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is a high-side single switch with active-high enable input.

Input and Output

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

(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 shuts off the output MOSFET if the die temperature exceeds 130℃ and 20℃ of

hysterics forces the switch turning off until the die temperature drops to 110℃.

Filtering

GND. However, higher capacitor values will further reduce the voltage drop at the input.

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

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recommended and higher capacitor values are also preferred.

In choosing these capacitors, special attention must be paid to the Effective Series Resistance, ESR, of

the capacitors to minimize the IR drop across the capacitor’s ESR. A lower ESR on this capacitor can

get a lower IR drop during the operation.

Ferrite beads in series with all power and ground lines are recommended to eliminate or significantly

reduce EMI. In selecting a ferrite bead, the DC resistance of the wire used must be kept to a minimum to

reduce the voltage drop.

Soft Start

In order to eliminate the upstream voltage droop caused by the large inrush current during hot-plug

events, the “soft-start” feature effectively isolates power supplies from such highly capacitive loads.

Under-voltage Lockout

UVLO prevents the MOSFET switch from turning on until input voltage exceeds 1.7V (typical). If input

voltage drops below 1.7V (typical), UVLO shuts off the MOSFET switch.

Current Limiting and Short Protection

The current limit circuit is designed to protect the system supply, the MOSFET switch and the load from

damage caused by excessive currents. The current limit threshold is set internally to limit the output

constant current 30mA until thermal shutdown or short condition removed.

HM9708