MIC2525 Datasheet, PDF (10/12 Pages) Micrel Semiconductor – USB Power Control Switch Not Recommended for New Designs

MIC2525
During the capacitance charging time, the device enters into
constant-current mode. As the capacitance is charged, the
current decreases below the short circuit current-limit thresh-
old, and the flag will then be deasserted.
In USB applications, it is required that output bulk capaci-
tance is utilized to support hot-plug events. When the MIC2525
is enabled, the flag may go active for about 1ms due to inrush
current exceeding the current-limit setpoint. Additionally,
during hot-plug events, inrush currents may also cause the
flag to go active for 30µs. Since these conditions are not valid
overcurrent faults, the USB controller must ignore the flag
during these events. To prevent this erroneous overcurrent
reporting, a 1ms RC filter as shown in Figure 4 may be used.
Micrel
Alternatively, a 1ms debounce routine may be programmed
into the USB logic controller, eliminating the need for the RC
filter.
USB Controller
OVERCURRENT
V+
10k
10k
0.1
µF
MIC2525
1 _EN
OUT ⁸
2 _FLG
IN ⁷
3 _{GND OUT} 6
4 _NC
NC ⁵
Figure 4. Transient Filter
MIC2525
10
January 2000