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US2076B Datasheet(PDF) 5 Page - Unisonic Technologies

Part No. US2076B
Description  DUAL USB HIGH-SIDE POWER SWITCHDUAL USB HIGH-SIDE POWER SWITCH
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Maker  UTC [Unisonic Technologies]
Homepage  http://www.utc-ic.com
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US2076B Datasheet(HTML) 5 Page - Unisonic Technologies

   
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US2076B
Preliminary
CMOS IC
UNISONICTECHNOLOGIESCO.,LTD
5 of 8
www.unisonic.com.tw
QW-R502-447.a
FUNCTIONAL DESCRIPTION
The UTC US2076B is dual high-side switch with active-high enable inputs. Fault conditions turn off or inhibit
turn-on one or both of the output transistors, controlling by the type of fault, and the FLG pin is pulled to ground by
being activated the open-drain error flag transistors.
Input and Output
IN (input) is the power supply connection to the logic circuitry and the source of the output MOSFET. OUTx
(output) is the drain of the output A or B MOSFET.
IN pin (input) is the power supply connection to the logic circuitry and the source of the output MOSFET. OUT
pin (output) is the output MOSFET’s drain. Current flows through the switch from IN pin to OUT pin toward the load
in many applications. All OUT pins must be connected together to the load.
The output MOSFET and driver circuit are also designed to allow the MOSFET drain to be externally forced to
a higher voltage than the source (VOUT > VIN) when the switch is off. This avoids undesirable drain-to-body diode
current flow by connecting the body to the most positive voltage. If VOUT >VIN when switch is enabled, current will
flow from VOUT to VIN.
Thermal Shutdown
Thermal shutdown is designed to prevent this device from being damaged due to excessive power dissipation.
It is used to turn off the output MOSFET if the temperature is higher than135°C, 10°C of hysteresis prevents the
switch from turning on until the die temperature drops to 125°C. Thermal shutdown circuit functions only when the
switch is enabled.
Undervoltage Lockout
UVLO (Undervoltage Lockout) turns off the MOSFET switch and signals the fault flag pin once the input voltage
falls below 2.3V (TYP.) and if the input voltage exceeds 2.5V (TYP.), the switch will be turned on. UVLO detection
functions only when the switch is enabled.
Current Sensing and Limiting
The current limit threshold is fixed internally, allowing a 0.5A minimum current to flow through the output
MOSFET. However, the current limit threshold can prevent the output MOSFET and external load from being
damage. A current sense circuit protects the MOSFET switch’s output current. If output current becomes higher than
the current limit threshold, the output MOSFET switch is turned off and a fault flag is pulled low. The reaction to an
overcurrent is measured with the following scenarios:
Switch Enable into Heavy Load
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 output voltage. The fault flag goes low until the load is reduced or thermal
shutdown occurs.
If the switch is powered on or enabled into a heavy load or short-circuit, the switch enters a constant-current
mode immediately, reducing the output voltage. The fault flag drops low until thermal shutdown occurs or the load is
reduced.
Heavy Load Applied Suddenly to Enabled Switch
When a heavy load is applied, a large-undesired transient current occurs which may damage the switch. Then
the current limit circuit may turn off the switch, folding back into constant-current mode. In that case, the fault flag
falls until the load is reduced.
Fault Flag
Fault flag is an open-drained output of an N-channel MOSFET. It drops low to indicate error conditions as
follows: current limiting, UVLO, or thermal shutdown. The flag output MOSFET is capable of sinking a 10mA load to
typically 100mV above ground. Both flag pins may be "wire-NORed" to a common pullup resistor.


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