US16855

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 8

www.unisonic.com.tw

QW-R502-558.a

FUNCTION DESCRIPTION

UNDER VOLTAGE LOCKED OUT

UVLO prevents malfunction of the switch because of voltage variation. When input voltage exceeds 2.5V (typical),

the output MOSFET turns on. If input voltage drops below 2.3V (typical), UVLO shuts off the both output MOSFET

switches and signals the FLAG.

POWER ON AND OFF

The UTC US16855 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.

OVER CURRENT DETECT

The specification of over current detect is 0.6 ~ 1.25 A (typ. 900mA) in this IC. (500 mA max. in USB standard)

This function is that flag-pin turns to Low-level and reports to the USB controller when over current is detected.

At this time, output of IC is operated as followed.

Output turns to off, and isn't based on the state of CTL-pin.

When CTL-pin turns to non-active, FLG-pin returns to High-level and Output-pin turn to OFF-state.

Immediately the controller should be inputted non-active level to CTL-pin after detecting FLG = “L” not to reach to

the state of thermal shutdown.

Then, in the case of FLG-pin is High-level and CTL-pin is active level, Output-pin turns to ON-state.

To prevent from detecting wrongly the current to the moment, over current detect delay time is set up.

This delay time is 10 ms (typ.).

Over current Detect

Over Current detect threshold

5V

5V

5V

5V

GND

GND

GND

IN (Input)

Flg (Output)

CTL (Input)

OUT (Output)

GND