IMP2525
Application Information
USB
Controller
IMP2525-2
8
7
6
1
VBUS
EN
OUT
IN
2
3
FLG
GND
NC
USB
Function
OUT
NC
USB Hub
4
5
4.7µF
CBULK
GND
Cable
USB Peripheral
2525_07.eps
Figure 3. Inrush Current-Limit Application
Transient Overcurrent Filter
V+
If a heavy capacitive load is suddenly connected to the output, the
switch current-limiting function may cause the fault-flag to go
low for 10µs to 200µs as the switch, in a constant current mode,
charges the capacitance. If this transient over-current fault report-
ing is not wanted, a simple 1ms RC low-pass filter in series with
the fault flag circuit will prevent this momentary flag (Figure 4).
10k
10k
USB Controller
IMP2525
FLG
2
OVERCURRENT
0.1µF
2525_05.eps
Figure 4. Transient Filter
V
CC
5.0V
10k
100k
Ferrite
Beads
Upstream
V
BUS
100mA max
VBUS
1
8
7
6
VBUS
D+
IN
OUT
V
ON/OFF
EN
OUT
IN
IN
2
OVERCURRENT
FLG
IMP2525-2
OUT
D+
3.3V
USB Controller
USB
Port
LDO
GND
D–
D–
150µF
+
GND
GND
3
GND
GND
1µF
1µF
0.1µF
2525_08.eps
Data
Data
Figure 5. Single-Port Self-Powered Hub Application
6
© 2000 IMP, Inc.
6
408-432-9100/www.impweb.com
A1PROS [ A1 PROS CO., LTD. ]
