US2076B

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 8

www.unisonic.com.tw

QW-R502-447.a

APPLICATIONS INFORMATION

Supply filtering

In order to control supply transients, a bypass capacitor is located nearly between IN to GND. 0.1µF ~ 1µF is

suitable (See Figure 1). Without a bypass capacitor, an output short may cause sufficient ringing on the input (from

supply lead inductance) to damage internal control circuitry.

Enable Input

For a clearly defined input, the EN pin must be driven logic high or logic low. Floating the input may cause

unpredictable operation. EN should not be allowed to go negative with respect to GND.

Soft Start

The UTC US2076B is high impedance when off and slowly becomes a low impedance as it turns on. This

reduces inrush current and related voltage drop that results from charging a capacitive load, satisfying the USB

voltage drop requirements, for bus-powered applications as shown in Figure 2.

Capactive

Load

Downstream USB Device

Cable

BUS Powered Hub

USB

Controller

ENA

ENB

FLGA

FLGB

OUTA

OUTB

GND

IN

8

7

6

5

1

2

3

4

4.7

µF

Cable

GND

USB Host

Figure 2. Soft Start (Single Channel)

UTC

US2076B