WT6621

WT6621 Dual USB Power Control Switch GENERAL DESCRIPTION The WT6621 is a dual integrated power switch optimized for self-powered and bus-powered Universal Serial Bus (USB) applications. Few external components are necessary to satisfy USB requirements. With independent enable and error flag functions, the WT6621 can ease control the supplied power conditions of USB down stream; each switch channel can supplies up to 500mA to downstream devices; the switch low on-resistance meets USB voltage drop requirements; fault current is limited to typically 750mA, and a flag output is available to indicate fault conditions to the local USB controller. Additional features include thermal shutdown to prevent switch failure from high-current loads, undervoltage lockout (UVLO) to ensure there is a valid input voltage present, and 3.3V and 5V logic compatible enable inputs. FEATURES ! ! ! ! ! ! ! ! ! ! ! ! ! Compliant to USB specifications Max. Continuous load current: 500mA 140mΩ maximum on-resistance per channel. 110uA typical on-state supply current 1uA typical off-state supply current Enable input is compatible with both 3V and 5V Logic Logic Over current output Undervoltage lockout Short Circuit Protection Thermal Shutdown Active-high or active-low enable versions 12KV output, 6KV input ESD protection. Packages: 8pin SOIC and 8pin DIP Applications ! ! ! USB host and Self-power hubs USB bus-powered hub General purpose power switch applications Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved
27 March, 2000 WT6621 Dual USB Power Control Switch PIN ASSIGNMENT WT6621 /EN1 1 8 OUT1 /FG1 2 7 IN /FG2 3 6 GND /EN2 4 5 OUT2 PIN DESCRIPTIONS Pin Number 1 Pin Name /EN1 I/O I Function Descriptions Enable input: Logic Compatible input to turns the power switch on. (-NX Active Low, -PX active High) Fault Flag: Logic output, open drain output. /FG1 is asserted active low to indicate Overcurrent, UVLO, and Thermal Shutdown. Fault Flag: Logic output, open drain output. /FG2 is asserted active low to indicate Overcurrent, UVLO, and Thermal Shutdown. Enable input: Logic Compatible input to turns the power switch on. (-NX Active Low, -PX active High) Power Switch output Ground Supply Input Power Switch output 2 /FG1 O 3 /FG2 O 4 /EN2 I 5 6 7 8 OUT2 GND IN OUT1 O I O Package and Ordering Information Part Number WT6621-SL WT6621-DL WT6621-SH WT6621-DH Enable (/EN) Active Low Active Low Active High Active High Package 8-pin SOIC 8-pin DIP 8-pin SOIC 8-pin DIP Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved  27 March, 2000 WT6621 Dual USB Power Control Switch Block Diagram IN Charge Pump /EN1 Gate Control Current Sense OUT1 /FG1 UVLO Thermal Sense /FG2 OUT2 /EN2 Gate Control Current Sense GND Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved  27 March, 2000 WT6621 Dual USB Power Control Switch FUNCTIONAL DESCRIPTION The WT6621 is a dual power switches with active low (or active high) enable inputs. Fault conditions; such as Overcurrent, UVLO, and Thermal Shutdown; turns off or inhibit turn on the output power switch, and activate the open drain transistor to sink current and asserts an error flag. Power Switch The Power Switch is a CMOS power switch with a maximum on-state resistance of 140mΩ(Vi(IN)=5V , IN (input) is the power supply connection to the drain of the switch and OUT (output) is the source of the switch to be connected to the load. Charge Pump The charge pump supplies power to the gate control circuit and provides the necessary voltage to the gate of the CMOS power switch. Thermal Shutdown Thermal Shutdown circuit shuts off the output of the power switch and the fault flag(/FG) is asserted when the die temperature rise to approximately 135°C. Approximate 30°C of Hysteresis prevents the switch from turning on until the die temperature drops to approximately 115°C. Current Limit Induced Thermal Shutdown Internal circuitry increases the output of the CMOS Power Switch on-resis-tance until the series combination of the CMOS Power Switch on-resis-tance and the load impedance limit current to typically 750mA. The increase in power dissipation, in most cases, will cause the WT6621 to go into thermal shutdown, disabling affected channels. When this is undesirable, thermal shutdown can be avoided by externally responding to the fault and disabling the current limited channel before the shutdown temperature is reached. The delay between the flag indication of a current limit fault and thermal shutdown will vary with ambient tem-perature, board layout, and load impedance, but is typically several hundred milliseconds. The USB controller must there-fore recognize a fault and disable the appropriate channel within this time. Undervoltage Lockout UVLO(Undervoltage lockout) circuit prevents the output of power switch from turning on until input voltage (IN) exceeds 2.5V typical. After the switch turns on, UVLO shuts off the output of power switch and the fault flag(/FG) is asserted if the input voltage drops below 2.3V. Current Sensing and Limiting As an overload or short circuit is encountered, the current sense circuit sends a signal to the gate control. Then gate control circuit in turn reduces the gate voltage and drives the power switch into a constant current mode. Switch Enabled into Short Circuit: If a switch is powered on or enabled into a heavy load or short-circuit, the switch immediately goes into a constant-current mode, reducing the output voltage. The fault flag goes low until the load is reduced. Short Circuit Applied to Output: When a heavy load is applied, a large transient current may flow until the current limit circuitry will respond. Once this occurs, the device limits current to less than the short-circuit current limit specification. Current-Limit Response: TheWT6621 current-limit profile exhibits a small foldback effect of approximately 500mA. Once this current-limit thresh-old is exceeded the device enters constant-current mode. This constant current is specified as the short circuit current limit in the Electrical Characteristics table. It is important to note that the WT6621will deliver load current up to the current-limit threshold which is typically 0.75A. Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved  27 March, 2000 WT6621 Dual USB Power Control Switch Fault Flag The fault flag (/FG) is active low for one or more of the following fault conditions: undervoltage, overload or short circuit, or thermal shutdown. /FG pin is capable of sinking a 10mA load. Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved  27 March, 2000 WT6621 Dual USB Power Control Switch Absolute Maximum Ratings Supply voltage(Vin) Output voltage(Vo) Output current(Io) Fault Flag voltage(VFG) Fault Flag current(IFG) Control Input(VEN) Storage Temperature(TS) Lead Temperature(Soldering 5 sec.) +6.0V +6.0V internallly limited +6.0V 50mA -0.3V to 12V -65°C to +150°C 260°C Operating Ratings Supply voltage(VIN) Ambient Operating Temperature(TA) Supply Voltage (VIN) Continuous output current, Io +4V to +5.5V -40°C to +85°C +3V to 5.5V 0.6A Max. ELECTRICAL CHARACTERISTICS VIN=5.0V + 5% , Ta=25 OC) Parameter Condition Supply Current Switch off, Open load Switch on, Open load Enable Input Treshold Low to high transition voltage High to low transition Enable Input current VEN = 0 to 5.5V Switch Reistnce VIN = 5V, Iout=500mA Output Turn on delay RL=10 Ohm each Output Output Turn on Rise Time RL=10 Ohm each Output Output Turn off Delay RL=10 Ohm each Output Output Turn off Fall Time RL=10 Ohm each Output Continous Load Current Each output Short Circuit Current Limit Each output, Vout = 4.0V Current limit threshold Ramp Load applied to Vout5V) VEN VFLAG VOUT IOUT RL=35 CL=10uF VEN VFLA VOUT IOUT RL=35 CL=220uF Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved 27 March, 2000 WT6621 Dual USB Power Control Switch Short-circuit response characteristics Test equipment: " Test power supplyAgilent E3631A " " Test scope:LeCory LC564A Test DC electronic loadZentech 2600A Short-circuit response (Short applied to output) VFLAG VOUT IOUT 1.6A Thermal Shoutdown Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved
27 March, 2000 WT6621 Dual USB Power Control Switch Short-circuit response (Enable into Short Circuit) VEN VFLAG VOUT IOUT 1.6A Thermal Shoutdown Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved

27 March, 2000 WT6621 Dual USB Power Control Switch Short-circuit transient response characteristics Test equipment: " Test power supplyAgilent E3631A " " Test scope:LeCory LC564A Test DC electronic loadZentech 2600A Short circuit transient response (Short applied to output) VOUT VFLAG 2.01A IOUT 0.64A Current limit Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved
 27 March, 2000 WT6621 Dual USB Power Control Switch Output Turn-On delay/rising time test Test equipment: " Test power supplyAgilent E3631A " " Test scope:LeCory LC564A Test DC electronic loadZentech 2600A Output Turn-On delay/rising time VEN VOU
 Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved
 27 March, 2000 WT6621 Dual USB Power Control Switch Output Turn-Off delay/falling time test Test equipment: " Test power supplyAgilent E3631A " " Test scope:LeCory LC564A Test DC electronic loadZentech 2600A VEN VOUTA Version1.0 Weltrend Semiconductor, Inc. All Rights Reserved
 27 March, 2000 WT6621 Dual USB Power Control Switch Typical Appication Circuit
    
  
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 27 March, 2000