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US202

100mΩ POWER DISTRIBUTION SWITCHES

Unisonic Technologies 

US202/A

CMOS IC

 APPLICATION INFORMATION

The UTC US202/A is a high-side single N-Channel MOSFET switch with active-high enable input.

Input and Output

VIN pin (input) is the power supply connection to the circuitry and the drain of the output MOSFET. VOUT pin (output)

is the source of the output MOSFET. In a typical circuit, current flows through the switch from VIN to VOUT toward the

load. Both VOUT pins must be short on the board and connected to the load and so do both VIN pins but connected to

the power source.

Thermal Shutdown

Thermal shutdown is used to turn off the output MOSFET when the if the temperature is higher than130°C, 20°C

of hysteresis prevents the switch turn on until the die temperature drops to 110°C.

Soft Start

When hot-plug events occur, the soft start is used to eliminate the upstream voltage droop due to the inrush

current. The soft-start protects power supplies from damage caused by highly capacitive loads.

Under-Voltage Lockout

UVLO (Under voltage Lockout) turn off the MOSFET switch once the input voltage falls below 1.8V (TYP.) and if

the input voltage exceeds 1.8V, the switch will be turned on.

Current Limiting and Short Protection

The current limit threshold is preset internally. The minimum value is 1.1A/2.1A. The current limit circuit protects

this device from damage resulting from undesired excess inrush current, which is encountered during hot plug-in

events. The output current is limited to approximately 1.5A/2.5A (TYP). When the output is short to ground, it will

limit to a constant current 1A until thermal shutdown or short condition removed.

Filtering

During the hot-plug events, in order to limit the input voltage drop, a 1μF ceramic capacitor is recommended to be

placed between VIN to GND. However special care must be taken to the values of the capacitor, because higher

capacitor values will further reduce the voltage drop at the input.

In order to prevent inductive parasitic from pulling VOUT negative during turn-off or EMI damage to other

components during the hot detachment, it’s better to connect a sufficient capacitor from VOUT to GND. This capacitor

is also necessary for meeting the USB specification during hot plug-in operation.

If the UTC US202/A is implanted in device and application, minimum 1μF capacitor from VOUT to GND is

recommended. If the VOUT is short to ground frequently during usage, large size input capacitor is necessary,

recommend 22μF.

Choosing these capacitors properly is critical. A lower ESR on the capacitor can get a lower IR drop during the

operation, so the Effective Series Resistance (ESR) of the capacitors must be considered.

For ferrite beads, if they are in series with all power and ground lines, the EMI will be eliminated or reduced. The

DC resistance of the wire kept to a minimum to reduce the voltage drop should be considered in choosing ferrite

beads.

UNISONIC TECHNOLOGIES CO., LTD

www.unisonic.com.tw

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QW-R502-445.F

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