SC2041

HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com DESCRIPTION USB power distribution switches are high-side N-channel MOSFET switches with built-in overcurrent protection and low on-state resistance. The SC2041 switch is designed to meet the USB requirements for power switching and maintenance-free fault protection for self-powered & bus-powered hub applications. The SC2041 features low on-state resistance to meet the USB requirement for voltage drop and regulation. The switch is controlled by a shutdown input that is compatible with 3V and 5V logic. The device is active when the shutdown input is low. See SC2051 for an active high version. The device provides short circuit current limiting at a value of less than 1.0A, 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 20°C. The switch will continue to cycle on and off until the fault is removed. Inrush current limiting prevents 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 revisions 1.1 •= •= •= •= •= •= •= •= •= •= and 2.0 power management requirements 500mA continuous load current High-side MOSFET switch with low RDS(ON) Short-circuit current protection Internal thermal shutdown Undervoltage lockout Open drain fault output Soft start circuit with slow turn-on time Wide supply voltage range: 2.8V to 5.5V 2.5kV ESD rating (Human Body Model) Full industrial temperature range 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 SC2041IS.TR (1) PACKAGE SO-8 Note: (1) Only available in tape and reel packaging. A reel contains 2500 devices. TYPICAL APPLICATION CIRCUIT U1 1 VBUS IN 2 3 Shutdown Signal From USB Controller R1 4 GND IN IN SHDN SC2041 OUT OUT OUT FLG 8 7 6 5 VBUS OUT Flag Output To USB Controller C1 0.1uF C2 0.1uF C3 22uF 1 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 ABSOLUTE MAXIMUM RATINGS Parameter Input Voltage Range Output Voltage Range Shutdown Input Flag Output Continuous Output Current Thermal Impedance Junction to Ambient Thermal Impedance Junction to Case Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering, 10 seconds) ESD Rating (Human Body Model) Symbol VIN VOUT VEN VFLG IO θJA θJC TA TJ TSTG TL ESD Maximum -0.3 to +7 -0.3 to +7 -0.3 to +7 -0.3 to (VIN + 0.3) Internally Limited 130 47 -40 to +85 -40 to +125 -65 to +150 300 2.5 Units V V V V mA °C/W °C/W °C °C °C °C kV ELECTRICAL CHARACTERISTICS Unless specified: TA = 25°C, VIN = 5V, VSHDN = GND, IOUT = 500mA. Values in bold apply over the full operating temperature range. Parameter IN Supply Voltage Range Supply Current Symbol Conditions Min Typ Max Units VIN IQ VIN = 3.3V VIN = 5.0V VSHDN = VIN = 5.5V (OFF) 2.8 85 5.5 130 200 100 130 200 0.1 1 V µA µA µA mΩ Power Switch On Resistance rON VIN = 3.3V VIN = 5.0V OUT Output Leakage Current Output Turn On Delay Output Turn On Rise Time Output Turn Off Delay Output Turn Off Fall Time IL(OFF) td(ON) tr td(OFF) tf VIN = VSHDN = 5.5V, VOUT = GND ROUT = 10Ω, COUT = 1µF ROUT = 10Ω, COUT = 1µF ROUT = 10Ω, COUT = 1µF ROUT = 10Ω, COUT = 1µF 0.01 0.9 1.7 20 25 1 µA ms ms µs µs 2 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 85 105 150 80 100 135 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 ELECTRICAL CHARACTERISTICS (Cont.) Unless specified: TA = 25°C, VIN = 5V, VSHDN = GND, IOUT = 500mA. Values in bold apply over the full operating temperature range. Parameter Current Limit Short Circuit Current Limit Current Limit Trip Threshold SHDN High Level Input Voltage Low Level Input Voltage Input Current Symbol Conditions Min Typ Max Units ICL ITH(CL) VIH VIL ISHDN VOUT = GND 0.60 0.85 1.10 1.5 A A 2.8V ≤ VIN ≤ 5.50V 2.8V ≤ VIN ≤ 5.50V VSHDN = VIN = 5.5V, VOUT = OPEN VSHDN = GND, IOUT = 0mA, VOUT = OPEN 2.4 0.8 1 1 V V µA Undervoltage Lockout UVLO Threshold VUVLO VIN rising VIN falling FLG Output Resistance Leakage Current (OFF) Over Temperature Protection High Trip Level Hysteresis THI THYST 150 20 °C °C rFLG IFLG IFLG = 10mA, VO = GND, Switch ON VFLG = 5.0V, Switch OFF 50 1 Ω µA 2.7 2.4 V V TIMING DIAGRAM: OUTPUT TURN ON/OFF DELAY TIMES AND RISE/FALL TIMES 3 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 BLOCK DIAGRAM PIN CONFIGURATION Top View (8-Pin SOIC) PIN DESCRIPTION Pin # 1 2, 3 4 5 6, 7,8 Pin Name GND IN SHDN FLG OUT Pin Function Ground. Input voltage: drain of N-channel power MOSFET. Connect to supply voltage. Shutdown input: TTL compatible. N-channel power MOSFET is turned on when this pin is pulled low. Error flag output: FLG is asserted active low during a fault condition (overcurrent, input undervoltage or thermal shutdown). Power switch output: source of N-channel power MOSFET. Connect to load. 4 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL CHARACTERISTICS On-State Quiescent Current vs. Junction Temperature vs. Input Voltage 120 VIN = 5.0V 100 VIN = 3.3V 80 IQ(ON) (µA) 60 40 20 0 -50 -25 0 25 TJ (°C) 50 75 100 125 IQ(ON) (µA) VIN = 3.0V 80 60 40 20 0 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 100 120 TJ = 25°C IOUT = 500mA VSHDN = GND On-State Quiescent Current vs. Input Voltage IOUT = 500mA VSHDN = GND Off-State Quiescent Current vs. Input Voltage vs. Junction Temperature 300 250 200 IQ(OFF) (nA) 150 100 50 VSHDN = VIN 0 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 TA = 25°C TA = -40°C rON (mΩ ) 135 125 TA = 125°C 115 105 95 85 75 65 55 Power Switch On Resistance vs. Junction Temperature vs. Input Voltage VSHDN = GND IOUT = 500mA Top to bottom: VIN = 3.0V VIN = 3.3V VIN = 5.0V -50 -25 0 25 TJ (°C) 50 75 100 125 Power Switch On Resistance vs. Input Voltage vs. Junction Temperature 135 125 115 rON (mΩ ) 105 95 85 75 65 55 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 TJ = -40°C 0.5 TJ = 25°C tr (ms) VSHDN = GND IOUT = 500mA TJ = 125°C 2.0 2.5 Output Turn-On Rise Time vs. Input Voltage vs Junction Temperature TJ = 125°C TJ = 25°C 1.5 1.0 TJ = -40°C COUT = 1µF ROUT = 6.6Ω (VIN = 2.8V and 3.3V) ROUT = 10Ω (VIN = 5V and 5.5V) 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 0.0 5 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL CHARACTERISTICS (Cont.) Short Circuit Current Limit vs. Input Voltage vs. Junction Temperature 0.95 0.90 0.85 0.80 ICL (A) Top to bottom: TJ = -40°C TJ = 25°C TJ = 125°C ICL (A) 0.80 0.75 0.70 0.65 0.60 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 VIN = 3.3V 0.75 0.70 0.65 0.60 -50 -25 0 25 TJ (°C) 50 75 100 125 VIN = 3.0V VSHDN = VIN VOUT = GND 0.90 0.85 VIN = 5.0V Short Circuit Current Limit vs. Junction Temperature vs. Input Voltage VSHDN = VIN VOUT = GND Current Limit Trip Threshold vs. Junction Temperature vs. Input Voltage 1.6 1.5 VIN = 5.0V VTH(SHDN) (V) 1.4 ITH(CL) (A) 1.3 VIN = 3.3V 1.2 1.1 1.0 -50 -25 0 25 TJ (°C) 50 75 100 125 2.00 1.75 1.50 1.25 1.00 0.75 0.50 VSHDN = VIN VOUT = GND VIN = 3.0V 0.25 0.00 2.5 Shutdown Threshold vs. Input Voltage vs. Junction Temperature Top to bottom: TJ = -40°C TJ = 25°C TJ = 125°C 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 Error Flag Output Resistance vs. Input Voltage vs. Junction Temperature 40 35 30 25 rFLG (Ω ) 20 15 10 5 0 2.5 3.0 3.5 4.0 VIN (V) 4.5 5.0 5.5 IFLG = 10mA VOUT = GND Switch ON Top to bottom: TJ = 125°C TJ = 25°C TJ = -40°C 2.80 2.75 2.70 VUVLO (V) 2.65 2.60 2.55 2.50 Undervoltage Lockout vs. Junction Temperature VIN rising VIN falling 2.45 2.40 -50 -25 0 25 TJ (°C) 50 75 100 125 6 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL CHARACTERISTICS (Cont.) Figure 1: Output Turn On Delay and Rise Time with 0.1µF Output Capacitor and No Load Figure 2: Output Turn On Delay and Rise Time with 1µF Output Capacitor and 10Ω Load Top Trace: VSHDN, 5V/div. Bottom Trace: VOUT, 2V/div. Timebase: 1ms/div. VIN = 5V, ROUT = open, COUT = 0.1µF Top Trace: VSHDN, 5V/div. Bottom Trace: VOUT, 2V/div. Timebase: 1ms/div. VIN = 5V, ROUT = 10Ω, COUT = 1µF Figure 3: Output Turn Off Delay and Fall Time with 1µF Output Capacitor and 10Ω Load Figure 4: Current Limit and Trip Threshold With Ramped Load on Enabled Device Top Trace: VOUT, 5V/div. Bottom Trace: IOUT, 0.5A/div. Timebase: 100ms/div. VIN = 5V, ROUT ramping from open to 1.1Ω, COUT = 22µF Top Trace: VOUT, 5V/div. Bottom Trace: IOUT, 0.5A/div. Timebase: 100ms/div. VIN = 5V, ROUT ramping from open to 1.1Ω, COUT = 22µF 7 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL CHARACTERISTICS (Cont.) Figure 5: Current Limit and Trip Threshold With Ramped Load on Enabled Device Figure 6: Short Circuit Current, Device Enabled Into Short Top Trace: VFLG, 5V/div. Bottom Trace: IOUT, 0.5A/div. Timebase: 100ms/div. VIN = 5V, ROUT ramping from open to 1.1Ω, COUT = 22µF Top Trace: VSHDN, 5V/div. Bottom Trace: IOUT, 0.2A/div. Timebase: 1ms/div. VIN = 5V, ROUT = 0Ω Figure 7: Short Circuit Current, Short Applied to Enabled Device Figure 8: Current Limit, 1.1Ω Load Applied to Enabled Device Top Trace: VFLG, 5V/div. Bottom Trace: IOUT, 5A/div. Timebase: 250µs/div. VIN = 5V, ROUT = 0Ω, COUT = 22µF Note initial output current spike from output capacitor discharge Top Trace: VFLG, 5V/div. Bottom Trace: IOUT, 1A/div. Timebase: 250µs/div. VIN = 5V, ROUT = 1.1Ω, COUT = 1µF 8 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL CHARACTERISTICS (Cont.) Figure 9: Inrush Current, Device Enabled Into 100µF and 10Ω Figure 10: Inrush Current, Device Enabled Into 470µF and 10Ω Top Trace: VSHDN, 5V/div. Bottom Trace: IOUT, 0.2A/div. Timebase: 2.5ms/div. VIN = 5V, ROUT = 10Ω, COUT = 100µF Top Trace: VSHDN, 5V/div. Bottom Trace: IOUT, 0.2A/div. Timebase: 2.5ms/div. VIN = 5V, ROUT = 10Ω, COUT = 470µF to shut the switch down (at TJ = 150°C typical). This will shut off the output current altogether, and also cause the Flag pin to be asserted low. Once the junction temperature has dropped by 20°C (typical), the device will start up once more in a controlled manner. The SC2041 will operate from supply voltages as low as 2.8V, and internal undervoltage lockout circuitry ensures that the power switch will be turned off at power-up, even if the device is enabled. Once the UVLO threshold voltage (2.7V typical) is reached, the switch will turn on (if enabled) and slowly ramp up the output. The SC2041 has been designed for use in USB applications such as: 1) hosts or self-powered hubs that need to current limit downstream ports and report overcurrent conditions; 2) bus-powered hubs that need to be able to switch power to downstream ports, limit inrush currents at power-up (to less than a 44Ω resistor in parallel with a 10µF capacitor) and power-up and draw less than 100mA; 3) bus-powered functions that need to limit inrush currents at power-up (to less than a 44Ω resistor in parallel with a 10µF capacitor) and power-up and draw less than 100mA. 9 APPLICATIONS INFORMATION Theory Of Operation The SC2041 is a current limited 80mΩ power switch with error reporting and enable features. The power switch is an N-channel MOSFET with its gate driven by an internal charge pump. The switch has been designed to turn on slowly (1.7ms typical) to minimize inrush currents at turn-on. The Shutdown pin (SHDN) is compatible with 3V or 5V logic, and when pulled high, shuts off the power switch, causing the device to enter a very low power shutdown mode, where it will draw less than 1µA from the supply. While enabled, the SC2041 draws only 100µA from the supply. The power switch has current limit detection circuitry which will limit the current through the switch to 0.85A (typical) and reduce the output voltage accordingly. When current limit is entered, the open drain Flag pin (FLG) is asserted low, indicating a fault condition. If an overcurrent or short condition is continuous, the power dissipation in the switch will cause the junction temperature to rise, triggering the thermal protection circuitry © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 APPLICATIONS INFORMATION (Cont.) Component Selection - General A 0.1µF or greater ceramic bypass capacitor is recommended at the device input. This should be placed U1 1 VBUS IN 2 3 Shutdown Signal From USB Controller R1 4 GND IN IN SHDN SC2041 OUT OUT OUT FLG 8 7 6 5 VBUS OUT overcurrent circuitry reacts. Once the current limit circuitry trips, the current is limited to 0.85A and FLG is asserted low. Refer to Figure 7 on page 8. 3) the load gradually increases beyond 500mA. In this case, the current will be allowed to rise until it reaches the Current Limit Trip Threshold, at which point the current will drop back to 0.85A and FLG will assert low. Refer to figures 4 and 5 on page 7 and 8. Thermal Sensing Flag Output To USB Controller C1 0.1uF C2 0.1uF C3 22uF close to the input pin (IN) and routed directly to ground. A low ESR electrolytic capacitor is recommended at the output, higher values should be used for heavy loads to reduce ringing at the output (and hence input). Bypass the output with a 0.1µF to 1µF ceramic capacitor to improve immunity to short circuit transients. Shutdown An internal thermal shutdown circuit turns off the power switch when the die temperature exceeds 150°C (typical). The FLG pin asserts low signaling a fault condition. Built-in hysteresis prevents the switch from turning back on until the die temperature has cooled approximately 20°C. 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 The shutdown pin (SHDN) input is a 3V or 5V compatible enable/disable. Pulling this pin high shuts down the power switch and the SC2041 will draw < 1µA from the supply. Pulling this pin low will enable the device. Error Flag The error flag (FLG) output is an open drain N-channel MOSFET. Its output is pulled low during overcurrent, input undervoltage and thermal shutdown conditions. Connection of high capacitance loads to the output can cause momentary overcurrent conditions due to inrush current and trigger false error flag assertion. This can be reduced by using low ESR output capacitors to provide a low impedance source for hot-plug events. The addition of an RC filter between FLG and the USB controller can resolve this easily. This pin also requires a pull-up resistor for a high signal when not asserted. Overcurrent There are three overcurrent situations to be considered: 1) the output is already short before the device is enabled or power is applied. In this case, the SC2041 immediately detects the short, and the output current will slowly ramp up to the current limit value, and FLG will assert low. Refer to Figure 6 on page 8. 2) a short occurs while the device is enabled. In this case, very high current may flow initially while the An undervoltage lockout circuit monitors the input voltage and prevents the power switch from turning on until the input voltage (IN) exceeds 2.7V (typical). If the input voltage falls and drops below 2.4V (typical), the undervoltage circuitry turns off the power switch and the FLG pin asserts low. The undervoltage lockout functions only when the switch is enabled. Thermal Considerations Since the on-resistance of the power switch is so low, the SC2041 can pass large currents without requiring a large package to dissipate the heat. The worst-case power dissipation (under normal operating conditions) is given by: PD ( M A X ) = (I O U T ) 2 • r O N ( M AX ) So for IOUT = 500mA and rON(MAX) = 150mΩ (at VIN = 3.3V), the maximum power dissipation is: PD ( M A X ) = ( 0 .5 ) 2 • 0 .1 5 0 = 3 7 .5 m W The junction temperature can be calculated using the following equation: TJ = T A + θ JA • PD ( M AX ) Inserting TA = 85°C, θJA = 130°C/W (package thermal impedance for minimum line widths and no internal 10 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 APPLICATIONS INFORMATION (Cont.) power planes) and PD(MAX) = 37.5mW, we calculate the worst-case TJ to be: T J = 85 + 130 • 0 .0375 = 90 ° C Layout Considerations The ceramic bypass capacitors for IN and OUT should be connected as close to the relevant device pins as possible. The bulk output capacitors required by the USB specification should be placed close to the USB connector to provide a low impedance source for hot plug purposes. Ferrite beads should be placed on the VBUS and Ground pins of the downstream connectors to reduce the droop on adjacent ports during hot plug events. Thus it can be seen that this device does not require any additional copper area for heatsinking under normal operating conditions. Sustained overcurrents or short circuits will rapidly heat TJ > 150°C, thus activating the thermal shutdown circuitry. TYPICAL APPLICATIONS CIRCUITS Self-Powered Hub, Individual 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 SC2041 to provide individual port overcurrent protection & power switching for maximum port protection. Under fault conditions, the SC2041 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 SC2041 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. The SC5205 LDO regulator is used to power the hub controller from the hub’s 5V power supply. +5V GND 5V Power Supply U3 1 R1 100k 2 3 EN OC U4 D+ DU2 VBUS GND Upstream Port C1 4.7uF 1 2 3 VIN GND EN BYP SC5205-3.3 C2 10nF 4 C3 4.7uF D1D+ D1DUSB Controller VO 5 VCC SRDA05-4 D0D+ D0DI/O3 REF2 I/O4 REF2 C4 0.1uF I/O1 REF1 I/O2 REF1 4 GND IN IN SHDN SC2041 OUT OUT OUT FLG 8 7 6 5 C5 33uF Ferrite Bead Ferrite Bead VBUS D+ DGND Downstream Port Notes: (1) One port only shown for simplicity. (2) 33µF output capacitor assumes four downstream ports for this hub, therefore meeting the USB specification requirement of 120µF minimum capacitance per hub. (3) The SRDA05-4 shown would also protect lines D2D+ and D2D-. 11 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL APPLICATIONS CIRCUITS (Cont.) 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 SC2041 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, additional SC2041s 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 SR05 provides ESD protection to the above levels for one line pair. The SC5205 LDO regulator is used to power the hub controller from the upstream bus. U3 1 R1 100k 2 3 U1 1 2 1 2 SR05 D+ DU2 VBUS GND Upstream Port C1 4.7uF 1 2 3 VIN GND EN BYP SC5205-3.3 C2 10nF 4 C3 4.7uF D1D+ D1DD2D+ D2DD3D+ D3DD4D+ D4DUSB Controller VO 5 VCC D0D+ D0D4 3 4 3 EN OC 4 GND IN IN SC2041 OUT OUT OUT FLG 8 7 6 5 C5 33uF Ferrite Bead Ferrite Bead VBUS D+ DGND Downstream Port Ferrite Bead SHDN U4 OC OC OC I/O3 REF2 I/O4 REF2 SRDA05-4 C4 0.1uF I/O1 REF1 I/O2 REF1 VBUS D+ C6 33uF Ferrite Bead DGND Downstream Port Ferrite Bead VBUS D+ U5 I/O1 REF1 I/O2 REF1 I/O3 REF2 I/O4 REF2 C7 33uF Ferrite Bead DGND Downstream Port Ferrite Bead SRDA05-4 C8 33uF Ferrite Bead VBUS D+ DGND Downstream Port Note: (1) 33µF output capacitor per port meets the USB specification minimum capacitance requirement of 120µF per hub. 12 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 TYPICAL APPLICATIONS CIRCUITS (Cont.) High-Power or Low-Power Bus-Powered Function: Both low-power and high-power bus-powered functions must draw less than 100mA at startup. At this time, they must also present a load of less than the parallel combination of a 44Ω resistor and a 10µF capacitor. After startup, high powered functions may then draw up to 500mA. The circuit below utilizes the SC2041 to provide inrush current limiting and power switching for the internal function. Since USB is a hot insertion and removal system, USB ports are subject to electrostatic discharge (ESD). The SR05 provides ESD protection on the upstream data and power lines. With proper layout the port is hardened to greater than 15kV, meeting the requirements of IEC 1000-4-2. The SC5205 LDO regulator is used to power the hub controller from the upstream bus. U3 1 R1 100k 2 3 U1 1 2 1 2 SR05 D+ DU2 VBUS GND Upstream Port C1 10uF 1 2 3 VIN GND EN BYP SC5205-3.3 C2 10nF 4 C3 4.7uF VO 5 VCC USB Controller D0D+ D0D4 3 4 3 EN OC 4 GND IN IN SC2041 OUT OUT OUT FLG 8 7 6 5 C5 10uF VCC GND Internal Function SHDN C4 0.1uF Note: (1) 33µF output capacitor per port meets the USB specification minimum capacitance of 120µF per hub. 13 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320 HotSwitch™ USB Power Distribution Switch With Shutdown July 18, 2000 SC2041 OUTLINE DRAWING - SO-8 JEDEC REF: MS-012AA LAND PATTERN - SO-8 ECN00-1199 14 © 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320