SET GND Copyright © 2014 Richtek Technology Corporation. All rights reserved. M H- is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8720B Function Pin Description Pin No. Pin Name Pin Function 1 OUT2 Output of H-Bridge for DC Motor. 2 H+ Positive Hall Input. 3 HB Hall Bias Voltage Output. 4 H Negative Hall Input. 5 FG Output for Rotation Speed. This is an open drain output. 6 SET Speed Slop Setting. 7 VCC Power Supply Input. 8 OUT1 Output of H-Bridge for DC Motor. 9 (Exposed Pad) GND Power Ground. The Exposed Pad should be soldered to a large PCB and connected to GND for maximum thermal dissipation. Function Block Diagram OUT2 VCC H+ OUT1 + - - + Duty Gen. Control H- SET + + - - OSC GND Lock Protection TSD OCP FG + Hall Bias - HB Operation Motor Lock Protection and Automatic Restart When the motor is locked, the RT8720B will try to restart the motor within 0.5 seconds typically (tON). If the motor fails to re-start, the driver will disable the output regardless of the PWM duty ratio to prevent the motor coil from burnout. After the lock off-time of 5 seconds in typical (tOFF), the driver will try to restart the motor again. If the motor is still locked, then the iteration of the lock detection and restart will be repeated until the lock condition is released or the PWM input is pulled low. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 H+ H- OUT1 OUT2 FG tON tOFF tON tOFF is a registered trademark of Richtek Technology Corporation. DS8720B-01 March 2014 RT8720B Absolute Maximum Ratings (Note 1) Supply Input Voltage, VCC (<300ns) ----------------------------------------------------------------------------- −0.3V to 10V Hall Input Voltage Range, H+, H− --------------------------------------------------------------------------------- −0.3V to 6V SET Input Voltage, SET --------------------------------------------------------------------------------------------- −0.3V to 6V Output Voltage, OUT1, OUT2, FG --------------------------------------------------------------------------------- −0.3V to 7V Maximum Output Current, OUT1, OUT2 ------------------------------------------------------------------------- 1A Power Dissipation, PD @ TA = 25°C UDFN-8SL 2x2 --------------------------------------------------------------------------------------------------------- 2.78W Package Thermal Resistance (Note 2) UDFN-8SL 2x2, θJA --------------------------------------------------------------------------------------------------- 35.9°C/W Junction Temperature ------------------------------------------------------------------------------------------------- 150°C Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260°C Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C ESD Susceptibility (Note 3) HBM (Human Body Model) ------------------------------------------------------------------------------------------ 4kV Recommended Operating Conditions (Note 4) Supply Input Voltage, VCC ------------------------------------------------------------------------------------------ 1.8V to 5.5V Hall Input Voltage, H+, H− ------------------------------------------------------------------------------------------- 0.4V to (VCC − 1.1V) SET Input Voltage, SET --------------------------------------------------------------------------------------------- 0.1V to VHB Junction Temperature Range ---------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ---------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VCC = 5V, TA = 25°C, Unless Otherwise specification) Parameter Min Typ Max Unit I CC1 Rotation Mode and Lock Protection Mode -- 3.5 5 mA High-Level ISET_H VSET = VCC -- -- 1 Low-Lev el ISET_L VSET = 0 -- -- 1 Input-Output Gain GIO VOUT / H+ H- (Ratio) 42 44.6 47 dB Output Voltage VO IO = 250mA, Upper and Lower Total -- 0.2 0.4 V FG Pin Low Voltage V FG IFG = 5mA -- 0.1 0.2 V FG Pin Leak Current I FG VFG = 5V -- -- 1 A Input Offset Voltage V HOFS -- -- 6 mV Input Hysteresis Voltage V Hys 5 10 15 mV Lock Detection On-Time t ON 0.35 0.5 0.65 s Lock Detection Off-Time t OFF 3.5 5 6.5 s -- 160 -- C Operating Current SET Input Leakage Symbol Test Conditions Thermal Shutdown Threshold Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8720B-01 March 2014 A is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8720B Parameter Symbol Test Conditions Thermal Shutdown Hysteresis Hall Bias Voltage VHB Supply Voltage Threshold VCC_TH IHB = 5mA Min Typ Max Unit -- 30 -- C 1.26 1.3 1.34 V 3 3.5 4 V Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability. Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS8720B-01 March 2014 RT8720B Typical Application Circuit Optional Supply Voltage RT8720B 7 VCC OUT2 1 D1 C1 D2 RFG Pull-High Voltage Single-Phase Brushless DC Motor 5 FG 6 SET Floating 9 (Exposed Pad) GND M OUT1 8 HB 3 H+ 2 4 H- Hall Figure 1. Fan Speed Controlled by Supply Voltage, it's known as “VCC Mode”. Optional Supply Voltage RT8720B 7 VCC OUT2 1 D1 C1 D2 Pull-High Voltage RFG Single-Phase Brushless DC Motor 5 FG HB 6 SET R2 OUT1 8 HB 3 R1 R1 + R2 = 100k M H+ 2 4 H- Hall GND 9 (Exposed Pad) Figure 2. Fan Speed Controlled by Supply Voltage with Slop Setting, it's known as “ADJ Mode”. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8720B-01 March 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8720B Application Information Frequency Generator (FG) Over-Current Protection The FG pin is an open drain output. A pull-up resistor (1kΩ to 10kΩ) is recommended to be connected from this pin to a high level voltage (<5.5V) for frequency generator function. The RT8720B includes an Over-Current Protection (OCP) feature to prevent the large supply current form supply voltage to output. When the over-current occurs, the circuit will disable the output and the motor rotor will stop. After a time duration (TOFF, typical 5s), the IC will automatically try to restart the motor. If the supply current is still larger, the output will be shut down immediately. Thermal Shutdown The RT8720B provides a thermal shutdown function to prevent overheating due to excessive power dissipation. The function shuts down the switching operation when the junction temperature exceeds 160°C. Once the junction temperature cools down by around 30°C, the main converter will automatically resume switching. To maintain continuous operation, the junction temperature should be kept below 130°C. Speed Control The motor speed can be controlled by the supply voltage. When the SET pin input is fixed at a voltage level, the motor speed will be controlled by the supply voltage. In “ADJ Mode” application, the RT8720B provides the function to adjust the motor speed slope of the supply voltage region. Input the SET pin voltage will modulating slow down the speed at the lower supply voltage by modulated the output switching duty, and the switching output frequency is equal to internal clock, fINT_CLK. When the SET pin input is floating, the motor will rotate with full speed, as in VCC mode. Force Start-Up Control The motor speed is controlled by the external SET pin. In order to successfully start the motor with lower output duty, a start-up mechanism is applied to check if output duty from the external SET voltage can drive the motor to rotate in a period (0.4 x tON, typ. 0.2s). If it cannot drive the motor to rotate because of its low output duty, an internal PWM signal with higher duty will be adopted to drive the motor. The internal PWM duty = 100%. SET = HB … Speed (rpm) SET Floating SET = 0.1V 1.8V VCC 4.6V 5V Figure 3. Fan Speed Controlled by Supply Voltage Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS8720B-01 March 2014 RT8720B VCC_TH = 3.5V VCC FG OUT Lower Duty 50% Duty 0.2s Max. ~0.3s Lower Duty Figure 4. Forced Start-Up when VCC > VCC_TH VCC_TH = 3.5V VCC FG OUT Lower Duty Output = VCC 0.2s Max. ~0.3s Lower Duty Figure 5. Forced Start-Up-1 when VCC ≤ VCC_TH FG Output when Motor is in the Lock State VCC Hall_Comp FG Lock Detection On-Time Lock Detection Off-Time 0.5s 5s Figure 6. FG Output when Motor is in the Lock State VCC Hall_Comp FG Lock Detection On-Time Lock Detection Off-Time 0.5s 5s Figure 7. FG Output when Motor is in the Lock State-1 Truth Table H+ H- OUT1 OUT2 FG H L H L L (Output : ON) L H L H Z (Output : OFF) H L L L Z (Output : OFF) L H L L Z (Output : OFF) Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8720B-01 March 2014 Mode Operation Mode Lock Mode is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 Thermal Considerations For continuous operation, do not exceed absolute maximum junction temperature. The maximum power dissipation depends on the thermal resistance of the IC package, PCB layout, rate of surrounding airflow, and difference between junction and ambient temperature. The maximum power dissipation can be calculated by the following formula : PD(MAX) = (TJ(MAX) − TA) / θJA where TJ(MAX) is the maximum junction temperature, TA is the ambient temperature, and θJA is the junction to ambient thermal resistance. For recommended operating condition specifications, the maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. For UDFN-8SL 2x2 package, the thermal resistance, θJA, is 35.9°C/W on a standard JEDEC 51-7 four-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : Maximum Power Dissipation (W)1 RT8720B 3.0 Four-Layer PCB 2.5 2.0 1.5 1.0 0.5 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 8. Derating Curve of Maximum Power Dissipation PD(MAX) = (125°C − 25°C) / (35.9°C/W) = 2.78W for UDFN-8SL 2x2 package The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 8 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS8720B-01 March 2014 RT8720B Outline Dimension 2 1 2 1 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min. Max. Min. Max. A 0.500 0.600 0.020 0.024 A1 0.000 0.050 0.000 0.002 A3 0.100 0.175 0.004 0.007 b 0.200 0.300 0.008 0.012 D 1.900 2.100 0.075 0.083 D2 1.650 1.750 0.065 0.069 E 1.900 2.100 0.075 0.083 E2 0.850 0.950 0.033 0.037 0.500 e L 0.250 0.020 0.350 0.010 0.014 U-Type 8SL DFN 2x2 Package Richtek Technology Corporation 14F, No. 8, Tai Yuen 1st Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries. DS8720B-01 March 2014 www.richtek.com 9