US2076B

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

7 of 8

www.unisonic.com.tw

QW-R502-447.a

APPLICATIONS INFORMATION (Cont.)

In Figure 3, the soft start circuit is shown, and the soft start circuit can be utilized to meet USB transient

for these applications.

USB

Controller

USB

Function

USB

Function

Cable

GND

USB Hub

ENA

ENB

FLGA

FLGB

GND

OUTA

OUTB

IN

1

2

3

4

8

7

6

5

USB Peripheral

Figure 3. Inrush Current-Limit Application

US2076B

4.7

µF

If an inrush current which is from the connection of a heavy capacitive load, the inrush current may cause the

fault flag to fall for a short duration, while the switch is in a constant-current mode, or charging the capacitance. In

that case, to protect this circuit from damage due to erroneous overcurrent reporting, the fault flag circuit can be in

series with a simple 1ms RC low-pass filter (see Figure 4)

ENA

ENB

FLGA

FLGB

OUTA

OUTB

GND

IN

1

2

3

4

5

6

7

8

10k

10k

USB Controller

Figure 4. Transient Filter

Transient Overcurrent Filter

UTC

US2076B

0.1µF

OC