RT9741AGV

® RT9741 100mΩ Ω, 1.5A/0.7A High-Side Power Switches General Description Features The RT9741 is a cost-effective, low-voltage, single NMOSFET high-side Power Switch IC for USB application. Low switch-on resistance (typ. 100mΩ) and low supply current (typ. 50μA) are realized in this IC.  The RT9741 integrates an over-current protection circuit, a short fold back circuit, a thermal shutdown circuit and an under-voltage lockout circuit for overall protection. Furthermore, the chip also integrates an embedded delay function to prevent miss-operation from happening due to inrush-current. The RT9741 is an ideal solution for USB power supply and can support flexible applications since it is available in the SOT-23-3 package.        100mΩ Ω (typ.) N-MOSFET Switch Operating Range : 2.7V to 5.5V Reverse Blocking Current Under-Voltage Lockout Thermal Protection with Foldback Over-Current Protection Short-Circuit Protection RoHS Compliant and Halogen Free Applications   USB Peripherals Notebook PCs Marking Information Ordering Information RT9741AGV RT9741 4F= : Product Code Package Type V : SOT-23-3 4F=DNN Lead Plating System G : Green (Halogen Free and Pb Free) Output Current A : 1.5A C : 0.7A DNN : Date Code RT9741CGV 4D= : Product Code 4D=DNN DNN : Date Code Note : Richtek products are :  RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.  Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit RT9741 VIN VOUT CIN VBUS FB + Supply Voltage 2.7V to 5.5V GND D+ DGND COUT FB Data Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9741-01 March 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9741 Functional Pin Description Pin Configurations (TOP VIEW) Pin No. GND 3 2 VIN Pin Name Pin Description 1 VIN Power Input. 2 VOUT Output Voltage. 3 GND Ground. VOUT SOT-23-3 Function Block Diagram VIN UVLO Current Limiting Bias Oscillator Charge Pump Thermal Protection Gate Control Output Voltage Detection Auto Discharge VOUT GND Operation Charge Pumps and Drivers Under-Voltage Lockout An internal charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate of the MOSFET above the source. The driver controls the gate voltage of the power switch. A voltage-sense circuit monitors the input voltage. When the input voltage is below approximately 1.3V, UVLO turns off the MOSFET switch. Thermal Shutdown Current Limit The RT9741 continuously monitors the output current for over-current protection to protect the system power, the power switch, and the load from damage during output short circuit. When an overload or short circuit occurs, the current-sense circuitry sends a control signal to the driver. The driver reduces the gate voltage and drives the power MOSFET into its saturation region, which switches the output into a constant-current mode and holds the current constant until the thermal shutdown occurs or the fault is removed. Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 The RT9741 continuously monitors the operating temperature of the power switch for over-temperature protection. The RT9741 turns off the power switch to prevent the device from damage if the junction temperature rises to approximately 120°C due to over-current or shortcircuit conditions. The pass element turns on again after the junction temperature cools to 80°C. The RT9741 lowers its OTP trip level from 120°C to 100°C when output short circuit occurs (VOUT < 1V). is a registered trademark of Richtek Technology Corporation. DS9741-01 March 2015 RT9741 Absolute Maximum Ratings (Note 1) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C SOT-23-3 ------------------------------------------------------------------------------------------------------------------- Package Thermal Resistance (Note 2) SOT-23-3, θJA -------------------------------------------------------------------------------------------------------------- Junction Temperature ---------------------------------------------------------------------------------------------------- Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------ Storage Temperature Range ------------------------------------------------------------------------------------------- ESD Susceptibility (Note 3) HBM (Human Body Model) --------------------------------------------------------------------------------------------- 6V  Recommended Operating Conditions    0.41W 243.3°C/W 150°C 260°C −65°C to 150°C 2kV (Note 4) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------- 2.7V to 5.5V Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C Electrical Characteristics (VIN = 5V, CIN = 1μF, COUT = 10μF, TA = 25°C, unless otherwise specified) Parameter Input Quiescent Current Switch OnResistance Current Limit RT9741A RT9741C RT9741A Symbol IQ RDS(ON) Test Conditions Min Typ Max Unit Switch On, VOUT = Open -- 50 70 A VIN = 5V, IOUT = 1.3A -- 100 120 VIN = 5V, IOUT = 0.6A -- 120 140 1.5 2 -- 0.7 1 -- m ILIM VOUT = 4V ISC_FB VOUT = 0V, Measured Prior to Thermal Shutdown -- 1.4 -- -- 0.7 -- Output Turn-On Rising Time TON_RISE 10% to 90% of VOUT Rising -- 200 -- s Under-Voltage Lockout VUVLO VIN Rising 1.3 1.7 2.1 V Under-Voltage Hysteresis VUVLO VIN Decreasing -- 0.1 -- V Thermal Shutdown Protection TSD VOUT > 1V -- 120 -- VOUT = 0V -- 100 -- Thermal Shutdown Hysteresis TSD VOUT = 0V -- 20 -- Short Current RT9741C RT9741A RT9741C A A C C 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 © 2015 Richtek Technology Corporation. All rights reserved. DS9741-01 March 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9741 Typical Application Circuit RT9741 CIN 1µF 1 VIN VOUT GND 3 2 VBUS FB + Supply Voltage 2.7V to 5.5V COUT 10µF 150µF FB D+ DGND Data Note : A low-ESR 150μF aluminum electrolytic or tantalum capacitor between VOUT and GND is strongly recommended to meet the 330mV maximum droop requirement in the hub VBUS. (see Application Information Section for further details) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS9741-01 March 2015 RT9741 Typical Operating Characteristics On Resistance vs. Input Voltage 125 RT9741A 130 121 On Resistance (mΩ) On Resistance (mΩ) 123 On Resistance vs. Temperature 140 119 117 115 113 111 109 120 110 100 90 80 70 107 IOUT = 1.5A 105 2.7 3.1 3.5 3.9 4.3 4.7 5.1 VIN = 5V, IOUT = 1.5A 60 5.5 -40 -20 0 Input Voltage (V) Quiescent Current vs. Input Voltage 46 40 60 80 Quiescent Current vs. Temperature 45 RT9741A 44 Quiescent Current (µA) 44 Quiescent Current (µA) 20 Temperature (°C) 42 40 38 36 34 32 43 42 41 40 39 38 37 36 No Load 30 VIN = 5V, No Load 35 2.7 3.1 3.5 3.9 4.3 4.7 5.1 -40 5.5 -20 Input Voltage (V) 0 20 40 60 80 100 Temperature (°C) Output Voltage vs. Output Current UVLO Threshold vs. Temperature 2.2 5.5 5.0 UVLO Threshold (V) Output Voltage (V) 2.0 VIN = 5V 4.5 4.0 3.5 3.0 VIN = 3.3V 2.5 2.0 1.5 1.0 Rising edge 1.8 1.6 Falling edge 1.4 1.2 0.5 0.0 1.0 0.5 0.75 1 1.25 1.5 1.75 2 Output Current (A) Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9741-01 March 2015 2.25 -40 -20 0 20 40 60 80 Temperature (°C) is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9741 Current Limit vs. Input Voltage 2.3 Current Limit vs. Temperature 2.00 RT9741A 1.90 2.1 Current Limit (A) Current Limit (A) RT9741A 1.95 2.2 2.0 1.9 1.8 1.7 1.85 1.80 1.75 1.70 1.65 1.60 1.6 1.55 1.5 1.50 2.7 3.1 3.5 3.9 4.3 4.7 5.1 -40 5.5 -20 Input Voltage (V) 1.48 40 60 80 Short Current vs. Temperature 1.50 RT9741A RT9741A 1.48 1.46 Short Current (A) 1.46 Short Current (A) 20 Temperature (°C) Short Current vs. Input Voltage 1.50 0 1.44 1.42 1.40 1.38 1.36 1.44 1.42 1.40 1.38 1.36 1.34 1.34 1.32 1.32 1.30 1.30 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 -40 0 20 40 Temperature (°C) Power On from VIN Power Off from VIN VIN (2V/Div) VIN (2V/Div) VOUT (2V/Div) VOUT (2V/Div) No Load Time (25ms/Div) Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 -20 Input Voltage (V) 60 80 No Load Time (25ms/Div) is a registered trademark of Richtek Technology Corporation. DS9741-01 March 2015 RT9741 Application Information The RT9741 is a single N-MOSFET high-side power switches, optimized for self-powered and bus-powered Universal Serial Bus (USB) applications. The RT9741 is equipped with a charge pump circuitry to drive the internal N-MOSFET switch; the switch's low RDS(ON) meets USB voltage drop requirements. Input and Output VIN (input) is the power source connection to the internal circuitry and the drain of the MOSFET. VOUT (output) is the source of the MOSFET. In a typical application, current flows through the switch from VIN to VOUT toward the load. If VOUT is greater than VIN, current will flow from VOUT to VIN since the MOSFET is bidirectional when on. Thermal Shutdown Thermal protection limits the power dissipation in RT9741. When the operation junction temperature exceeds 120°C, the OTP circuit starts the thermal shutdown function and turns the pass element off. The pass element turns on again after the junction temperature cools to 80°C. The RT9741 lowers its OTP trip level from 120°C to 100°C when output short circuit occurs (VOUT < 1V) as shown in Figure 1. V OUT Short to GND 1V V OUT IOUT Soft-Start for Hot Plug-In Applications In order to eliminate the upstream voltage droop caused by the large inrush current during hot-plug events, the “soft-start” feature effectively isolates the power source from extremely large capacitive loads, satisfying the USB voltage droop requirements. Thermal Shutdown 120  C 100 C  OTP Trip Point IC Temperature 100 C 80 C Under-Voltage Lockout Under-Voltage Lockout (UVLO) prevents the MOSFET switch from turning on until input the voltage exceeds approximately 1.7V. If input voltage drops below approximately 1.3V, UVLO turns off the MOSFET switch. Current Limiting and Short-Circuit Protection The current limit circuitry prevents damage to the MOSFET switch and the hub downstream port but can deliver load current up to the current limit threshold of typically 2A through the switch of the RT9741A and 1A for RT9741C respectively. When a heavy load or short circuit is applied to switch, a large transient current may flow until the current limit circuitry responds. Once this current limit threshold is exceeded, the device enters constant current mode until the thermal shutdown occurs or the fault is removed. Figure 1. Short Circuit Thermal Folded Back Protection when Output Short Circuit Occurs (Patent) Power Dissipation The junction temperature of the RT9741 series depends on several factors such as the load, PCB layout, ambient temperature and package type. The output pin of the RT9741 can deliver the current of up to 2A (RT9741A) and 1A (RT9741C) respectively over the full operating junction temperature range. However, the maximum output current must be decreased at higher ambient temperature to ensure the junction temperature does not exceed 100°C. With all possible conditions, the junction temperature must be within the range specified under operating conditions. Power dissipation can be calculated based on the output current and the RDS(ON) of the switch as below. PD = RDS(ON) x IOUT2 Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9741-01 March 2015 is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9741 Although the devices are rated for 2A and 1A of output current, but the application may limit the amount of output current based on the total power dissipation and the ambient temperature. The final operating junction temperature for any set of conditions can be estimated by the following thermal equation: PD(MAX) = ( TJ (MAX) − TA ) / θJA Where TJ (MAX) is the maximum junction temperature of the die (100°C) and TA is the maximum ambient temperature. The junction to ambient thermal resistance (θJA) for SOT-23-3 at recommended minimum footprint is 243.3°C/W (θJA is layout dependent). Universal Serial Bus (USB) & Power Distribution The goal of USB is to enable device from different vendors to interoperate in an open architecture. USB features include ease of use for the end user, a wide range of workloads and applications, robustness, synergy with the PC industry, and low-cost implementation. Benefits include self-identifying peripherals, dynamically attachable and reconfigurable peripherals, multiple connections (support for concurrent operation of many devices), support for as many as 127 physical devices, and compatibility with PC Plug-and-Play architecture. The Universal Serial Bus connects USB devices with a USB host: each USB system has one USB host. USB devices are classified either as hubs, which provide additional attachment points to the USB, or as functions, which provide capabilities to the system (for example, a digital joystick). Hub devices are then classified as either Bus-Power Hubs or Self-Powered Hubs. A Bus-Powered Hub draws all of the power to any internal functions and downstream ports from the USB connector power pins. The hub may draw up to 500mA from the upstream device. External ports in a Bus-Powered Hub can supply up to 100mA per port, with a maximum of four external ports. Self-Powered Hub power for the internal functions and downstream ports does not come from the USB, although the USB interface may draw up to 100mA from its upstream connect, to allow the interface to function when the remainder of the hub is powered down. The hub must Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 be able to supply up to 500mA on all of its external downstream ports. Please refer to Universal Serial Specification Revision 2.0 for more details on designing compliant USB hub and host systems. Over-Current protection devices such as fuses and PTC resistors (also called poly-fuse or poly-switch) have slow trip times, high on-resistance, and lack the necessary circuitry for USB-required fault reporting. The faster trip time of the RT9741 power distribution allows designers to design hubs that can operate through faults. The RT9741 provides low on-resistance to meet voltage regulation and fault notification requirements. Because the devices are also power switches, the designer of self-powered hubs has the flexibility to turn off power to output ports. Unlike a normal MOSFET, the devices have controlled rise and fall times to provide the needed inrush current limiting required for the bus-powered hub power switch. Supply Filter/Bypass Capacitor A 1μF low-ESR ceramic capacitor from VIN to GND, located at the device is strongly recommended to prevent the input voltage drooping during hot-plug events. However, higher capacitor values will further reduce the voltage droop on the input. Furthermore, without the bypass capacitor, an output short may cause sufficient ringing on the input (from source lead inductance) to destroy the internal control circuitry. The input transient must not exceed 6V of the absolute maximum supply voltage even for a short duration. Output Filter Capacitor A low-ESR 150μF aluminum electrolytic or tantalum between VOUT and GND is strongly recommended to meet the 330mV maximum droop requirement in the hub VBUS (Per USB 2.0, output ports must have a minimum 120μF of low-ESR bulk capacitance per hub). Standard bypass methods should be used to minimize inductance and resistance between the bypass capacitor and the downstream connector to reduce EMI and decouple voltage droop caused when downstream cables are hot-insertion transients. Ferrite beads in series with VBUS, the ground line and the 0.1μF bypass capacitors at the power is a registered trademark of Richtek Technology Corporation. DS9741-01 March 2015 RT9741 connector pins are recommended for EMI and ESD protection. The bypass capacitor itself should have a low dissipation factor to allow decoupling at higher frequencies. Voltage Drop The USB specification states a minimum port-output voltage in two locations on the bus, 4.75V out of a SelfPowered Hub port and 4.40V out of a Bus-Powered Hub port. As with the Self-Powered Hub, all resistive voltage drops for the Bus-Powered Hub must be accounted for to guarantee voltage regulation. The following calculation determines VOUT(MIN) for multiple ports (NPORTS) ganged together through one switch (if using one switch per port, NPORTS is equal to 1) : 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. (0.1A x NPORTS x RSWITCH) − VPCB For recommended operating condition specifications, the maximum junction temperature is 125°C. The junction to ambient thermal resistance, θJA, is layout dependent. For SOT-23-3 package, the thermal resistance, θ JA, is RCONN = Resistance of connector contacts (two contacts per connector) 243.3°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 : RCABLE = Resistance of upstream cable wires (one 5V and one GND) PD(MAX) = (125°C − 25°C) / (243.3°C/W) = 0.41W for SOT-23-3 package Where RSWITCH = Resistance of power switch (typical 100mΩ for RT9741A and 120mΩ for RT9741C) VPCB = PCB voltage drop The USB specification defines the maximum resistance per contact (RCONN) of the USB connector to be 30mΩ and the drop across the PCB and switch to be 100mV. This basically leaves two variables in the equation: the resistance of the switch and the resistance of the cable. If the hub consumes the maximum current (II) of 500mA, the maximum resistance of the cable is 90mΩ. The resistance of the switch is defined as follows : RSWITCH = { 4.75V − 4.4V − [ 0.5A x ( 4 x 30mΩ + 2 x 90mΩ) ] − VPCB }  ( 0.1A x NPORTS ) = (200mV − VPCB )  ( 0.1A x NPORTS ) If the voltage drop across the PCB is limited to 100mV, the maximum resistance for the switch is 250mΩ for four ports ganged together. The RT9741, with its maximum 120mΩ on resistance can fit the demand of this requirement. Copyright © 2015 Richtek Technology Corporation. All rights reserved. DS9741-01 March 2015 The maximum power dissipation depends on the operating ambient temperature for fixed T J(MAX) and thermal resistance, θJA. The derating curve in Figure 2 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. 0.5 Maximum Power Dissipation (W)1 VOUT(MIN) = 4.75V − [II x ( 4 x RCONN + 2 x RCABLE )] − Four-Layer PCB 0.4 0.3 0.2 0.1 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 2. Derating Curve of Maximum Power Dissipation is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9741 Layout Consideration  Avoid via as much as possible. If via are necessary, make them as large as feasible.  Locate the ceramic bypass capacitors as close as possible to the VIN pins of the RT9741. Place cuts in the ground plane between ports to help reduce the coupling of transients between ports.  Place a ground plane under all circuitry to lower both resistance and inductance and improve DC and transient performance (Use a separate ground and power plans if possible). Locate the output capacitor and ferrite beads as close to the USB connectors as possible to lower impedance (mainly inductance) between the port and the capacitor and improve transient load performance.  Locate the RT9741 as close as possible to the output port to limit switching noise. In order to meet the voltage drop, droop, and EMI requirements, careful PCB layout is necessary. The following guidelines must be followed :    Keep all VBUS traces as short as possible and use at least 50-mil, 2 ounce copper for all VBUS traces. The input capacitor should be placed as close as possible to the IC. VBUS + + + VIN VOUT GND GND_BUS Figure 3. PCB Layout Guide Copyright © 2015 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 is a registered trademark of Richtek Technology Corporation. DS9741-01 March 2015 RT9741 Outline Dimension H D L C B e A A1 b Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.889 1.295 0.035 0.051 A1 0.000 0.152 0.000 0.006 B 1.397 1.803 0.055 0.071 b 0.356 0.508 0.014 0.020 C 2.591 2.997 0.102 0.118 D 2.692 3.099 0.106 0.122 e 1.803 2.007 0.071 0.079 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 SOT-23-3 Surface Mount 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. DS9741-01 March 2015 www.richtek.com 11