® RT8725 Single-Phase BLDC Fan Driver IC General Description Features The RT8725 is a single-phase driver IC for fan motors. Rotation speed is controlled by PWM input signal. The RT8725 provides several protection features including standby mode, thermal shutdown, lock protection, overcurrent protection and under-voltage protection. The Builtin smart force start-up function overcomes and avoids wrong status when electrical noise occurs during startup. In the standby and thermal shutdown mode, the supply current is less than 100μA. The rotation frequency is generated by FG output. z Low Supply Current z Smart Force Start-up Function PWM Supply Voltage Control Fan Speed Built-in Motor Lock Protection and Automatic Restart Built-in Thermal Shutdown Built-in Over-Current Protection Built-in Frequency Generator with FG Output Signal RoHS Compliant and Halogen Free z z z z z z Applications Ordering Information z Single Phase Fan Motor for Notebook or PC RT8725 Package Type QU : UDFN-8L 2x3 (U-Type) Pin Configurations Lead Plating System G : Green (Halogen Free and Pb Free) (TOP VIEW) OUT2 VCC H+ H- Richtek products are : ` RoHS compliant and compatible with the current require- 1 2 3 4 GND Note : 9 8 7 6 5 GND OUT1 PWM FG ments of IPC/JEDEC J-STD-020. ` UDFN-8L 2x3 Suitable for use in SnPb or Pb-free soldering processes. Marking Information 0A : Product Code 0AW W : Date Code Simplified Application Circuit Supply Voltage D1 Optional D2 RT8725 VCC OUT2 C1 Hall Single-Phase Brushless DC Motor H+ H- M OUT1 FG RFG Pull-High Voltage GND PWM Control Signal Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8725-02 October 2013 PWM is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8725 Function Pin Description Pin No. Pin Name Pin Function 1 OUT2 H-Bridge Output for DC Motor. 2 VCC Supply Voltage Input. 3 H+ Positive Hall Input. 4 H− Negative Hall Input. 5 FG Frequency Generator Output for Rotation Speed. This is an open-drain output. 6 PWM PWM Signal Input. 7 OUT1 H-Bridge Output for DC Motor. Power Ground. The Exposed Pad should be soldered to a large PCB and connected to GND for maximum thermal dissipation. 8, 9 (Exposed Pad) GND Function Block Diagram OUT2 VCC OUT1 VCC - H+ + Control PWM + H- GND - OSC Lock Protection TSD OCP FG + - Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8725-02 October 2013 RT8725 Operation Operation Mode Motor Lock Protection and Automatic Restart The operation mode of the RT8725 is determined by the external PWM input. During power up, if the PWM input stays at a low-level voltage, the IC will enter low-power standby mode. If the PWM input is kept at a high-level voltage or with a periodic pulse signal, the IC will operate in normal mode. On the other hand, during normal mode operation, when the PWM input is set to a low-level voltage for more than 1ms (typ.), the IC will enter low-power standby mode. In the standby mode, the supply current can be reduced to 100μA. Once the PWM input is pulled high again, the IC will be activated immediately for normal operation. When the motor is locked, the RT8725 will try to re-start 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. H+ HtSD = 1ms PWM OUT1 Mode Normal Mode Standby Mode Normal Mode OUT2 FG ICC tON Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8725-02 October 2013 tOFF tON tOFF is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8725 Absolute Maximum Ratings z z z z z z z z z z (Note 1) Supply Input Voltage, VCC (<300ns) ----------------------------------------------------------------------------- −0.3V to 10V Hall Input Voltage Range, H+, H− --------------------------------------------------------------------------------- −0.3V to 6V PWM Input Voltage, PWM ------------------------------------------------------------------------------------------ −0.3V to 6V Output Voltage, OUT1, OUT2, FG --------------------------------------------------------------------------------- −0.3V to 6V Maximum Output Current, OUT1, OUT2 ------------------------------------------------------------------------- 1A Power Dissipation, PD @ TA = 25°C, θJA = 150°C UDFN-8L 2x3 (One-Layer) ------------------------------------------------------------------------------------------- 0.5W UDFN-8L 2x3 (Two-Layer) ------------------------------------------------------------------------------------------- 2.49W Package Thermal Resistance (Note 2) UDFN-8L 2x3 (One-Layer), θJA ------------------------------------------------------------------------------------- 245.8°C/W UDFN-8L 2x3 (One-Layer), θJC ------------------------------------------------------------------------------------- 8.3°C/W UDFN-8L 2x3 (Two-Layer), θJA -------------------------------------------------------------------------------------- 50.2°C/W UDFN-8L 2x3 (Two-Layer), θJC ------------------------------------------------------------------------------------- 8.3°C/W Junction Temperature ------------------------------------------------------------------------------------------------- 150°C Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260°C Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C Recommended Operating Conditions z z z z z (Note 4) Supply Input Voltage, VCC ------------------------------------------------------------------------------------------ 1.8V to 5.5V Hall Input Voltage, H+, H− ------------------------------------------------------------------------------------------- 0.4V to (VCC − 1.1V) PWM Input Voltage, PWM ------------------------------------------------------------------------------------------ 0V to VCC Junction Temperature Range ---------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range ---------------------------------------------------------------------------------------- −40°C to 105°C Electrical Characteristics (VCC = 5V, TA = 25°C, Unless Otherwise specification) Parameter Symbol Test Conditions Min Typ Max Unit 5 mA Operating Current ICC1 Rotation Mode and Lock Protection Mode -- 3.5 Standby Current ICC2 Standby Mode (PWM = 0) -- 100 200 μA V PWM Input Voltage High-Level V PWM_H 1.8 -- V CC + 0.5 Low-Level V PWM_L 0 -- 0.7 FPWM 2 -- 50 kHz μA PWM Input Frequency High-Level IPWM_H -- 0 5 Low-Level IPWM_L −30 −10 0 Supply Voltage Threshold V CC_TH 3 3.5 4 V Input-Output Gain GIO VOUT / H+ − H- 42 44.6 47 dB Output Voltage VO IO = 250mA -- 0.2 0.4 V PWM Input Leakage Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS8725-02 October 2013 RT8725 Parameter Symbol Test Conditions Min Typ Max Unit FG Low Voltage VFG IFG = 5mA -- 0.1 0.2 V FG Leak Current I FG VFG = 5V -- -- 1 μA Input Offset Voltage VHOFS -- -- ±6 mV Input Hysteresis Voltage VHys ±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 Thermal Shutdown Threshold -- 160 -- °C Thermal Shutdown Hysteresis -- 30 -- °C Quick Start Standby Detection Time t SD 0.7 1 1.3 ms Quick Start Enable Time t QS -- 30 -- μs 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 one/two-layer test board per JEDEC 51-3. θJC is measured at the exposed pad of the package. Note 3. Devices are ESD sensitive. Handling precaution is recommended. Note 4. The device is not guaranteed to function outside its operating conditions. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8725-02 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT8725 Typical Application Circuit Supply Voltage RT8725 2 VCC OUT2 1 Optional D1 D2 C1 Hall 3 H+ 4 H- Single-Phase Brushless DC Motor OUT1 7 FG PWM Control Signal Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 6 PWM M GND 5 RFG Pull-High Voltage 8, 9 (Exposed Pad) is a registered trademark of Richtek Technology Corporation. DS8725-02 October 2013 RT8725 Application Information Quick Start Function PWM Speed Control If the PWM is pulled low for a delay time, tSD, the RT8725 The motor speed can be controlled by the external signal at PWM pin and the supply input voltage. When a PWM signal is provided to the PWM pin, the driver output will follow the duty ratio of the PWM input signal. The switching frequency of the driver is dependent on the PWM input frequency. Therefore, the motor speed is controlled by the PWM signal. The available PWM input frequency range is from 2kHz to 50kHz. When the PWM input is fixed at a high-level voltage (>1.8V) or floating, the motor will rotate with full speed. When the PWM input is fixed at a lowlevel voltage (<0.7V), the motor will decelerate to stop. In standby mode, the supply current can be reduced to 100μA. will enter standby mode. Once a PWM signal is detected, the RT8725 will provide outputs after a delay time, tQS. Standby PWM FG OUT tSD Figure 1 Frequency Generator (FG) 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. Standby PWM FG Thermal Shutdown OUT The RT8725 provides a thermal shutdown function to prevent overheating due to excessive power dissipation. The function 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. tQS Figure 2 Truth Table H+ H- H L L H H L L H H L L H - - PWM H L L OUT1 OUT2 FG H L L (Output : ON) L H Z (Output : OFF) L L L (Output : ON) L L Z (Output : OFF) L L Z (Output : OFF) L L Z (Output : OFF) L L Z (Output : OFF) Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8725-02 October 2013 Mode Operation Mode Lock Mode Standby Mode is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT8725 Over-Current Protection Force Start-Up Control The RT8725 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. The motor speed is controlled by the external PMW signal. In order to successfully start the motor with lower PWM duty, a start-up mechanism is applied to check if output duty from the external PWM signal 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 duty, an internal PWM signal with higher duty will be adopted to drive the motor. The internal PWM duty varies according to input voltage VCC (VCC ≥ 3.5V, duty = 50%; VCC < 3.5V, duty = 100%). VCC_TH = 3.5V VCC FG OUT External PWM (Lower Duty) 50% Duty External PWM (Lower Duty) 0.4 x tON (typ. 0.2s) Max. ~0.6 x tON (typ. 0.3s) Figure 3. Forced Start-Up when VCC > VCC_TH VCC_TH = 3.5V VCC FG OUT External PWM (Lower Duty) Output = VCC 0.4 x tON (typ. 0.2s) Max. ~0.6 x tON (typ. 0.3s) External PWM (Lower Duty) Figure 4. 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 0.5s Lock Detection Off-Time 5s Figure 5. FG Output when Motor is in the Lock State Copyright © 2013 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 is a registered trademark of Richtek Technology Corporation. DS8725-02 October 2013 RT8725 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-1 Thermal Considerations 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-8L 2x3 package, the thermal resistance, θJA, is 245.8°C/W on a standard JEDEC 51-3 one-layer thermal test board. For UDFN-8L 2x3 package, the thermal resistance, θJA, is 50.2°C/W on a standard JEDEC 51-3 two-layer thermal test board. The maximum power dissipation at TA = 25°C can be calculated by the following formula : 2.5 Maximum Power Dissipation (W)1 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 : 2.0 1.5 Two-Layer PCB 1.0 One-Layer PCB 0.5 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 7. Derating Curve of Maximum Power Dissipation PD(MAX) = (125°C − 25°C) / (245.8°C/W) = 0.4W for UDFN-8L 2x3 package (One-Layer) PD(MAX) = (125°C − 25°C) / (50.2°C/W) = 1.99W for UDFN-8L 2x3 package (Two-Layer) The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 7 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Copyright © 2013 Richtek Technology Corporation. All rights reserved. DS8725-02 October 2013 is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT8725 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 1.600 1.700 0.063 0.067 E 2.900 3.100 0.114 0.122 E2 1.750 1.850 0.069 0.073 0.500 e L 0.350 0.020 0.450 0.014 0.018 U-Type 8L DFN 2x3 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. www.richtek.com 10 DS8725-02 October 2013