RT9742DGJ5

® RT9742 Ω, 3A/2.5A/2A/1.5A/1A/0.5A High-Side Power 70mΩ Ω/55mΩ Switches with Flag General Description Features The RT9742 is a cost-effective, low-voltage, single N-MOSFET high-side Power Switch IC for USB application. Low switch-on resistance and low supply current are realized in this IC.      The RT9742 integrates an over-current protection circuit, a short fold back circuit, a thermal shutdown circuit and an under-voltage lockout circuit for overall protection. Besides, a flag output is available to indicate fault conditions to the local USB controller. Furthermore, the chip also integrates an embedded delay function to prevent miss-operation from happening due to inrush-current. The RT9742 is an ideal solution for USB power supply and can support flexible applications since it is available in TSOT-23-5, TSOT-23-5 (FC) and SOT-23-3 package.      Ω (typ.) N-MOSFET Switch 70mΩ Ω/55mΩ Operating Range : 2.7V to 6V Reverse Blocking Current Under Voltage Lockout Deglitched Fault Report (FLG) Thermal Protection with Fold-back Over Current Protection Short Circuit Protection UL Approved−E219878 Nemko Approved-NO87949 Applications   USB Peripherals Notebook PCs Pin Configuration (TOP VIEW) VIN EN/EN 5 4 2 VOUT 5 3 VOUT GND FLG 2   TSOT-23-5 / TSOT-23-5 (FC) EN VOUT VIN GND 4 5 4 3 2 3 VOUT GND VIN 3 2 EN GND FLG   TSOT-23-5 For RT9742M only VIN   TSOT-23-5 For RT9742U only VOUT   SOT-23-3   Simplified Application Circuit USB Controller Supply Voltage 2.7V to 6V CIN Chip Enable Over-Current FLG VIN RT9742 VBUS VOUT GND + EN/EN D+ DGND COUT Data Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT9742 Ordering and Marking Information Version RT9742AGJ5F RT9742BGJ5F RT9742ANGJ5F RT9742BNGJ5F RT9742CGJ5F RT9742DGJ5F RT9742CNGJ5F RT9742DNGJ5F RT9742CGJ5 RT9742DGJ5 RT9742CNGJ5 RT9742DNGJ5 RT9742JNGV RT9742EGJ5F RT9742FGJ5F RT9742ENGJ5F RT9742FNGJ5F RT9742EGJ5 RT9742FGJ5 RT9742ENGJ5 RT9742FNGJ5 RT9742KNGV RT9742GGJ5F RT9742HGJ5F RT9742GNGJ5F RT9742HNGJ5F RT9742GGJ5 RT9742HGJ5 RT9742GNGJ5 RT9742HNGJ5 RT9742LNGV RT9742MGJ5 RT9742MNGJ5 RT9742NGJ5F RT9742PGJ5F RT9742NNGJ5F RT9742PNGJ5F RT9742NGJ5 RT9742QGJ5 RT9742RGJ5 RT9742QNGJ5 RT9742RNGJ5 RT9742SNGV RT9742UNGJ5 EN Function Package Discharge Product Current Function Active Active Internal TSOT-23-5 TSOT-23-5 SOT-23-3 Code High Low Pull High (FC) 07= 3A Yes V V 06= 3A Yes V V 0F= 3A No V V 0E= 3A No V V 05= 2A Yes V V 04= 2A Yes V V 0D= 2A No V V 0C= 2A No V V 0K= 2A Yes V V 0J= 2A Yes V V 11= 2A No V V 10= 2A No V V 6A= 2A No V V 03= 1.5A Yes V V 02= 1.5A Yes V V 0B= 1.5A No V V 0A= 1.5A No V V 0H= 1.5A Yes V V 0G= 1.5A Yes V V 0Z= 1.5A No V V 0Y= 1.5A No V V 69= 1.5A No V V 01= 1A Yes V V 00= 1A Yes V V 09= 1A No V V 08= 1A No V V 0F= 1A Yes V V 0E= 1A Yes V V 0X= 1A No V V 0W= 1A No V V 68= 1A No V V 14= 1.5A Yes V V 15= 1.5A No V V 43= 2.5A Yes V V DD= 2.5A Yes V V 42= 2.5A No V V CC= 2.5A No V V 9H 2.5A Yes V V 47= 0.5A Yes V V 45= 0.5A Yes V V 46= 0.5A No V V 44= 0.5A No V V 6V= 0.5A No V V 9F= 1.5A No V V Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 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. Functional Pin Description Pin Name Pin Function VOUT Output voltage. GND Ground. FLG Fault FLAG output. EN/EN Chip enable (Active High/Low). VIN Power input voltage. Functional Block Diagram TSOT-23-5 / TSOT-23-5 (FC) Package VIN EN/EN Bias UVLO Oscillator Charge Pump Current Limiting Gate Control Output Voltage Detection Thermal Protection VOUT Auto Discharge FLG Delay GND SOT-23-3 Package VIN UVLO Current Limiting Bias Oscillator Charge Pump Thermal Protection Gate Control Output Voltage Detection Auto Discharge Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 VOUT GND is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT9742 TSOT-23-5 Package (For RT9742M Only) VIN EN GND Bias UVLO Oscillator Charge Pump Thermal Protection Current Limiting Gate Control Output Voltage Detector VOUT VOUT Auto Discharge Operation Charge Pump 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 above 2.4V, UVLO turns on the MOSFET switch. Thermal Shutdown Current Limit The RT9742 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 © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 The RT9742 continuously monitors the operating temperature of the power switch for over-temperature protection. The RT9742 turns off the power switch to prevent the device from damage if the junction temperature rises to approximately 140°C due to over-current or shortcircuit conditions. The pass element turns on again after the junction temperature cools to 120°C. FLAG The RT9742 pulls low the open drain output FLAG after over current or over temperature condition occurring over approximately 10ms. is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 Absolute Maximum Ratings (Note 1) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------EN Voltage ----------------------------------------------------------------------------------------------------------------- FLAG Voltage ------------------------------------------------------------------------------------------------------------- Power Dissipation, PD @ TA = 25°C TSOT-23-5 ------------------------------------------------------------------------------------------------------------------TSOT-23-5 (FC) -----------------------------------------------------------------------------------------------------------SOT-23-3 ------------------------------------------------------------------------------------------------------------------- Package Thermal Resistance (Note 2) TSOT-23-5, θJA ------------------------------------------------------------------------------------------------------------TSOT-23-5 (FC), θJA -----------------------------------------------------------------------------------------------------SOT-23-3, θJA -------------------------------------------------------------------------------------------------------------- Junction Temperature ---------------------------------------------------------------------------------------------------- Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------ Storage Temperature Range ------------------------------------------------------------------------------------------- ESD Susceptibility (Note 3) HBM (Human Body Model) ---------------------------------------------------------------------------------------------  Recommended Operating Conditions     7V −0.3V to 7V 7V 0.49W 0.79W 0.41W 203°C/W 126.5°C/W 243.3°C/W 150°C 260°C −65°C to 150°C 2kV (Note 4) Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------EN Voltage -----------------------------------------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range -------------------------------------------------------------------------------------------- 2.7V to 6V 0V to 6V −40°C to 125°C −40°C to 85°C Electrical Characteristics (VIN = 5V, CIN = 10μF, COUT = 0.1μF, TA = 25°C, unless otherwise specified) Parameter Symbol Test Conditions Min Typ Max Input Quiescent Current IQ Switch on, VOUT = open -- 30 40 Input Shutdown Current ISHDN VIN = 5V, no load on OUT, device OFF, VEN = 0V or VEN = 5V -- 0.1 1 -- 55 -- -- 70 -- RT9742Q/R/S 0.65 0.89 1 RT9742G/H/L 1.05 1.4 1.5 1.55 2.1 2.25 2.05 2.8 3 RT9742N/P 2.55 3.5 3.75 RT9742A/B 3.05 4.2 4.5 Switch On Resistance Over Current Trip Threshold (Note 5) RT9742XXJ5F RT9742XXJ5/V RT9742E/F/K/M/U RT9742C/D/J RDS(ON) ITRIP Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 VIN = 5V, 100A/s Unit A m A is a registered trademark of Richtek Technology Corporation. www.richtek.com 5 RT9742 Parameter Current Limit Symbol Test Conditions Min Typ Max RT9742Q/R/S 0.6 0.7 0.8 RT9742G/H/L 1 1.1 1.2 1.5 1.65 1.8 2 2.2 2.4 RT9742N/P 2.5 2.75 3 RT9742A/B 3 3.3 3.6 1.8 2.15 2.5 RT9742E/F/K/M/U RT9742C/D ILIM VOUT = 1V RT9742J Unit A Logic_High Voltage VIH VIN = 2.7V to 6V 1.5 -- -- Logic_Low Voltage VIL VIN = 2.7V to 6V -- -- 0.75 EN/EN Input Current IEN/EN VEN = 0V, VEN = 5V 0.5 -- 0.5 A Output Leakage Current ILEAKAGE VEN = 0V, RLOAD = 0 -- 0.5 1 A Reverse Leakage Current IREV VOUT = 5V, VIN = 0V -- -- 1 A Reverse Voltage Trip Point VREV VOUT  VIN -- 200 -- mV Output Turn-On Rise Time tON_RISE 10% to 90% of VOUT rising -- 1.5 -- ms Turn-On Time tON From enable to 90% of VOUT -- 2.1 -- ms FLG Output Resistance RFLG ISINK = 1mA -- 10 --  FLG Off Current IFLG_OFF VFLG = 5V -- 0.01 1 A FLG Delay Time tD From fault condition to FLG assertion -- 10 -- ms Shutdown Auto-Discharge Resistance RDischarge VEN = 0V, VEN = 5V -- 100 --  Under-Voltage Lockout VUVLO VIN rising -- -- 2.4 V Under-Voltage Hysteresis VUVLO VIN decreasing -- 0.1 -- V Thermal Shutdown Protection TSD (Note 6) -- 140 -- °C Thermal Shutdown Hysteresis TSD (Note 6) -- 20 -- °C EN/EN Threshold 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. The thermal shutdown protection will react at high Ambient Temperature or low VIN due to RDS(ON) variation. Please refer to Application Information and Typical Operating Characteristics. Note 5. For a specific sample, Current Trip Threshold (ITRIP) is always higher than Current Limit Threshold (ILIM). Note 6. Guarantee by design. Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 6 is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 Typical Application Circuit Pull-Up Resistor (10k to 100k) USB Controller Supply Voltage 2.7V to 6V CIN 10µF EN/EN VOUT VBUS + RT9742A/C/E/G/N/Q/U Chip Enable Over -Current FLG VIN RT9742A/B/ C/D/E/F/G/H/ N/P/Q/R/U D+ D- COUT 0.1µF GND GND RT9742B/D/F/H/P/R Chip Enable Ferrite Beads Data RT9742J/K/L/S Supply Voltage 2.7V to 6V VIN VBUS + VOUT CIN 10µF D+ D- COUT 0.1µF GND GND Ferrite Beads Supply Voltage 2.7V to 6V VIN CIN 10µF VOUT RT9742M EN Data VBUS DS9742-08 October 2017 D- GND GND Ferrite Beads Copyright © 2017 Richtek Technology Corporation. All rights reserved. D+ COUT 0.1µF Data is a registered trademark of Richtek Technology Corporation. www.richtek.com 7 RT9742 Typical Operating Characteristics On Resistance vs. Input Voltage On Resistance vs. Temperature 120 100 90 100 On Resistance (mΩ) On Resistance (mΩ ) 110 90 TSOT-23-5 80 70 60 TSOT-23-5 (FC) 50 TSOT-23-5 80 70 60 TSOT-23-5 (FC) 50 40 40 VIN = 5V 30 30 2.5 3 3.5 4 4.5 5 5.5 -50 -25 0 Input Voltage (V) 50 100 125 Quiescent Current vs. Temperature 28.4 29.0 28.2 Quiescent Current (μA) 29.5 28.5 28.0 27.5 27.0 26.5 26.0 25.5 28.0 27.8 27.6 27.4 27.2 27.0 25.0 75 Temperature (°C) Quiescent Current vs. Input Voltage Quiescent Current (μA) 25 VIN = 5V, No Load No Load 24.5 26.8 2.5 3 3.5 4 4.5 5 5.5 -50 -25 0 Input Voltage (V) 25 50 75 100 125 Temperature (°C) Shutdown Current vs. Input Voltage Shutdown Current vs. Temperature 0.9 1.2 Shutdown Current (μA)1 Shutdown Current (μA)1 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 1 0.8 0.6 0.4 0.2 VEN = 0V 0 VIN = 5V, VEN = 0V 0 2.5 3 3.5 4 4.5 5 Input Voltage (V) Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 8 5.5 -50 -25 0 25 50 75 100 125 Temperature (°C) is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 Output Voltage vs. Output Current UVLO Threshold vs. Temperature 6 2.8 UVLO Threshold (V) Output Voltage (V) 2.6 VIN = 5V 5 4 3 VIN = 3.3V 2 1 2.4 Rising 2.2 2.0 1.8 Falling 1.6 1.4 1.2 1.0 0 0.8 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -50 -25 Output Current (A) Current Limit Threshold vs. Input Voltage 50 75 100 125 Current Limit Threshold vs. Temperature 3.6 3.5 3.4 3.4 Current Limit (A) Current Limit Threshold (A) 25 Temperature (°C) 3.6 3.3 3.2 3.1 3.0 2.9 2.8 3.2 3.0 2.8 2.6 2.4 2.7 VIN = 5V 2.2 2.6 2.5 3 3.5 4 4.5 5 5.5 -50 6 -25 0 25 50 75 100 Temperature (°C) Input Voltage (V) Over Current Trip Threshold vs. Temperature FLAG Delay Time vs. Input Voltage 5.0 9.9 4.8 9.8 FLAG Delay Time (ms) Over Current Trip Threshold (A) 0 4.6 4.4 4.2 4.0 3.8 9.7 9.6 9.5 9.4 9.3 9.2 VIN = 5V 9.1 3.6 -50 -25 0 25 50 75 Temperature (°C) Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 100 2.5 3 3.5 4 4.5 5 5.5 Input Voltage (V) is a registered trademark of Richtek Technology Corporation. www.richtek.com 9 RT9742 Power Off from VIN Power On from VIN VIN (2V/Div) VIN (2V/Div) VOUT (2V/Div) VOUT (2V/Div) No Load Time (2ms/Div) Time (10ms/Div) Power On from EN FLG Response FLG (5V/Div) EN (2V/Div) VOUT (2V/Div) VOUT (2V/Div) No Load Time (1ms/Div) Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 10 No Load I IN (2A/Div) VIN = 5V Time (2ms/Div) is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 Application Information The RT9742 is a single N-MOSFET high-side power switch with enable input, optimized for self-powered and buspowered Universal Serial Bus (USB) applications. The RT9742 is equipped with a charge pump circuitry to drive the internal N-MOSFET switch; the switch's low RDS(ON), 70mΩ/55mΩ, meets USB voltage drop requirements; and a flag output is available to indicate fault conditions to the local USB controller. 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. Unlike a normal MOSFET, there is no parasitic body diode between drain and source of the MOSFET, the RT9742 prevents reverse current flow if VOUT is externally forced to a higher voltage than VIN when the chip is disabled. S D G Normal MOSFET S D G RT9742 Chip Enable Input The switch will be disabled when the EN/EN pin is in a logic low/high condition. During this condition, the internal circuitry and MOSFET will be turned off. Floating the EN/EN may cause unpredictable operation. EN should not be allowed to go negative with respect to GND. The EN/EN pin may be directly tied to VIN (GND) to keep the part on. Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 Reverse Voltage Protection When the output voltage exceeds than input voltage by reverse voltage trip point (VREV), the reverse voltage protection circuitry will turn off MOSFET to protect the input power supply. The MOSFET will turn on again when output voltage return to the same level with input voltage. 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. Fault Flag The RT9742 series provides a FLG signal pin which is an N-Channel open drain MOSFET output. This open drain output goes low when current limit or the die temperature exceeds 140°C approximately. The FLG output is capable of sinking a 10mA load to typically 200mV above ground. The FLG pin requires a pull-up resistor, this resistor should be large in value to reduce energy drain. A 100kΩ pull-up resistor works well for most applications. In the case of an over-current condition, FLG will be asserted only after the flag response delay time, tD, has elapsed. This ensures that FLG is asserted only upon valid over-current conditions and that erroneous error reporting is eliminated. For example, false over-current conditions may occur during hot-plug events when extremely large capacitive loads are connected and causes a high transient inrush current that exceeds the current limit threshold. The FLG response delay time tD is typically 10ms. Under-Voltage Lockout Under-voltage lockout (UVLO) prevents the MOSFET switch from turning on until input the voltage exceeds 2.4V. If input voltage drops below than UVLO threshold, UVLO turns off the MOSFET switch. Under-voltage detection functions only when the switch is enabled. is a registered trademark of Richtek Technology Corporation. www.richtek.com 11 RT9742 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. When a heavy load or short circuit is applied to an enabled 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. Thermal Shutdown Thermal protection limits the power dissipation in the RT9742. When the operation junction temperature exceeds 140°C, the OTP circuit starts the thermal shutdown function and turns the pass element off. The pass element turn on again after the junction temperature cools to 120°C. Power Dissipation The junction temperature of the RT9742 series depend on several factors such as the load, PCB layout, ambient temperature and package type. The output pin of the RT9742 can deliver the current of up to the current limit threshold over the full operating junction temperature range. However, the maximum output current must be derated at higher ambient temperature to ensure the junction temperature does not exceed 125°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 Although the devices are rated for 3A, 2.5A, 2A, 1.5A, 1A and 0.5A , 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 : The junction to ambient thermal resistance (θJA) for TSOT23-5 package at recommended minimum footprint is 203°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 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. PD (MAX) = ( TJ (MAX) - TA ) / θJA Where TJ (MAX) is the maximum junction temperature of the die (125°C) and T A is the maximum ambient temperature. Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 12 is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 Over-Current protection devices such as fuses and PTC resistors (also called polyfuse or polyswitch) have slow trip times, high on-resistance, and lack the necessary circuitry for USB-required fault reporting. The faster trip time of the RT9742 power distribution allows designers to design hubs that can operate through faults. The RT9742 provides low on-resistance and internal faultreporting circuitry 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 10μF 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 7V 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 Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 the power 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 (see Figure 7-47 of Universal Serial Specification Revision 2.0). 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) : VOUT (MIN) = 4.75V − [ II x ( 4 x RCONN + 2 x RCABLE ) ] − (0.1A x NPORTS x RSWITCH ) − VPCB Where RCONN = Resistance of connector contacts (two contacts per connector) RCABLE = Resistance of upstream cable wires (one 5V and one GND) RSWITCH = Resistance of power switch 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 ) is a registered trademark of Richtek Technology Corporation. www.richtek.com 13 RT9742 0.9 Maximum Power Dissipation (W)1 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 RT9742, with its maximum 100mΩ on-resistance over temperature, can fit the demand of this requirement. 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 : 0.8 Four-Layer PCB TSOT-23-5 (FC) 0.7 0.6 TSOT-23-5 0.5 0.4 SOT-23-3 0.3 0.2 0.1 0.0 0 25 50 75 100 125 Ambient Temperature (°C) Figure 1. Derating Curve of Maximum Power Dissipation 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 SOT-23-3 package, the thermal resistance, θ JA, is 243.3°C/W on a standard JEDEC 51-7 four-layer thermal test board. For TSOT-23-5 package, the thermal resistance, θJA, is 203°C/W on a standard JEDEC 51-7 four-layer thermal test board. For TSOT-23-5 (FC) package, the thermal resistance, θJA, is 126.5°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 : Layout Consideration In order to meet the voltage drop, droop, and EMI requirements, careful PCB layout is necessary. The following guidelines must be followed :  Locate the ceramic bypass capacitors as close as possible to the VIN pins of the RT9742.  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).  Keep all VBUS traces as short as possible and use at least 50-mil, 2 ounce copper for all VBUS traces.  Avoid vias as much as possible. If vias are necessary, make them as large as feasible. PD(MAX) = (125°C − 25°C) / (243.3°C/W) = 0.41W for SOT-23-3 package  Place cuts in the ground plane between ports to help reduce the coupling of transients between ports. PD(MAX) = (125°C − 25°C) / (203°C/W) = 0.49W for TSOT-23-5 package  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 RT9742 as close as possible to the output port to limit switching noise. PD(MAX) = (125°C − 25°C) / (126.5°C/W) = 0.79W for TSOT-23-5 (FC) 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 1 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation. Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 14 is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 The input capacitor should be placed as close as possible to the IC. VIN VOUT VBUS GND GND_BUS FLG EN VIN The input capacitor should be placed as close as possible to the IC. VBUS + + + VIN VOUT GND GND_BUS Figure 2. PCB Layout Guide Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 is a registered trademark of Richtek Technology Corporation. www.richtek.com 15 RT9742 Outline Dimension H D L B C b A A1 e Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.300 0.559 0.012 0.022 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 TSOT-23-5 Surface Mount Package Copyright © 2017 Richtek Technology Corporation. All rights reserved. www.richtek.com 16 is a registered trademark of Richtek Technology Corporation. DS9742-08 October 2017 RT9742 Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 1.000 0.028 0.039 A1 0.000 0.100 0.000 0.004 B 1.397 1.803 0.055 0.071 b 0.300 0.559 0.012 0.022 C 2.591 3.000 0.102 0.118 D 2.692 3.099 0.106 0.122 e 0.838 1.041 0.033 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 TSOT-23-5 (FC) Surface Mount Package Copyright © 2017 Richtek Technology Corporation. All rights reserved. DS9742-08 October 2017 is a registered trademark of Richtek Technology Corporation. www.richtek.com 17 RT9742 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. 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 18 DS9742-08 October 2017