US3026A

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

7 of 11

www.unisonic.com.tw

QW-R502-086,A

FUNCTIONAL DESCRIPTION

The UTC US3026A is dual P-Channel switches with active-low and active-high enable inputs, respectively. Fault

conditions (such as UVLO, thermal shutdown and over-current) that appear will turn off the power switch, and the

FLAG pin will go low. Of course, the two internal FLAG circuits also operate respectively.

Input and Output

IN (Input) is the power supply connection to the control circuitry and the source of the output MOSFET. OUTX

(Output) is the connection to the drain of the output MOSFET. In a typical application circuit, current flows through

from OUTX to IN since the MOSFET is bi-directional.

Power ON and OFF

The UTC US3026A performs a soft-start operation on power application, which is to prevent an over-current or

inrush-current from flowing through the switch from IN to OUTX towards to the load, while the high-capacity

capacitor is connected to the OUTX.

Thermal Shutdown

The UTC US3026A is internally protected against excessive power dissipation by thermal shutdown protection

circuit. If device junction temperature rise above approximately 145 , both switches are turned off, both fault FLAG

℃

outputs are activated, and they goes low. Hysteresis ensures that both switches turned off by thermal shutdown will

not be turned on again until the die temperature is reduced to 135 . When the thermal shutd

℃

own circuit is activated,

the output pins are in the OFF status. However, the UTC US3026A enters the standby status when EN pins are all

inactive.

Current Limit

The current limit circuit is designed to protect the output MOSFET, the load and the IC supply from damage

caused by excessive currents. The current limit threshold is preset internally, If an over-current is detected, the IC

performs a slow-start operation again, it is assumed that output is short circuit, and FLAG pin will go low, FLAG

output is available to indicate fault conditions independently to the USB controller.

Under-Voltage Lockout

UVLO prevents the output MOSFET switch from turning on until input voltage exceeds 2.3V (typical). If input

voltage drops below 2.2V (typical), UVLO shuts off the both output MOSFET switches and signals the FLAG.

Fault FLAG

The fault FLAG is an output with open-drain of N-channel. The fault FLAG is pulled down when any of the

conditions such as under-voltage, current limit and thermal shutdown. In a typical application circuit, the FALG pin

has a pull-up resistor of 10kΩ to input voltage.