Global Mixed-mode Technology Inc.
G525A
USB
Controller
V
BUS
USB Hub
EN
4.7 2 FLG
µF 3
GND
4 NC
1
G525A
8
OUT
7
IN
OUT 6
NC 5
C
BULK
USB
Function
GND
USB Peripheral
Cable
Figure 3. Inrush Current-Limit Application
EN, the enable Input
EN, with 0.2V hysteresis, must be driven logic high or
logic low for a clearly defined input. Floating the input
may cause unpredictable operation. EN should not be
allowed to go negative with respect to GND.
Soft Start
The G525A 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 applica-
tions as shown in Figure 2.
The soft start circuit shown in Figure 3 can be utilized
to meet USB transient regulation specifications with
large load capacitances (C
BULK
>10µF). The G525A
will provide inrush current limiting for these applica-
tions.
Transient Overcurrent Filter
V
＋
10k
OVERCURRENT
To USB
10k
0.1 µF
G525A
1 EN
2
FLG
OUT
IN
OUT
NC
8
7
6
5
3 GND
4
NC
Figure 4. Transient Filter
The inrush current from the connection of a heavy ca-
pacitive load may cause the fault flag to fall for a short
duration while the switch is in a constant-current mode,
for charging the capacitance. If needed, a simple 1ms
RC low-pass filter in series with the fault flag circuit
will prevent erroneous overcurrent reporting (see Fig-
ure 4).
Ver: 1.2
Nov 11, 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
7
GMT [ GLOBAL MIXED-MODE TECHNOLOGY INC ]
