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| HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION USB power distribution switches are high-side nchannel MOSFET switches with built-in overcurrent protection and low on-state resistance. The SC5826 switch is designed to meet the USB requirements for power switching and maintenance-free fault protection for self-powered & bus-powered hub applications. The SC5826 features low on-state resistance to meet the USB requirement for voltage drop and regulation. The switch is controlled by an enable input that is compatible with 3V and 5V logic. The enable input is available with an active high or active low input for maximum design flexibility. The device provides short circuit current limiting at a value of less than 1.6A, well below the USB limit of 5A. During an overcurrent condition the device provides a fault notification to signal the USB controller. An integrated thermal protection circuit automatically shuts the switch off when the junction temperature reaches its thermal limit. The switch remains off until the junction temperature drops approximately 10C. The switch will continue to cycle on and off until the fault is removed. Inrush current limiting prevents the voltage drop on an upstream port when the switch is enabled. An undervoltage lockout circuit guarantees the switch is initially off during start-up. FEATURES * * * * * * * * Designed to meet USB specification 1.1 power management requirements 500mA continuous load current High-side MOSFET switch with low R DS(ON) Short-circuit current protection Internal thermal shutdown Undervoltage lockout Logic overcurrent output Soft start circuit with slow turn-on time APPLICATIONS * Universal Serial Bus (USB) power management * Self-powered or bus-powered USB hubs * Root hubs in desktop PCs & servers * Notebook PCs * Peripherals ORDERING INFORMATION DEVICE (1) ENABLE Active High Active Low PACKAGE SO-8 SO-8 SC5826-1CS SC5826-2CS Note: (1) Add suffix `TR' for tape and reel. PIN CONFIGURATION BLOCK DIAGRAM Top View (8-Pin SOIC) 1 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 ABSOLUTE MAXIMUM RATINGS Parameter Input Voltage Range Output Voltage Range Enable Input Continuous Output Current Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) 10 seconds Symbol VIN VOUT VEN IO TA TJ TSTG TL Maximum -0.3 to +7 -0.3 to +7 -0.3 to +7 Internally Limited -40 to +85 -40 to +125 -65 to +150 300 Units V V V mA C C C C PIN DESCRIPTION Pin # 1, 4 2, 3 6 7 5, 8 Pin Name ENA/ENB FLGA/FLGB GND IN OUTA/OUTB Pin Function Enable input: TTL compatible switch enable input. Error flag output: FLG is asserted active low during fault condition. Ground. Input voltage: Output MOSFET Drain. Connect to supply voltage. Power switch output: Output MOSFET Source. Connect to switched side of load. PIN CONFIGURATION Top View (8-Pin SOIC) 2 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 ELECTRICAL CHARACTERISTICS Parameter Power Switch On Resistance Output Leakage Current Output Turn On Rise Time Output Turn Off Fall Time Enable Input High Level Input Voltage Low Level Input Voltage Input Current VEN(HI) VEN(LO) IEN tD(ON) tD(OFF) IOS IIN(OFF) IIN(ON) VUVLO VHYST rFLG IFLG THI THYST rON IL(OFF) tR tF Symbol (1)(2) Unless specified: TA = 25C, VIN = 5V, IOA/IOB = 500mA (Switches ON). Conditions 4.25V VIN 5.50V VO = 5.5V, Switches OFF CO = 1F, RO = 10 CO = 1F, RO = 10 4.25V VIN 5.50V 4.25V VIN 5.50V EN = VIN, OUTA/B = OPEN EN = 0V, IOA/IOB = 0mA, OUTA/B = OPEN Min Typ Max Units 100 140 1 m A ms 1 0.1 1 ms 2.4 0.8 0 0 0.25 25 50 1 1 V V A Output Turn On Delay Output Turn Off Delay Current Limit Short Circuit Current Limit Supply Current Outputs Off Outputs On Undervoltage Lockout UVLO Threshold Hysteresis Error Flag Output Resistance Leakage Current (Off) Over Temperature Protection High Trip Level Hysteresis ms s VOA/VOB = GND, Switches ON Switches OFF IOA/IOB = 0mA 0.65 0.90 1.60 A 0.02 130 1 200 A A 2.2 90 2.7 V mV A IFLG = 10mA, VOA/VOB = GND, Switches ON VFLG = 5.0V, Switches OFF 10 0.01 50 1 160 10 C C NOTE: (1) For SC5826-1, Switch OFF is VEN 0.8V and Switch ON is VEN 2.4V ("Active High"). For SC5826-2, Switch ON is VEN 0.8V and Switch OFF is VEN 2.4V ("Active Low"). For testing purposes EN will be 0V or VIN as applicable, unless otherwise specified. (2) This device is ESD sensitive. Use of standard ESD handling precautions is required. 3 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 TYPICAL CHARACTERISTICS On Resistance vs. Junction Temperature vs. Input Voltage 150 140 130 150 120 VIN = 4.25V IIN(ON) (A) rON (m) 110 100 90 80 70 60 50 -50 -25 0 25 50 TJ (C) 75 100 125 150 25 0 -50 -25 0 25 50 TJ (C) 75 100 125 150 VIN = 5.5V 125 100 75 50 IO = 0.5A 175 200 VIN = 5V Supply Current (Outputs On) vs. Junction Temperature UVLO Threshold vs. Junction Temperature 3.000 2.900 2.800 2.700 VUVLO (V) 2.600 2.500 2.400 2.300 2.200 2.100 2.000 -50 -25 0 25 50 TJ (C) 75 100 125 150 VIN Falling VIN Rising 0.6 IOS (A) 0.5 0.4 0.3 0.2 0.1 0.0 -50 -25 1.0 0.9 0.8 0.7 Short Circuit Output Current vs. Junction Temperature V IN = 5V 0 25 50 T J (C) 75 100 125 150 4 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 DETAILED DESCRIPTION The SC5826 HotSwitchTM is a dual port, high-side switch optimized for power control & distribution in Universal Serial Bus (USB) applications. It features an nchannel power MOSFET with a low on-state resistance for meeting USB voltage regulation requirements. It available with active high (SC5826-1) or active low (SC5826-2) inputs. In/Out The input is the supply voltage connection to the drain of the power switch MOSFET. The output is connected to the source of the MOSFET. Under normal operating conditions when the power switch is enabled, current flows from the input to the output towards the load. The power switch is designed to sustain a minimum load current of 500mA in accordance with USB specifications. Charge Pump An internal charge pump powers the MOSFET gate drive circuit and provides the necessary voltage to pull the gate above the source. Control Logic The gate drive circuit controls the gate voltage of the MOSFET power switch. The gate drive circuit also controls the rise & fall times of the power switch output voltage. The typical "soft start" or output voltage rise time is 1ms. Enable Input A logic signal at the enable (EN) pin activates the power MOSFET switch. A logic 1 (SC5826-1) or logic 0 (SC5826-2) will bias the charge pump, gate drive, and control circuitry turning on the power switch. A logic signal of opposite polarity turns off the switch. If both outputs are off, the device powers down. The enable input is compatible with 3V & 5V logic levels. Error Flag The error flag (FLG) output is an n-channel, open drain MOSFET. The FLG pin is an active low during short circuit, undervoltage, or thermal shutdown conditions. The output remains low until the fault condition is removed. Thermal Sense An internal thermal shutdown circuit turns off the power switch output MOSFET when the die junction temperature exceeds 160C. The output FLG pin is asserted to a logic low signaling a fault condition. A built in hys- teresis prevents the switch from turning on until the die temperature has cooled approximately 10C. The switch will continue to cycle on and off until the fault condition is removed. The thermal sense circuit functions only when the switch is enabled. Undervoltage Lockout An undervoltage lockout circuit monitors the input voltage and prevents the power switch MOSFET from turning on until the input voltage (IN) exceeds 2.5V (typical). If the input voltage falls 90mV (typical) below that point after the switch has been turned on, the undervoltage lockout turns off the power switch output MOSFET and asserts the FLG output to logic low. The undervoltage lockout functions only when the switch is enabled. 5 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 TYPICAL APPLICATIONS Self-powered hub, indidual port power management: A self-powered hub must supply a continuous 500mA of current to each downstream port. Since an internal power supply is used to supply the power, self-powered hubs are required to implement overcurrent protection for safety. The self-powered hub must also have a method to detect and report fault conditions to the USB controller. The circuit below utilizes the SC5826 to provide individual port overcurrent protection & power switching for maximum port protection. Under fault conditions, the SC5826 provides the short-circuit current limiting function and has a fault flag logic output for notifying the hub controller. The USB hub can use the SC5826 to remove power from the faulty port, allowing the other ports to operate normally. Since USB is a hot insertion and removal system, USB ports are subject to electrostatic discharge (ESD). The SRDA05-4 provides ESD protection on the downstream data and power lines. Each device will protect two USB ports. With proper layout the port is hardened to greater than 15kV, meeting the requirements of IEC 1000-4-2. On the upstream port, the LCDA05 provides ESD protection to the above levels for one line pair. The SC5203 (or SC5205) LDO regulator is used to power the hub controller from the upstream bus. Figure 1 - Self-powered hub with individual port power management 6 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 TYPICAL APPLICATIONS Bus-powered hub, ganged port power management: A bus-powered hub distributes power and data from an input port to downstream ports. It must supply a continuous 100mA of current to each downstream port. A bus-powered hub must be able to switch power to downstream ports to prevent illegal device hook-up. Inrush current limiting is also required to prevent power supply drooping. The circuit below utilizes the SC5826 to provide ganged port power switching, inrush current limiting and overcurrent protection for maximum port protection. In a ganged switch configuration, all ports are switched simultaneously. Under fault conditions, the USB controller will remove power to all of the ganged ports. For individual port management, an additional SC5826 may be used. Since USB is a hot insertion and removal system, USB ports are subject to electrostatic discharge (ESD). The SRDA05-4 provides ESD protection on the downstream data and power lines. Each device will protect two USB ports. With proper layout the port is hardened to greater than 15kV, meeting the requirements of IEC 1000-4-2. On the upstream port, the LCDA05 provides ESD protection to the above levels for one line pair. The SC5203 (or SC5205) LDO regulator is used to power the hub controller from the upstream bus. Figure 2 - Bus-powered hub with ganged port power management 7 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitchTM USB Power Distribution Switch PRELIMINARY - February 18, 2000 SC5826 OUTLINE DRAWING - SO-8 JEDEC REF: MS-012AA LAND PATTERN - SO-8 ECN00-886 8 (c) 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 |
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